FreeBSD/Linux Kernel Cross Reference
sys/dev/hwpmc/hwpmc_mod.c

     /*-
      * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
      *
      * Copyright (c) 2003-2008 Joseph Koshy
      * Copyright (c) 2007 The FreeBSD Foundation
      * Copyright (c) 2018 Matthew Macy
      * All rights reserved.
      *
      * Portions of this software were developed by A. Joseph Koshy under
     * sponsorship from the FreeBSD Foundation and Google, Inc.
     *
     * Redistribution and use in source and binary forms, with or without
     * modification, are permitted provided that the following conditions
     * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     *
     * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD$");
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/domainset.h>
    #include <sys/eventhandler.h>
    #include <sys/jail.h>
    #include <sys/kernel.h>
    #include <sys/kthread.h>
    #include <sys/limits.h>
    #include <sys/lock.h>
    #include <sys/malloc.h>
    #include <sys/module.h>
    #include <sys/mount.h>
    #include <sys/mutex.h>
    #include <sys/pmc.h>
    #include <sys/pmckern.h>
    #include <sys/pmclog.h>
    #include <sys/priv.h>
    #include <sys/proc.h>
    #include <sys/queue.h>
    #include <sys/resourcevar.h>
    #include <sys/rwlock.h>
    #include <sys/sched.h>
    #include <sys/signalvar.h>
    #include <sys/smp.h>
    #include <sys/sx.h>
    #include <sys/sysctl.h>
    #include <sys/sysent.h>
    #include <sys/syslog.h>
    #include <sys/taskqueue.h>
    #include <sys/vnode.h>
    
    #include <sys/linker.h>         /* needs to be after <sys/malloc.h> */
    
    #include <machine/atomic.h>
    #include <machine/md_var.h>
    
    #include <vm/vm.h>
    #include <vm/vm_extern.h>
    #include <vm/pmap.h>
    #include <vm/vm_map.h>
    #include <vm/vm_object.h>
    
    #include "hwpmc_soft.h"
    
    #define PMC_EPOCH_ENTER() struct epoch_tracker pmc_et; epoch_enter_preempt(global_epoch_preempt, &pmc_et)
    #define PMC_EPOCH_EXIT() epoch_exit_preempt(global_epoch_preempt, &pmc_et)
    
    /*
     * Types
     */
    
    enum pmc_flags {
            PMC_FLAG_NONE     = 0x00, /* do nothing */
            PMC_FLAG_REMOVE   = 0x01, /* atomically remove entry from hash */
            PMC_FLAG_ALLOCATE = 0x02, /* add entry to hash if not found */
            PMC_FLAG_NOWAIT   = 0x04, /* do not wait for mallocs */
    };
    
    /*
     * The offset in sysent where the syscall is allocated.
     */
    
   static int pmc_syscall_num = NO_SYSCALL;
   struct pmc_cpu          **pmc_pcpu;      /* per-cpu state */
   pmc_value_t             *pmc_pcpu_saved; /* saved PMC values: CSW handling */
   
   #define PMC_PCPU_SAVED(C,R)     pmc_pcpu_saved[(R) + md->pmd_npmc*(C)]
   
   struct mtx_pool         *pmc_mtxpool;
   static int              *pmc_pmcdisp;    /* PMC row dispositions */
   
   #define PMC_ROW_DISP_IS_FREE(R)         (pmc_pmcdisp[(R)] == 0)
   #define PMC_ROW_DISP_IS_THREAD(R)       (pmc_pmcdisp[(R)] > 0)
   #define PMC_ROW_DISP_IS_STANDALONE(R)   (pmc_pmcdisp[(R)] < 0)
   
   #define PMC_MARK_ROW_FREE(R) do {                                         \
           pmc_pmcdisp[(R)] = 0;                                             \
   } while (0)
   
   #define PMC_MARK_ROW_STANDALONE(R) do {                                   \
           KASSERT(pmc_pmcdisp[(R)] <= 0, ("[pmc,%d] row disposition error", \
                       __LINE__));                                           \
           atomic_add_int(&pmc_pmcdisp[(R)], -1);                            \
           KASSERT(pmc_pmcdisp[(R)] >= (-pmc_cpu_max_active()),              \
                   ("[pmc,%d] row disposition error", __LINE__));            \
   } while (0)
   
   #define PMC_UNMARK_ROW_STANDALONE(R) do {                                 \
           atomic_add_int(&pmc_pmcdisp[(R)], 1);                             \
           KASSERT(pmc_pmcdisp[(R)] <= 0, ("[pmc,%d] row disposition error", \
                       __LINE__));                                           \
   } while (0)
   
   #define PMC_MARK_ROW_THREAD(R) do {                                       \
           KASSERT(pmc_pmcdisp[(R)] >= 0, ("[pmc,%d] row disposition error", \
                       __LINE__));                                           \
           atomic_add_int(&pmc_pmcdisp[(R)], 1);                             \
   } while (0)
   
   #define PMC_UNMARK_ROW_THREAD(R) do {                                     \
           atomic_add_int(&pmc_pmcdisp[(R)], -1);                            \
           KASSERT(pmc_pmcdisp[(R)] >= 0, ("[pmc,%d] row disposition error", \
                       __LINE__));                                           \
   } while (0)
   
   
   /* various event handlers */
   static eventhandler_tag pmc_exit_tag, pmc_fork_tag, pmc_kld_load_tag,
       pmc_kld_unload_tag;
   
   /* Module statistics */
   struct pmc_driverstats pmc_stats;
   
   
   /* Machine/processor dependent operations */
   static struct pmc_mdep  *md;
   
   /*
    * Hash tables mapping owner processes and target threads to PMCs.
    */
   
   struct mtx pmc_processhash_mtx;         /* spin mutex */
   static u_long pmc_processhashmask;
   static LIST_HEAD(pmc_processhash, pmc_process)  *pmc_processhash;
   
   /*
    * Hash table of PMC owner descriptors.  This table is protected by
    * the shared PMC "sx" lock.
    */
   
   static u_long pmc_ownerhashmask;
   static LIST_HEAD(pmc_ownerhash, pmc_owner)      *pmc_ownerhash;
   
   /*
    * List of PMC owners with system-wide sampling PMCs.
    */
   
   static CK_LIST_HEAD(, pmc_owner)                        pmc_ss_owners;
   
   /*
    * List of free thread entries. This is protected by the spin
    * mutex.
    */
   static struct mtx pmc_threadfreelist_mtx;       /* spin mutex */
   static LIST_HEAD(, pmc_thread)                  pmc_threadfreelist;
   static int pmc_threadfreelist_entries=0;
   #define THREADENTRY_SIZE                                                \
   (sizeof(struct pmc_thread) + (md->pmd_npmc * sizeof(struct pmc_threadpmcstate)))
   
   /*
    * Task to free thread descriptors
    */
   static struct task free_task;
   
   /*
    * A map of row indices to classdep structures.
    */
   static struct pmc_classdep **pmc_rowindex_to_classdep;
   
   /*
    * Prototypes
    */
   
   #ifdef  HWPMC_DEBUG
   static int      pmc_debugflags_sysctl_handler(SYSCTL_HANDLER_ARGS);
   static int      pmc_debugflags_parse(char *newstr, char *fence);
   #endif
   
   static int      load(struct module *module, int cmd, void *arg);
   static int      pmc_add_sample(ring_type_t ring, struct pmc *pm, struct trapframe *tf);
   static void     pmc_add_thread_descriptors_from_proc(struct proc *p,
       struct pmc_process *pp);
   static int      pmc_attach_process(struct proc *p, struct pmc *pm);
   static struct pmc *pmc_allocate_pmc_descriptor(void);
   static struct pmc_owner *pmc_allocate_owner_descriptor(struct proc *p);
   static int      pmc_attach_one_process(struct proc *p, struct pmc *pm);
   static int      pmc_can_allocate_rowindex(struct proc *p, unsigned int ri,
       int cpu);
   static int      pmc_can_attach(struct pmc *pm, struct proc *p);
   static void     pmc_capture_user_callchain(int cpu, int soft, struct trapframe *tf);
   static void     pmc_cleanup(void);
   static int      pmc_detach_process(struct proc *p, struct pmc *pm);
   static int      pmc_detach_one_process(struct proc *p, struct pmc *pm,
       int flags);
   static void     pmc_destroy_owner_descriptor(struct pmc_owner *po);
   static void     pmc_destroy_pmc_descriptor(struct pmc *pm);
   static void     pmc_destroy_process_descriptor(struct pmc_process *pp);
   static struct pmc_owner *pmc_find_owner_descriptor(struct proc *p);
   static int      pmc_find_pmc(pmc_id_t pmcid, struct pmc **pm);
   static struct pmc *pmc_find_pmc_descriptor_in_process(struct pmc_owner *po,
       pmc_id_t pmc);
   static struct pmc_process *pmc_find_process_descriptor(struct proc *p,
       uint32_t mode);
   static struct pmc_thread *pmc_find_thread_descriptor(struct pmc_process *pp,
       struct thread *td, uint32_t mode);
   static void     pmc_force_context_switch(void);
   static void     pmc_link_target_process(struct pmc *pm,
       struct pmc_process *pp);
   static void     pmc_log_all_process_mappings(struct pmc_owner *po);
   static void     pmc_log_kernel_mappings(struct pmc *pm);
   static void     pmc_log_process_mappings(struct pmc_owner *po, struct proc *p);
   static void     pmc_maybe_remove_owner(struct pmc_owner *po);
   static void     pmc_process_csw_in(struct thread *td);
   static void     pmc_process_csw_out(struct thread *td);
   static void     pmc_process_exit(void *arg, struct proc *p);
   static void     pmc_process_fork(void *arg, struct proc *p1,
       struct proc *p2, int n);
   static void     pmc_process_samples(int cpu, ring_type_t soft);
   static void     pmc_release_pmc_descriptor(struct pmc *pmc);
   static void     pmc_process_thread_add(struct thread *td);
   static void     pmc_process_thread_delete(struct thread *td);
   static void     pmc_process_thread_userret(struct thread *td);
   static void     pmc_remove_owner(struct pmc_owner *po);
   static void     pmc_remove_process_descriptor(struct pmc_process *pp);
   static int      pmc_start(struct pmc *pm);
   static int      pmc_stop(struct pmc *pm);
   static int      pmc_syscall_handler(struct thread *td, void *syscall_args);
   static struct pmc_thread *pmc_thread_descriptor_pool_alloc(void);
   static void     pmc_thread_descriptor_pool_drain(void);
   static void     pmc_thread_descriptor_pool_free(struct pmc_thread *pt);
   static void     pmc_unlink_target_process(struct pmc *pmc,
       struct pmc_process *pp);
   static int generic_switch_in(struct pmc_cpu *pc, struct pmc_process *pp);
   static int generic_switch_out(struct pmc_cpu *pc, struct pmc_process *pp);
   static struct pmc_mdep *pmc_generic_cpu_initialize(void);
   static void pmc_generic_cpu_finalize(struct pmc_mdep *md);
   static void pmc_post_callchain_callback(void);
   static void pmc_process_threadcreate(struct thread *td);
   static void pmc_process_threadexit(struct thread *td);
   static void pmc_process_proccreate(struct proc *p);
   static void pmc_process_allproc(struct pmc *pm);
   
   /*
    * Kernel tunables and sysctl(8) interface.
    */
   
   SYSCTL_DECL(_kern_hwpmc);
   SYSCTL_NODE(_kern_hwpmc, OID_AUTO, stats, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
       "HWPMC stats");
   
   
   /* Stats. */
   SYSCTL_COUNTER_U64(_kern_hwpmc_stats, OID_AUTO, intr_ignored, CTLFLAG_RW,
                                      &pmc_stats.pm_intr_ignored, "# of interrupts ignored");
   SYSCTL_COUNTER_U64(_kern_hwpmc_stats, OID_AUTO, intr_processed, CTLFLAG_RW,
                                      &pmc_stats.pm_intr_processed, "# of interrupts processed");
   SYSCTL_COUNTER_U64(_kern_hwpmc_stats, OID_AUTO, intr_bufferfull, CTLFLAG_RW,
                                      &pmc_stats.pm_intr_bufferfull, "# of interrupts where buffer was full");
   SYSCTL_COUNTER_U64(_kern_hwpmc_stats, OID_AUTO, syscalls, CTLFLAG_RW,
                                      &pmc_stats.pm_syscalls, "# of syscalls");
   SYSCTL_COUNTER_U64(_kern_hwpmc_stats, OID_AUTO, syscall_errors, CTLFLAG_RW,
                                      &pmc_stats.pm_syscall_errors, "# of syscall_errors");
   SYSCTL_COUNTER_U64(_kern_hwpmc_stats, OID_AUTO, buffer_requests, CTLFLAG_RW,
                                      &pmc_stats.pm_buffer_requests, "# of buffer requests");
   SYSCTL_COUNTER_U64(_kern_hwpmc_stats, OID_AUTO, buffer_requests_failed, CTLFLAG_RW,
                                      &pmc_stats.pm_buffer_requests_failed, "# of buffer requests which failed");
   SYSCTL_COUNTER_U64(_kern_hwpmc_stats, OID_AUTO, log_sweeps, CTLFLAG_RW,
                                      &pmc_stats.pm_log_sweeps, "# of times samples were processed");
   SYSCTL_COUNTER_U64(_kern_hwpmc_stats, OID_AUTO, merges, CTLFLAG_RW,
                                      &pmc_stats.pm_merges, "# of times kernel stack was found for user trace");
   SYSCTL_COUNTER_U64(_kern_hwpmc_stats, OID_AUTO, overwrites, CTLFLAG_RW,
                                      &pmc_stats.pm_overwrites, "# of times a sample was overwritten before being logged");
   
   static int pmc_callchaindepth = PMC_CALLCHAIN_DEPTH;
   SYSCTL_INT(_kern_hwpmc, OID_AUTO, callchaindepth, CTLFLAG_RDTUN,
       &pmc_callchaindepth, 0, "depth of call chain records");
   
   char pmc_cpuid[PMC_CPUID_LEN];
   SYSCTL_STRING(_kern_hwpmc, OID_AUTO, cpuid, CTLFLAG_RD,
           pmc_cpuid, 0, "cpu version string");
   #ifdef  HWPMC_DEBUG
   struct pmc_debugflags pmc_debugflags = PMC_DEBUG_DEFAULT_FLAGS;
   char    pmc_debugstr[PMC_DEBUG_STRSIZE];
   TUNABLE_STR(PMC_SYSCTL_NAME_PREFIX "debugflags", pmc_debugstr,
       sizeof(pmc_debugstr));
   SYSCTL_PROC(_kern_hwpmc, OID_AUTO, debugflags,
       CTLTYPE_STRING | CTLFLAG_RWTUN | CTLFLAG_NOFETCH | CTLFLAG_MPSAFE,
       0, 0, pmc_debugflags_sysctl_handler, "A",
       "debug flags");
   #endif
   
   
   /*
    * kern.hwpmc.hashrows -- determines the number of rows in the
    * of the hash table used to look up threads
    */
   
   static int pmc_hashsize = PMC_HASH_SIZE;
   SYSCTL_INT(_kern_hwpmc, OID_AUTO, hashsize, CTLFLAG_RDTUN,
       &pmc_hashsize, 0, "rows in hash tables");
   
   /*
    * kern.hwpmc.nsamples --- number of PC samples/callchain stacks per CPU
    */
   
   static int pmc_nsamples = PMC_NSAMPLES;
   SYSCTL_INT(_kern_hwpmc, OID_AUTO, nsamples, CTLFLAG_RDTUN,
       &pmc_nsamples, 0, "number of PC samples per CPU");
   
   static uint64_t pmc_sample_mask = PMC_NSAMPLES-1;
   
   /*
    * kern.hwpmc.mtxpoolsize -- number of mutexes in the mutex pool.
    */
   
   static int pmc_mtxpool_size = PMC_MTXPOOL_SIZE;
   SYSCTL_INT(_kern_hwpmc, OID_AUTO, mtxpoolsize, CTLFLAG_RDTUN,
       &pmc_mtxpool_size, 0, "size of spin mutex pool");
   
   
   /*
    * kern.hwpmc.threadfreelist_entries -- number of free entries
    */
   
   SYSCTL_INT(_kern_hwpmc, OID_AUTO, threadfreelist_entries, CTLFLAG_RD,
       &pmc_threadfreelist_entries, 0, "number of available thread entries");
   
   
   /*
    * kern.hwpmc.threadfreelist_max -- maximum number of free entries
    */
   
   static int pmc_threadfreelist_max = PMC_THREADLIST_MAX;
   SYSCTL_INT(_kern_hwpmc, OID_AUTO, threadfreelist_max, CTLFLAG_RW,
       &pmc_threadfreelist_max, 0,
       "maximum number of available thread entries before freeing some");
   
   
   /*
    * kern.hwpmc.mincount -- minimum sample count
    */
   static u_int pmc_mincount = 1000;
   SYSCTL_INT(_kern_hwpmc, OID_AUTO, mincount, CTLFLAG_RWTUN,
       &pmc_mincount, 0,
       "minimum count for sampling counters");
   
   /*
    * security.bsd.unprivileged_syspmcs -- allow non-root processes to
    * allocate system-wide PMCs.
    *
    * Allowing unprivileged processes to allocate system PMCs is convenient
    * if system-wide measurements need to be taken concurrently with other
    * per-process measurements.  This feature is turned off by default.
    */
   
   static int pmc_unprivileged_syspmcs = 0;
   SYSCTL_INT(_security_bsd, OID_AUTO, unprivileged_syspmcs, CTLFLAG_RWTUN,
       &pmc_unprivileged_syspmcs, 0,
       "allow unprivileged process to allocate system PMCs");
   
   /*
    * Hash function.  Discard the lower 2 bits of the pointer since
    * these are always zero for our uses.  The hash multiplier is
    * round((2^LONG_BIT) * ((sqrt(5)-1)/2)).
    */
   
   #if     LONG_BIT == 64
   #define _PMC_HM         11400714819323198486u
   #elif   LONG_BIT == 32
   #define _PMC_HM         2654435769u
   #else
   #error  Must know the size of 'long' to compile
   #endif
   
   #define PMC_HASH_PTR(P,M)       ((((unsigned long) (P) >> 2) * _PMC_HM) & (M))
   
   /*
    * Syscall structures
    */
   
   /* The `sysent' for the new syscall */
   static struct sysent pmc_sysent = {
           .sy_narg =      2,
           .sy_call =      pmc_syscall_handler,
   };
   
   static struct syscall_module_data pmc_syscall_mod = {
           .chainevh =     load,
           .chainarg =     NULL,
           .offset =       &pmc_syscall_num,
           .new_sysent =   &pmc_sysent,
           .old_sysent =   { .sy_narg = 0, .sy_call = NULL },
           .flags =        SY_THR_STATIC_KLD,
   };
   
   static moduledata_t pmc_mod = {
           .name =         PMC_MODULE_NAME,
           .evhand =       syscall_module_handler,
           .priv =         &pmc_syscall_mod,
   };
   
   #ifdef EARLY_AP_STARTUP
   DECLARE_MODULE(pmc, pmc_mod, SI_SUB_SYSCALLS, SI_ORDER_ANY);
   #else
   DECLARE_MODULE(pmc, pmc_mod, SI_SUB_SMP, SI_ORDER_ANY);
   #endif
   MODULE_VERSION(pmc, PMC_VERSION);
   
   #ifdef  HWPMC_DEBUG
   enum pmc_dbgparse_state {
           PMCDS_WS,               /* in whitespace */
           PMCDS_MAJOR,            /* seen a major keyword */
           PMCDS_MINOR
   };
   
   static int
   pmc_debugflags_parse(char *newstr, char *fence)
   {
           char c, *p, *q;
           struct pmc_debugflags *tmpflags;
           int error, found, *newbits, tmp;
           size_t kwlen;
   
           tmpflags = malloc(sizeof(*tmpflags), M_PMC, M_WAITOK|M_ZERO);
   
           p = newstr;
           error = 0;
   
           for (; p < fence && (c = *p); p++) {
   
                   /* skip white space */
                   if (c == ' ' || c == '\t')
                           continue;
   
                   /* look for a keyword followed by "=" */
                   for (q = p; p < fence && (c = *p) && c != '='; p++)
                           ;
                   if (c != '=') {
                           error = EINVAL;
                           goto done;
                   }
   
                   kwlen = p - q;
                   newbits = NULL;
   
                   /* lookup flag group name */
   #define DBG_SET_FLAG_MAJ(S,F)                                           \
                   if (kwlen == sizeof(S)-1 && strncmp(q, S, kwlen) == 0)  \
                           newbits = &tmpflags->pdb_ ## F;
   
                   DBG_SET_FLAG_MAJ("cpu",         CPU);
                   DBG_SET_FLAG_MAJ("csw",         CSW);
                   DBG_SET_FLAG_MAJ("logging",     LOG);
                   DBG_SET_FLAG_MAJ("module",      MOD);
                   DBG_SET_FLAG_MAJ("md",          MDP);
                   DBG_SET_FLAG_MAJ("owner",       OWN);
                   DBG_SET_FLAG_MAJ("pmc",         PMC);
                   DBG_SET_FLAG_MAJ("process",     PRC);
                   DBG_SET_FLAG_MAJ("sampling",    SAM);
   
                   if (newbits == NULL) {
                           error = EINVAL;
                           goto done;
                   }
   
                   p++;            /* skip the '=' */
   
                   /* Now parse the individual flags */
                   tmp = 0;
           newflag:
                   for (q = p; p < fence && (c = *p); p++)
                           if (c == ' ' || c == '\t' || c == ',')
                                   break;
   
                   /* p == fence or c == ws or c == "," or c == 0 */
   
                   if ((kwlen = p - q) == 0) {
                           *newbits = tmp;
                           continue;
                   }
   
                   found = 0;
   #define DBG_SET_FLAG_MIN(S,F)                                           \
                   if (kwlen == sizeof(S)-1 && strncmp(q, S, kwlen) == 0)  \
                           tmp |= found = (1 << PMC_DEBUG_MIN_ ## F)
   
                   /* a '*' denotes all possible flags in the group */
                   if (kwlen == 1 && *q == '*')
                           tmp = found = ~0;
                   /* look for individual flag names */
                   DBG_SET_FLAG_MIN("allocaterow", ALR);
                   DBG_SET_FLAG_MIN("allocate",    ALL);
                   DBG_SET_FLAG_MIN("attach",      ATT);
                   DBG_SET_FLAG_MIN("bind",        BND);
                   DBG_SET_FLAG_MIN("config",      CFG);
                   DBG_SET_FLAG_MIN("exec",        EXC);
                   DBG_SET_FLAG_MIN("exit",        EXT);
                   DBG_SET_FLAG_MIN("find",        FND);
                   DBG_SET_FLAG_MIN("flush",       FLS);
                   DBG_SET_FLAG_MIN("fork",        FRK);
                   DBG_SET_FLAG_MIN("getbuf",      GTB);
                   DBG_SET_FLAG_MIN("hook",        PMH);
                   DBG_SET_FLAG_MIN("init",        INI);
                   DBG_SET_FLAG_MIN("intr",        INT);
                   DBG_SET_FLAG_MIN("linktarget",  TLK);
                   DBG_SET_FLAG_MIN("mayberemove", OMR);
                   DBG_SET_FLAG_MIN("ops",         OPS);
                   DBG_SET_FLAG_MIN("read",        REA);
                   DBG_SET_FLAG_MIN("register",    REG);
                   DBG_SET_FLAG_MIN("release",     REL);
                   DBG_SET_FLAG_MIN("remove",      ORM);
                   DBG_SET_FLAG_MIN("sample",      SAM);
                   DBG_SET_FLAG_MIN("scheduleio",  SIO);
                   DBG_SET_FLAG_MIN("select",      SEL);
                   DBG_SET_FLAG_MIN("signal",      SIG);
                   DBG_SET_FLAG_MIN("swi",         SWI);
                   DBG_SET_FLAG_MIN("swo",         SWO);
                   DBG_SET_FLAG_MIN("start",       STA);
                   DBG_SET_FLAG_MIN("stop",        STO);
                   DBG_SET_FLAG_MIN("syscall",     PMS);
                   DBG_SET_FLAG_MIN("unlinktarget", TUL);
                   DBG_SET_FLAG_MIN("write",       WRI);
                   if (found == 0) {
                           /* unrecognized flag name */
                           error = EINVAL;
                           goto done;
                   }
   
                   if (c == 0 || c == ' ' || c == '\t') {  /* end of flag group */
                           *newbits = tmp;
                           continue;
                   }
   
                   p++;
                   goto newflag;
           }
   
           /* save the new flag set */
           bcopy(tmpflags, &pmc_debugflags, sizeof(pmc_debugflags));
   
    done:
           free(tmpflags, M_PMC);
           return error;
   }
   
   static int
   pmc_debugflags_sysctl_handler(SYSCTL_HANDLER_ARGS)
   {
           char *fence, *newstr;
           int error;
           unsigned int n;
   
           (void) arg1; (void) arg2; /* unused parameters */
   
           n = sizeof(pmc_debugstr);
           newstr = malloc(n, M_PMC, M_WAITOK|M_ZERO);
           (void) strlcpy(newstr, pmc_debugstr, n);
   
           error = sysctl_handle_string(oidp, newstr, n, req);
   
           /* if there is a new string, parse and copy it */
           if (error == 0 && req->newptr != NULL) {
                   fence = newstr + (n < req->newlen ? n : req->newlen + 1);
                   if ((error = pmc_debugflags_parse(newstr, fence)) == 0)
                           (void) strlcpy(pmc_debugstr, newstr,
                               sizeof(pmc_debugstr));
           }
   
           free(newstr, M_PMC);
   
           return error;
   }
   #endif
   
   /*
    * Map a row index to a classdep structure and return the adjusted row
    * index for the PMC class index.
    */
   static struct pmc_classdep *
   pmc_ri_to_classdep(struct pmc_mdep *md, int ri, int *adjri)
   {
           struct pmc_classdep *pcd;
   
           (void) md;
   
           KASSERT(ri >= 0 && ri < md->pmd_npmc,
               ("[pmc,%d] illegal row-index %d", __LINE__, ri));
   
           pcd = pmc_rowindex_to_classdep[ri];
   
           KASSERT(pcd != NULL,
               ("[pmc,%d] ri %d null pcd", __LINE__, ri));
   
           *adjri = ri - pcd->pcd_ri;
   
           KASSERT(*adjri >= 0 && *adjri < pcd->pcd_num,
               ("[pmc,%d] adjusted row-index %d", __LINE__, *adjri));
   
           return (pcd);
   }
   
   /*
    * Concurrency Control
    *
    * The driver manages the following data structures:
    *
    *   - target process descriptors, one per target process
    *   - owner process descriptors (and attached lists), one per owner process
    *   - lookup hash tables for owner and target processes
    *   - PMC descriptors (and attached lists)
    *   - per-cpu hardware state
    *   - the 'hook' variable through which the kernel calls into
    *     this module
    *   - the machine hardware state (managed by the MD layer)
    *
    * These data structures are accessed from:
    *
    * - thread context-switch code
    * - interrupt handlers (possibly on multiple cpus)
    * - kernel threads on multiple cpus running on behalf of user
    *   processes doing system calls
    * - this driver's private kernel threads
    *
    * = Locks and Locking strategy =
    *
    * The driver uses four locking strategies for its operation:
    *
    * - The global SX lock "pmc_sx" is used to protect internal
    *   data structures.
    *
    *   Calls into the module by syscall() start with this lock being
    *   held in exclusive mode.  Depending on the requested operation,
    *   the lock may be downgraded to 'shared' mode to allow more
    *   concurrent readers into the module.  Calls into the module from
    *   other parts of the kernel acquire the lock in shared mode.
    *
    *   This SX lock is held in exclusive mode for any operations that
    *   modify the linkages between the driver's internal data structures.
    *
    *   The 'pmc_hook' function pointer is also protected by this lock.
    *   It is only examined with the sx lock held in exclusive mode.  The
    *   kernel module is allowed to be unloaded only with the sx lock held
    *   in exclusive mode.  In normal syscall handling, after acquiring the
    *   pmc_sx lock we first check that 'pmc_hook' is non-null before
    *   proceeding.  This prevents races between the thread unloading the module
    *   and other threads seeking to use the module.
    *
    * - Lookups of target process structures and owner process structures
    *   cannot use the global "pmc_sx" SX lock because these lookups need
    *   to happen during context switches and in other critical sections
    *   where sleeping is not allowed.  We protect these lookup tables
    *   with their own private spin-mutexes, "pmc_processhash_mtx" and
    *   "pmc_ownerhash_mtx".
    *
    * - Interrupt handlers work in a lock free manner.  At interrupt
    *   time, handlers look at the PMC pointer (phw->phw_pmc) configured
    *   when the PMC was started.  If this pointer is NULL, the interrupt
    *   is ignored after updating driver statistics.  We ensure that this
    *   pointer is set (using an atomic operation if necessary) before the
    *   PMC hardware is started.  Conversely, this pointer is unset atomically
    *   only after the PMC hardware is stopped.
    *
    *   We ensure that everything needed for the operation of an
    *   interrupt handler is available without it needing to acquire any
    *   locks.  We also ensure that a PMC's software state is destroyed only
    *   after the PMC is taken off hardware (on all CPUs).
    *
    * - Context-switch handling with process-private PMCs needs more
    *   care.
    *
    *   A given process may be the target of multiple PMCs.  For example,
    *   PMCATTACH and PMCDETACH may be requested by a process on one CPU
    *   while the target process is running on another.  A PMC could also
    *   be getting released because its owner is exiting.  We tackle
    *   these situations in the following manner:
    *
    *   - each target process structure 'pmc_process' has an array
    *     of 'struct pmc *' pointers, one for each hardware PMC.
    *
    *   - At context switch IN time, each "target" PMC in RUNNING state
    *     gets started on hardware and a pointer to each PMC is copied into
    *     the per-cpu phw array.  The 'runcount' for the PMC is
    *     incremented.
    *
    *   - At context switch OUT time, all process-virtual PMCs are stopped
    *     on hardware.  The saved value is added to the PMCs value field
    *     only if the PMC is in a non-deleted state (the PMCs state could
    *     have changed during the current time slice).
    *
    *     Note that since in-between a switch IN on a processor and a switch
    *     OUT, the PMC could have been released on another CPU.  Therefore
    *     context switch OUT always looks at the hardware state to turn
    *     OFF PMCs and will update a PMC's saved value only if reachable
    *     from the target process record.
    *
    *   - OP PMCRELEASE could be called on a PMC at any time (the PMC could
    *     be attached to many processes at the time of the call and could
    *     be active on multiple CPUs).
    *
    *     We prevent further scheduling of the PMC by marking it as in
    *     state 'DELETED'.  If the runcount of the PMC is non-zero then
    *     this PMC is currently running on a CPU somewhere.  The thread
    *     doing the PMCRELEASE operation waits by repeatedly doing a
    *     pause() till the runcount comes to zero.
    *
    * The contents of a PMC descriptor (struct pmc) are protected using
    * a spin-mutex.  In order to save space, we use a mutex pool.
    *
    * In terms of lock types used by witness(4), we use:
    * - Type "pmc-sx", used by the global SX lock.
    * - Type "pmc-sleep", for sleep mutexes used by logger threads.
    * - Type "pmc-per-proc", for protecting PMC owner descriptors.
    * - Type "pmc-leaf", used for all other spin mutexes.
    */
   
   /*
    * save the cpu binding of the current kthread
    */
   
   void
   pmc_save_cpu_binding(struct pmc_binding *pb)
   {
           PMCDBG0(CPU,BND,2, "save-cpu");
           thread_lock(curthread);
           pb->pb_bound = sched_is_bound(curthread);
           pb->pb_cpu   = curthread->td_oncpu;
           pb->pb_priority = curthread->td_priority;
           thread_unlock(curthread);
           PMCDBG1(CPU,BND,2, "save-cpu cpu=%d", pb->pb_cpu);
   }
   
   /*
    * restore the cpu binding of the current thread
    */
   
   void
   pmc_restore_cpu_binding(struct pmc_binding *pb)
   {
           PMCDBG2(CPU,BND,2, "restore-cpu curcpu=%d restore=%d",
               curthread->td_oncpu, pb->pb_cpu);
           thread_lock(curthread);
           sched_bind(curthread, pb->pb_cpu);
           if (!pb->pb_bound)
                   sched_unbind(curthread);
           sched_prio(curthread, pb->pb_priority);
           thread_unlock(curthread);
           PMCDBG0(CPU,BND,2, "restore-cpu done");
   }
   
   /*
    * move execution over the specified cpu and bind it there.
    */
   
   void
   pmc_select_cpu(int cpu)
   {
           KASSERT(cpu >= 0 && cpu < pmc_cpu_max(),
               ("[pmc,%d] bad cpu number %d", __LINE__, cpu));
   
           /* Never move to an inactive CPU. */
           KASSERT(pmc_cpu_is_active(cpu), ("[pmc,%d] selecting inactive "
               "CPU %d", __LINE__, cpu));
   
           PMCDBG1(CPU,SEL,2, "select-cpu cpu=%d", cpu);
           thread_lock(curthread);
           sched_prio(curthread, PRI_MIN);
           sched_bind(curthread, cpu);
           thread_unlock(curthread);
   
           KASSERT(curthread->td_oncpu == cpu,
               ("[pmc,%d] CPU not bound [cpu=%d, curr=%d]", __LINE__,
                   cpu, curthread->td_oncpu));
   
           PMCDBG1(CPU,SEL,2, "select-cpu cpu=%d ok", cpu);
   }
   
   /*
    * Force a context switch.
    *
    * We do this by pause'ing for 1 tick -- invoking mi_switch() is not
    * guaranteed to force a context switch.
    */
   
   static void
   pmc_force_context_switch(void)
   {
   
           pause("pmcctx", 1);
   }
   
   uint64_t
   pmc_rdtsc(void)
   {
   #if defined(__i386__) || defined(__amd64__)
           if (__predict_true(amd_feature & AMDID_RDTSCP))
                   return rdtscp();
           else
                   return rdtsc();
   #else
           return get_cyclecount();
   #endif
   }
   
   /*
    * Get the file name for an executable.  This is a simple wrapper
    * around vn_fullpath(9).
    */
   
   static void
   pmc_getfilename(struct vnode *v, char **fullpath, char **freepath)
   {
   
           *fullpath = "unknown";
           *freepath = NULL;
           vn_fullpath(v, fullpath, freepath);
   }
   
   /*
    * remove an process owning PMCs
    */
   
   void
   pmc_remove_owner(struct pmc_owner *po)
   {
           struct pmc *pm, *tmp;
   
           sx_assert(&pmc_sx, SX_XLOCKED);
   
           PMCDBG1(OWN,ORM,1, "remove-owner po=%p", po);
   
           /* Remove descriptor from the owner hash table */
           LIST_REMOVE(po, po_next);
   
           /* release all owned PMC descriptors */
           LIST_FOREACH_SAFE(pm, &po->po_pmcs, pm_next, tmp) {
                   PMCDBG1(OWN,ORM,2, "pmc=%p", pm);
                   KASSERT(pm->pm_owner == po,
                       ("[pmc,%d] owner %p != po %p", __LINE__, pm->pm_owner, po));
   
                   pmc_release_pmc_descriptor(pm); /* will unlink from the list */
                   pmc_destroy_pmc_descriptor(pm);
           }
   
           KASSERT(po->po_sscount == 0,
               ("[pmc,%d] SS count not zero", __LINE__));
           KASSERT(LIST_EMPTY(&po->po_pmcs),
               ("[pmc,%d] PMC list not empty", __LINE__));
   
           /* de-configure the log file if present */
           if (po->po_flags & PMC_PO_OWNS_LOGFILE)
                   pmclog_deconfigure_log(po);
   }
   
   /*
    * remove an owner process record if all conditions are met.
    */
   
   static void
   pmc_maybe_remove_owner(struct pmc_owner *po)
   {
   
           PMCDBG1(OWN,OMR,1, "maybe-remove-owner po=%p", po);
   
           /*
            * Remove owner record if
            * - this process does not own any PMCs
            * - this process has not allocated a system-wide sampling buffer
            */
   
           if (LIST_EMPTY(&po->po_pmcs) &&
               ((po->po_flags & PMC_PO_OWNS_LOGFILE) == 0)) {
                   pmc_remove_owner(po);
                   pmc_destroy_owner_descriptor(po);
           }
   }
   
   /*
    * Add an association between a target process and a PMC.
    */
   
   static void
   pmc_link_target_process(struct pmc *pm, struct pmc_process *pp)
   {
           int ri;
           struct pmc_target *pt;
   #ifdef INVARIANTS
           struct pmc_thread *pt_td;
   #endif
   
           sx_assert(&pmc_sx, SX_XLOCKED);
   
           KASSERT(pm != NULL && pp != NULL,
               ("[pmc,%d] Null pm %p or pp %p", __LINE__, pm, pp));
           KASSERT(PMC_IS_VIRTUAL_MODE(PMC_TO_MODE(pm)),
               ("[pmc,%d] Attaching a non-process-virtual pmc=%p to pid=%d",
                   __LINE__, pm, pp->pp_proc->p_pid));
           KASSERT(pp->pp_refcnt >= 0 && pp->pp_refcnt <= ((int) md->pmd_npmc - 1),
               ("[pmc,%d] Illegal reference count %d for process record %p",
                   __LINE__, pp->pp_refcnt, (void *) pp));
   
           ri = PMC_TO_ROWINDEX(pm);
   
           PMCDBG3(PRC,TLK,1, "link-target pmc=%p ri=%d pmc-process=%p",
               pm, ri, pp);
   
   #ifdef  HWPMC_DEBUG
           LIST_FOREACH(pt, &pm->pm_targets, pt_next)
               if (pt->pt_process == pp)
                       KASSERT(0, ("[pmc,%d] pp %p already in pmc %p targets",
                                   __LINE__, pp, pm));
   #endif
   
           pt = malloc(sizeof(struct pmc_target), M_PMC, M_WAITOK|M_ZERO);
           pt->pt_process = pp;
   
           LIST_INSERT_HEAD(&pm->pm_targets, pt, pt_next);
   
           atomic_store_rel_ptr((uintptr_t *)&pp->pp_pmcs[ri].pp_pmc,
               (uintptr_t)pm);
   
           if (pm->pm_owner->po_owner == pp->pp_proc)
                   pm->pm_flags |= PMC_F_ATTACHED_TO_OWNER;
   
           /*
            * Initialize the per-process values at this row index.
            */
           pp->pp_pmcs[ri].pp_pmcval = PMC_TO_MODE(pm) == PMC_MODE_TS ?
               pm->pm_sc.pm_reloadcount : 0;
   
           pp->pp_refcnt++;
   
   #ifdef INVARIANTS
           /* Confirm that the per-thread values at this row index are cleared. */
           if (PMC_TO_MODE(pm) == PMC_MODE_TS) {
                   mtx_lock_spin(pp->pp_tdslock);
                   LIST_FOREACH(pt_td, &pp->pp_tds, pt_next) {
                           KASSERT(pt_td->pt_pmcs[ri].pt_pmcval == (pmc_value_t) 0,
                               ("[pmc,%d] pt_pmcval not cleared for pid=%d at "
                               "ri=%d", __LINE__, pp->pp_proc->p_pid, ri));
                   }
                   mtx_unlock_spin(pp->pp_tdslock);
           }
   #endif
   }
   
   /*
    * Removes the association between a target process and a PMC.
    */
   
   static void
   pmc_unlink_target_process(struct pmc *pm, struct pmc_process *pp)
   {
           int ri;
           struct proc *p;
           struct pmc_target *ptgt;
           struct pmc_thread *pt;
   
           sx_assert(&pmc_sx, SX_XLOCKED);
   
           KASSERT(pm != NULL && pp != NULL,
               ("[pmc,%d] Null pm %p or pp %p", __LINE__, pm, pp));
   
           KASSERT(pp->pp_refcnt >= 1 && pp->pp_refcnt <= (int) md->pmd_npmc,
               ("[pmc,%d] Illegal ref count %d on process record %p",
                   __LINE__, pp->pp_refcnt, (void *) pp));
   
           ri = PMC_TO_ROWINDEX(pm);
   
           PMCDBG3(PRC,TUL,1, "unlink-target pmc=%p ri=%d pmc-process=%p",
               pm, ri, pp);
   
           KASSERT(pp->pp_pmcs[ri].pp_pmc == pm,
              ("[pmc,%d] PMC ri %d mismatch pmc %p pp->[ri] %p", __LINE__,
                  ri, pm, pp->pp_pmcs[ri].pp_pmc));
  
          pp->pp_pmcs[ri].pp_pmc = NULL;
          pp->pp_pmcs[ri].pp_pmcval = (pmc_value_t) 0;
  
          /* Clear the per-thread values at this row index. */
          if (PMC_TO_MODE(pm) == PMC_MODE_TS) {
                  mtx_lock_spin(pp->pp_tdslock);
                  LIST_FOREACH(pt, &pp->pp_tds, pt_next)
                          pt->pt_pmcs[ri].pt_pmcval = (pmc_value_t) 0;
                  mtx_unlock_spin(pp->pp_tdslock);
          }
  
          /* Remove owner-specific flags */
          if (pm->pm_owner->po_owner == pp->pp_proc) {
                  pp->pp_flags &= ~PMC_PP_ENABLE_MSR_ACCESS;
                  pm->pm_flags &= ~PMC_F_ATTACHED_TO_OWNER;
          }
  
          pp->pp_refcnt--;
  
          /* Remove the target process from the PMC structure */
          LIST_FOREACH(ptgt, &pm->pm_targets, pt_next)
                  if (ptgt->pt_process == pp)
                          break;
  
          KASSERT(ptgt != NULL, ("[pmc,%d] process %p (pp: %p) not found "
                      "in pmc %p", __LINE__, pp->pp_proc, pp, pm));
  
          LIST_REMOVE(ptgt, pt_next);
          free(ptgt, M_PMC);
  
          /* if the PMC now lacks targets, send the owner a SIGIO */
          if (LIST_EMPTY(&pm->pm_targets)) {
                  p = pm->pm_owner->po_owner;
                  PROC_LOCK(p);
                  kern_psignal(p, SIGIO);
                  PROC_UNLOCK(p);
  
                  PMCDBG2(PRC,SIG,2, "signalling proc=%p signal=%d", p,
                      SIGIO);
          }
  }
  
  /*
   * Check if PMC 'pm' may be attached to target process 't'.
   */
  
  static int
  pmc_can_attach(struct pmc *pm, struct proc *t)
  {
          struct proc *o;         /* pmc owner */
          struct ucred *oc, *tc;  /* owner, target credentials */
          int decline_attach, i;
  
          /*
           * A PMC's owner can always attach that PMC to itself.
           */
  
          if ((o = pm->pm_owner->po_owner) == t)
                  return 0;
  
          PROC_LOCK(o);
          oc = o->p_ucred;
          crhold(oc);
          PROC_UNLOCK(o);
  
          PROC_LOCK(t);
          tc = t->p_ucred;
          crhold(tc);
          PROC_UNLOCK(t);
  
          /*
           * The effective uid of the PMC owner should match at least one
           * of the {effective,real,saved} uids of the target process.
           */
  
          decline_attach = oc->cr_uid != tc->cr_uid &&
              oc->cr_uid != tc->cr_svuid &&
              oc->cr_uid != tc->cr_ruid;
  
          /*
           * Every one of the target's group ids, must be in the owner's
           * group list.
           */
          for (i = 0; !decline_attach && i < tc->cr_ngroups; i++)
                  decline_attach = !groupmember(tc->cr_groups[i], oc);
  
          /* check the read and saved gids too */
          if (decline_attach == 0)
                  decline_attach = !groupmember(tc->cr_rgid, oc) ||
                      !groupmember(tc->cr_svgid, oc);
  
          crfree(tc);
          crfree(oc);
  
          return !decline_attach;
  }
  
  /*
   * Attach a process to a PMC.
   */
  
  static int
  pmc_attach_one_process(struct proc *p, struct pmc *pm)
  {
          int ri, error;
          char *fullpath, *freepath;
          struct pmc_process      *pp;
  
          sx_assert(&pmc_sx, SX_XLOCKED);
  
          PMCDBG5(PRC,ATT,2, "attach-one pm=%p ri=%d proc=%p (%d, %s)", pm,
              PMC_TO_ROWINDEX(pm), p, p->p_pid, p->p_comm);
  
          /*
           * Locate the process descriptor corresponding to process 'p',
           * allocating space as needed.
           *
           * Verify that rowindex 'pm_rowindex' is free in the process
           * descriptor.
           *
           * If not, allocate space for a descriptor and link the
           * process descriptor and PMC.
           */
          ri = PMC_TO_ROWINDEX(pm);
  
          /* mark process as using HWPMCs */
          PROC_LOCK(p);
          p->p_flag |= P_HWPMC;
          PROC_UNLOCK(p);
  
          if ((pp = pmc_find_process_descriptor(p, PMC_FLAG_ALLOCATE)) == NULL) {
                  error = ENOMEM;
                  goto fail;
          }
  
          if (pp->pp_pmcs[ri].pp_pmc == pm) {/* already present at slot [ri] */
                  error = EEXIST;
                  goto fail;
          }
  
          if (pp->pp_pmcs[ri].pp_pmc != NULL) {
                  error = EBUSY;
                  goto fail;
          }
  
          pmc_link_target_process(pm, pp);
  
          if (PMC_IS_SAMPLING_MODE(PMC_TO_MODE(pm)) &&
              (pm->pm_flags & PMC_F_ATTACHED_TO_OWNER) == 0)
                  pm->pm_flags |= PMC_F_NEEDS_LOGFILE;
  
          pm->pm_flags |= PMC_F_ATTACH_DONE; /* mark as attached */
  
          /* issue an attach event to a configured log file */
          if (pm->pm_owner->po_flags & PMC_PO_OWNS_LOGFILE) {
                  if (p->p_flag & P_KPROC) {
                          fullpath = kernelname;
                          freepath = NULL;
                  } else {
                          pmc_getfilename(p->p_textvp, &fullpath, &freepath);
                          pmclog_process_pmcattach(pm, p->p_pid, fullpath);
                  }
                  free(freepath, M_TEMP);
                  if (PMC_IS_SAMPLING_MODE(PMC_TO_MODE(pm)))
                          pmc_log_process_mappings(pm->pm_owner, p);
          }
  
          return (0);
   fail:
          PROC_LOCK(p);
          p->p_flag &= ~P_HWPMC;
          PROC_UNLOCK(p);
          return (error);
  }
  
  /*
   * Attach a process and optionally its children
   */
  
  static int
  pmc_attach_process(struct proc *p, struct pmc *pm)
  {
          int error;
          struct proc *top;
  
          sx_assert(&pmc_sx, SX_XLOCKED);
  
          PMCDBG5(PRC,ATT,1, "attach pm=%p ri=%d proc=%p (%d, %s)", pm,
              PMC_TO_ROWINDEX(pm), p, p->p_pid, p->p_comm);
  
  
          /*
           * If this PMC successfully allowed a GETMSR operation
           * in the past, disallow further ATTACHes.
           */
  
          if ((pm->pm_flags & PMC_PP_ENABLE_MSR_ACCESS) != 0)
                  return EPERM;
  
          if ((pm->pm_flags & PMC_F_DESCENDANTS) == 0)
                  return pmc_attach_one_process(p, pm);
  
          /*
           * Traverse all child processes, attaching them to
           * this PMC.
           */
  
          sx_slock(&proctree_lock);
  
          top = p;
  
          for (;;) {
                  if ((error = pmc_attach_one_process(p, pm)) != 0)
                          break;
                  if (!LIST_EMPTY(&p->p_children))
                          p = LIST_FIRST(&p->p_children);
                  else for (;;) {
                          if (p == top)
                                  goto done;
                          if (LIST_NEXT(p, p_sibling)) {
                                  p = LIST_NEXT(p, p_sibling);
                                  break;
                          }
                          p = p->p_pptr;
                  }
          }
  
          if (error)
                  (void) pmc_detach_process(top, pm);
  
   done:
          sx_sunlock(&proctree_lock);
          return error;
  }
  
  /*
   * Detach a process from a PMC.  If there are no other PMCs tracking
   * this process, remove the process structure from its hash table.  If
   * 'flags' contains PMC_FLAG_REMOVE, then free the process structure.
   */
  
  static int
  pmc_detach_one_process(struct proc *p, struct pmc *pm, int flags)
  {
          int ri;
          struct pmc_process *pp;
  
          sx_assert(&pmc_sx, SX_XLOCKED);
  
          KASSERT(pm != NULL,
              ("[pmc,%d] null pm pointer", __LINE__));
  
          ri = PMC_TO_ROWINDEX(pm);
  
          PMCDBG6(PRC,ATT,2, "detach-one pm=%p ri=%d proc=%p (%d, %s) flags=0x%x",
              pm, ri, p, p->p_pid, p->p_comm, flags);
  
          if ((pp = pmc_find_process_descriptor(p, 0)) == NULL)
                  return ESRCH;
  
          if (pp->pp_pmcs[ri].pp_pmc != pm)
                  return EINVAL;
  
          pmc_unlink_target_process(pm, pp);
  
          /* Issue a detach entry if a log file is configured */
          if (pm->pm_owner->po_flags & PMC_PO_OWNS_LOGFILE)
                  pmclog_process_pmcdetach(pm, p->p_pid);
  
          /*
           * If there are no PMCs targeting this process, we remove its
           * descriptor from the target hash table and unset the P_HWPMC
           * flag in the struct proc.
           */
          KASSERT(pp->pp_refcnt >= 0 && pp->pp_refcnt <= (int) md->pmd_npmc,
              ("[pmc,%d] Illegal refcnt %d for process struct %p",
                  __LINE__, pp->pp_refcnt, pp));
  
          if (pp->pp_refcnt != 0) /* still a target of some PMC */
                  return 0;
  
          pmc_remove_process_descriptor(pp);
  
          if (flags & PMC_FLAG_REMOVE)
                  pmc_destroy_process_descriptor(pp);
  
          PROC_LOCK(p);
          p->p_flag &= ~P_HWPMC;
          PROC_UNLOCK(p);
  
          return 0;
  }
  
  /*
   * Detach a process and optionally its descendants from a PMC.
   */
  
  static int
  pmc_detach_process(struct proc *p, struct pmc *pm)
  {
          struct proc *top;
  
          sx_assert(&pmc_sx, SX_XLOCKED);
  
          PMCDBG5(PRC,ATT,1, "detach pm=%p ri=%d proc=%p (%d, %s)", pm,
              PMC_TO_ROWINDEX(pm), p, p->p_pid, p->p_comm);
  
          if ((pm->pm_flags & PMC_F_DESCENDANTS) == 0)
                  return pmc_detach_one_process(p, pm, PMC_FLAG_REMOVE);
  
          /*
           * Traverse all children, detaching them from this PMC.  We
           * ignore errors since we could be detaching a PMC from a
           * partially attached proc tree.
           */
  
          sx_slock(&proctree_lock);
  
          top = p;
  
          for (;;) {
                  (void) pmc_detach_one_process(p, pm, PMC_FLAG_REMOVE);
  
                  if (!LIST_EMPTY(&p->p_children))
                          p = LIST_FIRST(&p->p_children);
                  else for (;;) {
                          if (p == top)
                                  goto done;
                          if (LIST_NEXT(p, p_sibling)) {
                                  p = LIST_NEXT(p, p_sibling);
                                  break;
                          }
                          p = p->p_pptr;
                  }
          }
  
   done:
          sx_sunlock(&proctree_lock);
  
          if (LIST_EMPTY(&pm->pm_targets))
                  pm->pm_flags &= ~PMC_F_ATTACH_DONE;
  
          return 0;
  }
  
  
  /*
   * Thread context switch IN
   */
  
  static void
  pmc_process_csw_in(struct thread *td)
  {
          int cpu;
          unsigned int adjri, ri;
          struct pmc *pm;
          struct proc *p;
          struct pmc_cpu *pc;
          struct pmc_hw *phw __diagused;
          pmc_value_t newvalue;
          struct pmc_process *pp;
          struct pmc_thread *pt;
          struct pmc_classdep *pcd;
  
          p = td->td_proc;
          pt = NULL;
          if ((pp = pmc_find_process_descriptor(p, PMC_FLAG_NONE)) == NULL)
                  return;
  
          KASSERT(pp->pp_proc == td->td_proc,
              ("[pmc,%d] not my thread state", __LINE__));
  
          critical_enter(); /* no preemption from this point */
  
          cpu = PCPU_GET(cpuid); /* td->td_oncpu is invalid */
  
          PMCDBG5(CSW,SWI,1, "cpu=%d proc=%p (%d, %s) pp=%p", cpu, p,
              p->p_pid, p->p_comm, pp);
  
          KASSERT(cpu >= 0 && cpu < pmc_cpu_max(),
              ("[pmc,%d] weird CPU id %d", __LINE__, cpu));
  
          pc = pmc_pcpu[cpu];
  
          for (ri = 0; ri < md->pmd_npmc; ri++) {
  
                  if ((pm = pp->pp_pmcs[ri].pp_pmc) == NULL)
                          continue;
  
                  KASSERT(PMC_IS_VIRTUAL_MODE(PMC_TO_MODE(pm)),
                      ("[pmc,%d] Target PMC in non-virtual mode (%d)",
                          __LINE__, PMC_TO_MODE(pm)));
  
                  KASSERT(PMC_TO_ROWINDEX(pm) == ri,
                      ("[pmc,%d] Row index mismatch pmc %d != ri %d",
                          __LINE__, PMC_TO_ROWINDEX(pm), ri));
  
                  /*
                   * Only PMCs that are marked as 'RUNNING' need
                   * be placed on hardware.
                   */
  
                  if (pm->pm_state != PMC_STATE_RUNNING)
                          continue;
  
                  KASSERT(counter_u64_fetch(pm->pm_runcount) >= 0,
              ("[pmc,%d] pm=%p runcount %ld", __LINE__, (void *) pm,
                   (unsigned long)counter_u64_fetch(pm->pm_runcount)));
  
                  /* increment PMC runcount */
                  counter_u64_add(pm->pm_runcount, 1);
  
                  /* configure the HWPMC we are going to use. */
                  pcd = pmc_ri_to_classdep(md, ri, &adjri);
                  pcd->pcd_config_pmc(cpu, adjri, pm);
  
                  phw = pc->pc_hwpmcs[ri];
  
                  KASSERT(phw != NULL,
                      ("[pmc,%d] null hw pointer", __LINE__));
  
                  KASSERT(phw->phw_pmc == pm,
                      ("[pmc,%d] hw->pmc %p != pmc %p", __LINE__,
                          phw->phw_pmc, pm));
  
                  /*
                   * Write out saved value and start the PMC.
                   *
                   * Sampling PMCs use a per-thread value, while
                   * counting mode PMCs use a per-pmc value that is
                   * inherited across descendants.
                   */
                  if (PMC_TO_MODE(pm) == PMC_MODE_TS) {
                          if (pt == NULL)
                                  pt = pmc_find_thread_descriptor(pp, td,
                                      PMC_FLAG_NONE);
  
                          KASSERT(pt != NULL,
                              ("[pmc,%d] No thread found for td=%p", __LINE__,
                              td));
  
                          mtx_pool_lock_spin(pmc_mtxpool, pm);
  
                          /*
                           * If we have a thread descriptor, use the per-thread
                           * counter in the descriptor. If not, we will use
                           * a per-process counter. 
                           *
                           * TODO: Remove the per-process "safety net" once
                           * we have thoroughly tested that we don't hit the
                           * above assert.
                           */
                          if (pt != NULL) {
                                  if (pt->pt_pmcs[ri].pt_pmcval > 0)
                                          newvalue = pt->pt_pmcs[ri].pt_pmcval;
                                  else
                                          newvalue = pm->pm_sc.pm_reloadcount;
                          } else {
                                  /*
                                   * Use the saved value calculated after the most
                                   * recent time a thread using the shared counter
                                   * switched out. Reset the saved count in case
                                   * another thread from this process switches in
                                   * before any threads switch out.
                                   */
  
                                  newvalue = pp->pp_pmcs[ri].pp_pmcval;
                                  pp->pp_pmcs[ri].pp_pmcval =
                                      pm->pm_sc.pm_reloadcount;
                          }
                          mtx_pool_unlock_spin(pmc_mtxpool, pm);
                          KASSERT(newvalue > 0 && newvalue <=
                              pm->pm_sc.pm_reloadcount,
                              ("[pmc,%d] pmcval outside of expected range cpu=%d "
                              "ri=%d pmcval=%jx pm_reloadcount=%jx", __LINE__,
                              cpu, ri, newvalue, pm->pm_sc.pm_reloadcount));
                  } else {
                          KASSERT(PMC_TO_MODE(pm) == PMC_MODE_TC,
                              ("[pmc,%d] illegal mode=%d", __LINE__,
                              PMC_TO_MODE(pm)));
                          mtx_pool_lock_spin(pmc_mtxpool, pm);
                          newvalue = PMC_PCPU_SAVED(cpu, ri) =
                              pm->pm_gv.pm_savedvalue;
                          mtx_pool_unlock_spin(pmc_mtxpool, pm);
                  }
  
                  PMCDBG3(CSW,SWI,1,"cpu=%d ri=%d new=%jd", cpu, ri, newvalue);
  
                  pcd->pcd_write_pmc(cpu, adjri, newvalue);
  
                  /* If a sampling mode PMC, reset stalled state. */
                  if (PMC_TO_MODE(pm) == PMC_MODE_TS)
                          pm->pm_pcpu_state[cpu].pps_stalled = 0;
  
                  /* Indicate that we desire this to run. */
                  pm->pm_pcpu_state[cpu].pps_cpustate = 1;
  
                  /* Start the PMC. */
                  pcd->pcd_start_pmc(cpu, adjri);
          }
  
          /*
           * perform any other architecture/cpu dependent thread
           * switch-in actions.
           */
  
          (void) (*md->pmd_switch_in)(pc, pp);
  
          critical_exit();
  
  }
  
  /*
   * Thread context switch OUT.
   */
  
  static void
  pmc_process_csw_out(struct thread *td)
  {
          int cpu;
          int64_t tmp;
          struct pmc *pm;
          struct proc *p;
          enum pmc_mode mode;
          struct pmc_cpu *pc;
          pmc_value_t newvalue;
          unsigned int adjri, ri;
          struct pmc_process *pp;
          struct pmc_thread *pt = NULL;
          struct pmc_classdep *pcd;
  
  
          /*
           * Locate our process descriptor; this may be NULL if
           * this process is exiting and we have already removed
           * the process from the target process table.
           *
           * Note that due to kernel preemption, multiple
           * context switches may happen while the process is
           * exiting.
           *
           * Note also that if the target process cannot be
           * found we still need to deconfigure any PMCs that
           * are currently running on hardware.
           */
  
          p = td->td_proc;
          pp = pmc_find_process_descriptor(p, PMC_FLAG_NONE);
  
          /*
           * save PMCs
           */
  
          critical_enter();
  
          cpu = PCPU_GET(cpuid); /* td->td_oncpu is invalid */
  
          PMCDBG5(CSW,SWO,1, "cpu=%d proc=%p (%d, %s) pp=%p", cpu, p,
              p->p_pid, p->p_comm, pp);
  
          KASSERT(cpu >= 0 && cpu < pmc_cpu_max(),
              ("[pmc,%d weird CPU id %d", __LINE__, cpu));
  
          pc = pmc_pcpu[cpu];
  
          /*
           * When a PMC gets unlinked from a target PMC, it will
           * be removed from the target's pp_pmc[] array.
           *
           * However, on a MP system, the target could have been
           * executing on another CPU at the time of the unlink.
           * So, at context switch OUT time, we need to look at
           * the hardware to determine if a PMC is scheduled on
           * it.
           */
  
          for (ri = 0; ri < md->pmd_npmc; ri++) {
  
                  pcd = pmc_ri_to_classdep(md, ri, &adjri);
                  pm  = NULL;
                  (void) (*pcd->pcd_get_config)(cpu, adjri, &pm);
  
                  if (pm == NULL) /* nothing at this row index */
                          continue;
  
                  mode = PMC_TO_MODE(pm);
                  if (!PMC_IS_VIRTUAL_MODE(mode))
                          continue; /* not a process virtual PMC */
  
                  KASSERT(PMC_TO_ROWINDEX(pm) == ri,
                      ("[pmc,%d] ri mismatch pmc(%d) ri(%d)",
                          __LINE__, PMC_TO_ROWINDEX(pm), ri));
  
                  /*
                   * Change desired state, and then stop if not stalled.
                   * This two-step dance should avoid race conditions where
                   * an interrupt re-enables the PMC after this code has
                   * already checked the pm_stalled flag.
                   */
                  pm->pm_pcpu_state[cpu].pps_cpustate = 0;
                  if (pm->pm_pcpu_state[cpu].pps_stalled == 0)
                          pcd->pcd_stop_pmc(cpu, adjri);
  
                  KASSERT(counter_u64_fetch(pm->pm_runcount) > 0,
                          ("[pmc,%d] pm=%p runcount %ld", __LINE__, (void *) pm,
                           (unsigned long)counter_u64_fetch(pm->pm_runcount)));
  
                  /* reduce this PMC's runcount */
                  counter_u64_add(pm->pm_runcount, -1);
  
                  /*
                   * If this PMC is associated with this process,
                   * save the reading.
                   */
  
                  if (pm->pm_state != PMC_STATE_DELETED && pp != NULL &&
                      pp->pp_pmcs[ri].pp_pmc != NULL) {
                          KASSERT(pm == pp->pp_pmcs[ri].pp_pmc,
                              ("[pmc,%d] pm %p != pp_pmcs[%d] %p", __LINE__,
                                  pm, ri, pp->pp_pmcs[ri].pp_pmc));
  
                          KASSERT(pp->pp_refcnt > 0,
                              ("[pmc,%d] pp refcnt = %d", __LINE__,
                                  pp->pp_refcnt));
  
                          pcd->pcd_read_pmc(cpu, adjri, &newvalue);
  
                          if (mode == PMC_MODE_TS) {
                                  PMCDBG3(CSW,SWO,1,"cpu=%d ri=%d val=%jd (samp)",
                                      cpu, ri, newvalue);
  
                                  if (pt == NULL)
                                          pt = pmc_find_thread_descriptor(pp, td,
                                              PMC_FLAG_NONE);
  
                                  KASSERT(pt != NULL,
                                      ("[pmc,%d] No thread found for td=%p",
                                      __LINE__, td));
  
                                  mtx_pool_lock_spin(pmc_mtxpool, pm);
  
                                  /*
                                   * If we have a thread descriptor, save the
                                   * per-thread counter in the descriptor. If not,
                                   * we will update the per-process counter.
                                   *
                                   * TODO: Remove the per-process "safety net"
                                   * once we have thoroughly tested that we
                                   * don't hit the above assert.
                                   */
                                  if (pt != NULL)
                                          pt->pt_pmcs[ri].pt_pmcval = newvalue;
                                  else {
                                          /*
                                           * For sampling process-virtual PMCs,
                                           * newvalue is the number of events to
                                           * be seen until the next sampling
                                           * interrupt. We can just add the events
                                           * left from this invocation to the
                                           * counter, then adjust in case we
                                           * overflow our range.
                                           *
                                           * (Recall that we reload the counter
                                           * every time we use it.)
                                           */
                                          pp->pp_pmcs[ri].pp_pmcval += newvalue;
                                          if (pp->pp_pmcs[ri].pp_pmcval >
                                              pm->pm_sc.pm_reloadcount)
                                                  pp->pp_pmcs[ri].pp_pmcval -=
                                                      pm->pm_sc.pm_reloadcount;
                                  }
                                  mtx_pool_unlock_spin(pmc_mtxpool, pm);
                          } else {
                                  tmp = newvalue - PMC_PCPU_SAVED(cpu,ri);
  
                                  PMCDBG3(CSW,SWO,1,"cpu=%d ri=%d tmp=%jd (count)",
                                      cpu, ri, tmp);
  
                                  /*
                                   * For counting process-virtual PMCs,
                                   * we expect the count to be
                                   * increasing monotonically, modulo a 64
                                   * bit wraparound.
                                   */
                                  KASSERT(tmp >= 0,
                                      ("[pmc,%d] negative increment cpu=%d "
                                       "ri=%d newvalue=%jx saved=%jx "
                                       "incr=%jx", __LINE__, cpu, ri,
                                       newvalue, PMC_PCPU_SAVED(cpu,ri), tmp));
  
                                  mtx_pool_lock_spin(pmc_mtxpool, pm);
                                  pm->pm_gv.pm_savedvalue += tmp;
                                  pp->pp_pmcs[ri].pp_pmcval += tmp;
                                  mtx_pool_unlock_spin(pmc_mtxpool, pm);
  
                                  if (pm->pm_flags & PMC_F_LOG_PROCCSW)
                                          pmclog_process_proccsw(pm, pp, tmp, td);
                          }
                  }
  
                  /* mark hardware as free */
                  pcd->pcd_config_pmc(cpu, adjri, NULL);
          }
  
          /*
           * perform any other architecture/cpu dependent thread
           * switch out functions.
           */
  
          (void) (*md->pmd_switch_out)(pc, pp);
  
          critical_exit();
  }
  
  /*
   * A new thread for a process.
   */
  static void
  pmc_process_thread_add(struct thread *td)
  {
          struct pmc_process *pmc;
  
          pmc = pmc_find_process_descriptor(td->td_proc, PMC_FLAG_NONE);
          if (pmc != NULL)
                  pmc_find_thread_descriptor(pmc, td, PMC_FLAG_ALLOCATE);
  }
  
  /*
   * A thread delete for a process.
   */
  static void
  pmc_process_thread_delete(struct thread *td)
  {
          struct pmc_process *pmc;
  
          pmc = pmc_find_process_descriptor(td->td_proc, PMC_FLAG_NONE);
          if (pmc != NULL)
                  pmc_thread_descriptor_pool_free(pmc_find_thread_descriptor(pmc,
                      td, PMC_FLAG_REMOVE));
  }
  
  /*
   * A userret() call for a thread.
   */
  static void
  pmc_process_thread_userret(struct thread *td)
  {
          sched_pin();
          pmc_capture_user_callchain(curcpu, PMC_UR, td->td_frame);
          sched_unpin();
  }
  
  /*
   * A mapping change for a process.
   */
  
  static void
  pmc_process_mmap(struct thread *td, struct pmckern_map_in *pkm)
  {
          int ri;
          pid_t pid;
          char *fullpath, *freepath;
          const struct pmc *pm;
          struct pmc_owner *po;
          const struct pmc_process *pp;
  
          freepath = fullpath = NULL;
          MPASS(!in_epoch(global_epoch_preempt));
          pmc_getfilename((struct vnode *) pkm->pm_file, &fullpath, &freepath);
  
          pid = td->td_proc->p_pid;
  
          PMC_EPOCH_ENTER();
          /* Inform owners of all system-wide sampling PMCs. */
          CK_LIST_FOREACH(po, &pmc_ss_owners, po_ssnext)
              if (po->po_flags & PMC_PO_OWNS_LOGFILE)
                          pmclog_process_map_in(po, pid, pkm->pm_address, fullpath);
  
          if ((pp = pmc_find_process_descriptor(td->td_proc, 0)) == NULL)
                  goto done;
  
          /*
           * Inform sampling PMC owners tracking this process.
           */
          for (ri = 0; ri < md->pmd_npmc; ri++)
                  if ((pm = pp->pp_pmcs[ri].pp_pmc) != NULL &&
                      PMC_IS_SAMPLING_MODE(PMC_TO_MODE(pm)))
                          pmclog_process_map_in(pm->pm_owner,
                              pid, pkm->pm_address, fullpath);
  
    done:
          if (freepath)
                  free(freepath, M_TEMP);
          PMC_EPOCH_EXIT();
  }
  
  
  /*
   * Log an munmap request.
   */
  
  static void
  pmc_process_munmap(struct thread *td, struct pmckern_map_out *pkm)
  {
          int ri;
          pid_t pid;
          struct pmc_owner *po;
          const struct pmc *pm;
          const struct pmc_process *pp;
  
          pid = td->td_proc->p_pid;
  
          PMC_EPOCH_ENTER();
          CK_LIST_FOREACH(po, &pmc_ss_owners, po_ssnext)
              if (po->po_flags & PMC_PO_OWNS_LOGFILE)
                  pmclog_process_map_out(po, pid, pkm->pm_address,
                      pkm->pm_address + pkm->pm_size);
          PMC_EPOCH_EXIT();
  
          if ((pp = pmc_find_process_descriptor(td->td_proc, 0)) == NULL)
                  return;
  
          for (ri = 0; ri < md->pmd_npmc; ri++)
                  if ((pm = pp->pp_pmcs[ri].pp_pmc) != NULL &&
                      PMC_IS_SAMPLING_MODE(PMC_TO_MODE(pm)))
                          pmclog_process_map_out(pm->pm_owner, pid,
                              pkm->pm_address, pkm->pm_address + pkm->pm_size);
  }
  
  /*
   * Log mapping information about the kernel.
   */
  
  static void
  pmc_log_kernel_mappings(struct pmc *pm)
  {
          struct pmc_owner *po;
          struct pmckern_map_in *km, *kmbase;
  
          MPASS(in_epoch(global_epoch_preempt) || sx_xlocked(&pmc_sx));
          KASSERT(PMC_IS_SAMPLING_MODE(PMC_TO_MODE(pm)),
              ("[pmc,%d] non-sampling PMC (%p) desires mapping information",
                  __LINE__, (void *) pm));
  
          po = pm->pm_owner;
  
          if (po->po_flags & PMC_PO_INITIAL_MAPPINGS_DONE)
                  return;
          if (PMC_TO_MODE(pm) == PMC_MODE_SS)
                  pmc_process_allproc(pm);
          /*
           * Log the current set of kernel modules.
           */
          kmbase = linker_hwpmc_list_objects();
          for (km = kmbase; km->pm_file != NULL; km++) {
                  PMCDBG2(LOG,REG,1,"%s %p", (char *) km->pm_file,
                      (void *) km->pm_address);
                  pmclog_process_map_in(po, (pid_t) -1, km->pm_address,
                      km->pm_file);
          }
          free(kmbase, M_LINKER);
  
          po->po_flags |= PMC_PO_INITIAL_MAPPINGS_DONE;
  }
  
  /*
   * Log the mappings for a single process.
   */
  
  static void
  pmc_log_process_mappings(struct pmc_owner *po, struct proc *p)
  {
          vm_map_t map;
          struct vnode *vp;
          struct vmspace *vm;
          vm_map_entry_t entry;
          vm_offset_t last_end;
          u_int last_timestamp;
          struct vnode *last_vp;
          vm_offset_t start_addr;
          vm_object_t obj, lobj, tobj;
          char *fullpath, *freepath;
  
          last_vp = NULL;
          last_end = (vm_offset_t) 0;
          fullpath = freepath = NULL;
  
          if ((vm = vmspace_acquire_ref(p)) == NULL)
                  return;
  
          map = &vm->vm_map;
          vm_map_lock_read(map);
  
          VM_MAP_ENTRY_FOREACH(entry, map) {
  
                  if (entry == NULL) {
                          PMCDBG2(LOG,OPS,2, "hwpmc: vm_map entry unexpectedly "
                              "NULL! pid=%d vm_map=%p\n", p->p_pid, map);
                          break;
                  }
  
                  /*
                   * We only care about executable map entries.
                   */
                  if ((entry->eflags & MAP_ENTRY_IS_SUB_MAP) ||
                      !(entry->protection & VM_PROT_EXECUTE) ||
                      (entry->object.vm_object == NULL)) {
                          continue;
                  }
  
                  obj = entry->object.vm_object;
                  VM_OBJECT_RLOCK(obj);
  
                  /* 
                   * Walk the backing_object list to find the base
                   * (non-shadowed) vm_object.
                   */
                  for (lobj = tobj = obj; tobj != NULL; tobj = tobj->backing_object) {
                          if (tobj != obj)
                                  VM_OBJECT_RLOCK(tobj);
                          if (lobj != obj)
                                  VM_OBJECT_RUNLOCK(lobj);
                          lobj = tobj;
                  }
  
                  /*
                   * At this point lobj is the base vm_object and it is locked.
                   */
                  if (lobj == NULL) {
                          PMCDBG3(LOG,OPS,2, "hwpmc: lobj unexpectedly NULL! pid=%d "
                              "vm_map=%p vm_obj=%p\n", p->p_pid, map, obj);
                          VM_OBJECT_RUNLOCK(obj);
                          continue;
                  }
  
                  vp = vm_object_vnode(lobj);
                  if (vp == NULL) {
                          if (lobj != obj)
                                  VM_OBJECT_RUNLOCK(lobj);
                          VM_OBJECT_RUNLOCK(obj);
                          continue;
                  }
  
                  /*
                   * Skip contiguous regions that point to the same
                   * vnode, so we don't emit redundant MAP-IN
                   * directives.
                   */
                  if (entry->start == last_end && vp == last_vp) {
                          last_end = entry->end;
                          if (lobj != obj)
                                  VM_OBJECT_RUNLOCK(lobj);
                          VM_OBJECT_RUNLOCK(obj);
                          continue;
                  }
  
                  /* 
                   * We don't want to keep the proc's vm_map or this
                   * vm_object locked while we walk the pathname, since
                   * vn_fullpath() can sleep.  However, if we drop the
                   * lock, it's possible for concurrent activity to
                   * modify the vm_map list.  To protect against this,
                   * we save the vm_map timestamp before we release the
                   * lock, and check it after we reacquire the lock
                   * below.
                   */
                  start_addr = entry->start;
                  last_end = entry->end;
                  last_timestamp = map->timestamp;
                  vm_map_unlock_read(map);
  
                  vref(vp);
                  if (lobj != obj)
                          VM_OBJECT_RUNLOCK(lobj);
  
                  VM_OBJECT_RUNLOCK(obj);
  
                  freepath = NULL;
                  pmc_getfilename(vp, &fullpath, &freepath);
                  last_vp = vp;
  
                  vrele(vp);
  
                  vp = NULL;
                  pmclog_process_map_in(po, p->p_pid, start_addr, fullpath);
                  if (freepath)
                          free(freepath, M_TEMP);
  
                  vm_map_lock_read(map);
  
                  /*
                   * If our saved timestamp doesn't match, this means
                   * that the vm_map was modified out from under us and
                   * we can't trust our current "entry" pointer.  Do a
                   * new lookup for this entry.  If there is no entry
                   * for this address range, vm_map_lookup_entry() will
                   * return the previous one, so we always want to go to
                   * the next entry on the next loop iteration.
                   * 
                   * There is an edge condition here that can occur if
                   * there is no entry at or before this address.  In
                   * this situation, vm_map_lookup_entry returns
                   * &map->header, which would cause our loop to abort
                   * without processing the rest of the map.  However,
                   * in practice this will never happen for process
                   * vm_map.  This is because the executable's text
                   * segment is the first mapping in the proc's address
                   * space, and this mapping is never removed until the
                   * process exits, so there will always be a non-header
                   * entry at or before the requested address for
                   * vm_map_lookup_entry to return.
                   */
                  if (map->timestamp != last_timestamp)
                          vm_map_lookup_entry(map, last_end - 1, &entry);
          }
  
          vm_map_unlock_read(map);
          vmspace_free(vm);
          return;
  }
  
  /*
   * Log mappings for all processes in the system.
   */
  
  static void
  pmc_log_all_process_mappings(struct pmc_owner *po)
  {
          struct proc *p, *top;
  
          sx_assert(&pmc_sx, SX_XLOCKED);
  
          if ((p = pfind(1)) == NULL)
                  panic("[pmc,%d] Cannot find init", __LINE__);
  
          PROC_UNLOCK(p);
  
          sx_slock(&proctree_lock);
  
          top = p;
  
          for (;;) {
                  pmc_log_process_mappings(po, p);
                  if (!LIST_EMPTY(&p->p_children))
                          p = LIST_FIRST(&p->p_children);
                  else for (;;) {
                          if (p == top)
                                  goto done;
                          if (LIST_NEXT(p, p_sibling)) {
                                  p = LIST_NEXT(p, p_sibling);
                                  break;
                          }
                          p = p->p_pptr;
                  }
          }
   done:
          sx_sunlock(&proctree_lock);
  }
  
  /*
   * The 'hook' invoked from the kernel proper
   */
  
  
  #ifdef  HWPMC_DEBUG
  const char *pmc_hooknames[] = {
          /* these strings correspond to PMC_FN_* in <sys/pmckern.h> */
          "",
          "EXEC",
          "CSW-IN",
          "CSW-OUT",
          "SAMPLE",
          "UNUSED1",
          "UNUSED2",
          "MMAP",
          "MUNMAP",
          "CALLCHAIN-NMI",
          "CALLCHAIN-SOFT",
          "SOFTSAMPLING",
          "THR-CREATE",
          "THR-EXIT",
          "THR-USERRET",
          "THR-CREATE-LOG",
          "THR-EXIT-LOG",
          "PROC-CREATE-LOG"
  };
  #endif
  
  static int
  pmc_hook_handler(struct thread *td, int function, void *arg)
  {
          int cpu;
  
          PMCDBG4(MOD,PMH,1, "hook td=%p func=%d \"%s\" arg=%p", td, function,
              pmc_hooknames[function], arg);
  
          switch (function)
          {
  
          /*
           * Process exec()
           */
  
          case PMC_FN_PROCESS_EXEC:
          {
                  char *fullpath, *freepath;
                  unsigned int ri;
                  int is_using_hwpmcs;
                  struct pmc *pm;
                  struct proc *p;
                  struct pmc_owner *po;
                  struct pmc_process *pp;
                  struct pmckern_procexec *pk;
  
                  sx_assert(&pmc_sx, SX_XLOCKED);
  
                  p = td->td_proc;
                  pmc_getfilename(p->p_textvp, &fullpath, &freepath);
  
                  pk = (struct pmckern_procexec *) arg;
  
                  PMC_EPOCH_ENTER();
                  /* Inform owners of SS mode PMCs of the exec event. */
                  CK_LIST_FOREACH(po, &pmc_ss_owners, po_ssnext)
                      if (po->po_flags & PMC_PO_OWNS_LOGFILE)
                              pmclog_process_procexec(po, PMC_ID_INVALID,
                                  p->p_pid, pk->pm_entryaddr, fullpath);
                  PMC_EPOCH_EXIT();
  
                  PROC_LOCK(p);
                  is_using_hwpmcs = p->p_flag & P_HWPMC;
                  PROC_UNLOCK(p);
  
                  if (!is_using_hwpmcs) {
                          if (freepath)
                                  free(freepath, M_TEMP);
                          break;
                  }
  
                  /*
                   * PMCs are not inherited across an exec():  remove any
                   * PMCs that this process is the owner of.
                   */
  
                  if ((po = pmc_find_owner_descriptor(p)) != NULL) {
                          pmc_remove_owner(po);
                          pmc_destroy_owner_descriptor(po);
                  }
  
                  /*
                   * If the process being exec'ed is not the target of any
                   * PMC, we are done.
                   */
                  if ((pp = pmc_find_process_descriptor(p, 0)) == NULL) {
                          if (freepath)
                                  free(freepath, M_TEMP);
                          break;
                  }
  
                  /*
                   * Log the exec event to all monitoring owners.  Skip
                   * owners who have already received the event because
                   * they had system sampling PMCs active.
                   */
                  for (ri = 0; ri < md->pmd_npmc; ri++)
                          if ((pm = pp->pp_pmcs[ri].pp_pmc) != NULL) {
                                  po = pm->pm_owner;
                                  if (po->po_sscount == 0 &&
                                      po->po_flags & PMC_PO_OWNS_LOGFILE)
                                          pmclog_process_procexec(po, pm->pm_id,
                                              p->p_pid, pk->pm_entryaddr,
                                              fullpath);
                          }
  
                  if (freepath)
                          free(freepath, M_TEMP);
  
  
                  PMCDBG4(PRC,EXC,1, "exec proc=%p (%d, %s) cred-changed=%d",
                      p, p->p_pid, p->p_comm, pk->pm_credentialschanged);
  
                  if (pk->pm_credentialschanged == 0) /* no change */
                          break;
  
                  /*
                   * If the newly exec()'ed process has a different credential
                   * than before, allow it to be the target of a PMC only if
                   * the PMC's owner has sufficient privilege.
                   */
  
                  for (ri = 0; ri < md->pmd_npmc; ri++)
                          if ((pm = pp->pp_pmcs[ri].pp_pmc) != NULL)
                                  if (pmc_can_attach(pm, td->td_proc) != 0)
                                          pmc_detach_one_process(td->td_proc,
                                              pm, PMC_FLAG_NONE);
  
                  KASSERT(pp->pp_refcnt >= 0 && pp->pp_refcnt <= (int) md->pmd_npmc,
                      ("[pmc,%d] Illegal ref count %d on pp %p", __LINE__,
                          pp->pp_refcnt, pp));
  
                  /*
                   * If this process is no longer the target of any
                   * PMCs, we can remove the process entry and free
                   * up space.
                   */
  
                  if (pp->pp_refcnt == 0) {
                          pmc_remove_process_descriptor(pp);
                          pmc_destroy_process_descriptor(pp);
                          break;
                  }
  
          }
          break;
  
          case PMC_FN_CSW_IN:
                  pmc_process_csw_in(td);
                  break;
  
          case PMC_FN_CSW_OUT:
                  pmc_process_csw_out(td);
                  break;
  
          /*
           * Process accumulated PC samples.
           *
           * This function is expected to be called by hardclock() for
           * each CPU that has accumulated PC samples.
           *
           * This function is to be executed on the CPU whose samples
           * are being processed.
           */
          case PMC_FN_DO_SAMPLES:
  
                  /*
                   * Clear the cpu specific bit in the CPU mask before
                   * do the rest of the processing.  If the NMI handler
                   * gets invoked after the "atomic_clear_int()" call
                   * below but before "pmc_process_samples()" gets
                   * around to processing the interrupt, then we will
                   * come back here at the next hardclock() tick (and
                   * may find nothing to do if "pmc_process_samples()"
                   * had already processed the interrupt).  We don't
                   * lose the interrupt sample.
                   */
                  DPCPU_SET(pmc_sampled, 0);
                  cpu = PCPU_GET(cpuid);
                  pmc_process_samples(cpu, PMC_HR);
                  pmc_process_samples(cpu, PMC_SR);
                  pmc_process_samples(cpu, PMC_UR);
                  break;
  
          case PMC_FN_MMAP:
                  pmc_process_mmap(td, (struct pmckern_map_in *) arg);
                  break;
  
          case PMC_FN_MUNMAP:
                  MPASS(in_epoch(global_epoch_preempt) || sx_xlocked(&pmc_sx));
                  pmc_process_munmap(td, (struct pmckern_map_out *) arg);
                  break;
  
          case PMC_FN_PROC_CREATE_LOG:
                  pmc_process_proccreate((struct proc *)arg);
                  break;
  
          case PMC_FN_USER_CALLCHAIN:
                  /*
                   * Record a call chain.
                   */
                  KASSERT(td == curthread, ("[pmc,%d] td != curthread",
                      __LINE__));
  
                  pmc_capture_user_callchain(PCPU_GET(cpuid), PMC_HR,
                      (struct trapframe *) arg);
  
                  KASSERT(td->td_pinned == 1,
                          ("[pmc,%d] invalid td_pinned value", __LINE__));
                  sched_unpin();  /* Can migrate safely now. */
  
                  td->td_pflags &= ~TDP_CALLCHAIN;
                  break;
  
          case PMC_FN_USER_CALLCHAIN_SOFT:
                  /*
                   * Record a call chain.
                   */
                  KASSERT(td == curthread, ("[pmc,%d] td != curthread",
                      __LINE__));
  
                  cpu = PCPU_GET(cpuid);
                  pmc_capture_user_callchain(cpu, PMC_SR,
                      (struct trapframe *) arg);
  
                  KASSERT(td->td_pinned == 1,
                      ("[pmc,%d] invalid td_pinned value", __LINE__));
  
                  sched_unpin();  /* Can migrate safely now. */
  
                  td->td_pflags &= ~TDP_CALLCHAIN;
                  break;
  
          case PMC_FN_SOFT_SAMPLING:
                  /*
                   * Call soft PMC sampling intr.
                   */
                  pmc_soft_intr((struct pmckern_soft *) arg);
                  break;
  
          case PMC_FN_THR_CREATE:
                  pmc_process_thread_add(td);
                  pmc_process_threadcreate(td);
                  break;
  
          case PMC_FN_THR_CREATE_LOG:
                  pmc_process_threadcreate(td);
                  break;
  
          case PMC_FN_THR_EXIT:
                  KASSERT(td == curthread, ("[pmc,%d] td != curthread",
                      __LINE__));
                  pmc_process_thread_delete(td);
                  pmc_process_threadexit(td);
                  break;
          case PMC_FN_THR_EXIT_LOG:
                  pmc_process_threadexit(td);
                  break;
          case PMC_FN_THR_USERRET:
                  KASSERT(td == curthread, ("[pmc,%d] td != curthread",
                      __LINE__));
                  pmc_process_thread_userret(td);
                  break;
  
          default:
  #ifdef  HWPMC_DEBUG
                  KASSERT(0, ("[pmc,%d] unknown hook %d\n", __LINE__, function));
  #endif
                  break;
  
          }
  
          return 0;
  }
  
  /*
   * allocate a 'struct pmc_owner' descriptor in the owner hash table.
   */
  
  static struct pmc_owner *
  pmc_allocate_owner_descriptor(struct proc *p)
  {
          uint32_t hindex;
          struct pmc_owner *po;
          struct pmc_ownerhash *poh;
  
          hindex = PMC_HASH_PTR(p, pmc_ownerhashmask);
          poh = &pmc_ownerhash[hindex];
  
          /* allocate space for N pointers and one descriptor struct */
          po = malloc(sizeof(struct pmc_owner), M_PMC, M_WAITOK|M_ZERO);
          po->po_owner = p;
          LIST_INSERT_HEAD(poh, po, po_next); /* insert into hash table */
  
          TAILQ_INIT(&po->po_logbuffers);
          mtx_init(&po->po_mtx, "pmc-owner-mtx", "pmc-per-proc", MTX_SPIN);
  
          PMCDBG4(OWN,ALL,1, "allocate-owner proc=%p (%d, %s) pmc-owner=%p",
              p, p->p_pid, p->p_comm, po);
  
          return po;
  }
  
  static void
  pmc_destroy_owner_descriptor(struct pmc_owner *po)
  {
  
          PMCDBG4(OWN,REL,1, "destroy-owner po=%p proc=%p (%d, %s)",
              po, po->po_owner, po->po_owner->p_pid, po->po_owner->p_comm);
  
          mtx_destroy(&po->po_mtx);
          free(po, M_PMC);
  }
  
  /*
   * Allocate a thread descriptor from the free pool.
   *
   * NOTE: This *can* return NULL.
   */
  static struct pmc_thread *
  pmc_thread_descriptor_pool_alloc(void)
  {
          struct pmc_thread *pt;
  
          mtx_lock_spin(&pmc_threadfreelist_mtx);
          if ((pt = LIST_FIRST(&pmc_threadfreelist)) != NULL) {
                  LIST_REMOVE(pt, pt_next);
                  pmc_threadfreelist_entries--;
          }
          mtx_unlock_spin(&pmc_threadfreelist_mtx);
  
          return (pt);
  }
  
  /*
   * Add a thread descriptor to the free pool. We use this instead of free()
   * to maintain a cache of free entries. Additionally, we can safely call
   * this function when we cannot call free(), such as in a critical section.
   * 
   */
  static void
  pmc_thread_descriptor_pool_free(struct pmc_thread *pt)
  {
  
          if (pt == NULL)
                  return;
  
          memset(pt, 0, THREADENTRY_SIZE);
          mtx_lock_spin(&pmc_threadfreelist_mtx);
          LIST_INSERT_HEAD(&pmc_threadfreelist, pt, pt_next);
          pmc_threadfreelist_entries++;
          if (pmc_threadfreelist_entries > pmc_threadfreelist_max)
                  taskqueue_enqueue(taskqueue_fast, &free_task);
          mtx_unlock_spin(&pmc_threadfreelist_mtx);
  }
  
  /*
   * An asynchronous task to manage the free list.
   */
  static void
  pmc_thread_descriptor_pool_free_task(void *arg __unused, int pending __unused)
  {
          struct pmc_thread *pt;
          LIST_HEAD(, pmc_thread) tmplist;
          int delta;
  
          LIST_INIT(&tmplist);
  
          /* Determine what changes, if any, we need to make. */
          mtx_lock_spin(&pmc_threadfreelist_mtx);
          delta = pmc_threadfreelist_entries - pmc_threadfreelist_max;
          while (delta > 0 && (pt = LIST_FIRST(&pmc_threadfreelist)) != NULL) {
                  delta--;
                  pmc_threadfreelist_entries--;
                  LIST_REMOVE(pt, pt_next);
                  LIST_INSERT_HEAD(&tmplist, pt, pt_next);
          }
          mtx_unlock_spin(&pmc_threadfreelist_mtx);
  
          /* If there are entries to free, free them. */
          while (!LIST_EMPTY(&tmplist)) {
                  pt = LIST_FIRST(&tmplist);
                  LIST_REMOVE(pt, pt_next);
                  free(pt, M_PMC);
          }
  }
  
  /*
   * Drain the thread free pool, freeing all allocations.
   */
  static void
  pmc_thread_descriptor_pool_drain(void)
  {
          struct pmc_thread *pt, *next;
  
          LIST_FOREACH_SAFE(pt, &pmc_threadfreelist, pt_next, next) {
                  LIST_REMOVE(pt, pt_next);
                  free(pt, M_PMC);
          }
  }
  
  /*
   * find the descriptor corresponding to thread 'td', adding or removing it
   * as specified by 'mode'.
   *
   * Note that this supports additional mode flags in addition to those
   * supported by pmc_find_process_descriptor():
   * PMC_FLAG_NOWAIT: Causes the function to not wait for mallocs.
   *     This makes it safe to call while holding certain other locks.
   */
  
  static struct pmc_thread *
  pmc_find_thread_descriptor(struct pmc_process *pp, struct thread *td,
      uint32_t mode)
  {
          struct pmc_thread *pt = NULL, *ptnew = NULL;
          int wait_flag;
  
          KASSERT(td != NULL, ("[pmc,%d] called to add NULL td", __LINE__));
  
          /*
           * Pre-allocate memory in the PMC_FLAG_ALLOCATE case prior to
           * acquiring the lock.
           */
          if (mode & PMC_FLAG_ALLOCATE) {
                  if ((ptnew = pmc_thread_descriptor_pool_alloc()) == NULL) {
                          wait_flag = M_WAITOK;
                          if ((mode & PMC_FLAG_NOWAIT) || in_epoch(global_epoch_preempt))
                                  wait_flag = M_NOWAIT;
  
                          ptnew = malloc(THREADENTRY_SIZE, M_PMC,
                              wait_flag|M_ZERO);
                  }
          }
  
          mtx_lock_spin(pp->pp_tdslock);
  
          LIST_FOREACH(pt, &pp->pp_tds, pt_next)
                  if (pt->pt_td == td)
                          break;
  
          if ((mode & PMC_FLAG_REMOVE) && pt != NULL)
                  LIST_REMOVE(pt, pt_next);
  
          if ((mode & PMC_FLAG_ALLOCATE) && pt == NULL && ptnew != NULL) {
                  pt = ptnew;
                  ptnew = NULL;
                  pt->pt_td = td;
                  LIST_INSERT_HEAD(&pp->pp_tds, pt, pt_next);
          }
  
          mtx_unlock_spin(pp->pp_tdslock);
  
          if (ptnew != NULL) {
                  free(ptnew, M_PMC);
          }
  
          return pt;
  }
  
  /*
   * Try to add thread descriptors for each thread in a process.
   */
  
  static void
  pmc_add_thread_descriptors_from_proc(struct proc *p, struct pmc_process *pp)
  {
          struct thread *curtd;
          struct pmc_thread **tdlist;
          int i, tdcnt, tdlistsz;
  
          KASSERT(!PROC_LOCKED(p), ("[pmc,%d] proc unexpectedly locked",
              __LINE__));
          tdcnt = 32;
   restart:
          tdlistsz = roundup2(tdcnt, 32);
  
          tdcnt = 0;
          tdlist = malloc(sizeof(struct pmc_thread*) * tdlistsz, M_TEMP, M_WAITOK);
  
          PROC_LOCK(p);
          FOREACH_THREAD_IN_PROC(p, curtd)
                  tdcnt++;
          if (tdcnt >= tdlistsz) {
                  PROC_UNLOCK(p);
                  free(tdlist, M_TEMP);
                  goto restart;
          }
          /*
           * Try to add each thread to the list without sleeping. If unable,
           * add to a queue to retry after dropping the process lock.
           */
          tdcnt = 0;
          FOREACH_THREAD_IN_PROC(p, curtd) {
                  tdlist[tdcnt] = pmc_find_thread_descriptor(pp, curtd,
                                                     PMC_FLAG_ALLOCATE|PMC_FLAG_NOWAIT);
                  if (tdlist[tdcnt] == NULL) {
                          PROC_UNLOCK(p);
                          for (i = 0; i <= tdcnt; i++)
                                  pmc_thread_descriptor_pool_free(tdlist[i]);
                          free(tdlist, M_TEMP);
                          goto restart;
                  }
                  tdcnt++;
          }
          PROC_UNLOCK(p);
          free(tdlist, M_TEMP);
  }
  
  /*
   * find the descriptor corresponding to process 'p', adding or removing it
   * as specified by 'mode'.
   */
  
  static struct pmc_process *
  pmc_find_process_descriptor(struct proc *p, uint32_t mode)
  {
          uint32_t hindex;
          struct pmc_process *pp, *ppnew;
          struct pmc_processhash *pph;
  
          hindex = PMC_HASH_PTR(p, pmc_processhashmask);
          pph = &pmc_processhash[hindex];
  
          ppnew = NULL;
  
          /*
           * Pre-allocate memory in the PMC_FLAG_ALLOCATE case since we
           * cannot call malloc(9) once we hold a spin lock.
           */
          if (mode & PMC_FLAG_ALLOCATE)
                  ppnew = malloc(sizeof(struct pmc_process) + md->pmd_npmc *
                      sizeof(struct pmc_targetstate), M_PMC, M_WAITOK|M_ZERO);
  
          mtx_lock_spin(&pmc_processhash_mtx);
          LIST_FOREACH(pp, pph, pp_next)
              if (pp->pp_proc == p)
                      break;
  
          if ((mode & PMC_FLAG_REMOVE) && pp != NULL)
                  LIST_REMOVE(pp, pp_next);
  
          if ((mode & PMC_FLAG_ALLOCATE) && pp == NULL &&
              ppnew != NULL) {
                  ppnew->pp_proc = p;
                  LIST_INIT(&ppnew->pp_tds);
                  ppnew->pp_tdslock = mtx_pool_find(pmc_mtxpool, ppnew);
                  LIST_INSERT_HEAD(pph, ppnew, pp_next);
                  mtx_unlock_spin(&pmc_processhash_mtx);
                  pp = ppnew;
                  ppnew = NULL;
  
                  /* Add thread descriptors for this process' current threads. */
                  pmc_add_thread_descriptors_from_proc(p, pp);
          }
          else
                  mtx_unlock_spin(&pmc_processhash_mtx);
  
          if (ppnew != NULL)
                  free(ppnew, M_PMC);
  
          return pp;
  }
  
  /*
   * remove a process descriptor from the process hash table.
   */
  
  static void
  pmc_remove_process_descriptor(struct pmc_process *pp)
  {
          KASSERT(pp->pp_refcnt == 0,
              ("[pmc,%d] Removing process descriptor %p with count %d",
                  __LINE__, pp, pp->pp_refcnt));
  
          mtx_lock_spin(&pmc_processhash_mtx);
          LIST_REMOVE(pp, pp_next);
          mtx_unlock_spin(&pmc_processhash_mtx);
  }
  
  /*
   * destroy a process descriptor.
   */
  
  static void
  pmc_destroy_process_descriptor(struct pmc_process *pp)
  {
          struct pmc_thread *pmc_td;
  
          while ((pmc_td = LIST_FIRST(&pp->pp_tds)) != NULL) {
                  LIST_REMOVE(pmc_td, pt_next);
                  pmc_thread_descriptor_pool_free(pmc_td);
          }
          free(pp, M_PMC);
  }
  
  
  /*
   * find an owner descriptor corresponding to proc 'p'
   */
  
  static struct pmc_owner *
  pmc_find_owner_descriptor(struct proc *p)
  {
          uint32_t hindex;
          struct pmc_owner *po;
          struct pmc_ownerhash *poh;
  
          hindex = PMC_HASH_PTR(p, pmc_ownerhashmask);
          poh = &pmc_ownerhash[hindex];
  
          po = NULL;
          LIST_FOREACH(po, poh, po_next)
              if (po->po_owner == p)
                      break;
  
          PMCDBG5(OWN,FND,1, "find-owner proc=%p (%d, %s) hindex=0x%x -> "
              "pmc-owner=%p", p, p->p_pid, p->p_comm, hindex, po);
  
          return po;
  }
  
  /*
   * pmc_allocate_pmc_descriptor
   *
   * Allocate a pmc descriptor and initialize its
   * fields.
   */
  
  static struct pmc *
  pmc_allocate_pmc_descriptor(void)
  {
          struct pmc *pmc;
  
          pmc = malloc(sizeof(struct pmc), M_PMC, M_WAITOK|M_ZERO);
          pmc->pm_runcount = counter_u64_alloc(M_WAITOK);
          pmc->pm_pcpu_state = malloc(sizeof(struct pmc_pcpu_state)*mp_ncpus, M_PMC, M_WAITOK|M_ZERO);
          PMCDBG1(PMC,ALL,1, "allocate-pmc -> pmc=%p", pmc);
  
          return pmc;
  }
  
  /*
   * Destroy a pmc descriptor.
   */
  
  static void
  pmc_destroy_pmc_descriptor(struct pmc *pm)
  {
  
          KASSERT(pm->pm_state == PMC_STATE_DELETED ||
              pm->pm_state == PMC_STATE_FREE,
              ("[pmc,%d] destroying non-deleted PMC", __LINE__));
          KASSERT(LIST_EMPTY(&pm->pm_targets),
              ("[pmc,%d] destroying pmc with targets", __LINE__));
          KASSERT(pm->pm_owner == NULL,
              ("[pmc,%d] destroying pmc attached to an owner", __LINE__));
          KASSERT(counter_u64_fetch(pm->pm_runcount) == 0,
              ("[pmc,%d] pmc has non-zero run count %ld", __LINE__,
                   (unsigned long)counter_u64_fetch(pm->pm_runcount)));
  
          counter_u64_free(pm->pm_runcount);
          free(pm->pm_pcpu_state, M_PMC);
          free(pm, M_PMC);
  }
  
  static void
  pmc_wait_for_pmc_idle(struct pmc *pm)
  {
  #ifdef INVARIANTS
          volatile int maxloop;
  
          maxloop = 100 * pmc_cpu_max();
  #endif
          /*
           * Loop (with a forced context switch) till the PMC's runcount
           * comes down to zero.
           */
          pmclog_flush(pm->pm_owner, 1);
          while (counter_u64_fetch(pm->pm_runcount) > 0) {
                  pmclog_flush(pm->pm_owner, 1);
  #ifdef INVARIANTS
                  maxloop--;
                  KASSERT(maxloop > 0,
                      ("[pmc,%d] (ri%d, rc%ld) waiting too long for "
                          "pmc to be free", __LINE__,
                           PMC_TO_ROWINDEX(pm), (unsigned long)counter_u64_fetch(pm->pm_runcount)));
  #endif
                  pmc_force_context_switch();
          }
  }
  
  /*
   * This function does the following things:
   *
   *  - detaches the PMC from hardware
   *  - unlinks all target threads that were attached to it
   *  - removes the PMC from its owner's list
   *  - destroys the PMC private mutex
   *
   * Once this function completes, the given pmc pointer can be freed by
   * calling pmc_destroy_pmc_descriptor().
   */
  
  static void
  pmc_release_pmc_descriptor(struct pmc *pm)
  {
          enum pmc_mode mode;
          struct pmc_hw *phw __diagused;
          u_int adjri, ri, cpu;
          struct pmc_owner *po;
          struct pmc_binding pb;
          struct pmc_process *pp;
          struct pmc_classdep *pcd;
          struct pmc_target *ptgt, *tmp;
  
          sx_assert(&pmc_sx, SX_XLOCKED);
  
          KASSERT(pm, ("[pmc,%d] null pmc", __LINE__));
  
          ri   = PMC_TO_ROWINDEX(pm);
          pcd  = pmc_ri_to_classdep(md, ri, &adjri);
          mode = PMC_TO_MODE(pm);
  
          PMCDBG3(PMC,REL,1, "release-pmc pmc=%p ri=%d mode=%d", pm, ri,
              mode);
  
          /*
           * First, we take the PMC off hardware.
           */
          cpu = 0;
          if (PMC_IS_SYSTEM_MODE(mode)) {
  
                  /*
                   * A system mode PMC runs on a specific CPU.  Switch
                   * to this CPU and turn hardware off.
                   */
                  pmc_save_cpu_binding(&pb);
  
                  cpu = PMC_TO_CPU(pm);
  
                  pmc_select_cpu(cpu);
  
                  /* switch off non-stalled CPUs */
                  pm->pm_pcpu_state[cpu].pps_cpustate = 0;
                  if (pm->pm_state == PMC_STATE_RUNNING &&
                          pm->pm_pcpu_state[cpu].pps_stalled == 0) {
  
                          phw = pmc_pcpu[cpu]->pc_hwpmcs[ri];
  
                          KASSERT(phw->phw_pmc == pm,
                              ("[pmc, %d] pmc ptr ri(%d) hw(%p) pm(%p)",
                                  __LINE__, ri, phw->phw_pmc, pm));
                          PMCDBG2(PMC,REL,2, "stopping cpu=%d ri=%d", cpu, ri);
  
                          critical_enter();
                          pcd->pcd_stop_pmc(cpu, adjri);
                          critical_exit();
                  }
  
                  PMCDBG2(PMC,REL,2, "decfg cpu=%d ri=%d", cpu, ri);
  
                  critical_enter();
                  pcd->pcd_config_pmc(cpu, adjri, NULL);
                  critical_exit();
  
                  /* adjust the global and process count of SS mode PMCs */
                  if (mode == PMC_MODE_SS && pm->pm_state == PMC_STATE_RUNNING) {
                          po = pm->pm_owner;
                          po->po_sscount--;
                          if (po->po_sscount == 0) {
                                  atomic_subtract_rel_int(&pmc_ss_count, 1);
                                  CK_LIST_REMOVE(po, po_ssnext);
                                  epoch_wait_preempt(global_epoch_preempt);
                          }
                  }
  
                  pm->pm_state = PMC_STATE_DELETED;
  
                  pmc_restore_cpu_binding(&pb);
  
                  /*
                   * We could have references to this PMC structure in
                   * the per-cpu sample queues.  Wait for the queue to
                   * drain.
                   */
                  pmc_wait_for_pmc_idle(pm);
  
          } else if (PMC_IS_VIRTUAL_MODE(mode)) {
  
                  /*
                   * A virtual PMC could be running on multiple CPUs at
                   * a given instant.
                   *
                   * By marking its state as DELETED, we ensure that
                   * this PMC is never further scheduled on hardware.
                   *
                   * Then we wait till all CPUs are done with this PMC.
                   */
                  pm->pm_state = PMC_STATE_DELETED;
  
  
                  /* Wait for the PMCs runcount to come to zero. */
                  pmc_wait_for_pmc_idle(pm);
  
                  /*
                   * At this point the PMC is off all CPUs and cannot be
                   * freshly scheduled onto a CPU.  It is now safe to
                   * unlink all targets from this PMC.  If a
                   * process-record's refcount falls to zero, we remove
                   * it from the hash table.  The module-wide SX lock
                   * protects us from races.
                   */
                  LIST_FOREACH_SAFE(ptgt, &pm->pm_targets, pt_next, tmp) {
                          pp = ptgt->pt_process;
                          pmc_unlink_target_process(pm, pp); /* frees 'ptgt' */
  
                          PMCDBG1(PMC,REL,3, "pp->refcnt=%d", pp->pp_refcnt);
  
                          /*
                           * If the target process record shows that no
                           * PMCs are attached to it, reclaim its space.
                           */
  
                          if (pp->pp_refcnt == 0) {
                                  pmc_remove_process_descriptor(pp);
                                  pmc_destroy_process_descriptor(pp);
                          }
                  }
  
                  cpu = curthread->td_oncpu; /* setup cpu for pmd_release() */
  
          }
  
          /*
           * Release any MD resources
           */
          (void) pcd->pcd_release_pmc(cpu, adjri, pm);
  
          /*
           * Update row disposition
           */
  
          if (PMC_IS_SYSTEM_MODE(PMC_TO_MODE(pm)))
                  PMC_UNMARK_ROW_STANDALONE(ri);
          else
                  PMC_UNMARK_ROW_THREAD(ri);
  
          /* unlink from the owner's list */
          if (pm->pm_owner) {
                  LIST_REMOVE(pm, pm_next);
                  pm->pm_owner = NULL;
          }
  }
  
  /*
   * Register an owner and a pmc.
   */
  
  static int
  pmc_register_owner(struct proc *p, struct pmc *pmc)
  {
          struct pmc_owner *po;
  
          sx_assert(&pmc_sx, SX_XLOCKED);
  
          if ((po = pmc_find_owner_descriptor(p)) == NULL)
                  if ((po = pmc_allocate_owner_descriptor(p)) == NULL)
                          return ENOMEM;
  
          KASSERT(pmc->pm_owner == NULL,
              ("[pmc,%d] attempting to own an initialized PMC", __LINE__));
          pmc->pm_owner  = po;
  
          LIST_INSERT_HEAD(&po->po_pmcs, pmc, pm_next);
  
          PROC_LOCK(p);
          p->p_flag |= P_HWPMC;
          PROC_UNLOCK(p);
  
          if (po->po_flags & PMC_PO_OWNS_LOGFILE)
                  pmclog_process_pmcallocate(pmc);
  
          PMCDBG2(PMC,REG,1, "register-owner pmc-owner=%p pmc=%p",
              po, pmc);
  
          return 0;
  }
  
  /*
   * Return the current row disposition:
   * == 0 => FREE
   *  > 0 => PROCESS MODE
   *  < 0 => SYSTEM MODE
   */
  
  int
  pmc_getrowdisp(int ri)
  {
          return pmc_pmcdisp[ri];
  }
  
  /*
   * Check if a PMC at row index 'ri' can be allocated to the current
   * process.
   *
   * Allocation can fail if:
   *   - the current process is already being profiled by a PMC at index 'ri',
   *     attached to it via OP_PMCATTACH.
   *   - the current process has already allocated a PMC at index 'ri'
   *     via OP_ALLOCATE.
   */
  
  static int
  pmc_can_allocate_rowindex(struct proc *p, unsigned int ri, int cpu)
  {
          enum pmc_mode mode;
          struct pmc *pm;
          struct pmc_owner *po;
          struct pmc_process *pp;
  
          PMCDBG5(PMC,ALR,1, "can-allocate-rowindex proc=%p (%d, %s) ri=%d "
              "cpu=%d", p, p->p_pid, p->p_comm, ri, cpu);
  
          /*
           * We shouldn't have already allocated a process-mode PMC at
           * row index 'ri'.
           *
           * We shouldn't have allocated a system-wide PMC on the same
           * CPU and same RI.
           */
          if ((po = pmc_find_owner_descriptor(p)) != NULL)
                  LIST_FOREACH(pm, &po->po_pmcs, pm_next) {
                      if (PMC_TO_ROWINDEX(pm) == ri) {
                              mode = PMC_TO_MODE(pm);
                              if (PMC_IS_VIRTUAL_MODE(mode))
                                      return EEXIST;
                              if (PMC_IS_SYSTEM_MODE(mode) &&
                                  (int) PMC_TO_CPU(pm) == cpu)
                                      return EEXIST;
                      }
                  }
  
          /*
           * We also shouldn't be the target of any PMC at this index
           * since otherwise a PMC_ATTACH to ourselves will fail.
           */
          if ((pp = pmc_find_process_descriptor(p, 0)) != NULL)
                  if (pp->pp_pmcs[ri].pp_pmc)
                          return EEXIST;
  
          PMCDBG4(PMC,ALR,2, "can-allocate-rowindex proc=%p (%d, %s) ri=%d ok",
              p, p->p_pid, p->p_comm, ri);
  
          return 0;
  }
  
  /*
   * Check if a given PMC at row index 'ri' can be currently used in
   * mode 'mode'.
   */
  
  static int
  pmc_can_allocate_row(int ri, enum pmc_mode mode)
  {
          enum pmc_disp   disp;
  
          sx_assert(&pmc_sx, SX_XLOCKED);
  
          PMCDBG2(PMC,ALR,1, "can-allocate-row ri=%d mode=%d", ri, mode);
  
          if (PMC_IS_SYSTEM_MODE(mode))
                  disp = PMC_DISP_STANDALONE;
          else
                  disp = PMC_DISP_THREAD;
  
          /*
           * check disposition for PMC row 'ri':
           *
           * Expected disposition         Row-disposition         Result
           *
           * STANDALONE                   STANDALONE or FREE      proceed
           * STANDALONE                   THREAD                  fail
           * THREAD                       THREAD or FREE          proceed
           * THREAD                       STANDALONE              fail
           */
  
          if (!PMC_ROW_DISP_IS_FREE(ri) &&
              !(disp == PMC_DISP_THREAD && PMC_ROW_DISP_IS_THREAD(ri)) &&
              !(disp == PMC_DISP_STANDALONE && PMC_ROW_DISP_IS_STANDALONE(ri)))
                  return EBUSY;
  
          /*
           * All OK
           */
  
          PMCDBG2(PMC,ALR,2, "can-allocate-row ri=%d mode=%d ok", ri, mode);
  
          return 0;
  
  }
  
  /*
   * Find a PMC descriptor with user handle 'pmcid' for thread 'td'.
   */
  
  static struct pmc *
  pmc_find_pmc_descriptor_in_process(struct pmc_owner *po, pmc_id_t pmcid)
  {
          struct pmc *pm;
  
          KASSERT(PMC_ID_TO_ROWINDEX(pmcid) < md->pmd_npmc,
              ("[pmc,%d] Illegal pmc index %d (max %d)", __LINE__,
                  PMC_ID_TO_ROWINDEX(pmcid), md->pmd_npmc));
  
          LIST_FOREACH(pm, &po->po_pmcs, pm_next)
              if (pm->pm_id == pmcid)
                      return pm;
  
          return NULL;
  }
  
  static int
  pmc_find_pmc(pmc_id_t pmcid, struct pmc **pmc)
  {
  
          struct pmc *pm, *opm;
          struct pmc_owner *po;
          struct pmc_process *pp;
  
          PMCDBG1(PMC,FND,1, "find-pmc id=%d", pmcid);
          if (PMC_ID_TO_ROWINDEX(pmcid) >= md->pmd_npmc)
                  return (EINVAL);
  
          if ((po = pmc_find_owner_descriptor(curthread->td_proc)) == NULL) {
                  /*
                   * In case of PMC_F_DESCENDANTS child processes we will not find
                   * the current process in the owners hash list.  Find the owner
                   * process first and from there lookup the po.
                   */
                  if ((pp = pmc_find_process_descriptor(curthread->td_proc,
                      PMC_FLAG_NONE)) == NULL) {
                          return ESRCH;
                  } else {
                          opm = pp->pp_pmcs[PMC_ID_TO_ROWINDEX(pmcid)].pp_pmc;
                          if (opm == NULL)
                                  return ESRCH;
                          if ((opm->pm_flags & (PMC_F_ATTACHED_TO_OWNER|
                              PMC_F_DESCENDANTS)) != (PMC_F_ATTACHED_TO_OWNER|
                              PMC_F_DESCENDANTS))
                                  return ESRCH;
                          po = opm->pm_owner;
                  }
          }
  
          if ((pm = pmc_find_pmc_descriptor_in_process(po, pmcid)) == NULL)
                  return EINVAL;
  
          PMCDBG2(PMC,FND,2, "find-pmc id=%d -> pmc=%p", pmcid, pm);
  
          *pmc = pm;
          return 0;
  }
  
  /*
   * Start a PMC.
   */
  
  static int
  pmc_start(struct pmc *pm)
  {
          enum pmc_mode mode;
          struct pmc_owner *po;
          struct pmc_binding pb;
          struct pmc_classdep *pcd;
          int adjri, error, cpu, ri;
  
          KASSERT(pm != NULL,
              ("[pmc,%d] null pm", __LINE__));
  
          mode = PMC_TO_MODE(pm);
          ri   = PMC_TO_ROWINDEX(pm);
          pcd  = pmc_ri_to_classdep(md, ri, &adjri);
  
          error = 0;
  
          PMCDBG3(PMC,OPS,1, "start pmc=%p mode=%d ri=%d", pm, mode, ri);
  
          po = pm->pm_owner;
  
          /*
           * Disallow PMCSTART if a logfile is required but has not been
           * configured yet.
           */
          if ((pm->pm_flags & PMC_F_NEEDS_LOGFILE) &&
              (po->po_flags & PMC_PO_OWNS_LOGFILE) == 0)
                  return (EDOOFUS);       /* programming error */
  
          /*
           * If this is a sampling mode PMC, log mapping information for
           * the kernel modules that are currently loaded.
           */
          if (PMC_IS_SAMPLING_MODE(PMC_TO_MODE(pm)))
              pmc_log_kernel_mappings(pm);
  
          if (PMC_IS_VIRTUAL_MODE(mode)) {
  
                  /*
                   * If a PMCATTACH has never been done on this PMC,
                   * attach it to its owner process.
                   */
  
                  if (LIST_EMPTY(&pm->pm_targets))
                          error = (pm->pm_flags & PMC_F_ATTACH_DONE) ? ESRCH :
                              pmc_attach_process(po->po_owner, pm);
  
                  /*
                   * If the PMC is attached to its owner, then force a context
                   * switch to ensure that the MD state gets set correctly.
                   */
  
                  if (error == 0) {
                          pm->pm_state = PMC_STATE_RUNNING;
                          if (pm->pm_flags & PMC_F_ATTACHED_TO_OWNER)
                                  pmc_force_context_switch();
                  }
  
                  return (error);
          }
  
  
          /*
           * A system-wide PMC.
           *
           * Add the owner to the global list if this is a system-wide
           * sampling PMC.
           */
  
          if (mode == PMC_MODE_SS) {
                  /*
                   * Log mapping information for all existing processes in the
                   * system.  Subsequent mappings are logged as they happen;
                   * see pmc_process_mmap().
                   */
                  if (po->po_logprocmaps == 0) {
                          pmc_log_all_process_mappings(po);
                          po->po_logprocmaps = 1;
                  }
                  po->po_sscount++;
                  if (po->po_sscount == 1) {
                          atomic_add_rel_int(&pmc_ss_count, 1);
                          CK_LIST_INSERT_HEAD(&pmc_ss_owners, po, po_ssnext);
                          PMCDBG1(PMC,OPS,1, "po=%p in global list", po);
                  }
          }
  
          /*
           * Move to the CPU associated with this
           * PMC, and start the hardware.
           */
  
          pmc_save_cpu_binding(&pb);
  
          cpu = PMC_TO_CPU(pm);
  
          if (!pmc_cpu_is_active(cpu))
                  return (ENXIO);
  
          pmc_select_cpu(cpu);
  
          /*
           * global PMCs are configured at allocation time
           * so write out the initial value and start the PMC.
           */
  
          pm->pm_state = PMC_STATE_RUNNING;
  
          critical_enter();
          if ((error = pcd->pcd_write_pmc(cpu, adjri,
                   PMC_IS_SAMPLING_MODE(mode) ?
                   pm->pm_sc.pm_reloadcount :
                   pm->pm_sc.pm_initial)) == 0) {
                  /* If a sampling mode PMC, reset stalled state. */
                  if (PMC_IS_SAMPLING_MODE(mode))
                          pm->pm_pcpu_state[cpu].pps_stalled = 0;
  
                  /* Indicate that we desire this to run. Start it. */
                  pm->pm_pcpu_state[cpu].pps_cpustate = 1;
                  error = pcd->pcd_start_pmc(cpu, adjri);
          }
          critical_exit();
  
          pmc_restore_cpu_binding(&pb);
  
          return (error);
  }
  
  /*
   * Stop a PMC.
   */
  
  static int
  pmc_stop(struct pmc *pm)
  {
          struct pmc_owner *po;
          struct pmc_binding pb;
          struct pmc_classdep *pcd;
          int adjri, cpu, error, ri;
  
          KASSERT(pm != NULL, ("[pmc,%d] null pmc", __LINE__));
  
          PMCDBG3(PMC,OPS,1, "stop pmc=%p mode=%d ri=%d", pm,
              PMC_TO_MODE(pm), PMC_TO_ROWINDEX(pm));
  
          pm->pm_state = PMC_STATE_STOPPED;
  
          /*
           * If the PMC is a virtual mode one, changing the state to
           * non-RUNNING is enough to ensure that the PMC never gets
           * scheduled.
           *
           * If this PMC is current running on a CPU, then it will
           * handled correctly at the time its target process is context
           * switched out.
           */
  
          if (PMC_IS_VIRTUAL_MODE(PMC_TO_MODE(pm)))
                  return 0;
  
          /*
           * A system-mode PMC.  Move to the CPU associated with
           * this PMC, and stop the hardware.  We update the
           * 'initial count' so that a subsequent PMCSTART will
           * resume counting from the current hardware count.
           */
  
          pmc_save_cpu_binding(&pb);
  
          cpu = PMC_TO_CPU(pm);
  
          KASSERT(cpu >= 0 && cpu < pmc_cpu_max(),
              ("[pmc,%d] illegal cpu=%d", __LINE__, cpu));
  
          if (!pmc_cpu_is_active(cpu))
                  return ENXIO;
  
          pmc_select_cpu(cpu);
  
          ri = PMC_TO_ROWINDEX(pm);
          pcd = pmc_ri_to_classdep(md, ri, &adjri);
  
          pm->pm_pcpu_state[cpu].pps_cpustate = 0;
          critical_enter();
          if ((error = pcd->pcd_stop_pmc(cpu, adjri)) == 0)
                  error = pcd->pcd_read_pmc(cpu, adjri, &pm->pm_sc.pm_initial);
          critical_exit();
  
          pmc_restore_cpu_binding(&pb);
  
          po = pm->pm_owner;
  
          /* remove this owner from the global list of SS PMC owners */
          if (PMC_TO_MODE(pm) == PMC_MODE_SS) {
                  po->po_sscount--;
                  if (po->po_sscount == 0) {
                          atomic_subtract_rel_int(&pmc_ss_count, 1);
                          CK_LIST_REMOVE(po, po_ssnext);
                          epoch_wait_preempt(global_epoch_preempt);
                          PMCDBG1(PMC,OPS,2,"po=%p removed from global list", po);
                  }
          }
  
          return (error);
  }
  
  static struct pmc_classdep *
  pmc_class_to_classdep(enum pmc_class class)
  {
          int n;
  
          for (n = 0; n < md->pmd_nclass; n++)
                  if (md->pmd_classdep[n].pcd_class == class)
                          return (&md->pmd_classdep[n]);
          return (NULL);
  }
  
  #if defined(HWPMC_DEBUG) && defined(KTR)
  static const char *pmc_op_to_name[] = {
  #undef  __PMC_OP
  #define __PMC_OP(N, D)  #N ,
          __PMC_OPS()
          NULL
  };
  #endif
  
  /*
   * The syscall interface
   */
  
  #define PMC_GET_SX_XLOCK(...) do {              \
          sx_xlock(&pmc_sx);                      \
          if (pmc_hook == NULL) {                 \
                  sx_xunlock(&pmc_sx);            \
                  return __VA_ARGS__;             \
          }                                       \
  } while (0)
  
  #define PMC_DOWNGRADE_SX() do {                 \
          sx_downgrade(&pmc_sx);                  \
          is_sx_downgraded = 1;                   \
  } while (0)
  
  static int
  pmc_syscall_handler(struct thread *td, void *syscall_args)
  {
          int error, is_sx_downgraded, op;
          struct pmc_syscall_args *c;
          void *pmclog_proc_handle;
          void *arg;
  
          c = (struct pmc_syscall_args *)syscall_args;
          op = c->pmop_code;
          arg = c->pmop_data;
          /* PMC isn't set up yet */
          if (pmc_hook == NULL)
                  return (EINVAL);
          if (op == PMC_OP_CONFIGURELOG) {
                  /*
                   * We cannot create the logging process inside
                   * pmclog_configure_log() because there is a LOR
                   * between pmc_sx and process structure locks.
                   * Instead, pre-create the process and ignite the loop
                   * if everything is fine, otherwise direct the process
                   * to exit.
                   */
                  error = pmclog_proc_create(td, &pmclog_proc_handle);
                  if (error != 0)
                          goto done_syscall;
          }
  
          PMC_GET_SX_XLOCK(ENOSYS);
          is_sx_downgraded = 0;
          PMCDBG3(MOD,PMS,1, "syscall op=%d \"%s\" arg=%p", op,
              pmc_op_to_name[op], arg);
  
          error = 0;
          counter_u64_add(pmc_stats.pm_syscalls, 1);
  
          switch (op) {
  
  
          /*
           * Configure a log file.
           *
           * XXX This OP will be reworked.
           */
  
          case PMC_OP_CONFIGURELOG:
          {
                  struct proc *p;
                  struct pmc *pm;
                  struct pmc_owner *po;
                  struct pmc_op_configurelog cl;
  
                  if ((error = copyin(arg, &cl, sizeof(cl))) != 0) {
                          pmclog_proc_ignite(pmclog_proc_handle, NULL);
                          break;
                  }
  
                  /* mark this process as owning a log file */
                  p = td->td_proc;
                  if ((po = pmc_find_owner_descriptor(p)) == NULL)
                          if ((po = pmc_allocate_owner_descriptor(p)) == NULL) {
                                  pmclog_proc_ignite(pmclog_proc_handle, NULL);
                                  error = ENOMEM;
                                  break;
                          }
  
                  /*
                   * If a valid fd was passed in, try to configure that,
                   * otherwise if 'fd' was less than zero and there was
                   * a log file configured, flush its buffers and
                   * de-configure it.
                   */
                  if (cl.pm_logfd >= 0) {
                          error = pmclog_configure_log(md, po, cl.pm_logfd);
                          pmclog_proc_ignite(pmclog_proc_handle, error == 0 ?
                              po : NULL);
                  } else if (po->po_flags & PMC_PO_OWNS_LOGFILE) {
                          pmclog_proc_ignite(pmclog_proc_handle, NULL);
                          error = pmclog_close(po);
                          if (error == 0) {
                                  LIST_FOREACH(pm, &po->po_pmcs, pm_next)
                                      if (pm->pm_flags & PMC_F_NEEDS_LOGFILE &&
                                          pm->pm_state == PMC_STATE_RUNNING)
                                              pmc_stop(pm);
                                  error = pmclog_deconfigure_log(po);
                          }
                  } else {
                          pmclog_proc_ignite(pmclog_proc_handle, NULL);
                          error = EINVAL;
                  }
          }
          break;
  
          /*
           * Flush a log file.
           */
  
          case PMC_OP_FLUSHLOG:
          {
                  struct pmc_owner *po;
  
                  sx_assert(&pmc_sx, SX_XLOCKED);
  
                  if ((po = pmc_find_owner_descriptor(td->td_proc)) == NULL) {
                          error = EINVAL;
                          break;
                  }
  
                  error = pmclog_flush(po, 0);
          }
          break;
  
          /*
           * Close a log file.
           */
  
          case PMC_OP_CLOSELOG:
          {
                  struct pmc_owner *po;
  
                  sx_assert(&pmc_sx, SX_XLOCKED);
  
                  if ((po = pmc_find_owner_descriptor(td->td_proc)) == NULL) {
                          error = EINVAL;
                          break;
                  }
  
                  error = pmclog_close(po);
          }
          break;
  
          /*
           * Retrieve hardware configuration.
           */
  
          case PMC_OP_GETCPUINFO: /* CPU information */
          {
                  struct pmc_op_getcpuinfo gci;
                  struct pmc_classinfo *pci;
                  struct pmc_classdep *pcd;
                  int cl;
  
                  memset(&gci, 0, sizeof(gci));
                  gci.pm_cputype = md->pmd_cputype;
                  gci.pm_ncpu    = pmc_cpu_max();
                  gci.pm_npmc    = md->pmd_npmc;
                  gci.pm_nclass  = md->pmd_nclass;
                  pci = gci.pm_classes;
                  pcd = md->pmd_classdep;
                  for (cl = 0; cl < md->pmd_nclass; cl++, pci++, pcd++) {
                          pci->pm_caps  = pcd->pcd_caps;
                          pci->pm_class = pcd->pcd_class;
                          pci->pm_width = pcd->pcd_width;
                          pci->pm_num   = pcd->pcd_num;
                  }
                  error = copyout(&gci, arg, sizeof(gci));
          }
          break;
  
          /*
           * Retrieve soft events list.
           */
          case PMC_OP_GETDYNEVENTINFO:
          {
                  enum pmc_class                  cl;
                  enum pmc_event                  ev;
                  struct pmc_op_getdyneventinfo   *gei;
                  struct pmc_dyn_event_descr      dev;
                  struct pmc_soft                 *ps;
                  uint32_t                        nevent;
  
                  sx_assert(&pmc_sx, SX_LOCKED);
  
                  gei = (struct pmc_op_getdyneventinfo *) arg;
  
                  if ((error = copyin(&gei->pm_class, &cl, sizeof(cl))) != 0)
                          break;
  
                  /* Only SOFT class is dynamic. */
                  if (cl != PMC_CLASS_SOFT) {
                          error = EINVAL;
                          break;
                  }
  
                  nevent = 0;
                  for (ev = PMC_EV_SOFT_FIRST; (int)ev <= PMC_EV_SOFT_LAST; ev++) {
                          ps = pmc_soft_ev_acquire(ev);
                          if (ps == NULL)
                                  continue;
                          bcopy(&ps->ps_ev, &dev, sizeof(dev));
                          pmc_soft_ev_release(ps);
  
                          error = copyout(&dev,
                              &gei->pm_events[nevent],
                              sizeof(struct pmc_dyn_event_descr));
                          if (error != 0)
                                  break;
                          nevent++;
                  }
                  if (error != 0)
                          break;
  
                  error = copyout(&nevent, &gei->pm_nevent,
                      sizeof(nevent));
          }
          break;
  
          /*
           * Get module statistics
           */
  
          case PMC_OP_GETDRIVERSTATS:
          {
                  struct pmc_op_getdriverstats gms;
  #define CFETCH(a, b, field) a.field = counter_u64_fetch(b.field)
                  CFETCH(gms, pmc_stats, pm_intr_ignored);
                  CFETCH(gms, pmc_stats, pm_intr_processed);
                  CFETCH(gms, pmc_stats, pm_intr_bufferfull);
                  CFETCH(gms, pmc_stats, pm_syscalls);
                  CFETCH(gms, pmc_stats, pm_syscall_errors);
                  CFETCH(gms, pmc_stats, pm_buffer_requests);
                  CFETCH(gms, pmc_stats, pm_buffer_requests_failed);
                  CFETCH(gms, pmc_stats, pm_log_sweeps);
  #undef CFETCH
                  error = copyout(&gms, arg, sizeof(gms));
          }
          break;
  
  
          /*
           * Retrieve module version number
           */
  
          case PMC_OP_GETMODULEVERSION:
          {
                  uint32_t cv, modv;
  
                  /* retrieve the client's idea of the ABI version */
                  if ((error = copyin(arg, &cv, sizeof(uint32_t))) != 0)
                          break;
                  /* don't service clients newer than our driver */
                  modv = PMC_VERSION;
                  if ((cv & 0xFFFF0000) > (modv & 0xFFFF0000)) {
                          error = EPROGMISMATCH;
                          break;
                  }
                  error = copyout(&modv, arg, sizeof(int));
          }
          break;
  
  
          /*
           * Retrieve the state of all the PMCs on a given
           * CPU.
           */
  
          case PMC_OP_GETPMCINFO:
          {
                  int ari;
                  struct pmc *pm;
                  size_t pmcinfo_size;
                  uint32_t cpu, n, npmc;
                  struct pmc_owner *po;
                  struct pmc_binding pb;
                  struct pmc_classdep *pcd;
                  struct pmc_info *p, *pmcinfo;
                  struct pmc_op_getpmcinfo *gpi;
  
                  PMC_DOWNGRADE_SX();
  
                  gpi = (struct pmc_op_getpmcinfo *) arg;
  
                  if ((error = copyin(&gpi->pm_cpu, &cpu, sizeof(cpu))) != 0)
                          break;
  
                  if (cpu >= pmc_cpu_max()) {
                          error = EINVAL;
                          break;
                  }
  
                  if (!pmc_cpu_is_active(cpu)) {
                          error = ENXIO;
                          break;
                  }
  
                  /* switch to CPU 'cpu' */
                  pmc_save_cpu_binding(&pb);
                  pmc_select_cpu(cpu);
  
                  npmc = md->pmd_npmc;
  
                  pmcinfo_size = npmc * sizeof(struct pmc_info);
                  pmcinfo = malloc(pmcinfo_size, M_PMC, M_WAITOK | M_ZERO);
  
                  p = pmcinfo;
  
                  for (n = 0; n < md->pmd_npmc; n++, p++) {
  
                          pcd = pmc_ri_to_classdep(md, n, &ari);
  
                          KASSERT(pcd != NULL,
                              ("[pmc,%d] null pcd ri=%d", __LINE__, n));
  
                          if ((error = pcd->pcd_describe(cpu, ari, p, &pm)) != 0)
                                  break;
  
                          if (PMC_ROW_DISP_IS_STANDALONE(n))
                                  p->pm_rowdisp = PMC_DISP_STANDALONE;
                          else if (PMC_ROW_DISP_IS_THREAD(n))
                                  p->pm_rowdisp = PMC_DISP_THREAD;
                          else
                                  p->pm_rowdisp = PMC_DISP_FREE;
  
                          p->pm_ownerpid = -1;
  
                          if (pm == NULL) /* no PMC associated */
                                  continue;
  
                          po = pm->pm_owner;
  
                          KASSERT(po->po_owner != NULL,
                              ("[pmc,%d] pmc_owner had a null proc pointer",
                                  __LINE__));
  
                          p->pm_ownerpid = po->po_owner->p_pid;
                          p->pm_mode     = PMC_TO_MODE(pm);
                          p->pm_event    = pm->pm_event;
                          p->pm_flags    = pm->pm_flags;
  
                          if (PMC_IS_SAMPLING_MODE(PMC_TO_MODE(pm)))
                                  p->pm_reloadcount =
                                      pm->pm_sc.pm_reloadcount;
                  }
  
                  pmc_restore_cpu_binding(&pb);
  
                  /* now copy out the PMC info collected */
                  if (error == 0)
                          error = copyout(pmcinfo, &gpi->pm_pmcs, pmcinfo_size);
  
                  free(pmcinfo, M_PMC);
          }
          break;
  
  
          /*
           * Set the administrative state of a PMC.  I.e. whether
           * the PMC is to be used or not.
           */
  
          case PMC_OP_PMCADMIN:
          {
                  int cpu, ri;
                  enum pmc_state request;
                  struct pmc_cpu *pc;
                  struct pmc_hw *phw;
                  struct pmc_op_pmcadmin pma;
                  struct pmc_binding pb;
  
                  sx_assert(&pmc_sx, SX_XLOCKED);
  
                  KASSERT(td == curthread,
                      ("[pmc,%d] td != curthread", __LINE__));
  
                  error = priv_check(td, PRIV_PMC_MANAGE);
                  if (error)
                          break;
  
                  if ((error = copyin(arg, &pma, sizeof(pma))) != 0)
                          break;
  
                  cpu = pma.pm_cpu;
  
                  if (cpu < 0 || cpu >= (int) pmc_cpu_max()) {
                          error = EINVAL;
                          break;
                  }
  
                  if (!pmc_cpu_is_active(cpu)) {
                          error = ENXIO;
                          break;
                  }
  
                  request = pma.pm_state;
  
                  if (request != PMC_STATE_DISABLED &&
                      request != PMC_STATE_FREE) {
                          error = EINVAL;
                          break;
                  }
  
                  ri = pma.pm_pmc; /* pmc id == row index */
                  if (ri < 0 || ri >= (int) md->pmd_npmc) {
                          error = EINVAL;
                          break;
                  }
  
                  /*
                   * We can't disable a PMC with a row-index allocated
                   * for process virtual PMCs.
                   */
  
                  if (PMC_ROW_DISP_IS_THREAD(ri) &&
                      request == PMC_STATE_DISABLED) {
                          error = EBUSY;
                          break;
                  }
  
                  /*
                   * otherwise, this PMC on this CPU is either free or
                   * in system-wide mode.
                   */
  
                  pmc_save_cpu_binding(&pb);
                  pmc_select_cpu(cpu);
  
                  pc  = pmc_pcpu[cpu];
                  phw = pc->pc_hwpmcs[ri];
  
                  /*
                   * XXX do we need some kind of 'forced' disable?
                   */
  
                  if (phw->phw_pmc == NULL) {
                          if (request == PMC_STATE_DISABLED &&
                              (phw->phw_state & PMC_PHW_FLAG_IS_ENABLED)) {
                                  phw->phw_state &= ~PMC_PHW_FLAG_IS_ENABLED;
                                  PMC_MARK_ROW_STANDALONE(ri);
                          } else if (request == PMC_STATE_FREE &&
                              (phw->phw_state & PMC_PHW_FLAG_IS_ENABLED) == 0) {
                                  phw->phw_state |=  PMC_PHW_FLAG_IS_ENABLED;
                                  PMC_UNMARK_ROW_STANDALONE(ri);
                          }
                          /* other cases are a no-op */
                  } else
                          error = EBUSY;
  
                  pmc_restore_cpu_binding(&pb);
          }
          break;
  
  
          /*
           * Allocate a PMC.
           */
  
          case PMC_OP_PMCALLOCATE:
          {
                  int adjri, n;
                  u_int cpu;
                  uint32_t caps;
                  struct pmc *pmc;
                  enum pmc_mode mode;
                  struct pmc_hw *phw;
                  struct pmc_binding pb;
                  struct pmc_classdep *pcd;
                  struct pmc_op_pmcallocate pa;
  
                  if ((error = copyin(arg, &pa, sizeof(pa))) != 0)
                          break;
  
                  caps = pa.pm_caps;
                  mode = pa.pm_mode;
                  cpu  = pa.pm_cpu;
  
                  if ((mode != PMC_MODE_SS  &&  mode != PMC_MODE_SC  &&
                       mode != PMC_MODE_TS  &&  mode != PMC_MODE_TC) ||
                      (cpu != (u_int) PMC_CPU_ANY && cpu >= pmc_cpu_max())) {
                          error = EINVAL;
                          break;
                  }
  
                  /*
                   * Virtual PMCs should only ask for a default CPU.
                   * System mode PMCs need to specify a non-default CPU.
                   */
  
                  if ((PMC_IS_VIRTUAL_MODE(mode) && cpu != (u_int) PMC_CPU_ANY) ||
                      (PMC_IS_SYSTEM_MODE(mode) && cpu == (u_int) PMC_CPU_ANY)) {
                          error = EINVAL;
                          break;
                  }
  
                  /*
                   * Check that an inactive CPU is not being asked for.
                   */
  
                  if (PMC_IS_SYSTEM_MODE(mode) && !pmc_cpu_is_active(cpu)) {
                          error = ENXIO;
                          break;
                  }
  
                  /*
                   * Refuse an allocation for a system-wide PMC if this
                   * process has been jailed, or if this process lacks
                   * super-user credentials and the sysctl tunable
                   * 'security.bsd.unprivileged_syspmcs' is zero.
                   */
  
                  if (PMC_IS_SYSTEM_MODE(mode)) {
                          if (jailed(curthread->td_ucred)) {
                                  error = EPERM;
                                  break;
                          }
                          if (!pmc_unprivileged_syspmcs) {
                                  error = priv_check(curthread,
                                      PRIV_PMC_SYSTEM);
                                  if (error)
                                          break;
                          }
                  }
  
                  /*
                   * Look for valid values for 'pm_flags'
                   */
  
                  if ((pa.pm_flags & ~(PMC_F_DESCENDANTS | PMC_F_LOG_PROCCSW |
                      PMC_F_LOG_PROCEXIT | PMC_F_CALLCHAIN |
                      PMC_F_USERCALLCHAIN)) != 0) {
                          error = EINVAL;
                          break;
                  }
  
                  /* PMC_F_USERCALLCHAIN is only valid with PMC_F_CALLCHAIN */
                  if ((pa.pm_flags & (PMC_F_CALLCHAIN | PMC_F_USERCALLCHAIN)) ==
                      PMC_F_USERCALLCHAIN) {
                          error = EINVAL;
                          break;
                  }
  
                  /* PMC_F_USERCALLCHAIN is only valid for sampling mode */
                  if (pa.pm_flags & PMC_F_USERCALLCHAIN &&
                          mode != PMC_MODE_TS && mode != PMC_MODE_SS) {
                          error = EINVAL;
                          break;
                  }
  
                  /* process logging options are not allowed for system PMCs */
                  if (PMC_IS_SYSTEM_MODE(mode) && (pa.pm_flags &
                      (PMC_F_LOG_PROCCSW | PMC_F_LOG_PROCEXIT))) {
                          error = EINVAL;
                          break;
                  }
  
                  /*
                   * All sampling mode PMCs need to be able to interrupt the
                   * CPU.
                   */
                  if (PMC_IS_SAMPLING_MODE(mode))
                          caps |= PMC_CAP_INTERRUPT;
  
                  /* A valid class specifier should have been passed in. */
                  pcd = pmc_class_to_classdep(pa.pm_class);
                  if (pcd == NULL) {
                          error = EINVAL;
                          break;
                  }
  
                  /* The requested PMC capabilities should be feasible. */
                  if ((pcd->pcd_caps & caps) != caps) {
                          error = EOPNOTSUPP;
                          break;
                  }
  
                  PMCDBG4(PMC,ALL,2, "event=%d caps=0x%x mode=%d cpu=%d",
                      pa.pm_ev, caps, mode, cpu);
  
                  pmc = pmc_allocate_pmc_descriptor();
                  pmc->pm_id    = PMC_ID_MAKE_ID(cpu,pa.pm_mode,pa.pm_class,
                      PMC_ID_INVALID);
                  pmc->pm_event = pa.pm_ev;
                  pmc->pm_state = PMC_STATE_FREE;
                  pmc->pm_caps  = caps;
                  pmc->pm_flags = pa.pm_flags;
  
                  /* XXX set lower bound on sampling for process counters */
                  if (PMC_IS_SAMPLING_MODE(mode)) {
                          /*
                           * Don't permit requested sample rate to be
                           * less than pmc_mincount.
                           */
                          if (pa.pm_count < MAX(1, pmc_mincount))
                                  log(LOG_WARNING, "pmcallocate: passed sample "
                                      "rate %ju - setting to %u\n",
                                      (uintmax_t)pa.pm_count,
                                      MAX(1, pmc_mincount));
                          pmc->pm_sc.pm_reloadcount = MAX(MAX(1, pmc_mincount),
                              pa.pm_count);
                  } else
                          pmc->pm_sc.pm_initial = pa.pm_count;
  
                  /* switch thread to CPU 'cpu' */
                  pmc_save_cpu_binding(&pb);
  
  #define PMC_IS_SHAREABLE_PMC(cpu, n)                            \
          (pmc_pcpu[(cpu)]->pc_hwpmcs[(n)]->phw_state &           \
           PMC_PHW_FLAG_IS_SHAREABLE)
  #define PMC_IS_UNALLOCATED(cpu, n)                              \
          (pmc_pcpu[(cpu)]->pc_hwpmcs[(n)]->phw_pmc == NULL)
  
                  if (PMC_IS_SYSTEM_MODE(mode)) {
                          pmc_select_cpu(cpu);
                          for (n = pcd->pcd_ri; n < (int) md->pmd_npmc; n++) {
                                  pcd = pmc_ri_to_classdep(md, n, &adjri);
                                  if (pmc_can_allocate_row(n, mode) == 0 &&
                                      pmc_can_allocate_rowindex(
                                              curthread->td_proc, n, cpu) == 0 &&
                                      (PMC_IS_UNALLOCATED(cpu, n) ||
                                       PMC_IS_SHAREABLE_PMC(cpu, n)) &&
                                      pcd->pcd_allocate_pmc(cpu, adjri, pmc,
                                          &pa) == 0)
                                          break;
                          }
                  } else {
                          /* Process virtual mode */
                          for (n = pcd->pcd_ri; n < (int) md->pmd_npmc; n++) {
                                  pcd = pmc_ri_to_classdep(md, n, &adjri);
                                  if (pmc_can_allocate_row(n, mode) == 0 &&
                                      pmc_can_allocate_rowindex(
                                              curthread->td_proc, n,
                                              PMC_CPU_ANY) == 0 &&
                                      pcd->pcd_allocate_pmc(curthread->td_oncpu,
                                          adjri, pmc, &pa) == 0)
                                          break;
                          }
                  }
  
  #undef  PMC_IS_UNALLOCATED
  #undef  PMC_IS_SHAREABLE_PMC
  
                  pmc_restore_cpu_binding(&pb);
  
                  if (n == (int) md->pmd_npmc) {
                          pmc_destroy_pmc_descriptor(pmc);
                          pmc = NULL;
                          error = EINVAL;
                          break;
                  }
  
                  /* Fill in the correct value in the ID field */
                  pmc->pm_id = PMC_ID_MAKE_ID(cpu,mode,pa.pm_class,n);
  
                  PMCDBG5(PMC,ALL,2, "ev=%d class=%d mode=%d n=%d -> pmcid=%x",
                      pmc->pm_event, pa.pm_class, mode, n, pmc->pm_id);
  
                  /* Process mode PMCs with logging enabled need log files */
                  if (pmc->pm_flags & (PMC_F_LOG_PROCEXIT | PMC_F_LOG_PROCCSW))
                          pmc->pm_flags |= PMC_F_NEEDS_LOGFILE;
  
                  /* All system mode sampling PMCs require a log file */
                  if (PMC_IS_SAMPLING_MODE(mode) && PMC_IS_SYSTEM_MODE(mode))
                          pmc->pm_flags |= PMC_F_NEEDS_LOGFILE;
  
                  /*
                   * Configure global pmc's immediately
                   */
  
                  if (PMC_IS_SYSTEM_MODE(PMC_TO_MODE(pmc))) {
  
                          pmc_save_cpu_binding(&pb);
                          pmc_select_cpu(cpu);
  
                          phw = pmc_pcpu[cpu]->pc_hwpmcs[n];
                          pcd = pmc_ri_to_classdep(md, n, &adjri);
  
                          if ((phw->phw_state & PMC_PHW_FLAG_IS_ENABLED) == 0 ||
                              (error = pcd->pcd_config_pmc(cpu, adjri, pmc)) != 0) {
                                  (void) pcd->pcd_release_pmc(cpu, adjri, pmc);
                                  pmc_destroy_pmc_descriptor(pmc);
                                  pmc = NULL;
                                  pmc_restore_cpu_binding(&pb);
                                  error = EPERM;
                                  break;
                          }
  
                          pmc_restore_cpu_binding(&pb);
                  }
  
                  pmc->pm_state    = PMC_STATE_ALLOCATED;
                  pmc->pm_class   = pa.pm_class;
  
                  /*
                   * mark row disposition
                   */
  
                  if (PMC_IS_SYSTEM_MODE(mode))
                          PMC_MARK_ROW_STANDALONE(n);
                  else
                          PMC_MARK_ROW_THREAD(n);
  
                  /*
                   * Register this PMC with the current thread as its owner.
                   */
  
                  if ((error =
                      pmc_register_owner(curthread->td_proc, pmc)) != 0) {
                          pmc_release_pmc_descriptor(pmc);
                          pmc_destroy_pmc_descriptor(pmc);
                          pmc = NULL;
                          break;
                  }
  
  
                  /*
                   * Return the allocated index.
                   */
  
                  pa.pm_pmcid = pmc->pm_id;
  
                  error = copyout(&pa, arg, sizeof(pa));
          }
          break;
  
  
          /*
           * Attach a PMC to a process.
           */
  
          case PMC_OP_PMCATTACH:
          {
                  struct pmc *pm;
                  struct proc *p;
                  struct pmc_op_pmcattach a;
  
                  sx_assert(&pmc_sx, SX_XLOCKED);
  
                  if ((error = copyin(arg, &a, sizeof(a))) != 0)
                          break;
  
                  if (a.pm_pid < 0) {
                          error = EINVAL;
                          break;
                  } else if (a.pm_pid == 0)
                          a.pm_pid = td->td_proc->p_pid;
  
                  if ((error = pmc_find_pmc(a.pm_pmc, &pm)) != 0)
                          break;
  
                  if (PMC_IS_SYSTEM_MODE(PMC_TO_MODE(pm))) {
                          error = EINVAL;
                          break;
                  }
  
                  /* PMCs may be (re)attached only when allocated or stopped */
                  if (pm->pm_state == PMC_STATE_RUNNING) {
                          error = EBUSY;
                          break;
                  } else if (pm->pm_state != PMC_STATE_ALLOCATED &&
                      pm->pm_state != PMC_STATE_STOPPED) {
                          error = EINVAL;
                          break;
                  }
  
                  /* lookup pid */
                  if ((p = pfind(a.pm_pid)) == NULL) {
                          error = ESRCH;
                          break;
                  }
  
                  /*
                   * Ignore processes that are working on exiting.
                   */
                  if (p->p_flag & P_WEXIT) {
                          error = ESRCH;
                          PROC_UNLOCK(p); /* pfind() returns a locked process */
                          break;
                  }
  
                  /*
                   * we are allowed to attach a PMC to a process if
                   * we can debug it.
                   */
                  error = p_candebug(curthread, p);
  
                  PROC_UNLOCK(p);
  
                  if (error == 0)
                          error = pmc_attach_process(p, pm);
          }
          break;
  
  
          /*
           * Detach an attached PMC from a process.
           */
  
          case PMC_OP_PMCDETACH:
          {
                  struct pmc *pm;
                  struct proc *p;
                  struct pmc_op_pmcattach a;
  
                  if ((error = copyin(arg, &a, sizeof(a))) != 0)
                          break;
  
                  if (a.pm_pid < 0) {
                          error = EINVAL;
                          break;
                  } else if (a.pm_pid == 0)
                          a.pm_pid = td->td_proc->p_pid;
  
                  if ((error = pmc_find_pmc(a.pm_pmc, &pm)) != 0)
                          break;
  
                  if ((p = pfind(a.pm_pid)) == NULL) {
                          error = ESRCH;
                          break;
                  }
  
                  /*
                   * Treat processes that are in the process of exiting
                   * as if they were not present.
                   */
  
                  if (p->p_flag & P_WEXIT)
                          error = ESRCH;
  
                  PROC_UNLOCK(p); /* pfind() returns a locked process */
  
                  if (error == 0)
                          error = pmc_detach_process(p, pm);
          }
          break;
  
  
          /*
           * Retrieve the MSR number associated with the counter
           * 'pmc_id'.  This allows processes to directly use RDPMC
           * instructions to read their PMCs, without the overhead of a
           * system call.
           */
  
          case PMC_OP_PMCGETMSR:
          {
                  int adjri, ri;
                  struct pmc *pm;
                  struct pmc_target *pt;
                  struct pmc_op_getmsr gm;
                  struct pmc_classdep *pcd;
  
                  PMC_DOWNGRADE_SX();
  
                  if ((error = copyin(arg, &gm, sizeof(gm))) != 0)
                          break;
  
                  if ((error = pmc_find_pmc(gm.pm_pmcid, &pm)) != 0)
                          break;
  
                  /*
                   * The allocated PMC has to be a process virtual PMC,
                   * i.e., of type MODE_T[CS].  Global PMCs can only be
                   * read using the PMCREAD operation since they may be
                   * allocated on a different CPU than the one we could
                   * be running on at the time of the RDPMC instruction.
                   *
                   * The GETMSR operation is not allowed for PMCs that
                   * are inherited across processes.
                   */
  
                  if (!PMC_IS_VIRTUAL_MODE(PMC_TO_MODE(pm)) ||
                      (pm->pm_flags & PMC_F_DESCENDANTS)) {
                          error = EINVAL;
                          break;
                  }
  
                  /*
                   * It only makes sense to use a RDPMC (or its
                   * equivalent instruction on non-x86 architectures) on
                   * a process that has allocated and attached a PMC to
                   * itself.  Conversely the PMC is only allowed to have
                   * one process attached to it -- its owner.
                   */
  
                  if ((pt = LIST_FIRST(&pm->pm_targets)) == NULL ||
                      LIST_NEXT(pt, pt_next) != NULL ||
                      pt->pt_process->pp_proc != pm->pm_owner->po_owner) {
                          error = EINVAL;
                          break;
                  }
  
                  ri = PMC_TO_ROWINDEX(pm);
                  pcd = pmc_ri_to_classdep(md, ri, &adjri);
  
                  /* PMC class has no 'GETMSR' support */
                  if (pcd->pcd_get_msr == NULL) {
                          error = ENOSYS;
                          break;
                  }
  
                  if ((error = (*pcd->pcd_get_msr)(adjri, &gm.pm_msr)) < 0)
                          break;
  
                  if ((error = copyout(&gm, arg, sizeof(gm))) < 0)
                          break;
  
                  /*
                   * Mark our process as using MSRs.  Update machine
                   * state using a forced context switch.
                   */
  
                  pt->pt_process->pp_flags |= PMC_PP_ENABLE_MSR_ACCESS;
                  pmc_force_context_switch();
  
          }
          break;
  
          /*
           * Release an allocated PMC
           */
  
          case PMC_OP_PMCRELEASE:
          {
                  pmc_id_t pmcid;
                  struct pmc *pm;
                  struct pmc_owner *po;
                  struct pmc_op_simple sp;
  
                  /*
                   * Find PMC pointer for the named PMC.
                   *
                   * Use pmc_release_pmc_descriptor() to switch off the
                   * PMC, remove all its target threads, and remove the
                   * PMC from its owner's list.
                   *
                   * Remove the owner record if this is the last PMC
                   * owned.
                   *
                   * Free up space.
                   */
  
                  if ((error = copyin(arg, &sp, sizeof(sp))) != 0)
                          break;
  
                  pmcid = sp.pm_pmcid;
  
                  if ((error = pmc_find_pmc(pmcid, &pm)) != 0)
                          break;
  
                  po = pm->pm_owner;
                  pmc_release_pmc_descriptor(pm);
                  pmc_maybe_remove_owner(po);
                  pmc_destroy_pmc_descriptor(pm);
          }
          break;
  
  
          /*
           * Read and/or write a PMC.
           */
  
          case PMC_OP_PMCRW:
          {
                  int adjri;
                  struct pmc *pm;
                  uint32_t cpu, ri;
                  pmc_value_t oldvalue;
                  struct pmc_binding pb;
                  struct pmc_op_pmcrw prw;
                  struct pmc_classdep *pcd;
                  struct pmc_op_pmcrw *pprw;
  
                  PMC_DOWNGRADE_SX();
  
                  if ((error = copyin(arg, &prw, sizeof(prw))) != 0)
                          break;
  
                  PMCDBG2(PMC,OPS,1, "rw id=%d flags=0x%x", prw.pm_pmcid,
                      prw.pm_flags);
  
                  /* must have at least one flag set */
                  if ((prw.pm_flags & (PMC_F_OLDVALUE|PMC_F_NEWVALUE)) == 0) {
                          error = EINVAL;
                          break;
                  }
  
                  /* locate pmc descriptor */
                  if ((error = pmc_find_pmc(prw.pm_pmcid, &pm)) != 0)
                          break;
  
                  /* Can't read a PMC that hasn't been started. */
                  if (pm->pm_state != PMC_STATE_ALLOCATED &&
                      pm->pm_state != PMC_STATE_STOPPED &&
                      pm->pm_state != PMC_STATE_RUNNING) {
                          error = EINVAL;
                          break;
                  }
  
                  /* writing a new value is allowed only for 'STOPPED' pmcs */
                  if (pm->pm_state == PMC_STATE_RUNNING &&
                      (prw.pm_flags & PMC_F_NEWVALUE)) {
                          error = EBUSY;
                          break;
                  }
  
                  if (PMC_IS_VIRTUAL_MODE(PMC_TO_MODE(pm))) {
  
                          /*
                           * If this PMC is attached to its owner (i.e.,
                           * the process requesting this operation) and
                           * is running, then attempt to get an
                           * upto-date reading from hardware for a READ.
                           * Writes are only allowed when the PMC is
                           * stopped, so only update the saved value
                           * field.
                           *
                           * If the PMC is not running, or is not
                           * attached to its owner, read/write to the
                           * savedvalue field.
                           */
  
                          ri = PMC_TO_ROWINDEX(pm);
                          pcd = pmc_ri_to_classdep(md, ri, &adjri);
  
                          mtx_pool_lock_spin(pmc_mtxpool, pm);
                          cpu = curthread->td_oncpu;
  
                          if (prw.pm_flags & PMC_F_OLDVALUE) {
                                  if ((pm->pm_flags & PMC_F_ATTACHED_TO_OWNER) &&
                                      (pm->pm_state == PMC_STATE_RUNNING))
                                          error = (*pcd->pcd_read_pmc)(cpu, adjri,
                                              &oldvalue);
                                  else
                                          oldvalue = pm->pm_gv.pm_savedvalue;
                          }
                          if (prw.pm_flags & PMC_F_NEWVALUE)
                                  pm->pm_gv.pm_savedvalue = prw.pm_value;
  
                          mtx_pool_unlock_spin(pmc_mtxpool, pm);
  
                  } else { /* System mode PMCs */
                          cpu = PMC_TO_CPU(pm);
                          ri  = PMC_TO_ROWINDEX(pm);
                          pcd = pmc_ri_to_classdep(md, ri, &adjri);
  
                          if (!pmc_cpu_is_active(cpu)) {
                                  error = ENXIO;
                                  break;
                          }
  
                          /* move this thread to CPU 'cpu' */
                          pmc_save_cpu_binding(&pb);
                          pmc_select_cpu(cpu);
  
                          critical_enter();
                          /* save old value */
                          if (prw.pm_flags & PMC_F_OLDVALUE)
                                  if ((error = (*pcd->pcd_read_pmc)(cpu, adjri,
                                           &oldvalue)))
                                          goto error;
                          /* write out new value */
                          if (prw.pm_flags & PMC_F_NEWVALUE)
                                  error = (*pcd->pcd_write_pmc)(cpu, adjri,
                                      prw.pm_value);
                  error:
                          critical_exit();
                          pmc_restore_cpu_binding(&pb);
                          if (error)
                                  break;
                  }
  
                  pprw = (struct pmc_op_pmcrw *) arg;
  
  #ifdef  HWPMC_DEBUG
                  if (prw.pm_flags & PMC_F_NEWVALUE)
                          PMCDBG3(PMC,OPS,2, "rw id=%d new %jx -> old %jx",
                              ri, prw.pm_value, oldvalue);
                  else if (prw.pm_flags & PMC_F_OLDVALUE)
                          PMCDBG2(PMC,OPS,2, "rw id=%d -> old %jx", ri, oldvalue);
  #endif
  
                  /* return old value if requested */
                  if (prw.pm_flags & PMC_F_OLDVALUE)
                          if ((error = copyout(&oldvalue, &pprw->pm_value,
                                   sizeof(prw.pm_value))))
                                  break;
  
          }
          break;
  
  
          /*
           * Set the sampling rate for a sampling mode PMC and the
           * initial count for a counting mode PMC.
           */
  
          case PMC_OP_PMCSETCOUNT:
          {
                  struct pmc *pm;
                  struct pmc_op_pmcsetcount sc;
  
                  PMC_DOWNGRADE_SX();
  
                  if ((error = copyin(arg, &sc, sizeof(sc))) != 0)
                          break;
  
                  if ((error = pmc_find_pmc(sc.pm_pmcid, &pm)) != 0)
                          break;
  
                  if (pm->pm_state == PMC_STATE_RUNNING) {
                          error = EBUSY;
                          break;
                  }
  
                  if (PMC_IS_SAMPLING_MODE(PMC_TO_MODE(pm))) {
                          /*
                           * Don't permit requested sample rate to be
                           * less than pmc_mincount.
                           */
                          if (sc.pm_count < MAX(1, pmc_mincount))
                                  log(LOG_WARNING, "pmcsetcount: passed sample "
                                      "rate %ju - setting to %u\n",
                                      (uintmax_t)sc.pm_count,
                                      MAX(1, pmc_mincount));
                          pm->pm_sc.pm_reloadcount = MAX(MAX(1, pmc_mincount),
                              sc.pm_count);
                  } else
                          pm->pm_sc.pm_initial = sc.pm_count;
          }
          break;
  
  
          /*
           * Start a PMC.
           */
  
          case PMC_OP_PMCSTART:
          {
                  pmc_id_t pmcid;
                  struct pmc *pm;
                  struct pmc_op_simple sp;
  
                  sx_assert(&pmc_sx, SX_XLOCKED);
  
                  if ((error = copyin(arg, &sp, sizeof(sp))) != 0)
                          break;
  
                  pmcid = sp.pm_pmcid;
  
                  if ((error = pmc_find_pmc(pmcid, &pm)) != 0)
                          break;
  
                  KASSERT(pmcid == pm->pm_id,
                      ("[pmc,%d] pmcid %x != id %x", __LINE__,
                          pm->pm_id, pmcid));
  
                  if (pm->pm_state == PMC_STATE_RUNNING) /* already running */
                          break;
                  else if (pm->pm_state != PMC_STATE_STOPPED &&
                      pm->pm_state != PMC_STATE_ALLOCATED) {
                          error = EINVAL;
                          break;
                  }
  
                  error = pmc_start(pm);
          }
          break;
  
  
          /*
           * Stop a PMC.
           */
  
          case PMC_OP_PMCSTOP:
          {
                  pmc_id_t pmcid;
                  struct pmc *pm;
                  struct pmc_op_simple sp;
  
                  PMC_DOWNGRADE_SX();
  
                  if ((error = copyin(arg, &sp, sizeof(sp))) != 0)
                          break;
  
                  pmcid = sp.pm_pmcid;
  
                  /*
                   * Mark the PMC as inactive and invoke the MD stop
                   * routines if needed.
                   */
  
                  if ((error = pmc_find_pmc(pmcid, &pm)) != 0)
                          break;
  
                  KASSERT(pmcid == pm->pm_id,
                      ("[pmc,%d] pmc id %x != pmcid %x", __LINE__,
                          pm->pm_id, pmcid));
  
                  if (pm->pm_state == PMC_STATE_STOPPED) /* already stopped */
                          break;
                  else if (pm->pm_state != PMC_STATE_RUNNING) {
                          error = EINVAL;
                          break;
                  }
  
                  error = pmc_stop(pm);
          }
          break;
  
  
          /*
           * Write a user supplied value to the log file.
           */
  
          case PMC_OP_WRITELOG:
          {
                  struct pmc_op_writelog wl;
                  struct pmc_owner *po;
  
                  PMC_DOWNGRADE_SX();
  
                  if ((error = copyin(arg, &wl, sizeof(wl))) != 0)
                          break;
  
                  if ((po = pmc_find_owner_descriptor(td->td_proc)) == NULL) {
                          error = EINVAL;
                          break;
                  }
  
                  if ((po->po_flags & PMC_PO_OWNS_LOGFILE) == 0) {
                          error = EINVAL;
                          break;
                  }
  
                  error = pmclog_process_userlog(po, &wl);
          }
          break;
  
  
          default:
                  error = EINVAL;
                  break;
          }
  
          if (is_sx_downgraded)
                  sx_sunlock(&pmc_sx);
          else
                  sx_xunlock(&pmc_sx);
  done_syscall:
          if (error)
                  counter_u64_add(pmc_stats.pm_syscall_errors, 1);
  
          return (error);
  }
  
  /*
   * Helper functions
   */
  
  
  /*
   * Mark the thread as needing callchain capture and post an AST.  The
   * actual callchain capture will be done in a context where it is safe
   * to take page faults.
   */
  
  static void
  pmc_post_callchain_callback(void)
  {
          struct thread *td;
  
          td = curthread;
  
          /*
           * If there is multiple PMCs for the same interrupt ignore new post
           */
          if (td->td_pflags & TDP_CALLCHAIN)
                  return;
  
          /*
           * Mark this thread as needing callchain capture.
           * `td->td_pflags' will be safe to touch because this thread
           * was in user space when it was interrupted.
           */
          td->td_pflags |= TDP_CALLCHAIN;
  
          /*
           * Don't let this thread migrate between CPUs until callchain
           * capture completes.
           */
          sched_pin();
  
          return;
  }
  
  /*
   * Find a free slot in the per-cpu array of samples and capture the
   * current callchain there.  If a sample was successfully added, a bit
   * is set in mask 'pmc_cpumask' denoting that the DO_SAMPLES hook
   * needs to be invoked from the clock handler.
   *
   * This function is meant to be called from an NMI handler.  It cannot
   * use any of the locking primitives supplied by the OS.
   */
  
  static int
  pmc_add_sample(ring_type_t ring, struct pmc *pm, struct trapframe *tf)
  {
          int error, cpu, callchaindepth, inuserspace;
          struct thread *td;
          struct pmc_sample *ps;
          struct pmc_samplebuffer *psb;
  
          error = 0;
  
          /*
           * Allocate space for a sample buffer.
           */
          cpu = curcpu;
          psb = pmc_pcpu[cpu]->pc_sb[ring];
          inuserspace = TRAPF_USERMODE(tf);
          ps = PMC_PROD_SAMPLE(psb);
          if (psb->ps_considx != psb->ps_prodidx &&
                  ps->ps_nsamples) {      /* in use, reader hasn't caught up */
                  pm->pm_pcpu_state[cpu].pps_stalled = 1;
                  counter_u64_add(pmc_stats.pm_intr_bufferfull, 1);
                  PMCDBG6(SAM,INT,1,"(spc) cpu=%d pm=%p tf=%p um=%d wr=%d rd=%d",
                      cpu, pm, (void *) tf, inuserspace,
                      (int) (psb->ps_prodidx & pmc_sample_mask),
                      (int) (psb->ps_considx & pmc_sample_mask));
                  callchaindepth = 1;
                  error = ENOMEM;
                  goto done;
          }
  
          /* Fill in entry. */
          PMCDBG6(SAM,INT,1,"cpu=%d pm=%p tf=%p um=%d wr=%d rd=%d", cpu, pm,
              (void *) tf, inuserspace,
              (int) (psb->ps_prodidx & pmc_sample_mask),
              (int) (psb->ps_considx & pmc_sample_mask));
  
          td = curthread;
          ps->ps_pmc = pm;
          ps->ps_td = td;
          ps->ps_pid = td->td_proc->p_pid;
          ps->ps_tid = td->td_tid;
          ps->ps_tsc = pmc_rdtsc();
          ps->ps_ticks = ticks;
          ps->ps_cpu = cpu;
          ps->ps_flags = inuserspace ? PMC_CC_F_USERSPACE : 0;
  
          callchaindepth = (pm->pm_flags & PMC_F_CALLCHAIN) ?
              pmc_callchaindepth : 1;
  
          MPASS(ps->ps_pc != NULL);
          if (callchaindepth == 1)
                  ps->ps_pc[0] = PMC_TRAPFRAME_TO_PC(tf);
          else {
                  /*
                   * Kernel stack traversals can be done immediately,
                   * while we defer to an AST for user space traversals.
                   */
                  if (!inuserspace) {
                          callchaindepth =
                              pmc_save_kernel_callchain(ps->ps_pc,
                                  callchaindepth, tf);
                  } else {
                          pmc_post_callchain_callback();
                          callchaindepth = PMC_USER_CALLCHAIN_PENDING;
                  }
          }
  
          ps->ps_nsamples = callchaindepth;       /* mark entry as in use */
          if (ring == PMC_UR) {
                  ps->ps_nsamples_actual = callchaindepth;        /* mark entry as in use */
                  ps->ps_nsamples = PMC_USER_CALLCHAIN_PENDING;
          } else
                  ps->ps_nsamples = callchaindepth;       /* mark entry as in use */
  
          KASSERT(counter_u64_fetch(pm->pm_runcount) >= 0,
              ("[pmc,%d] pm=%p runcount %ld", __LINE__, (void *) pm,
                   (unsigned long)counter_u64_fetch(pm->pm_runcount)));
  
          counter_u64_add(pm->pm_runcount, 1);    /* hold onto PMC */
          /* increment write pointer */
          psb->ps_prodidx++;
   done:
          /* mark CPU as needing processing */
          if (callchaindepth != PMC_USER_CALLCHAIN_PENDING)
                  DPCPU_SET(pmc_sampled, 1);
  
          return (error);
  }
  
  /*
   * Interrupt processing.
   *
   * This function is meant to be called from an NMI handler.  It cannot
   * use any of the locking primitives supplied by the OS.
   */
  
  int
  pmc_process_interrupt(int ring, struct pmc *pm, struct trapframe *tf)
  {
          struct thread *td;
  
          td = curthread;
          if ((pm->pm_flags & PMC_F_USERCALLCHAIN) &&
              (td->td_proc->p_flag & P_KPROC) == 0 &&
              !TRAPF_USERMODE(tf)) {
                  atomic_add_int(&td->td_pmcpend, 1);
                  return (pmc_add_sample(PMC_UR, pm, tf));
          }
          return (pmc_add_sample(ring, pm, tf));
  }
  
  /*
   * Capture a user call chain.  This function will be called from ast()
   * before control returns to userland and before the process gets
   * rescheduled.
   */
  
  static void
  pmc_capture_user_callchain(int cpu, int ring, struct trapframe *tf)
  {
          struct pmc *pm;
          struct thread *td;
          struct pmc_sample *ps;
          struct pmc_samplebuffer *psb;
          uint64_t considx, prodidx;
          int nsamples, nrecords, pass, iter;
  #ifdef  INVARIANTS
          int start_ticks = ticks;
  #endif
          psb = pmc_pcpu[cpu]->pc_sb[ring];
          td = curthread;
  
          KASSERT(td->td_pflags & TDP_CALLCHAIN,
              ("[pmc,%d] Retrieving callchain for thread that doesn't want it",
                  __LINE__));
  
          nrecords = INT_MAX;
          pass = 0;
   restart:
          if (ring == PMC_UR)
                  nrecords = atomic_readandclear_32(&td->td_pmcpend);
  
          for (iter = 0, considx = psb->ps_considx, prodidx = psb->ps_prodidx;
              considx < prodidx && iter < pmc_nsamples; considx++, iter++) {
                  ps = PMC_CONS_SAMPLE_OFF(psb, considx);
  
          /*
           * Iterate through all deferred callchain requests.
           * Walk from the current read pointer to the current
           * write pointer.
           */
  
  #ifdef  INVARIANTS
                  if (ps->ps_nsamples == PMC_SAMPLE_FREE) {
                          continue;
                  }
  #endif
                  if (ps->ps_td != td ||
                     ps->ps_nsamples != PMC_USER_CALLCHAIN_PENDING ||
                     ps->ps_pmc->pm_state != PMC_STATE_RUNNING)
                          continue;
  
                  KASSERT(ps->ps_cpu == cpu,
                      ("[pmc,%d] cpu mismatch ps_cpu=%d pcpu=%d", __LINE__,
                          ps->ps_cpu, PCPU_GET(cpuid)));
  
                  pm = ps->ps_pmc;
  
                  KASSERT(pm->pm_flags & PMC_F_CALLCHAIN,
                      ("[pmc,%d] Retrieving callchain for PMC that doesn't "
                          "want it", __LINE__));
  
                  KASSERT(counter_u64_fetch(pm->pm_runcount) > 0,
                      ("[pmc,%d] runcount %ld", __LINE__, (unsigned long)counter_u64_fetch(pm->pm_runcount)));
  
                  if (ring == PMC_UR) {
                          nsamples = ps->ps_nsamples_actual;
                          counter_u64_add(pmc_stats.pm_merges, 1);
                  } else
                          nsamples = 0;
  
                  /*
                   * Retrieve the callchain and mark the sample buffer
                   * as 'processable' by the timer tick sweep code.
                   */
  
                  if (__predict_true(nsamples < pmc_callchaindepth - 1))
                          nsamples += pmc_save_user_callchain(ps->ps_pc + nsamples,
                         pmc_callchaindepth - nsamples - 1, tf);
  
                  /*
                   * We have to prevent hardclock from potentially overwriting
                   * this sample between when we read the value and when we set
                   * it
                   */
                  spinlock_enter();
                  /*
                   * Verify that the sample hasn't been dropped in the meantime
                   */
                  if (ps->ps_nsamples == PMC_USER_CALLCHAIN_PENDING) {
                          ps->ps_nsamples = nsamples;
                          /*
                           * If we couldn't get a sample, simply drop the reference
                           */
                          if (nsamples == 0)
                                  counter_u64_add(pm->pm_runcount, -1);
                  }
                  spinlock_exit();
                  if (nrecords-- == 1)
                          break;
          }
          if (__predict_false(ring == PMC_UR && td->td_pmcpend)) {
                  if (pass == 0) {
                          pass = 1;
                          goto restart;
                  }
                  /* only collect samples for this part once */
                  td->td_pmcpend = 0;
          }
  
  #ifdef INVARIANTS
          if ((ticks - start_ticks) > hz)
                  log(LOG_ERR, "%s took %d ticks\n", __func__, (ticks - start_ticks));
  #endif
  
          /* mark CPU as needing processing */
          DPCPU_SET(pmc_sampled, 1);
  }
  
  /*
   * Process saved PC samples.
   */
  
  static void
  pmc_process_samples(int cpu, ring_type_t ring)
  {
          struct pmc *pm;
          int adjri, n;
          struct thread *td;
          struct pmc_owner *po;
          struct pmc_sample *ps;
          struct pmc_classdep *pcd;
          struct pmc_samplebuffer *psb;
          uint64_t delta __diagused;
  
          KASSERT(PCPU_GET(cpuid) == cpu,
              ("[pmc,%d] not on the correct CPU pcpu=%d cpu=%d", __LINE__,
                  PCPU_GET(cpuid), cpu));
  
          psb = pmc_pcpu[cpu]->pc_sb[ring];
          delta = psb->ps_prodidx - psb->ps_considx;
          MPASS(delta <= pmc_nsamples);
          MPASS(psb->ps_considx <= psb->ps_prodidx);
          for (n = 0; psb->ps_considx < psb->ps_prodidx; psb->ps_considx++, n++) {
                  ps = PMC_CONS_SAMPLE(psb);
  
                  if (__predict_false(ps->ps_nsamples == PMC_SAMPLE_FREE))
                          continue;
                  pm = ps->ps_pmc;
                  /* skip non-running samples */
                  if (pm->pm_state != PMC_STATE_RUNNING)
                          goto entrydone;
  
                  KASSERT(counter_u64_fetch(pm->pm_runcount) > 0,
                      ("[pmc,%d] pm=%p runcount %ld", __LINE__, (void *) pm,
                           (unsigned long)counter_u64_fetch(pm->pm_runcount)));
  
                  po = pm->pm_owner;
  
                  KASSERT(PMC_IS_SAMPLING_MODE(PMC_TO_MODE(pm)),
                      ("[pmc,%d] pmc=%p non-sampling mode=%d", __LINE__,
                          pm, PMC_TO_MODE(pm)));
  
  
                  /* If there is a pending AST wait for completion */
                  if (ps->ps_nsamples == PMC_USER_CALLCHAIN_PENDING) {
                          /* if we've been waiting more than 1 tick to 
                           * collect a callchain for this record then
                           * drop it and move on.
                           */
                          if (ticks - ps->ps_ticks > 1) {
                                  /*
                                   * track how often we hit this as it will
                                   * preferentially lose user samples
                                   * for long running system calls 
                                   */
                                  counter_u64_add(pmc_stats.pm_overwrites, 1);
                                  goto entrydone;
                          }
                          /* Need a rescan at a later time. */
                          DPCPU_SET(pmc_sampled, 1);
                          break;
                  }
  
                  PMCDBG6(SAM,OPS,1,"cpu=%d pm=%p n=%d fl=%x wr=%d rd=%d", cpu,
                      pm, ps->ps_nsamples, ps->ps_flags,
                      (int) (psb->ps_prodidx & pmc_sample_mask),
                      (int) (psb->ps_considx & pmc_sample_mask));
  
                  /*
                   * If this is a process-mode PMC that is attached to
                   * its owner, and if the PC is in user mode, update
                   * profiling statistics like timer-based profiling
                   * would have done.
                   *
                   * Otherwise, this is either a sampling-mode PMC that
                   * is attached to a different process than its owner,
                   * or a system-wide sampling PMC. Dispatch a log
                   * entry to the PMC's owner process.
                   */
                  if (pm->pm_flags & PMC_F_ATTACHED_TO_OWNER) {
                          if (ps->ps_flags & PMC_CC_F_USERSPACE) {
                                  td = FIRST_THREAD_IN_PROC(po->po_owner);
                                  addupc_intr(td, ps->ps_pc[0], 1);
                          }
                  } else
                          pmclog_process_callchain(pm, ps);
  
          entrydone:
                  ps->ps_nsamples = 0; /* mark entry as free */
                  KASSERT(counter_u64_fetch(pm->pm_runcount) > 0,
                                  ("[pmc,%d] pm=%p runcount %ld", __LINE__, (void *) pm,
                                   (unsigned long)counter_u64_fetch(pm->pm_runcount)));
  
                  counter_u64_add(pm->pm_runcount, -1);
          }
  
          counter_u64_add(pmc_stats.pm_log_sweeps, 1);
  
          /* Do not re-enable stalled PMCs if we failed to process any samples */
          if (n == 0)
                  return;
  
          /*
           * Restart any stalled sampling PMCs on this CPU.
           *
           * If the NMI handler sets the pm_stalled field of a PMC after
           * the check below, we'll end up processing the stalled PMC at
           * the next hardclock tick.
           */
          for (n = 0; n < md->pmd_npmc; n++) {
                  pcd = pmc_ri_to_classdep(md, n, &adjri);
                  KASSERT(pcd != NULL,
                      ("[pmc,%d] null pcd ri=%d", __LINE__, n));
                  (void) (*pcd->pcd_get_config)(cpu,adjri,&pm);
  
                  if (pm == NULL ||                        /* !cfg'ed */
                      pm->pm_state != PMC_STATE_RUNNING || /* !active */
                      !PMC_IS_SAMPLING_MODE(PMC_TO_MODE(pm)) || /* !sampling */
                          !pm->pm_pcpu_state[cpu].pps_cpustate  || /* !desired */
                      !pm->pm_pcpu_state[cpu].pps_stalled) /* !stalled */
                          continue;
  
                  pm->pm_pcpu_state[cpu].pps_stalled = 0;
                  (*pcd->pcd_start_pmc)(cpu, adjri);
          }
  }
  
  /*
   * Event handlers.
   */
  
  /*
   * Handle a process exit.
   *
   * Remove this process from all hash tables.  If this process
   * owned any PMCs, turn off those PMCs and deallocate them,
   * removing any associations with target processes.
   *
   * This function will be called by the last 'thread' of a
   * process.
   *
   * XXX This eventhandler gets called early in the exit process.
   * Consider using a 'hook' invocation from thread_exit() or equivalent
   * spot.  Another negative is that kse_exit doesn't seem to call
   * exit1() [??].
   *
   */
  
  static void
  pmc_process_exit(void *arg __unused, struct proc *p)
  {
          struct pmc *pm;
          int adjri, cpu;
          unsigned int ri;
          int is_using_hwpmcs;
          struct pmc_owner *po;
          struct pmc_process *pp;
          struct pmc_classdep *pcd;
          pmc_value_t newvalue, tmp;
  
          PROC_LOCK(p);
          is_using_hwpmcs = p->p_flag & P_HWPMC;
          PROC_UNLOCK(p);
  
          /*
           * Log a sysexit event to all SS PMC owners.
           */
          PMC_EPOCH_ENTER();
          CK_LIST_FOREACH(po, &pmc_ss_owners, po_ssnext)
              if (po->po_flags & PMC_PO_OWNS_LOGFILE)
                      pmclog_process_sysexit(po, p->p_pid);
          PMC_EPOCH_EXIT();
  
          if (!is_using_hwpmcs)
                  return;
  
          PMC_GET_SX_XLOCK();
          PMCDBG3(PRC,EXT,1,"process-exit proc=%p (%d, %s)", p, p->p_pid,
              p->p_comm);
  
          /*
           * Since this code is invoked by the last thread in an exiting
           * process, we would have context switched IN at some prior
           * point.  However, with PREEMPTION, kernel mode context
           * switches may happen any time, so we want to disable a
           * context switch OUT till we get any PMCs targeting this
           * process off the hardware.
           *
           * We also need to atomically remove this process'
           * entry from our target process hash table, using
           * PMC_FLAG_REMOVE.
           */
          PMCDBG3(PRC,EXT,1, "process-exit proc=%p (%d, %s)", p, p->p_pid,
              p->p_comm);
  
          critical_enter(); /* no preemption */
  
          cpu = curthread->td_oncpu;
  
          if ((pp = pmc_find_process_descriptor(p,
                   PMC_FLAG_REMOVE)) != NULL) {
  
                  PMCDBG2(PRC,EXT,2,
                      "process-exit proc=%p pmc-process=%p", p, pp);
  
                  /*
                   * The exiting process could the target of
                   * some PMCs which will be running on
                   * currently executing CPU.
                   *
                   * We need to turn these PMCs off like we
                   * would do at context switch OUT time.
                   */
                  for (ri = 0; ri < md->pmd_npmc; ri++) {
  
                          /*
                           * Pick up the pmc pointer from hardware
                           * state similar to the CSW_OUT code.
                           */
                          pm = NULL;
  
                          pcd = pmc_ri_to_classdep(md, ri, &adjri);
  
                          (void) (*pcd->pcd_get_config)(cpu, adjri, &pm);
  
                          PMCDBG2(PRC,EXT,2, "ri=%d pm=%p", ri, pm);
  
                          if (pm == NULL ||
                              !PMC_IS_VIRTUAL_MODE(PMC_TO_MODE(pm)))
                                  continue;
  
                          PMCDBG4(PRC,EXT,2, "ppmcs[%d]=%p pm=%p "
                              "state=%d", ri, pp->pp_pmcs[ri].pp_pmc,
                              pm, pm->pm_state);
  
                          KASSERT(PMC_TO_ROWINDEX(pm) == ri,
                              ("[pmc,%d] ri mismatch pmc(%d) ri(%d)",
                                  __LINE__, PMC_TO_ROWINDEX(pm), ri));
  
                          KASSERT(pm == pp->pp_pmcs[ri].pp_pmc,
                              ("[pmc,%d] pm %p != pp_pmcs[%d] %p",
                                  __LINE__, pm, ri, pp->pp_pmcs[ri].pp_pmc));
  
                          KASSERT(counter_u64_fetch(pm->pm_runcount) > 0,
                              ("[pmc,%d] bad runcount ri %d rc %ld",
                                   __LINE__, ri, (unsigned long)counter_u64_fetch(pm->pm_runcount)));
  
                          /*
                           * Change desired state, and then stop if not
                           * stalled. This two-step dance should avoid
                           * race conditions where an interrupt re-enables
                           * the PMC after this code has already checked
                           * the pm_stalled flag.
                           */
                          if (pm->pm_pcpu_state[cpu].pps_cpustate) {
                                  pm->pm_pcpu_state[cpu].pps_cpustate = 0;
                                  if (!pm->pm_pcpu_state[cpu].pps_stalled) {
                                          (void) pcd->pcd_stop_pmc(cpu, adjri);
  
                                          if (PMC_TO_MODE(pm) == PMC_MODE_TC) {
                                                  pcd->pcd_read_pmc(cpu, adjri,
                                                      &newvalue);
                                                  tmp = newvalue -
                                                      PMC_PCPU_SAVED(cpu,ri);
  
                                                  mtx_pool_lock_spin(pmc_mtxpool,
                                                      pm);
                                                  pm->pm_gv.pm_savedvalue += tmp;
                                                  pp->pp_pmcs[ri].pp_pmcval +=
                                                      tmp;
                                                  mtx_pool_unlock_spin(
                                                      pmc_mtxpool, pm);
                                          }
                                  }
                          }
  
                          KASSERT((int64_t) counter_u64_fetch(pm->pm_runcount) > 0,
                              ("[pmc,%d] runcount is %d", __LINE__, ri));
  
                          counter_u64_add(pm->pm_runcount, -1);
  
                          (void) pcd->pcd_config_pmc(cpu, adjri, NULL);
                  }
  
                  /*
                   * Inform the MD layer of this pseudo "context switch
                   * out"
                   */
                  (void) md->pmd_switch_out(pmc_pcpu[cpu], pp);
  
                  critical_exit(); /* ok to be pre-empted now */
  
                  /*
                   * Unlink this process from the PMCs that are
                   * targeting it.  This will send a signal to
                   * all PMC owner's whose PMCs are orphaned.
                   *
                   * Log PMC value at exit time if requested.
                   */
                  for (ri = 0; ri < md->pmd_npmc; ri++)
                          if ((pm = pp->pp_pmcs[ri].pp_pmc) != NULL) {
                                  if (pm->pm_flags & PMC_F_NEEDS_LOGFILE &&
                                      PMC_IS_COUNTING_MODE(PMC_TO_MODE(pm)))
                                          pmclog_process_procexit(pm, pp);
                                  pmc_unlink_target_process(pm, pp);
                          }
                  free(pp, M_PMC);
  
          } else
                  critical_exit(); /* pp == NULL */
  
  
          /*
           * If the process owned PMCs, free them up and free up
           * memory.
           */
          if ((po = pmc_find_owner_descriptor(p)) != NULL) {
                  pmc_remove_owner(po);
                  pmc_destroy_owner_descriptor(po);
          }
  
          sx_xunlock(&pmc_sx);
  }
  
  /*
   * Handle a process fork.
   *
   * If the parent process 'p1' is under HWPMC monitoring, then copy
   * over any attached PMCs that have 'do_descendants' semantics.
   */
  
  static void
  pmc_process_fork(void *arg __unused, struct proc *p1, struct proc *newproc,
      int flags)
  {
          int is_using_hwpmcs;
          unsigned int ri;
          uint32_t do_descendants;
          struct pmc *pm;
          struct pmc_owner *po;
          struct pmc_process *ppnew, *ppold;
  
          (void) flags;           /* unused parameter */
  
          PROC_LOCK(p1);
          is_using_hwpmcs = p1->p_flag & P_HWPMC;
          PROC_UNLOCK(p1);
  
          /*
           * If there are system-wide sampling PMCs active, we need to
           * log all fork events to their owner's logs.
           */
          PMC_EPOCH_ENTER();
          CK_LIST_FOREACH(po, &pmc_ss_owners, po_ssnext)
              if (po->po_flags & PMC_PO_OWNS_LOGFILE) {
                      pmclog_process_procfork(po, p1->p_pid, newproc->p_pid);
                          pmclog_process_proccreate(po, newproc, 1);
                  }
          PMC_EPOCH_EXIT();
  
          if (!is_using_hwpmcs)
                  return;
  
          PMC_GET_SX_XLOCK();
          PMCDBG4(PMC,FRK,1, "process-fork proc=%p (%d, %s) -> %p", p1,
              p1->p_pid, p1->p_comm, newproc);
  
          /*
           * If the parent process (curthread->td_proc) is a
           * target of any PMCs, look for PMCs that are to be
           * inherited, and link these into the new process
           * descriptor.
           */
          if ((ppold = pmc_find_process_descriptor(curthread->td_proc,
                   PMC_FLAG_NONE)) == NULL)
                  goto done;              /* nothing to do */
  
          do_descendants = 0;
          for (ri = 0; ri < md->pmd_npmc; ri++)
                  if ((pm = ppold->pp_pmcs[ri].pp_pmc) != NULL)
                          do_descendants |= pm->pm_flags & PMC_F_DESCENDANTS;
          if (do_descendants == 0) /* nothing to do */
                  goto done;
  
          /*
           * Now mark the new process as being tracked by this driver.
           */
          PROC_LOCK(newproc);
          newproc->p_flag |= P_HWPMC;
          PROC_UNLOCK(newproc);
  
          /* allocate a descriptor for the new process  */
          if ((ppnew = pmc_find_process_descriptor(newproc,
                   PMC_FLAG_ALLOCATE)) == NULL)
                  goto done;
  
          /*
           * Run through all PMCs that were targeting the old process
           * and which specified F_DESCENDANTS and attach them to the
           * new process.
           *
           * Log the fork event to all owners of PMCs attached to this
           * process, if not already logged.
           */
          for (ri = 0; ri < md->pmd_npmc; ri++)
                  if ((pm = ppold->pp_pmcs[ri].pp_pmc) != NULL &&
                      (pm->pm_flags & PMC_F_DESCENDANTS)) {
                          pmc_link_target_process(pm, ppnew);
                          po = pm->pm_owner;
                          if (po->po_sscount == 0 &&
                              po->po_flags & PMC_PO_OWNS_LOGFILE)
                                  pmclog_process_procfork(po, p1->p_pid,
                                      newproc->p_pid);
                  }
  
   done:
          sx_xunlock(&pmc_sx);
  }
  
  static void
  pmc_process_threadcreate(struct thread *td)
  {
          struct pmc_owner *po;
  
          PMC_EPOCH_ENTER();
          CK_LIST_FOREACH(po, &pmc_ss_owners, po_ssnext)
              if (po->po_flags & PMC_PO_OWNS_LOGFILE)
                          pmclog_process_threadcreate(po, td, 1);
          PMC_EPOCH_EXIT();
  }
  
  static void
  pmc_process_threadexit(struct thread *td)
  {
          struct pmc_owner *po;
  
          PMC_EPOCH_ENTER();
          CK_LIST_FOREACH(po, &pmc_ss_owners, po_ssnext)
              if (po->po_flags & PMC_PO_OWNS_LOGFILE)
                          pmclog_process_threadexit(po, td);
          PMC_EPOCH_EXIT();
  }
  
  static void
  pmc_process_proccreate(struct proc *p)
  {
          struct pmc_owner *po;
  
          PMC_EPOCH_ENTER();
          CK_LIST_FOREACH(po, &pmc_ss_owners, po_ssnext)
              if (po->po_flags & PMC_PO_OWNS_LOGFILE)
                          pmclog_process_proccreate(po, p, 1 /* sync */);
          PMC_EPOCH_EXIT();
  }
  
  static void
  pmc_process_allproc(struct pmc *pm)
  {
          struct pmc_owner *po;
          struct thread *td;
          struct proc *p;
  
          po = pm->pm_owner;
          if ((po->po_flags & PMC_PO_OWNS_LOGFILE) == 0)
                  return;
          sx_slock(&allproc_lock);
          FOREACH_PROC_IN_SYSTEM(p) {
                  pmclog_process_proccreate(po, p, 0 /* sync */);
                  PROC_LOCK(p);
                  FOREACH_THREAD_IN_PROC(p, td)
                          pmclog_process_threadcreate(po, td, 0 /* sync */);
                  PROC_UNLOCK(p);
          }
          sx_sunlock(&allproc_lock);
          pmclog_flush(po, 0);
  }
  
  static void
  pmc_kld_load(void *arg __unused, linker_file_t lf)
  {
          struct pmc_owner *po;
  
          /*
           * Notify owners of system sampling PMCs about KLD operations.
           */
          PMC_EPOCH_ENTER();
          CK_LIST_FOREACH(po, &pmc_ss_owners, po_ssnext)
                  if (po->po_flags & PMC_PO_OWNS_LOGFILE)
                          pmclog_process_map_in(po, (pid_t) -1,
                              (uintfptr_t) lf->address, lf->filename);
          PMC_EPOCH_EXIT();
  
          /*
           * TODO: Notify owners of (all) process-sampling PMCs too.
           */
  }
  
  static void
  pmc_kld_unload(void *arg __unused, const char *filename __unused,
      caddr_t address, size_t size)
  {
          struct pmc_owner *po;
  
          PMC_EPOCH_ENTER();
          CK_LIST_FOREACH(po, &pmc_ss_owners, po_ssnext)
                  if (po->po_flags & PMC_PO_OWNS_LOGFILE)
                          pmclog_process_map_out(po, (pid_t) -1,
                              (uintfptr_t) address, (uintfptr_t) address + size);
          PMC_EPOCH_EXIT();
  
          /*
           * TODO: Notify owners of process-sampling PMCs.
           */
  }
  
  /*
   * initialization
   */
  static const char *
  pmc_name_of_pmcclass(enum pmc_class class)
  {
  
          switch (class) {
  #undef  __PMC_CLASS
  #define __PMC_CLASS(S,V,D)                                              \
          case PMC_CLASS_##S:                                             \
                  return #S;
          __PMC_CLASSES();
          default:
                  return ("<unknown>");
          }
  }
  
  /*
   * Base class initializer: allocate structure and set default classes.
   */
  struct pmc_mdep *
  pmc_mdep_alloc(int nclasses)
  {
          struct pmc_mdep *md;
          int     n;
  
          /* SOFT + md classes */
          n = 1 + nclasses;
          md = malloc(sizeof(struct pmc_mdep) + n *
              sizeof(struct pmc_classdep), M_PMC, M_WAITOK|M_ZERO);
          md->pmd_nclass = n;
  
          /* Add base class. */
          pmc_soft_initialize(md);
          return md;
  }
  
  void
  pmc_mdep_free(struct pmc_mdep *md)
  {
          pmc_soft_finalize(md);
          free(md, M_PMC);
  }
  
  static int
  generic_switch_in(struct pmc_cpu *pc, struct pmc_process *pp)
  {
          (void) pc; (void) pp;
  
          return (0);
  }
  
  static int
  generic_switch_out(struct pmc_cpu *pc, struct pmc_process *pp)
  {
          (void) pc; (void) pp;
  
          return (0);
  }
  
  static struct pmc_mdep *
  pmc_generic_cpu_initialize(void)
  {
          struct pmc_mdep *md;
  
          md = pmc_mdep_alloc(0);
  
          md->pmd_cputype    = PMC_CPU_GENERIC;
  
          md->pmd_pcpu_init  = NULL;
          md->pmd_pcpu_fini  = NULL;
          md->pmd_switch_in  = generic_switch_in;
          md->pmd_switch_out = generic_switch_out;
  
          return (md);
  }
  
  static void
  pmc_generic_cpu_finalize(struct pmc_mdep *md)
  {
          (void) md;
  }
  
  
  static int
  pmc_initialize(void)
  {
          int c, cpu, error, n, ri;
          unsigned int maxcpu, domain;
          struct pcpu *pc;
          struct pmc_binding pb;
          struct pmc_sample *ps;
          struct pmc_classdep *pcd;
          struct pmc_samplebuffer *sb;
  
          md = NULL;
          error = 0;
  
          pmc_stats.pm_intr_ignored = counter_u64_alloc(M_WAITOK);
          pmc_stats.pm_intr_processed = counter_u64_alloc(M_WAITOK);
          pmc_stats.pm_intr_bufferfull = counter_u64_alloc(M_WAITOK);
          pmc_stats.pm_syscalls = counter_u64_alloc(M_WAITOK);
          pmc_stats.pm_syscall_errors = counter_u64_alloc(M_WAITOK);
          pmc_stats.pm_buffer_requests = counter_u64_alloc(M_WAITOK);
          pmc_stats.pm_buffer_requests_failed = counter_u64_alloc(M_WAITOK);
          pmc_stats.pm_log_sweeps = counter_u64_alloc(M_WAITOK);
          pmc_stats.pm_merges = counter_u64_alloc(M_WAITOK);
          pmc_stats.pm_overwrites = counter_u64_alloc(M_WAITOK);
  
  #ifdef  HWPMC_DEBUG
          /* parse debug flags first */
          if (TUNABLE_STR_FETCH(PMC_SYSCTL_NAME_PREFIX "debugflags",
                  pmc_debugstr, sizeof(pmc_debugstr)))
                  pmc_debugflags_parse(pmc_debugstr,
                      pmc_debugstr+strlen(pmc_debugstr));
  #endif
  
          PMCDBG1(MOD,INI,0, "PMC Initialize (version %x)", PMC_VERSION);
  
          /* check kernel version */
          if (pmc_kernel_version != PMC_VERSION) {
                  if (pmc_kernel_version == 0)
                          printf("hwpmc: this kernel has not been compiled with "
                              "'options HWPMC_HOOKS'.\n");
                  else
                          printf("hwpmc: kernel version (0x%x) does not match "
                              "module version (0x%x).\n", pmc_kernel_version,
                              PMC_VERSION);
                  return EPROGMISMATCH;
          }
  
          /*
           * check sysctl parameters
           */
  
          if (pmc_hashsize <= 0) {
                  (void) printf("hwpmc: tunable \"hashsize\"=%d must be "
                      "greater than zero.\n", pmc_hashsize);
                  pmc_hashsize = PMC_HASH_SIZE;
          }
  
          if (pmc_nsamples <= 0 || pmc_nsamples > 65535) {
                  (void) printf("hwpmc: tunable \"nsamples\"=%d out of "
                      "range.\n", pmc_nsamples);
                  pmc_nsamples = PMC_NSAMPLES;
          }
          pmc_sample_mask = pmc_nsamples-1;
  
          if (pmc_callchaindepth <= 0 ||
              pmc_callchaindepth > PMC_CALLCHAIN_DEPTH_MAX) {
                  (void) printf("hwpmc: tunable \"callchaindepth\"=%d out of "
                      "range - using %d.\n", pmc_callchaindepth,
                      PMC_CALLCHAIN_DEPTH_MAX);
                  pmc_callchaindepth = PMC_CALLCHAIN_DEPTH_MAX;
          }
  
          md = pmc_md_initialize();
          if (md == NULL) {
                  /* Default to generic CPU. */
                  md = pmc_generic_cpu_initialize();
                  if (md == NULL)
                          return (ENOSYS);
          }
  
          /*
           * Refresh classes base ri. Optional classes may come in different
           * order.
           */
          for (ri = c = 0; c < md->pmd_nclass; c++) {
                  pcd = &md->pmd_classdep[c];
                  pcd->pcd_ri = ri;
                  ri += pcd->pcd_num;
          }
  
          KASSERT(md->pmd_nclass >= 1 && md->pmd_npmc >= 1,
              ("[pmc,%d] no classes or pmcs", __LINE__));
  
          /* Compute the map from row-indices to classdep pointers. */
          pmc_rowindex_to_classdep = malloc(sizeof(struct pmc_classdep *) *
              md->pmd_npmc, M_PMC, M_WAITOK|M_ZERO);
  
          for (n = 0; n < md->pmd_npmc; n++)
                  pmc_rowindex_to_classdep[n] = NULL;
          for (ri = c = 0; c < md->pmd_nclass; c++) {
                  pcd = &md->pmd_classdep[c];
                  for (n = 0; n < pcd->pcd_num; n++, ri++)
                          pmc_rowindex_to_classdep[ri] = pcd;
          }
  
          KASSERT(ri == md->pmd_npmc,
              ("[pmc,%d] npmc miscomputed: ri=%d, md->npmc=%d", __LINE__,
              ri, md->pmd_npmc));
  
          maxcpu = pmc_cpu_max();
  
          /* allocate space for the per-cpu array */
          pmc_pcpu = malloc(maxcpu * sizeof(struct pmc_cpu *), M_PMC,
              M_WAITOK|M_ZERO);
  
          /* per-cpu 'saved values' for managing process-mode PMCs */
          pmc_pcpu_saved = malloc(sizeof(pmc_value_t) * maxcpu * md->pmd_npmc,
              M_PMC, M_WAITOK);
  
          /* Perform CPU-dependent initialization. */
          pmc_save_cpu_binding(&pb);
          error = 0;
          for (cpu = 0; error == 0 && cpu < maxcpu; cpu++) {
                  if (!pmc_cpu_is_active(cpu))
                          continue;
                  pmc_select_cpu(cpu);
                  pmc_pcpu[cpu] = malloc(sizeof(struct pmc_cpu) +
                      md->pmd_npmc * sizeof(struct pmc_hw *), M_PMC,
                      M_WAITOK|M_ZERO);
                  if (md->pmd_pcpu_init)
                          error = md->pmd_pcpu_init(md, cpu);
                  for (n = 0; error == 0 && n < md->pmd_nclass; n++)
                          if (md->pmd_classdep[n].pcd_num > 0)
                                  error = md->pmd_classdep[n].pcd_pcpu_init(md,
                                      cpu);
          }
          pmc_restore_cpu_binding(&pb);
  
          if (error)
                  return (error);
  
          /* allocate space for the sample array */
          for (cpu = 0; cpu < maxcpu; cpu++) {
                  if (!pmc_cpu_is_active(cpu))
                          continue;
                  pc = pcpu_find(cpu);
                  domain = pc->pc_domain;
                  sb = malloc_domainset(sizeof(struct pmc_samplebuffer) +
                      pmc_nsamples * sizeof(struct pmc_sample), M_PMC,
                      DOMAINSET_PREF(domain), M_WAITOK | M_ZERO);
  
                  KASSERT(pmc_pcpu[cpu] != NULL,
                      ("[pmc,%d] cpu=%d Null per-cpu data", __LINE__, cpu));
  
                  sb->ps_callchains = malloc_domainset(pmc_callchaindepth *
                      pmc_nsamples * sizeof(uintptr_t), M_PMC,
                      DOMAINSET_PREF(domain), M_WAITOK | M_ZERO);
  
                  for (n = 0, ps = sb->ps_samples; n < pmc_nsamples; n++, ps++)
                          ps->ps_pc = sb->ps_callchains +
                              (n * pmc_callchaindepth);
  
                  pmc_pcpu[cpu]->pc_sb[PMC_HR] = sb;
  
                  sb = malloc_domainset(sizeof(struct pmc_samplebuffer) +
                      pmc_nsamples * sizeof(struct pmc_sample), M_PMC,
                      DOMAINSET_PREF(domain), M_WAITOK | M_ZERO);
  
                  sb->ps_callchains = malloc_domainset(pmc_callchaindepth *
                      pmc_nsamples * sizeof(uintptr_t), M_PMC,
                      DOMAINSET_PREF(domain), M_WAITOK | M_ZERO);
                  for (n = 0, ps = sb->ps_samples; n < pmc_nsamples; n++, ps++)
                          ps->ps_pc = sb->ps_callchains +
                              (n * pmc_callchaindepth);
  
                  pmc_pcpu[cpu]->pc_sb[PMC_SR] = sb;
  
                  sb = malloc_domainset(sizeof(struct pmc_samplebuffer) +
                      pmc_nsamples * sizeof(struct pmc_sample), M_PMC,
                      DOMAINSET_PREF(domain), M_WAITOK | M_ZERO);
                  sb->ps_callchains = malloc_domainset(pmc_callchaindepth *
                      pmc_nsamples * sizeof(uintptr_t), M_PMC,
                      DOMAINSET_PREF(domain), M_WAITOK | M_ZERO);
                  for (n = 0, ps = sb->ps_samples; n < pmc_nsamples; n++, ps++)
                          ps->ps_pc = sb->ps_callchains + n * pmc_callchaindepth;
  
                  pmc_pcpu[cpu]->pc_sb[PMC_UR] = sb;
          }
  
          /* allocate space for the row disposition array */
          pmc_pmcdisp = malloc(sizeof(enum pmc_mode) * md->pmd_npmc,
              M_PMC, M_WAITOK|M_ZERO);
  
          /* mark all PMCs as available */
          for (n = 0; n < (int) md->pmd_npmc; n++)
                  PMC_MARK_ROW_FREE(n);
  
          /* allocate thread hash tables */
          pmc_ownerhash = hashinit(pmc_hashsize, M_PMC,
              &pmc_ownerhashmask);
  
          pmc_processhash = hashinit(pmc_hashsize, M_PMC,
              &pmc_processhashmask);
          mtx_init(&pmc_processhash_mtx, "pmc-process-hash", "pmc-leaf",
              MTX_SPIN);
  
          CK_LIST_INIT(&pmc_ss_owners);
          pmc_ss_count = 0;
  
          /* allocate a pool of spin mutexes */
          pmc_mtxpool = mtx_pool_create("pmc-leaf", pmc_mtxpool_size,
              MTX_SPIN);
  
          PMCDBG4(MOD,INI,1, "pmc_ownerhash=%p, mask=0x%lx "
              "targethash=%p mask=0x%lx", pmc_ownerhash, pmc_ownerhashmask,
              pmc_processhash, pmc_processhashmask);
  
          /* Initialize a spin mutex for the thread free list. */
          mtx_init(&pmc_threadfreelist_mtx, "pmc-threadfreelist", "pmc-leaf",
              MTX_SPIN);
  
          /* Initialize the task to prune the thread free list. */
          TASK_INIT(&free_task, 0, pmc_thread_descriptor_pool_free_task, NULL);
  
          /* register process {exit,fork,exec} handlers */
          pmc_exit_tag = EVENTHANDLER_REGISTER(process_exit,
              pmc_process_exit, NULL, EVENTHANDLER_PRI_ANY);
          pmc_fork_tag = EVENTHANDLER_REGISTER(process_fork,
              pmc_process_fork, NULL, EVENTHANDLER_PRI_ANY);
  
          /* register kld event handlers */
          pmc_kld_load_tag = EVENTHANDLER_REGISTER(kld_load, pmc_kld_load,
              NULL, EVENTHANDLER_PRI_ANY);
          pmc_kld_unload_tag = EVENTHANDLER_REGISTER(kld_unload, pmc_kld_unload,
              NULL, EVENTHANDLER_PRI_ANY);
  
          /* initialize logging */
          pmclog_initialize();
  
          /* set hook functions */
          pmc_intr = md->pmd_intr;
          wmb();
          pmc_hook = pmc_hook_handler;
  
          if (error == 0) {
                  printf(PMC_MODULE_NAME ":");
                  for (n = 0; n < (int) md->pmd_nclass; n++) {
                          if (md->pmd_classdep[n].pcd_num == 0)
                                  continue;
                          pcd = &md->pmd_classdep[n];
                          printf(" %s/%d/%d/0x%b",
                              pmc_name_of_pmcclass(pcd->pcd_class),
                              pcd->pcd_num,
                              pcd->pcd_width,
                              pcd->pcd_caps,
                              "\2"
                              "\1INT\2USR\3SYS\4EDG\5THR"
                              "\6REA\7WRI\10INV\11QUA\12PRC"
                              "\13TAG\14CSC");
                  }
                  printf("\n");
          }
  
          return (error);
  }
  
  /* prepare to be unloaded */
  static void
  pmc_cleanup(void)
  {
          int c, cpu;
          unsigned int maxcpu;
          struct pmc_ownerhash *ph;
          struct pmc_owner *po, *tmp;
          struct pmc_binding pb;
  #ifdef  HWPMC_DEBUG
          struct pmc_processhash *prh;
  #endif
  
          PMCDBG0(MOD,INI,0, "cleanup");
  
          /* switch off sampling */
          CPU_FOREACH(cpu)
                  DPCPU_ID_SET(cpu, pmc_sampled, 0);
          pmc_intr = NULL;
  
          sx_xlock(&pmc_sx);
          if (pmc_hook == NULL) { /* being unloaded already */
                  sx_xunlock(&pmc_sx);
                  return;
          }
  
          pmc_hook = NULL; /* prevent new threads from entering module */
  
          /* deregister event handlers */
          EVENTHANDLER_DEREGISTER(process_fork, pmc_fork_tag);
          EVENTHANDLER_DEREGISTER(process_exit, pmc_exit_tag);
          EVENTHANDLER_DEREGISTER(kld_load, pmc_kld_load_tag);
          EVENTHANDLER_DEREGISTER(kld_unload, pmc_kld_unload_tag);
  
          /* send SIGBUS to all owner threads, free up allocations */
          if (pmc_ownerhash)
                  for (ph = pmc_ownerhash;
                       ph <= &pmc_ownerhash[pmc_ownerhashmask];
                       ph++) {
                          LIST_FOREACH_SAFE(po, ph, po_next, tmp) {
                                  pmc_remove_owner(po);
  
                                  /* send SIGBUS to owner processes */
                                  PMCDBG3(MOD,INI,2, "cleanup signal proc=%p "
                                      "(%d, %s)", po->po_owner,
                                      po->po_owner->p_pid,
                                      po->po_owner->p_comm);
  
                                  PROC_LOCK(po->po_owner);
                                  kern_psignal(po->po_owner, SIGBUS);
                                  PROC_UNLOCK(po->po_owner);
  
                                  pmc_destroy_owner_descriptor(po);
                          }
                  }
  
          /* reclaim allocated data structures */
          taskqueue_drain(taskqueue_fast, &free_task);
          mtx_destroy(&pmc_threadfreelist_mtx);
          pmc_thread_descriptor_pool_drain();
  
          if (pmc_mtxpool)
                  mtx_pool_destroy(&pmc_mtxpool);
  
          mtx_destroy(&pmc_processhash_mtx);
          if (pmc_processhash) {
  #ifdef  HWPMC_DEBUG
                  struct pmc_process *pp;
  
                  PMCDBG0(MOD,INI,3, "destroy process hash");
                  for (prh = pmc_processhash;
                       prh <= &pmc_processhash[pmc_processhashmask];
                       prh++)
                          LIST_FOREACH(pp, prh, pp_next)
                              PMCDBG1(MOD,INI,3, "pid=%d", pp->pp_proc->p_pid);
  #endif
  
                  hashdestroy(pmc_processhash, M_PMC, pmc_processhashmask);
                  pmc_processhash = NULL;
          }
  
          if (pmc_ownerhash) {
                  PMCDBG0(MOD,INI,3, "destroy owner hash");
                  hashdestroy(pmc_ownerhash, M_PMC, pmc_ownerhashmask);
                  pmc_ownerhash = NULL;
          }
  
          KASSERT(CK_LIST_EMPTY(&pmc_ss_owners),
              ("[pmc,%d] Global SS owner list not empty", __LINE__));
          KASSERT(pmc_ss_count == 0,
              ("[pmc,%d] Global SS count not empty", __LINE__));
  
          /* do processor and pmc-class dependent cleanup */
          maxcpu = pmc_cpu_max();
  
          PMCDBG0(MOD,INI,3, "md cleanup");
          if (md) {
                  pmc_save_cpu_binding(&pb);
                  for (cpu = 0; cpu < maxcpu; cpu++) {
                          PMCDBG2(MOD,INI,1,"pmc-cleanup cpu=%d pcs=%p",
                              cpu, pmc_pcpu[cpu]);
                          if (!pmc_cpu_is_active(cpu) || pmc_pcpu[cpu] == NULL)
                                  continue;
                          pmc_select_cpu(cpu);
                          for (c = 0; c < md->pmd_nclass; c++)
                                  if (md->pmd_classdep[c].pcd_num > 0)
                                          md->pmd_classdep[c].pcd_pcpu_fini(md,
                                              cpu);
                          if (md->pmd_pcpu_fini)
                                  md->pmd_pcpu_fini(md, cpu);
                  }
  
                  if (md->pmd_cputype == PMC_CPU_GENERIC)
                          pmc_generic_cpu_finalize(md);
                  else
                          pmc_md_finalize(md);
  
                  pmc_mdep_free(md);
                  md = NULL;
                  pmc_restore_cpu_binding(&pb);
          }
  
          /* Free per-cpu descriptors. */
          for (cpu = 0; cpu < maxcpu; cpu++) {
                  if (!pmc_cpu_is_active(cpu))
                          continue;
                  KASSERT(pmc_pcpu[cpu]->pc_sb[PMC_HR] != NULL,
                      ("[pmc,%d] Null hw cpu sample buffer cpu=%d", __LINE__,
                          cpu));
                  KASSERT(pmc_pcpu[cpu]->pc_sb[PMC_SR] != NULL,
                      ("[pmc,%d] Null sw cpu sample buffer cpu=%d", __LINE__,
                          cpu));
                  KASSERT(pmc_pcpu[cpu]->pc_sb[PMC_UR] != NULL,
                      ("[pmc,%d] Null userret cpu sample buffer cpu=%d", __LINE__,
                          cpu));
                  free(pmc_pcpu[cpu]->pc_sb[PMC_HR]->ps_callchains, M_PMC);
                  free(pmc_pcpu[cpu]->pc_sb[PMC_HR], M_PMC);
                  free(pmc_pcpu[cpu]->pc_sb[PMC_SR]->ps_callchains, M_PMC);
                  free(pmc_pcpu[cpu]->pc_sb[PMC_SR], M_PMC);
                  free(pmc_pcpu[cpu]->pc_sb[PMC_UR]->ps_callchains, M_PMC);
                  free(pmc_pcpu[cpu]->pc_sb[PMC_UR], M_PMC);
                  free(pmc_pcpu[cpu], M_PMC);
          }
  
          free(pmc_pcpu, M_PMC);
          pmc_pcpu = NULL;
  
          free(pmc_pcpu_saved, M_PMC);
          pmc_pcpu_saved = NULL;
  
          if (pmc_pmcdisp) {
                  free(pmc_pmcdisp, M_PMC);
                  pmc_pmcdisp = NULL;
          }
  
          if (pmc_rowindex_to_classdep) {
                  free(pmc_rowindex_to_classdep, M_PMC);
                  pmc_rowindex_to_classdep = NULL;
          }
  
          pmclog_shutdown();
          counter_u64_free(pmc_stats.pm_intr_ignored);
          counter_u64_free(pmc_stats.pm_intr_processed);
          counter_u64_free(pmc_stats.pm_intr_bufferfull);
          counter_u64_free(pmc_stats.pm_syscalls);
          counter_u64_free(pmc_stats.pm_syscall_errors);
          counter_u64_free(pmc_stats.pm_buffer_requests);
          counter_u64_free(pmc_stats.pm_buffer_requests_failed);
          counter_u64_free(pmc_stats.pm_log_sweeps);
          counter_u64_free(pmc_stats.pm_merges);
          counter_u64_free(pmc_stats.pm_overwrites);
          sx_xunlock(&pmc_sx);    /* we are done */
  }
  
  /*
   * The function called at load/unload.
   */
  
  static int
  load (struct module *module __unused, int cmd, void *arg __unused)
  {
          int error;
  
          error = 0;
  
          switch (cmd) {
          case MOD_LOAD :
                  /* initialize the subsystem */
                  error = pmc_initialize();
                  if (error != 0)
                          break;
                  PMCDBG2(MOD,INI,1, "syscall=%d maxcpu=%d",
                      pmc_syscall_num, pmc_cpu_max());
                  break;
  
  
          case MOD_UNLOAD :
          case MOD_SHUTDOWN:
                  pmc_cleanup();
                  PMCDBG0(MOD,INI,1, "unloaded");
                  break;
  
          default :
                  error = EINVAL; /* XXX should panic(9) */
                  break;
          }
  
          return error;
  }