The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/kern/subr_trap.c

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    1 /*-
    2  * Copyright (C) 1994, David Greenman
    3  * Copyright (c) 1990, 1993
    4  *      The Regents of the University of California.  All rights reserved.
    5  * Copyright (c) 2007 The FreeBSD Foundation
    6  *
    7  * This code is derived from software contributed to Berkeley by
    8  * the University of Utah, and William Jolitz.
    9  *
   10  * Portions of this software were developed by A. Joseph Koshy under
   11  * sponsorship from the FreeBSD Foundation and Google, Inc.
   12  *
   13  * Redistribution and use in source and binary forms, with or without
   14  * modification, are permitted provided that the following conditions
   15  * are met:
   16  * 1. Redistributions of source code must retain the above copyright
   17  *    notice, this list of conditions and the following disclaimer.
   18  * 2. Redistributions in binary form must reproduce the above copyright
   19  *    notice, this list of conditions and the following disclaimer in the
   20  *    documentation and/or other materials provided with the distribution.
   21  * 3. All advertising materials mentioning features or use of this software
   22  *    must display the following acknowledgement:
   23  *      This product includes software developed by the University of
   24  *      California, Berkeley and its contributors.
   25  * 4. Neither the name of the University nor the names of its contributors
   26  *    may be used to endorse or promote products derived from this software
   27  *    without specific prior written permission.
   28  *
   29  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   30  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   31  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   32  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   33  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   34  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   35  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   36  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   37  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   38  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   39  * SUCH DAMAGE.
   40  *
   41  *      from: @(#)trap.c        7.4 (Berkeley) 5/13/91
   42  */
   43 
   44 #include <sys/cdefs.h>
   45 __FBSDID("$FreeBSD: releng/10.1/sys/kern/subr_trap.c 263875 2014-03-28 15:38:38Z kib $");
   46 
   47 #include "opt_hwpmc_hooks.h"
   48 #include "opt_ktrace.h"
   49 #include "opt_kdtrace.h"
   50 #include "opt_sched.h"
   51 
   52 #include <sys/param.h>
   53 #include <sys/bus.h>
   54 #include <sys/capability.h>
   55 #include <sys/kernel.h>
   56 #include <sys/lock.h>
   57 #include <sys/mutex.h>
   58 #include <sys/pmckern.h>
   59 #include <sys/proc.h>
   60 #include <sys/ktr.h>
   61 #include <sys/pioctl.h>
   62 #include <sys/ptrace.h>
   63 #include <sys/resourcevar.h>
   64 #include <sys/sched.h>
   65 #include <sys/signalvar.h>
   66 #include <sys/syscall.h>
   67 #include <sys/syscallsubr.h>
   68 #include <sys/sysent.h>
   69 #include <sys/systm.h>
   70 #include <sys/vmmeter.h>
   71 #ifdef KTRACE
   72 #include <sys/uio.h>
   73 #include <sys/ktrace.h>
   74 #endif
   75 #include <security/audit/audit.h>
   76 
   77 #include <machine/cpu.h>
   78 
   79 #ifdef VIMAGE
   80 #include <net/vnet.h>
   81 #endif
   82 
   83 #ifdef XEN
   84 #include <vm/vm.h>
   85 #include <vm/vm_param.h>
   86 #include <vm/pmap.h>
   87 #endif
   88 
   89 #ifdef  HWPMC_HOOKS
   90 #include <sys/pmckern.h>
   91 #endif
   92 
   93 #include <security/mac/mac_framework.h>
   94 
   95 /*
   96  * Define the code needed before returning to user mode, for trap and
   97  * syscall.
   98  */
   99 void
  100 userret(struct thread *td, struct trapframe *frame)
  101 {
  102         struct proc *p = td->td_proc;
  103 
  104         CTR3(KTR_SYSC, "userret: thread %p (pid %d, %s)", td, p->p_pid,
  105             td->td_name);
  106         KASSERT((p->p_flag & P_WEXIT) == 0,
  107             ("Exiting process returns to usermode"));
  108 #if 0
  109 #ifdef DIAGNOSTIC
  110         /* Check that we called signotify() enough. */
  111         PROC_LOCK(p);
  112         thread_lock(td);
  113         if (SIGPENDING(td) && ((td->td_flags & TDF_NEEDSIGCHK) == 0 ||
  114             (td->td_flags & TDF_ASTPENDING) == 0))
  115                 printf("failed to set signal flags properly for ast()\n");
  116         thread_unlock(td);
  117         PROC_UNLOCK(p);
  118 #endif
  119 #endif
  120 #ifdef KTRACE
  121         KTRUSERRET(td);
  122 #endif
  123         /*
  124          * If this thread tickled GEOM, we need to wait for the giggling to
  125          * stop before we return to userland
  126          */
  127         if (td->td_pflags & TDP_GEOM)
  128                 g_waitidle();
  129 
  130         /*
  131          * Charge system time if profiling.
  132          */
  133         if (p->p_flag & P_PROFIL)
  134                 addupc_task(td, TRAPF_PC(frame), td->td_pticks * psratio);
  135         /*
  136          * Let the scheduler adjust our priority etc.
  137          */
  138         sched_userret(td);
  139 #ifdef XEN
  140         PT_UPDATES_FLUSH();
  141 #endif
  142 
  143         /*
  144          * Check for misbehavior.
  145          *
  146          * In case there is a callchain tracing ongoing because of
  147          * hwpmc(4), skip the scheduler pinning check.
  148          * hwpmc(4) subsystem, infact, will collect callchain informations
  149          * at ast() checkpoint, which is past userret().
  150          */
  151         WITNESS_WARN(WARN_PANIC, NULL, "userret: returning");
  152         KASSERT(td->td_critnest == 0,
  153             ("userret: Returning in a critical section"));
  154         KASSERT(td->td_locks == 0,
  155             ("userret: Returning with %d locks held", td->td_locks));
  156         KASSERT((td->td_pflags & TDP_NOFAULTING) == 0,
  157             ("userret: Returning with pagefaults disabled"));
  158         KASSERT((td->td_pflags & TDP_DEVMEMIO) == 0,
  159             ("userret: Returning with /dev/mem i/o leaked"));
  160         KASSERT(td->td_no_sleeping == 0,
  161             ("userret: Returning with sleep disabled"));
  162         KASSERT(td->td_pinned == 0 || (td->td_pflags & TDP_CALLCHAIN) != 0,
  163             ("userret: Returning with with pinned thread"));
  164         KASSERT(td->td_vp_reserv == 0,
  165             ("userret: Returning while holding vnode reservation"));
  166         KASSERT((td->td_flags & TDF_SBDRY) == 0,
  167             ("userret: Returning with stop signals deferred"));
  168 #ifdef VIMAGE
  169         /* Unfortunately td_vnet_lpush needs VNET_DEBUG. */
  170         VNET_ASSERT(curvnet == NULL,
  171             ("%s: Returning on td %p (pid %d, %s) with vnet %p set in %s",
  172             __func__, td, p->p_pid, td->td_name, curvnet,
  173             (td->td_vnet_lpush != NULL) ? td->td_vnet_lpush : "N/A"));
  174 #endif
  175 #ifdef  RACCT
  176         PROC_LOCK(p);
  177         while (p->p_throttled == 1)
  178                 msleep(p->p_racct, &p->p_mtx, 0, "racct", 0);
  179         PROC_UNLOCK(p);
  180 #endif
  181 }
  182 
  183 /*
  184  * Process an asynchronous software trap.
  185  * This is relatively easy.
  186  * This function will return with preemption disabled.
  187  */
  188 void
  189 ast(struct trapframe *framep)
  190 {
  191         struct thread *td;
  192         struct proc *p;
  193         int flags;
  194         int sig;
  195 
  196         td = curthread;
  197         p = td->td_proc;
  198 
  199         CTR3(KTR_SYSC, "ast: thread %p (pid %d, %s)", td, p->p_pid,
  200             p->p_comm);
  201         KASSERT(TRAPF_USERMODE(framep), ("ast in kernel mode"));
  202         WITNESS_WARN(WARN_PANIC, NULL, "Returning to user mode");
  203         mtx_assert(&Giant, MA_NOTOWNED);
  204         THREAD_LOCK_ASSERT(td, MA_NOTOWNED);
  205         td->td_frame = framep;
  206         td->td_pticks = 0;
  207 
  208         /*
  209          * This updates the td_flag's for the checks below in one
  210          * "atomic" operation with turning off the astpending flag.
  211          * If another AST is triggered while we are handling the
  212          * AST's saved in flags, the astpending flag will be set and
  213          * ast() will be called again.
  214          */
  215         thread_lock(td);
  216         flags = td->td_flags;
  217         td->td_flags &= ~(TDF_ASTPENDING | TDF_NEEDSIGCHK | TDF_NEEDSUSPCHK |
  218             TDF_NEEDRESCHED | TDF_ALRMPEND | TDF_PROFPEND | TDF_MACPEND);
  219         thread_unlock(td);
  220         PCPU_INC(cnt.v_trap);
  221 
  222         if (td->td_ucred != p->p_ucred) 
  223                 cred_update_thread(td);
  224         if (td->td_pflags & TDP_OWEUPC && p->p_flag & P_PROFIL) {
  225                 addupc_task(td, td->td_profil_addr, td->td_profil_ticks);
  226                 td->td_profil_ticks = 0;
  227                 td->td_pflags &= ~TDP_OWEUPC;
  228         }
  229 #ifdef HWPMC_HOOKS
  230         /* Handle Software PMC callchain capture. */
  231         if (PMC_IS_PENDING_CALLCHAIN(td))
  232                 PMC_CALL_HOOK_UNLOCKED(td, PMC_FN_USER_CALLCHAIN_SOFT, (void *) framep);
  233 #endif
  234         if (flags & TDF_ALRMPEND) {
  235                 PROC_LOCK(p);
  236                 kern_psignal(p, SIGVTALRM);
  237                 PROC_UNLOCK(p);
  238         }
  239         if (flags & TDF_PROFPEND) {
  240                 PROC_LOCK(p);
  241                 kern_psignal(p, SIGPROF);
  242                 PROC_UNLOCK(p);
  243         }
  244 #ifdef MAC
  245         if (flags & TDF_MACPEND)
  246                 mac_thread_userret(td);
  247 #endif
  248         if (flags & TDF_NEEDRESCHED) {
  249 #ifdef KTRACE
  250                 if (KTRPOINT(td, KTR_CSW))
  251                         ktrcsw(1, 1, __func__);
  252 #endif
  253                 thread_lock(td);
  254                 sched_prio(td, td->td_user_pri);
  255                 mi_switch(SW_INVOL | SWT_NEEDRESCHED, NULL);
  256                 thread_unlock(td);
  257 #ifdef KTRACE
  258                 if (KTRPOINT(td, KTR_CSW))
  259                         ktrcsw(0, 1, __func__);
  260 #endif
  261         }
  262 
  263         /*
  264          * Check for signals. Unlocked reads of p_pendingcnt or
  265          * p_siglist might cause process-directed signal to be handled
  266          * later.
  267          */
  268         if (flags & TDF_NEEDSIGCHK || p->p_pendingcnt > 0 ||
  269             !SIGISEMPTY(p->p_siglist)) {
  270                 PROC_LOCK(p);
  271                 mtx_lock(&p->p_sigacts->ps_mtx);
  272                 while ((sig = cursig(td)) != 0)
  273                         postsig(sig);
  274                 mtx_unlock(&p->p_sigacts->ps_mtx);
  275                 PROC_UNLOCK(p);
  276         }
  277         /*
  278          * We need to check to see if we have to exit or wait due to a
  279          * single threading requirement or some other STOP condition.
  280          */
  281         if (flags & TDF_NEEDSUSPCHK) {
  282                 PROC_LOCK(p);
  283                 thread_suspend_check(0);
  284                 PROC_UNLOCK(p);
  285         }
  286 
  287         if (td->td_pflags & TDP_OLDMASK) {
  288                 td->td_pflags &= ~TDP_OLDMASK;
  289                 kern_sigprocmask(td, SIG_SETMASK, &td->td_oldsigmask, NULL, 0);
  290         }
  291 
  292         userret(td, framep);
  293 }
  294 
  295 const char *
  296 syscallname(struct proc *p, u_int code)
  297 {
  298         static const char unknown[] = "unknown";
  299         struct sysentvec *sv;
  300 
  301         sv = p->p_sysent;
  302         if (sv->sv_syscallnames == NULL || code >= sv->sv_size)
  303                 return (unknown);
  304         return (sv->sv_syscallnames[code]);
  305 }

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