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("$FreeBSD$");
   46 
   47 #include "opt_capsicum.h"
   48 #include "opt_hwpmc_hooks.h"
   49 #include "opt_ktrace.h"
   50 #include "opt_kdtrace.h"
   51 #include "opt_sched.h"
   52 
   53 #include <sys/param.h>
   54 #include <sys/bus.h>
   55 #include <sys/capability.h>
   56 #include <sys/kernel.h>
   57 #include <sys/lock.h>
   58 #include <sys/mutex.h>
   59 #include <sys/pmckern.h>
   60 #include <sys/proc.h>
   61 #include <sys/ktr.h>
   62 #include <sys/pioctl.h>
   63 #include <sys/ptrace.h>
   64 #include <sys/resourcevar.h>
   65 #include <sys/sched.h>
   66 #include <sys/signalvar.h>
   67 #include <sys/syscall.h>
   68 #include <sys/syscallsubr.h>
   69 #include <sys/sysent.h>
   70 #include <sys/systm.h>
   71 #include <sys/vmmeter.h>
   72 #ifdef KTRACE
   73 #include <sys/uio.h>
   74 #include <sys/ktrace.h>
   75 #endif
   76 #include <security/audit/audit.h>
   77 
   78 #include <machine/cpu.h>
   79 
   80 #ifdef VIMAGE
   81 #include <net/vnet.h>
   82 #endif
   83 
   84 #ifdef XEN
   85 #include <vm/vm.h>
   86 #include <vm/vm_param.h>
   87 #include <vm/pmap.h>
   88 #endif
   89 
   90 #ifdef  HWPMC_HOOKS
   91 #include <sys/pmckern.h>
   92 #endif
   93 
   94 #include <security/mac/mac_framework.h>
   95 
   96 /*
   97  * Define the code needed before returning to user mode, for trap and
   98  * syscall.
   99  */
  100 void
  101 userret(struct thread *td, struct trapframe *frame)
  102 {
  103         struct proc *p = td->td_proc;
  104 
  105         CTR3(KTR_SYSC, "userret: thread %p (pid %d, %s)", td, p->p_pid,
  106             td->td_name);
  107         KASSERT((p->p_flag & P_WEXIT) == 0,
  108             ("Exiting process returns to usermode"));
  109 #if 0
  110 #ifdef DIAGNOSTIC
  111         /* Check that we called signotify() enough. */
  112         PROC_LOCK(p);
  113         thread_lock(td);
  114         if (SIGPENDING(td) && ((td->td_flags & TDF_NEEDSIGCHK) == 0 ||
  115             (td->td_flags & TDF_ASTPENDING) == 0))
  116                 printf("failed to set signal flags properly for ast()\n");
  117         thread_unlock(td);
  118         PROC_UNLOCK(p);
  119 #endif
  120 #endif
  121 #ifdef KTRACE
  122         KTRUSERRET(td);
  123 #endif
  124         /*
  125          * If this thread tickled GEOM, we need to wait for the giggling to
  126          * stop before we return to userland
  127          */
  128         if (td->td_pflags & TDP_GEOM)
  129                 g_waitidle();
  130 
  131         /*
  132          * Charge system time if profiling.
  133          */
  134         if (p->p_flag & P_PROFIL)
  135                 addupc_task(td, TRAPF_PC(frame), td->td_pticks * psratio);
  136         /*
  137          * Let the scheduler adjust our priority etc.
  138          */
  139         sched_userret(td);
  140         KASSERT(td->td_locks == 0,
  141             ("userret: Returning with %d locks held.", td->td_locks));
  142         KASSERT((td->td_pflags & TDP_DEVMEMIO) == 0,
  143             ("userret: Returning with /dev/mem i/o leaked"));
  144         KASSERT(td->td_vp_reserv == 0,
  145             ("userret: Returning while holding vnode reservation"));
  146         KASSERT((td->td_flags & TDF_SBDRY) == 0,
  147             ("userret: Returning with stop signals deferred"));
  148 #ifdef VIMAGE
  149         /* Unfortunately td_vnet_lpush needs VNET_DEBUG. */
  150         VNET_ASSERT(curvnet == NULL,
  151             ("%s: Returning on td %p (pid %d, %s) with vnet %p set in %s",
  152             __func__, td, p->p_pid, td->td_name, curvnet,
  153             (td->td_vnet_lpush != NULL) ? td->td_vnet_lpush : "N/A"));
  154 #endif
  155 #ifdef XEN
  156         PT_UPDATES_FLUSH();
  157 #endif
  158 #ifdef  RACCT
  159         PROC_LOCK(p);
  160         while (p->p_throttled == 1)
  161                 msleep(p->p_racct, &p->p_mtx, 0, "racct", 0);
  162         PROC_UNLOCK(p);
  163 #endif
  164 }
  165 
  166 /*
  167  * Process an asynchronous software trap.
  168  * This is relatively easy.
  169  * This function will return with preemption disabled.
  170  */
  171 void
  172 ast(struct trapframe *framep)
  173 {
  174         struct thread *td;
  175         struct proc *p;
  176         int flags;
  177         int sig;
  178 
  179         td = curthread;
  180         p = td->td_proc;
  181 
  182         CTR3(KTR_SYSC, "ast: thread %p (pid %d, %s)", td, p->p_pid,
  183             p->p_comm);
  184         KASSERT(TRAPF_USERMODE(framep), ("ast in kernel mode"));
  185         WITNESS_WARN(WARN_PANIC, NULL, "Returning to user mode");
  186         mtx_assert(&Giant, MA_NOTOWNED);
  187         THREAD_LOCK_ASSERT(td, MA_NOTOWNED);
  188         td->td_frame = framep;
  189         td->td_pticks = 0;
  190 
  191         /*
  192          * This updates the td_flag's for the checks below in one
  193          * "atomic" operation with turning off the astpending flag.
  194          * If another AST is triggered while we are handling the
  195          * AST's saved in flags, the astpending flag will be set and
  196          * ast() will be called again.
  197          */
  198         thread_lock(td);
  199         flags = td->td_flags;
  200         td->td_flags &= ~(TDF_ASTPENDING | TDF_NEEDSIGCHK | TDF_NEEDSUSPCHK |
  201             TDF_NEEDRESCHED | TDF_ALRMPEND | TDF_PROFPEND | TDF_MACPEND);
  202         thread_unlock(td);
  203         PCPU_INC(cnt.v_trap);
  204 
  205         if (td->td_ucred != p->p_ucred) 
  206                 cred_update_thread(td);
  207         if (td->td_pflags & TDP_OWEUPC && p->p_flag & P_PROFIL) {
  208                 addupc_task(td, td->td_profil_addr, td->td_profil_ticks);
  209                 td->td_profil_ticks = 0;
  210                 td->td_pflags &= ~TDP_OWEUPC;
  211         }
  212 #ifdef HWPMC_HOOKS
  213         /* Handle Software PMC callchain capture. */
  214         if (PMC_IS_PENDING_CALLCHAIN(td))
  215                 PMC_CALL_HOOK_UNLOCKED(td, PMC_FN_USER_CALLCHAIN_SOFT, (void *) framep);
  216 #endif
  217         if (flags & TDF_ALRMPEND) {
  218                 PROC_LOCK(p);
  219                 kern_psignal(p, SIGVTALRM);
  220                 PROC_UNLOCK(p);
  221         }
  222         if (flags & TDF_PROFPEND) {
  223                 PROC_LOCK(p);
  224                 kern_psignal(p, SIGPROF);
  225                 PROC_UNLOCK(p);
  226         }
  227 #ifdef MAC
  228         if (flags & TDF_MACPEND)
  229                 mac_thread_userret(td);
  230 #endif
  231         if (flags & TDF_NEEDRESCHED) {
  232 #ifdef KTRACE
  233                 if (KTRPOINT(td, KTR_CSW))
  234                         ktrcsw(1, 1, __func__);
  235 #endif
  236                 thread_lock(td);
  237                 sched_prio(td, td->td_user_pri);
  238                 mi_switch(SW_INVOL | SWT_NEEDRESCHED, NULL);
  239                 thread_unlock(td);
  240 #ifdef KTRACE
  241                 if (KTRPOINT(td, KTR_CSW))
  242                         ktrcsw(0, 1, __func__);
  243 #endif
  244         }
  245 
  246         /*
  247          * Check for signals. Unlocked reads of p_pendingcnt or
  248          * p_siglist might cause process-directed signal to be handled
  249          * later.
  250          */
  251         if (flags & TDF_NEEDSIGCHK || p->p_pendingcnt > 0 ||
  252             !SIGISEMPTY(p->p_siglist)) {
  253                 PROC_LOCK(p);
  254                 mtx_lock(&p->p_sigacts->ps_mtx);
  255                 while ((sig = cursig(td, SIG_STOP_ALLOWED)) != 0)
  256                         postsig(sig);
  257                 mtx_unlock(&p->p_sigacts->ps_mtx);
  258                 PROC_UNLOCK(p);
  259         }
  260         /*
  261          * We need to check to see if we have to exit or wait due to a
  262          * single threading requirement or some other STOP condition.
  263          */
  264         if (flags & TDF_NEEDSUSPCHK) {
  265                 PROC_LOCK(p);
  266                 thread_suspend_check(0);
  267                 PROC_UNLOCK(p);
  268         }
  269 
  270         if (td->td_pflags & TDP_OLDMASK) {
  271                 td->td_pflags &= ~TDP_OLDMASK;
  272                 kern_sigprocmask(td, SIG_SETMASK, &td->td_oldsigmask, NULL, 0);
  273         }
  274 
  275         userret(td, framep);
  276         mtx_assert(&Giant, MA_NOTOWNED);
  277 }
  278 
  279 const char *
  280 syscallname(struct proc *p, u_int code)
  281 {
  282         static const char unknown[] = "unknown";
  283         struct sysentvec *sv;
  284 
  285         sv = p->p_sysent;
  286         if (sv->sv_syscallnames == NULL || code >= sv->sv_size)
  287                 return (unknown);
  288         return (sv->sv_syscallnames[code]);
  289 }

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