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  * SPDX-License-Identifier: BSD-4-Clause
    3  *
    4  * Copyright (C) 1994, David Greenman
    5  * Copyright (c) 1990, 1993
    6  *      The Regents of the University of California.  All rights reserved.
    7  * Copyright (c) 2007 The FreeBSD Foundation
    8  *
    9  * This code is derived from software contributed to Berkeley by
   10  * the University of Utah, and William Jolitz.
   11  *
   12  * Portions of this software were developed by A. Joseph Koshy under
   13  * sponsorship from the FreeBSD Foundation and Google, Inc.
   14  *
   15  * Redistribution and use in source and binary forms, with or without
   16  * modification, are permitted provided that the following conditions
   17  * are met:
   18  * 1. Redistributions of source code must retain the above copyright
   19  *    notice, this list of conditions and the following disclaimer.
   20  * 2. Redistributions in binary form must reproduce the above copyright
   21  *    notice, this list of conditions and the following disclaimer in the
   22  *    documentation and/or other materials provided with the distribution.
   23  * 3. All advertising materials mentioning features or use of this software
   24  *    must display the following acknowledgement:
   25  *      This product includes software developed by the University of
   26  *      California, Berkeley and its contributors.
   27  * 4. Neither the name of the University nor the names of its contributors
   28  *    may be used to endorse or promote products derived from this software
   29  *    without specific prior written permission.
   30  *
   31  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   32  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   33  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   34  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   35  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   36  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   37  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   38  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   39  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   40  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   41  * SUCH DAMAGE.
   42  *
   43  *      from: @(#)trap.c        7.4 (Berkeley) 5/13/91
   44  */
   45 
   46 #include <sys/cdefs.h>
   47 __FBSDID("$FreeBSD$");
   48 
   49 #include "opt_hwpmc_hooks.h"
   50 #include "opt_ktrace.h"
   51 #include "opt_sched.h"
   52 
   53 #include <sys/param.h>
   54 #include <sys/bus.h>
   55 #include <sys/capsicum.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/racct.h>
   65 #include <sys/resourcevar.h>
   66 #include <sys/sched.h>
   67 #include <sys/signalvar.h>
   68 #include <sys/syscall.h>
   69 #include <sys/syscallsubr.h>
   70 #include <sys/sysent.h>
   71 #include <sys/systm.h>
   72 #include <sys/vmmeter.h>
   73 #ifdef KTRACE
   74 #include <sys/uio.h>
   75 #include <sys/ktrace.h>
   76 #endif
   77 #include <security/audit/audit.h>
   78 
   79 #include <machine/cpu.h>
   80 
   81 #ifdef VIMAGE
   82 #include <net/vnet.h>
   83 #endif
   84 
   85 #ifdef  HWPMC_HOOKS
   86 #include <sys/pmckern.h>
   87 #endif
   88 
   89 #include <security/mac/mac_framework.h>
   90 
   91 void (*softdep_ast_cleanup)(struct thread *);
   92 
   93 /*
   94  * Define the code needed before returning to user mode, for trap and
   95  * syscall.
   96  */
   97 void
   98 userret(struct thread *td, struct trapframe *frame)
   99 {
  100         struct proc *p = td->td_proc;
  101 
  102         CTR3(KTR_SYSC, "userret: thread %p (pid %d, %s)", td, p->p_pid,
  103             td->td_name);
  104         KASSERT((p->p_flag & P_WEXIT) == 0,
  105             ("Exiting process returns to usermode"));
  106 #ifdef DIAGNOSTIC
  107         /*
  108          * Check that we called signotify() enough.  For
  109          * multi-threaded processes, where signal distribution might
  110          * change due to other threads changing sigmask, the check is
  111          * racy and cannot be performed reliably.
  112          * If current process is vfork child, indicated by P_PPWAIT, then
  113          * issignal() ignores stops, so we block the check to avoid
  114          * classifying pending signals.
  115          */
  116         if (p->p_numthreads == 1) {
  117                 PROC_LOCK(p);
  118                 thread_lock(td);
  119                 if ((p->p_flag & P_PPWAIT) == 0) {
  120                         KASSERT(!SIGPENDING(td) || (td->td_flags &
  121                             (TDF_NEEDSIGCHK | TDF_ASTPENDING)) ==
  122                             (TDF_NEEDSIGCHK | TDF_ASTPENDING),
  123                             ("failed to set signal flags for ast p %p "
  124                             "td %p fl %x", p, td, td->td_flags));
  125                 }
  126                 thread_unlock(td);
  127                 PROC_UNLOCK(p);
  128         }
  129 #endif
  130 #ifdef KTRACE
  131         KTRUSERRET(td);
  132 #endif
  133         td_softdep_cleanup(td);
  134         MPASS(td->td_su == NULL);
  135 
  136         /*
  137          * If this thread tickled GEOM, we need to wait for the giggling to
  138          * stop before we return to userland
  139          */
  140         if (td->td_pflags & TDP_GEOM)
  141                 g_waitidle();
  142 
  143         /*
  144          * Charge system time if profiling.
  145          */
  146         if (p->p_flag & P_PROFIL)
  147                 addupc_task(td, TRAPF_PC(frame), td->td_pticks * psratio);
  148 
  149 #ifdef HWPMC_HOOKS
  150         if (PMC_THREAD_HAS_SAMPLES(td))
  151                 PMC_CALL_HOOK(td, PMC_FN_THR_USERRET, NULL);
  152 #endif
  153         /*
  154          * Let the scheduler adjust our priority etc.
  155          */
  156         sched_userret(td);
  157 
  158         /*
  159          * Check for misbehavior.
  160          *
  161          * In case there is a callchain tracing ongoing because of
  162          * hwpmc(4), skip the scheduler pinning check.
  163          * hwpmc(4) subsystem, infact, will collect callchain informations
  164          * at ast() checkpoint, which is past userret().
  165          */
  166         WITNESS_WARN(WARN_PANIC, NULL, "userret: returning");
  167         KASSERT(td->td_critnest == 0,
  168             ("userret: Returning in a critical section"));
  169         KASSERT(td->td_epochnest == 0,
  170             ("userret: Returning in an epoch section"));
  171         KASSERT(td->td_locks == 0,
  172             ("userret: Returning with %d locks held", td->td_locks));
  173         KASSERT(td->td_rw_rlocks == 0,
  174             ("userret: Returning with %d rwlocks held in read mode",
  175             td->td_rw_rlocks));
  176         KASSERT(td->td_sx_slocks == 0,
  177             ("userret: Returning with %d sx locks held in shared mode",
  178             td->td_sx_slocks));
  179         KASSERT(td->td_lk_slocks == 0,
  180             ("userret: Returning with %d lockmanager locks held in shared mode",
  181             td->td_lk_slocks));
  182         KASSERT((td->td_pflags & TDP_NOFAULTING) == 0,
  183             ("userret: Returning with pagefaults disabled"));
  184         KASSERT(td->td_no_sleeping == 0,
  185             ("userret: Returning with sleep disabled"));
  186         KASSERT(td->td_pinned == 0 || (td->td_pflags & TDP_CALLCHAIN) != 0,
  187             ("userret: Returning with with pinned thread"));
  188         KASSERT(td->td_vp_reserv == 0,
  189             ("userret: Returning while holding vnode reservation"));
  190         KASSERT((td->td_flags & (TDF_SBDRY | TDF_SEINTR | TDF_SERESTART)) == 0,
  191             ("userret: Returning with stop signals deferred"));
  192         KASSERT(td->td_su == NULL,
  193             ("userret: Returning with SU cleanup request not handled"));
  194         KASSERT(td->td_vslock_sz == 0,
  195             ("userret: Returning with vslock-wired space"));
  196 #ifdef VIMAGE
  197         /* Unfortunately td_vnet_lpush needs VNET_DEBUG. */
  198         VNET_ASSERT(curvnet == NULL,
  199             ("%s: Returning on td %p (pid %d, %s) with vnet %p set in %s",
  200             __func__, td, p->p_pid, td->td_name, curvnet,
  201             (td->td_vnet_lpush != NULL) ? td->td_vnet_lpush : "N/A"));
  202 #endif
  203 #ifdef RACCT
  204         if (racct_enable && p->p_throttled != 0) {
  205                 PROC_LOCK(p);
  206                 while (p->p_throttled != 0) {
  207                         msleep(p->p_racct, &p->p_mtx, 0, "racct",
  208                             p->p_throttled < 0 ? 0 : p->p_throttled);
  209                         if (p->p_throttled > 0)
  210                                 p->p_throttled = 0;
  211                 }
  212                 PROC_UNLOCK(p);
  213         }
  214 #endif
  215 }
  216 
  217 /*
  218  * Process an asynchronous software trap.
  219  * This is relatively easy.
  220  * This function will return with preemption disabled.
  221  */
  222 void
  223 ast(struct trapframe *framep)
  224 {
  225         struct thread *td;
  226         struct proc *p;
  227         int flags;
  228         int sig;
  229 
  230         td = curthread;
  231         p = td->td_proc;
  232 
  233         CTR3(KTR_SYSC, "ast: thread %p (pid %d, %s)", td, p->p_pid,
  234             p->p_comm);
  235         KASSERT(TRAPF_USERMODE(framep), ("ast in kernel mode"));
  236         WITNESS_WARN(WARN_PANIC, NULL, "Returning to user mode");
  237         mtx_assert(&Giant, MA_NOTOWNED);
  238         THREAD_LOCK_ASSERT(td, MA_NOTOWNED);
  239         td->td_frame = framep;
  240         td->td_pticks = 0;
  241 
  242         /*
  243          * This updates the td_flag's for the checks below in one
  244          * "atomic" operation with turning off the astpending flag.
  245          * If another AST is triggered while we are handling the
  246          * AST's saved in flags, the astpending flag will be set and
  247          * ast() will be called again.
  248          */
  249         thread_lock(td);
  250         flags = td->td_flags;
  251         td->td_flags &= ~(TDF_ASTPENDING | TDF_NEEDSIGCHK | TDF_NEEDSUSPCHK |
  252             TDF_NEEDRESCHED | TDF_ALRMPEND | TDF_PROFPEND | TDF_MACPEND);
  253         thread_unlock(td);
  254         VM_CNT_INC(v_trap);
  255 
  256         if (td->td_cowgen != p->p_cowgen)
  257                 thread_cow_update(td);
  258         if (td->td_pflags & TDP_OWEUPC && p->p_flag & P_PROFIL) {
  259                 addupc_task(td, td->td_profil_addr, td->td_profil_ticks);
  260                 td->td_profil_ticks = 0;
  261                 td->td_pflags &= ~TDP_OWEUPC;
  262         }
  263 #ifdef HWPMC_HOOKS
  264         /* Handle Software PMC callchain capture. */
  265         if (PMC_IS_PENDING_CALLCHAIN(td))
  266                 PMC_CALL_HOOK_UNLOCKED(td, PMC_FN_USER_CALLCHAIN_SOFT, (void *) framep);
  267 #endif
  268         if (flags & TDF_ALRMPEND) {
  269                 PROC_LOCK(p);
  270                 kern_psignal(p, SIGVTALRM);
  271                 PROC_UNLOCK(p);
  272         }
  273         if (flags & TDF_PROFPEND) {
  274                 PROC_LOCK(p);
  275                 kern_psignal(p, SIGPROF);
  276                 PROC_UNLOCK(p);
  277         }
  278 #ifdef MAC
  279         if (flags & TDF_MACPEND)
  280                 mac_thread_userret(td);
  281 #endif
  282         if (flags & TDF_NEEDRESCHED) {
  283 #ifdef KTRACE
  284                 if (KTRPOINT(td, KTR_CSW))
  285                         ktrcsw(1, 1, __func__);
  286 #endif
  287                 thread_lock(td);
  288                 sched_prio(td, td->td_user_pri);
  289                 mi_switch(SW_INVOL | SWT_NEEDRESCHED, NULL);
  290                 thread_unlock(td);
  291 #ifdef KTRACE
  292                 if (KTRPOINT(td, KTR_CSW))
  293                         ktrcsw(0, 1, __func__);
  294 #endif
  295         }
  296 
  297 #ifdef DIAGNOSTIC
  298         if (p->p_numthreads == 1 && (flags & TDF_NEEDSIGCHK) == 0) {
  299                 PROC_LOCK(p);
  300                 thread_lock(td);
  301                 /*
  302                  * Note that TDF_NEEDSIGCHK should be re-read from
  303                  * td_flags, since signal might have been delivered
  304                  * after we cleared td_flags above.  This is one of
  305                  * the reason for looping check for AST condition.
  306                  * See comment in userret() about P_PPWAIT.
  307                  */
  308                 if ((p->p_flag & P_PPWAIT) == 0) {
  309                         KASSERT(!SIGPENDING(td) || (td->td_flags &
  310                             (TDF_NEEDSIGCHK | TDF_ASTPENDING)) ==
  311                             (TDF_NEEDSIGCHK | TDF_ASTPENDING),
  312                             ("failed2 to set signal flags for ast p %p td %p "
  313                             "fl %x %x", p, td, flags, td->td_flags));
  314                 }
  315                 thread_unlock(td);
  316                 PROC_UNLOCK(p);
  317         }
  318 #endif
  319 
  320         /*
  321          * Check for signals. Unlocked reads of p_pendingcnt or
  322          * p_siglist might cause process-directed signal to be handled
  323          * later.
  324          */
  325         if (flags & TDF_NEEDSIGCHK || p->p_pendingcnt > 0 ||
  326             !SIGISEMPTY(p->p_siglist)) {
  327                 PROC_LOCK(p);
  328                 mtx_lock(&p->p_sigacts->ps_mtx);
  329                 while ((sig = cursig(td)) != 0) {
  330                         KASSERT(sig >= 0, ("sig %d", sig));
  331                         postsig(sig);
  332                 }
  333                 mtx_unlock(&p->p_sigacts->ps_mtx);
  334                 PROC_UNLOCK(p);
  335         }
  336         /*
  337          * We need to check to see if we have to exit or wait due to a
  338          * single threading requirement or some other STOP condition.
  339          */
  340         if (flags & TDF_NEEDSUSPCHK) {
  341                 PROC_LOCK(p);
  342                 thread_suspend_check(0);
  343                 PROC_UNLOCK(p);
  344         }
  345 
  346         if (td->td_pflags & TDP_OLDMASK) {
  347                 td->td_pflags &= ~TDP_OLDMASK;
  348                 kern_sigprocmask(td, SIG_SETMASK, &td->td_oldsigmask, NULL, 0);
  349         }
  350 
  351         userret(td, framep);
  352 }
  353 
  354 const char *
  355 syscallname(struct proc *p, u_int code)
  356 {
  357         static const char unknown[] = "unknown";
  358         struct sysentvec *sv;
  359 
  360         sv = p->p_sysent;
  361         if (sv->sv_syscallnames == NULL || code >= sv->sv_size)
  362                 return (unknown);
  363         return (sv->sv_syscallnames[code]);
  364 }

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