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/11.2/sys/kern/subr_trap.c 331842 2018-03-31 13:19:27Z kib $");
   46 
   47 #include "opt_hwpmc_hooks.h"
   48 #include "opt_ktrace.h"
   49 #include "opt_sched.h"
   50 
   51 #include <sys/param.h>
   52 #include <sys/bus.h>
   53 #include <sys/capsicum.h>
   54 #include <sys/kernel.h>
   55 #include <sys/lock.h>
   56 #include <sys/mutex.h>
   57 #include <sys/pmckern.h>
   58 #include <sys/proc.h>
   59 #include <sys/ktr.h>
   60 #include <sys/pioctl.h>
   61 #include <sys/ptrace.h>
   62 #include <sys/racct.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  HWPMC_HOOKS
   84 #include <sys/pmckern.h>
   85 #endif
   86 
   87 #include <security/mac/mac_framework.h>
   88 
   89 void (*softdep_ast_cleanup)(struct thread *);
   90 
   91 /*
   92  * Define the code needed before returning to user mode, for trap and
   93  * syscall.
   94  */
   95 void
   96 userret(struct thread *td, struct trapframe *frame)
   97 {
   98         struct proc *p = td->td_proc;
   99 
  100         CTR3(KTR_SYSC, "userret: thread %p (pid %d, %s)", td, p->p_pid,
  101             td->td_name);
  102         KASSERT((p->p_flag & P_WEXIT) == 0,
  103             ("Exiting process returns to usermode"));
  104 #ifdef DIAGNOSTIC
  105         /*
  106          * Check that we called signotify() enough.  For
  107          * multi-threaded processes, where signal distribution might
  108          * change due to other threads changing sigmask, the check is
  109          * racy and cannot be performed reliably.
  110          * If current process is vfork child, indicated by P_PPWAIT, then
  111          * issignal() ignores stops, so we block the check to avoid
  112          * classifying pending signals.
  113          */
  114         if (p->p_numthreads == 1) {
  115                 PROC_LOCK(p);
  116                 thread_lock(td);
  117                 if ((p->p_flag & P_PPWAIT) == 0) {
  118                         KASSERT(!SIGPENDING(td) || (td->td_flags &
  119                             (TDF_NEEDSIGCHK | TDF_ASTPENDING)) ==
  120                             (TDF_NEEDSIGCHK | TDF_ASTPENDING),
  121                             ("failed to set signal flags for ast p %p "
  122                             "td %p fl %x", p, td, td->td_flags));
  123                 }
  124                 thread_unlock(td);
  125                 PROC_UNLOCK(p);
  126         }
  127 #endif
  128 #ifdef KTRACE
  129         KTRUSERRET(td);
  130 #endif
  131         td_softdep_cleanup(td);
  132         MPASS(td->td_su == NULL);
  133 
  134         /*
  135          * If this thread tickled GEOM, we need to wait for the giggling to
  136          * stop before we return to userland
  137          */
  138         if (td->td_pflags & TDP_GEOM)
  139                 g_waitidle();
  140 
  141         /*
  142          * Charge system time if profiling.
  143          */
  144         if (p->p_flag & P_PROFIL)
  145                 addupc_task(td, TRAPF_PC(frame), td->td_pticks * psratio);
  146         /*
  147          * Let the scheduler adjust our priority etc.
  148          */
  149         sched_userret(td);
  150 
  151         /*
  152          * Check for misbehavior.
  153          *
  154          * In case there is a callchain tracing ongoing because of
  155          * hwpmc(4), skip the scheduler pinning check.
  156          * hwpmc(4) subsystem, infact, will collect callchain informations
  157          * at ast() checkpoint, which is past userret().
  158          */
  159         WITNESS_WARN(WARN_PANIC, NULL, "userret: returning");
  160         KASSERT(td->td_critnest == 0,
  161             ("userret: Returning in a critical section"));
  162         KASSERT(td->td_locks == 0,
  163             ("userret: Returning with %d locks held", td->td_locks));
  164         KASSERT(td->td_rw_rlocks == 0,
  165             ("userret: Returning with %d rwlocks held in read mode",
  166             td->td_rw_rlocks));
  167         KASSERT((td->td_pflags & TDP_NOFAULTING) == 0,
  168             ("userret: Returning with pagefaults disabled"));
  169         KASSERT(td->td_no_sleeping == 0,
  170             ("userret: Returning with sleep disabled"));
  171         KASSERT(td->td_pinned == 0 || (td->td_pflags & TDP_CALLCHAIN) != 0,
  172             ("userret: Returning with with pinned thread"));
  173         KASSERT(td->td_vp_reserv == 0,
  174             ("userret: Returning while holding vnode reservation"));
  175         KASSERT((td->td_flags & (TDF_SBDRY | TDF_SEINTR | TDF_SERESTART)) == 0,
  176             ("userret: Returning with stop signals deferred"));
  177         KASSERT(td->td_su == NULL,
  178             ("userret: Returning with SU cleanup request not handled"));
  179         KASSERT(td->td_vslock_sz == 0,
  180             ("userret: Returning with vslock-wired space"));
  181 #ifdef VIMAGE
  182         /* Unfortunately td_vnet_lpush needs VNET_DEBUG. */
  183         VNET_ASSERT(curvnet == NULL,
  184             ("%s: Returning on td %p (pid %d, %s) with vnet %p set in %s",
  185             __func__, td, p->p_pid, td->td_name, curvnet,
  186             (td->td_vnet_lpush != NULL) ? td->td_vnet_lpush : "N/A"));
  187 #endif
  188 #ifdef RACCT
  189         if (racct_enable && p->p_throttled != 0) {
  190                 PROC_LOCK(p);
  191                 while (p->p_throttled != 0) {
  192                         msleep(p->p_racct, &p->p_mtx, 0, "racct",
  193                             p->p_throttled < 0 ? 0 : p->p_throttled);
  194                         if (p->p_throttled > 0)
  195                                 p->p_throttled = 0;
  196                 }
  197                 PROC_UNLOCK(p);
  198         }
  199 #endif
  200 }
  201 
  202 /*
  203  * Process an asynchronous software trap.
  204  * This is relatively easy.
  205  * This function will return with preemption disabled.
  206  */
  207 void
  208 ast(struct trapframe *framep)
  209 {
  210         struct thread *td;
  211         struct proc *p;
  212         int flags;
  213         int sig;
  214 
  215         td = curthread;
  216         p = td->td_proc;
  217 
  218         CTR3(KTR_SYSC, "ast: thread %p (pid %d, %s)", td, p->p_pid,
  219             p->p_comm);
  220         KASSERT(TRAPF_USERMODE(framep), ("ast in kernel mode"));
  221         WITNESS_WARN(WARN_PANIC, NULL, "Returning to user mode");
  222         mtx_assert(&Giant, MA_NOTOWNED);
  223         THREAD_LOCK_ASSERT(td, MA_NOTOWNED);
  224         td->td_frame = framep;
  225         td->td_pticks = 0;
  226 
  227         /*
  228          * This updates the td_flag's for the checks below in one
  229          * "atomic" operation with turning off the astpending flag.
  230          * If another AST is triggered while we are handling the
  231          * AST's saved in flags, the astpending flag will be set and
  232          * ast() will be called again.
  233          */
  234         thread_lock(td);
  235         flags = td->td_flags;
  236         td->td_flags &= ~(TDF_ASTPENDING | TDF_NEEDSIGCHK | TDF_NEEDSUSPCHK |
  237             TDF_NEEDRESCHED | TDF_ALRMPEND | TDF_PROFPEND | TDF_MACPEND);
  238         thread_unlock(td);
  239         PCPU_INC(cnt.v_trap);
  240 
  241         if (td->td_cowgen != p->p_cowgen)
  242                 thread_cow_update(td);
  243         if (td->td_pflags & TDP_OWEUPC && p->p_flag & P_PROFIL) {
  244                 addupc_task(td, td->td_profil_addr, td->td_profil_ticks);
  245                 td->td_profil_ticks = 0;
  246                 td->td_pflags &= ~TDP_OWEUPC;
  247         }
  248 #ifdef HWPMC_HOOKS
  249         /* Handle Software PMC callchain capture. */
  250         if (PMC_IS_PENDING_CALLCHAIN(td))
  251                 PMC_CALL_HOOK_UNLOCKED(td, PMC_FN_USER_CALLCHAIN_SOFT, (void *) framep);
  252 #endif
  253         if (flags & TDF_ALRMPEND) {
  254                 PROC_LOCK(p);
  255                 kern_psignal(p, SIGVTALRM);
  256                 PROC_UNLOCK(p);
  257         }
  258         if (flags & TDF_PROFPEND) {
  259                 PROC_LOCK(p);
  260                 kern_psignal(p, SIGPROF);
  261                 PROC_UNLOCK(p);
  262         }
  263 #ifdef MAC
  264         if (flags & TDF_MACPEND)
  265                 mac_thread_userret(td);
  266 #endif
  267         if (flags & TDF_NEEDRESCHED) {
  268 #ifdef KTRACE
  269                 if (KTRPOINT(td, KTR_CSW))
  270                         ktrcsw(1, 1, __func__);
  271 #endif
  272                 thread_lock(td);
  273                 sched_prio(td, td->td_user_pri);
  274                 mi_switch(SW_INVOL | SWT_NEEDRESCHED, NULL);
  275                 thread_unlock(td);
  276 #ifdef KTRACE
  277                 if (KTRPOINT(td, KTR_CSW))
  278                         ktrcsw(0, 1, __func__);
  279 #endif
  280         }
  281 
  282 #ifdef DIAGNOSTIC
  283         if (p->p_numthreads == 1 && (flags & TDF_NEEDSIGCHK) == 0) {
  284                 PROC_LOCK(p);
  285                 thread_lock(td);
  286                 /*
  287                  * Note that TDF_NEEDSIGCHK should be re-read from
  288                  * td_flags, since signal might have been delivered
  289                  * after we cleared td_flags above.  This is one of
  290                  * the reason for looping check for AST condition.
  291                  * See comment in userret() about P_PPWAIT.
  292                  */
  293                 if ((p->p_flag & P_PPWAIT) == 0) {
  294                         KASSERT(!SIGPENDING(td) || (td->td_flags &
  295                             (TDF_NEEDSIGCHK | TDF_ASTPENDING)) ==
  296                             (TDF_NEEDSIGCHK | TDF_ASTPENDING),
  297                             ("failed2 to set signal flags for ast p %p td %p "
  298                             "fl %x %x", p, td, flags, td->td_flags));
  299                 }
  300                 thread_unlock(td);
  301                 PROC_UNLOCK(p);
  302         }
  303 #endif
  304 
  305         /*
  306          * Check for signals. Unlocked reads of p_pendingcnt or
  307          * p_siglist might cause process-directed signal to be handled
  308          * later.
  309          */
  310         if (flags & TDF_NEEDSIGCHK || p->p_pendingcnt > 0 ||
  311             !SIGISEMPTY(p->p_siglist)) {
  312                 PROC_LOCK(p);
  313                 mtx_lock(&p->p_sigacts->ps_mtx);
  314                 while ((sig = cursig(td)) != 0)
  315                         postsig(sig);
  316                 mtx_unlock(&p->p_sigacts->ps_mtx);
  317                 PROC_UNLOCK(p);
  318         }
  319         /*
  320          * We need to check to see if we have to exit or wait due to a
  321          * single threading requirement or some other STOP condition.
  322          */
  323         if (flags & TDF_NEEDSUSPCHK) {
  324                 PROC_LOCK(p);
  325                 thread_suspend_check(0);
  326                 PROC_UNLOCK(p);
  327         }
  328 
  329         if (td->td_pflags & TDP_OLDMASK) {
  330                 td->td_pflags &= ~TDP_OLDMASK;
  331                 kern_sigprocmask(td, SIG_SETMASK, &td->td_oldsigmask, NULL, 0);
  332         }
  333 
  334         userret(td, framep);
  335 }
  336 
  337 const char *
  338 syscallname(struct proc *p, u_int code)
  339 {
  340         static const char unknown[] = "unknown";
  341         struct sysentvec *sv;
  342 
  343         sv = p->p_sysent;
  344         if (sv->sv_syscallnames == NULL || code >= sv->sv_size)
  345                 return (unknown);
  346         return (sv->sv_syscallnames[code]);
  347 }

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