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/8.4/sys/kern/subr_trap.c 249524 2013-04-15 19:45:09Z smh $");
   46 
   47 #include "opt_ktrace.h"
   48 #include "opt_kdtrace.h"
   49 #include "opt_sched.h"
   50 
   51 #include <sys/param.h>
   52 #include <sys/bus.h>
   53 #include <sys/kernel.h>
   54 #include <sys/lock.h>
   55 #include <sys/mutex.h>
   56 #include <sys/pmckern.h>
   57 #include <sys/proc.h>
   58 #include <sys/ktr.h>
   59 #include <sys/pioctl.h>
   60 #include <sys/ptrace.h>
   61 #include <sys/resourcevar.h>
   62 #include <sys/sched.h>
   63 #include <sys/signalvar.h>
   64 #include <sys/syscall.h>
   65 #include <sys/syscallsubr.h>
   66 #include <sys/sysent.h>
   67 #include <sys/systm.h>
   68 #include <sys/vmmeter.h>
   69 #ifdef KTRACE
   70 #include <sys/uio.h>
   71 #include <sys/ktrace.h>
   72 #endif
   73 #include <security/audit/audit.h>
   74 
   75 #include <machine/cpu.h>
   76 
   77 #ifdef VIMAGE
   78 #include <net/vnet.h>
   79 #endif
   80 
   81 #ifdef XEN
   82 #include <vm/vm.h>
   83 #include <vm/vm_param.h>
   84 #include <vm/pmap.h>
   85 #endif
   86 
   87 #include <security/mac/mac_framework.h>
   88 
   89 /*
   90  * Define the code needed before returning to user mode, for trap and
   91  * syscall.
   92  */
   93 void
   94 userret(struct thread *td, struct trapframe *frame)
   95 {
   96         struct proc *p = td->td_proc;
   97 
   98         CTR3(KTR_SYSC, "userret: thread %p (pid %d, %s)", td, p->p_pid,
   99             td->td_name);
  100         KASSERT((p->p_flag & P_WEXIT) == 0,
  101             ("Exiting process returns to usermode"));
  102 #if 0
  103 #ifdef DIAGNOSTIC
  104         /* Check that we called signotify() enough. */
  105         PROC_LOCK(p);
  106         thread_lock(td);
  107         if (SIGPENDING(td) && ((td->td_flags & TDF_NEEDSIGCHK) == 0 ||
  108             (td->td_flags & TDF_ASTPENDING) == 0))
  109                 printf("failed to set signal flags properly for ast()\n");
  110         thread_unlock(td);
  111         PROC_UNLOCK(p);
  112 #endif
  113 #endif
  114 #ifdef KTRACE
  115         KTRUSERRET(td);
  116 #endif
  117         /*
  118          * If this thread tickled GEOM, we need to wait for the giggling to
  119          * stop before we return to userland
  120          */
  121         if (td->td_pflags & TDP_GEOM)
  122                 g_waitidle();
  123 
  124         /*
  125          * Charge system time if profiling.
  126          */
  127         if (p->p_flag & P_PROFIL)
  128                 addupc_task(td, TRAPF_PC(frame), td->td_pticks * psratio);
  129         /*
  130          * Let the scheduler adjust our priority etc.
  131          */
  132         sched_userret(td);
  133         KASSERT(td->td_locks == 0,
  134             ("userret: Returning with %d locks held.", td->td_locks));
  135         KASSERT(td->td_vp_reserv == 0,
  136             ("userret: Returning while holding vnode reservation"));
  137 #ifdef VIMAGE
  138         /* Unfortunately td_vnet_lpush needs VNET_DEBUG. */
  139         VNET_ASSERT(curvnet == NULL,
  140             ("%s: Returning on td %p (pid %d, %s) with vnet %p set in %s",
  141             __func__, td, p->p_pid, td->td_name, curvnet,
  142             (td->td_vnet_lpush != NULL) ? td->td_vnet_lpush : "N/A"));
  143 #endif
  144 #ifdef XEN
  145         PT_UPDATES_FLUSH();
  146 #endif
  147 }
  148 
  149 /*
  150  * Process an asynchronous software trap.
  151  * This is relatively easy.
  152  * This function will return with preemption disabled.
  153  */
  154 void
  155 ast(struct trapframe *framep)
  156 {
  157         struct thread *td;
  158         struct proc *p;
  159         int flags;
  160         int sig;
  161 
  162         td = curthread;
  163         p = td->td_proc;
  164 
  165         CTR3(KTR_SYSC, "ast: thread %p (pid %d, %s)", td, p->p_pid,
  166             p->p_comm);
  167         KASSERT(TRAPF_USERMODE(framep), ("ast in kernel mode"));
  168         WITNESS_WARN(WARN_PANIC, NULL, "Returning to user mode");
  169         mtx_assert(&Giant, MA_NOTOWNED);
  170         THREAD_LOCK_ASSERT(td, MA_NOTOWNED);
  171         td->td_frame = framep;
  172         td->td_pticks = 0;
  173 
  174         /*
  175          * This updates the td_flag's for the checks below in one
  176          * "atomic" operation with turning off the astpending flag.
  177          * If another AST is triggered while we are handling the
  178          * AST's saved in flags, the astpending flag will be set and
  179          * ast() will be called again.
  180          */
  181         thread_lock(td);
  182         flags = td->td_flags;
  183         td->td_flags &= ~(TDF_ASTPENDING | TDF_NEEDSIGCHK | TDF_NEEDSUSPCHK |
  184             TDF_NEEDRESCHED | TDF_ALRMPEND | TDF_PROFPEND | TDF_MACPEND);
  185         thread_unlock(td);
  186         PCPU_INC(cnt.v_trap);
  187 
  188         if (td->td_ucred != p->p_ucred) 
  189                 cred_update_thread(td);
  190         if (td->td_pflags & TDP_OWEUPC && p->p_flag & P_PROFIL) {
  191                 addupc_task(td, td->td_profil_addr, td->td_profil_ticks);
  192                 td->td_profil_ticks = 0;
  193                 td->td_pflags &= ~TDP_OWEUPC;
  194         }
  195         if (flags & TDF_ALRMPEND) {
  196                 PROC_LOCK(p);
  197                 psignal(p, SIGVTALRM);
  198                 PROC_UNLOCK(p);
  199         }
  200         if (flags & TDF_PROFPEND) {
  201                 PROC_LOCK(p);
  202                 psignal(p, SIGPROF);
  203                 PROC_UNLOCK(p);
  204         }
  205 #ifdef MAC
  206         if (flags & TDF_MACPEND)
  207                 mac_thread_userret(td);
  208 #endif
  209         if (flags & TDF_NEEDRESCHED) {
  210 #ifdef KTRACE
  211                 if (KTRPOINT(td, KTR_CSW))
  212                         ktrcsw(1, 1, __func__);
  213 #endif
  214                 thread_lock(td);
  215                 sched_prio(td, td->td_user_pri);
  216                 mi_switch(SW_INVOL | SWT_NEEDRESCHED, NULL);
  217                 thread_unlock(td);
  218 #ifdef KTRACE
  219                 if (KTRPOINT(td, KTR_CSW))
  220                         ktrcsw(0, 1, __func__);
  221 #endif
  222         }
  223 
  224         /*
  225          * Check for signals. Unlocked reads of p_pendingcnt or
  226          * p_siglist might cause process-directed signal to be handled
  227          * later.
  228          */
  229         if (flags & TDF_NEEDSIGCHK || p->p_pendingcnt > 0 ||
  230             !SIGISEMPTY(p->p_siglist)) {
  231                 PROC_LOCK(p);
  232                 mtx_lock(&p->p_sigacts->ps_mtx);
  233                 while ((sig = cursig(td, SIG_STOP_ALLOWED)) != 0)
  234                         postsig(sig);
  235                 mtx_unlock(&p->p_sigacts->ps_mtx);
  236                 PROC_UNLOCK(p);
  237         }
  238         /*
  239          * We need to check to see if we have to exit or wait due to a
  240          * single threading requirement or some other STOP condition.
  241          */
  242         if (flags & TDF_NEEDSUSPCHK) {
  243                 PROC_LOCK(p);
  244                 thread_suspend_check(0);
  245                 PROC_UNLOCK(p);
  246         }
  247 
  248         if (td->td_pflags & TDP_OLDMASK) {
  249                 td->td_pflags &= ~TDP_OLDMASK;
  250                 kern_sigprocmask(td, SIG_SETMASK, &td->td_oldsigmask, NULL, 0);
  251         }
  252 
  253         userret(td, framep);
  254         mtx_assert(&Giant, MA_NOTOWNED);
  255 }
  256 
  257 const char *
  258 syscallname(struct proc *p, u_int code)
  259 {
  260         static const char unknown[] = "unknown";
  261         struct sysentvec *sv;
  262 
  263         sv = p->p_sysent;
  264         if (sv->sv_syscallnames == NULL || code >= sv->sv_size)
  265                 return (unknown);
  266         return (sv->sv_syscallnames[code]);
  267 }

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