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_syscall.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) 2010 Konstantin Belousov <kib@freebsd.org>
    6  *
    7  * This code is derived from software contributed to Berkeley by
    8  * the University of Utah, and William Jolitz.
    9  *
   10  * Redistribution and use in source and binary forms, with or without
   11  * modification, are permitted provided that the following conditions
   12  * are met:
   13  * 1. Redistributions of source code must retain the above copyright
   14  *    notice, this list of conditions and the following disclaimer.
   15  * 2. Redistributions in binary form must reproduce the above copyright
   16  *    notice, this list of conditions and the following disclaimer in the
   17  *    documentation and/or other materials provided with the distribution.
   18  * 3. All advertising materials mentioning features or use of this software
   19  *    must display the following acknowledgement:
   20  *      This product includes software developed by the University of
   21  *      California, Berkeley and its contributors.
   22  * 4. Neither the name of the University nor the names of its contributors
   23  *    may be used to endorse or promote products derived from this software
   24  *    without specific prior written permission.
   25  *
   26  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   27  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   28  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   29  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   30  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   31  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   32  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   33  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   34  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   35  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   36  * SUCH DAMAGE.
   37  *
   38  *      from: @(#)trap.c        7.4 (Berkeley) 5/13/91
   39  */
   40 
   41 #include "opt_capsicum.h"
   42 #include "opt_ktrace.h"
   43 #include "opt_kdtrace.h"
   44 
   45 __FBSDID("$FreeBSD: releng/9.2/sys/kern/subr_syscall.c 236648 2012-06-06 01:01:12Z kib $");
   46 
   47 #include <sys/capability.h>
   48 #include <sys/ktr.h>
   49 #ifdef KTRACE
   50 #include <sys/uio.h>
   51 #include <sys/ktrace.h>
   52 #endif
   53 #include <security/audit/audit.h>
   54 
   55 static inline int
   56 syscallenter(struct thread *td, struct syscall_args *sa)
   57 {
   58         struct proc *p;
   59         int error, traced;
   60 
   61         PCPU_INC(cnt.v_syscall);
   62         p = td->td_proc;
   63 
   64         td->td_pticks = 0;
   65         if (td->td_ucred != p->p_ucred)
   66                 cred_update_thread(td);
   67         if (p->p_flag & P_TRACED) {
   68                 traced = 1;
   69                 PROC_LOCK(p);
   70                 td->td_dbgflags &= ~TDB_USERWR;
   71                 td->td_dbgflags |= TDB_SCE;
   72                 PROC_UNLOCK(p);
   73         } else
   74                 traced = 0;
   75         error = (p->p_sysent->sv_fetch_syscall_args)(td, sa);
   76 #ifdef KTRACE
   77         if (KTRPOINT(td, KTR_SYSCALL))
   78                 ktrsyscall(sa->code, sa->narg, sa->args);
   79 #endif
   80 
   81         CTR6(KTR_SYSC,
   82 "syscall: td=%p pid %d %s (%#lx, %#lx, %#lx)",
   83             td, td->td_proc->p_pid, syscallname(p, sa->code),
   84             sa->args[0], sa->args[1], sa->args[2]);
   85 
   86         if (error == 0) {
   87                 STOPEVENT(p, S_SCE, sa->narg);
   88                 if (p->p_flag & P_TRACED && p->p_stops & S_PT_SCE) {
   89                         PROC_LOCK(p);
   90                         ptracestop((td), SIGTRAP);
   91                         PROC_UNLOCK(p);
   92                 }
   93                 if (td->td_dbgflags & TDB_USERWR) {
   94                         /*
   95                          * Reread syscall number and arguments if
   96                          * debugger modified registers or memory.
   97                          */
   98                         error = (p->p_sysent->sv_fetch_syscall_args)(td, sa);
   99 #ifdef KTRACE
  100                         if (KTRPOINT(td, KTR_SYSCALL))
  101                                 ktrsyscall(sa->code, sa->narg, sa->args);
  102 #endif
  103                         if (error != 0)
  104                                 goto retval;
  105                 }
  106 
  107 #ifdef CAPABILITY_MODE
  108                 /*
  109                  * In capability mode, we only allow access to system calls
  110                  * flagged with SYF_CAPENABLED.
  111                  */
  112                 if (IN_CAPABILITY_MODE(td) &&
  113                     !(sa->callp->sy_flags & SYF_CAPENABLED)) {
  114                         error = ECAPMODE;
  115                         goto retval;
  116                 }
  117 #endif
  118 
  119                 error = syscall_thread_enter(td, sa->callp);
  120                 if (error != 0)
  121                         goto retval;
  122 
  123 #ifdef KDTRACE_HOOKS
  124                 /*
  125                  * If the systrace module has registered it's probe
  126                  * callback and if there is a probe active for the
  127                  * syscall 'entry', process the probe.
  128                  */
  129                 if (systrace_probe_func != NULL && sa->callp->sy_entry != 0)
  130                         (*systrace_probe_func)(sa->callp->sy_entry, sa->code,
  131                             sa->callp, sa->args, 0);
  132 #endif
  133 
  134                 AUDIT_SYSCALL_ENTER(sa->code, td);
  135                 error = (sa->callp->sy_call)(td, sa->args);
  136                 AUDIT_SYSCALL_EXIT(error, td);
  137 
  138                 /* Save the latest error return value. */
  139                 if ((td->td_pflags & TDP_NERRNO) == 0)
  140                         td->td_errno = error;
  141 
  142 #ifdef KDTRACE_HOOKS
  143                 /*
  144                  * If the systrace module has registered it's probe
  145                  * callback and if there is a probe active for the
  146                  * syscall 'return', process the probe.
  147                  */
  148                 if (systrace_probe_func != NULL && sa->callp->sy_return != 0)
  149                         (*systrace_probe_func)(sa->callp->sy_return, sa->code,
  150                             sa->callp, NULL, (error) ? -1 : td->td_retval[0]);
  151 #endif
  152                 syscall_thread_exit(td, sa->callp);
  153                 CTR4(KTR_SYSC, "syscall: p=%p error=%d return %#lx %#lx",
  154                     p, error, td->td_retval[0], td->td_retval[1]);
  155         }
  156  retval:
  157         if (traced) {
  158                 PROC_LOCK(p);
  159                 td->td_dbgflags &= ~TDB_SCE;
  160                 PROC_UNLOCK(p);
  161         }
  162         (p->p_sysent->sv_set_syscall_retval)(td, error);
  163         return (error);
  164 }
  165 
  166 static inline void
  167 syscallret(struct thread *td, int error, struct syscall_args *sa __unused)
  168 {
  169         struct proc *p, *p2;
  170         int traced;
  171 
  172         p = td->td_proc;
  173 
  174         /*
  175          * Check for misbehavior.
  176          */
  177         WITNESS_WARN(WARN_PANIC, NULL, "System call %s returning",
  178             syscallname(p, sa->code));
  179         KASSERT(td->td_critnest == 0,
  180             ("System call %s returning in a critical section",
  181             syscallname(p, sa->code)));
  182         KASSERT(td->td_locks == 0,
  183             ("System call %s returning with %d locks held",
  184              syscallname(p, sa->code), td->td_locks));
  185         KASSERT((td->td_pflags & TDP_NOFAULTING) == 0,
  186             ("System call %s returning with pagefaults disabled",
  187              syscallname(p, sa->code)));
  188         KASSERT((td->td_pflags & TDP_NOSLEEPING) == 0,
  189             ("System call %s returning with sleep disabled",
  190              syscallname(p, sa->code)));
  191 
  192         /*
  193          * Handle reschedule and other end-of-syscall issues
  194          */
  195         userret(td, td->td_frame);
  196 
  197         CTR4(KTR_SYSC, "syscall %s exit thread %p pid %d proc %s",
  198             syscallname(p, sa->code), td, td->td_proc->p_pid, td->td_name);
  199 
  200 #ifdef KTRACE
  201         if (KTRPOINT(td, KTR_SYSRET)) {
  202                 ktrsysret(sa->code, (td->td_pflags & TDP_NERRNO) == 0 ?
  203                     error : td->td_errno, td->td_retval[0]);
  204         }
  205 #endif
  206         td->td_pflags &= ~TDP_NERRNO;
  207 
  208         if (p->p_flag & P_TRACED) {
  209                 traced = 1;
  210                 PROC_LOCK(p);
  211                 td->td_dbgflags |= TDB_SCX;
  212                 PROC_UNLOCK(p);
  213         } else
  214                 traced = 0;
  215         /*
  216          * This works because errno is findable through the
  217          * register set.  If we ever support an emulation where this
  218          * is not the case, this code will need to be revisited.
  219          */
  220         STOPEVENT(p, S_SCX, sa->code);
  221         if (traced || (td->td_dbgflags & (TDB_EXEC | TDB_FORK)) != 0) {
  222                 PROC_LOCK(p);
  223                 /*
  224                  * If tracing the execed process, trap to the debugger
  225                  * so that breakpoints can be set before the program
  226                  * executes.  If debugger requested tracing of syscall
  227                  * returns, do it now too.
  228                  */
  229                 if (traced &&
  230                     ((td->td_dbgflags & (TDB_FORK | TDB_EXEC)) != 0 ||
  231                     (p->p_stops & S_PT_SCX) != 0))
  232                         ptracestop(td, SIGTRAP);
  233                 td->td_dbgflags &= ~(TDB_SCX | TDB_EXEC | TDB_FORK);
  234                 PROC_UNLOCK(p);
  235         }
  236 
  237         if (td->td_pflags & TDP_RFPPWAIT) {
  238                 /*
  239                  * Preserve synchronization semantics of vfork.  If
  240                  * waiting for child to exec or exit, fork set
  241                  * P_PPWAIT on child, and there we sleep on our proc
  242                  * (in case of exit).
  243                  *
  244                  * Do it after the ptracestop() above is finished, to
  245                  * not block our debugger until child execs or exits
  246                  * to finish vfork wait.
  247                  */
  248                 td->td_pflags &= ~TDP_RFPPWAIT;
  249                 p2 = td->td_rfppwait_p;
  250                 PROC_LOCK(p2);
  251                 while (p2->p_flag & P_PPWAIT)
  252                         cv_wait(&p2->p_pwait, &p2->p_mtx);
  253                 PROC_UNLOCK(p2);
  254         }
  255 }

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