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: stable/10/sys/kern/subr_syscall.c 315949 2017-03-25 13:33:23Z badger $");
   46 
   47 #include <sys/capsicum.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         traced = (p->p_flag & P_TRACED) != 0;
   68         if (traced || td->td_dbgflags & TDB_USERWR) {
   69                 PROC_LOCK(p);
   70                 td->td_dbgflags &= ~TDB_USERWR;
   71                 if (traced)
   72                         td->td_dbgflags |= TDB_SCE;
   73                 PROC_UNLOCK(p);
   74         }
   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         KTR_START4(KTR_SYSC, "syscall", syscallname(p, sa->code),
   81             (uintptr_t)td, "pid:%d", td->td_proc->p_pid, "arg0:%p", sa->args[0],
   82             "arg1:%p", sa->args[1], "arg2:%p", sa->args[2]);
   83 
   84         if (error == 0) {
   85 
   86                 STOPEVENT(p, S_SCE, sa->narg);
   87                 if (p->p_flag & P_TRACED) {
   88                         PROC_LOCK(p);
   89                         td->td_dbg_sc_code = sa->code;
   90                         td->td_dbg_sc_narg = sa->narg;
   91                         if (p->p_ptevents & PTRACE_SCE)
   92                                 ptracestop((td), SIGTRAP, NULL);
   93                         PROC_UNLOCK(p);
   94                 }
   95                 if (td->td_dbgflags & TDB_USERWR) {
   96                         /*
   97                          * Reread syscall number and arguments if
   98                          * debugger modified registers or memory.
   99                          */
  100                         error = (p->p_sysent->sv_fetch_syscall_args)(td, sa);
  101                         PROC_LOCK(p);
  102                         td->td_dbg_sc_code = sa->code;
  103                         td->td_dbg_sc_narg = sa->narg;
  104                         PROC_UNLOCK(p);
  105 #ifdef KTRACE
  106                         if (KTRPOINT(td, KTR_SYSCALL))
  107                                 ktrsyscall(sa->code, sa->narg, sa->args);
  108 #endif
  109                         if (error != 0)
  110                                 goto retval;
  111                 }
  112 
  113 #ifdef CAPABILITY_MODE
  114                 /*
  115                  * In capability mode, we only allow access to system calls
  116                  * flagged with SYF_CAPENABLED.
  117                  */
  118                 if (IN_CAPABILITY_MODE(td) &&
  119                     !(sa->callp->sy_flags & SYF_CAPENABLED)) {
  120                         error = ECAPMODE;
  121                         goto retval;
  122                 }
  123 #endif
  124 
  125                 error = syscall_thread_enter(td, sa->callp);
  126                 if (error != 0)
  127                         goto retval;
  128 
  129 #ifdef KDTRACE_HOOKS
  130                 /*
  131                  * If the systrace module has registered it's probe
  132                  * callback and if there is a probe active for the
  133                  * syscall 'entry', process the probe.
  134                  */
  135                 if (systrace_probe_func != NULL && sa->callp->sy_entry != 0)
  136                         (*systrace_probe_func)(sa->callp->sy_entry, sa->code,
  137                             sa->callp, sa->args, 0);
  138 #endif
  139 
  140                 AUDIT_SYSCALL_ENTER(sa->code, td);
  141                 error = (sa->callp->sy_call)(td, sa->args);
  142                 AUDIT_SYSCALL_EXIT(error, td);
  143 
  144                 /* Save the latest error return value. */
  145                 if ((td->td_pflags & TDP_NERRNO) == 0)
  146                         td->td_errno = error;
  147 
  148 #ifdef KDTRACE_HOOKS
  149                 /*
  150                  * If the systrace module has registered it's probe
  151                  * callback and if there is a probe active for the
  152                  * syscall 'return', process the probe.
  153                  */
  154                 if (systrace_probe_func != NULL && sa->callp->sy_return != 0)
  155                         (*systrace_probe_func)(sa->callp->sy_return, sa->code,
  156                             sa->callp, NULL, (error) ? -1 : td->td_retval[0]);
  157 #endif
  158                 syscall_thread_exit(td, sa->callp);
  159         }
  160  retval:
  161         KTR_STOP4(KTR_SYSC, "syscall", syscallname(p, sa->code),
  162             (uintptr_t)td, "pid:%d", td->td_proc->p_pid, "error:%d", error,
  163             "retval0:%#lx", td->td_retval[0], "retval1:%#lx",
  164             td->td_retval[1]);
  165         if (traced) {
  166                 PROC_LOCK(p);
  167                 td->td_dbgflags &= ~TDB_SCE;
  168                 PROC_UNLOCK(p);
  169         }
  170         (p->p_sysent->sv_set_syscall_retval)(td, error);
  171         return (error);
  172 }
  173 
  174 static inline void
  175 syscallret(struct thread *td, int error, struct syscall_args *sa __unused)
  176 {
  177         struct proc *p, *p2;
  178         int traced;
  179 
  180         p = td->td_proc;
  181 
  182         /*
  183          * Handle reschedule and other end-of-syscall issues
  184          */
  185         userret(td, td->td_frame);
  186 
  187 #ifdef KTRACE
  188         if (KTRPOINT(td, KTR_SYSRET)) {
  189                 ktrsysret(sa->code, (td->td_pflags & TDP_NERRNO) == 0 ?
  190                     error : td->td_errno, td->td_retval[0]);
  191         }
  192 #endif
  193         td->td_pflags &= ~TDP_NERRNO;
  194 
  195         if (p->p_flag & P_TRACED) {
  196                 traced = 1;
  197                 PROC_LOCK(p);
  198                 td->td_dbgflags |= TDB_SCX;
  199                 PROC_UNLOCK(p);
  200         } else
  201                 traced = 0;
  202         /*
  203          * This works because errno is findable through the
  204          * register set.  If we ever support an emulation where this
  205          * is not the case, this code will need to be revisited.
  206          */
  207         STOPEVENT(p, S_SCX, sa->code);
  208         if (traced || (td->td_dbgflags & (TDB_EXEC | TDB_FORK)) != 0) {
  209                 PROC_LOCK(p);
  210                 /*
  211                  * If tracing the execed process, trap to the debugger
  212                  * so that breakpoints can be set before the program
  213                  * executes.  If debugger requested tracing of syscall
  214                  * returns, do it now too.
  215                  */
  216                 if (traced &&
  217                     ((td->td_dbgflags & (TDB_FORK | TDB_EXEC)) != 0 ||
  218                     (p->p_ptevents & PTRACE_SCX) != 0))
  219                         ptracestop(td, SIGTRAP, NULL);
  220                 td->td_dbgflags &= ~(TDB_SCX | TDB_EXEC | TDB_FORK);
  221                 PROC_UNLOCK(p);
  222         }
  223 
  224         if (td->td_pflags & TDP_RFPPWAIT) {
  225                 /*
  226                  * Preserve synchronization semantics of vfork.  If
  227                  * waiting for child to exec or exit, fork set
  228                  * P_PPWAIT on child, and there we sleep on our proc
  229                  * (in case of exit).
  230                  *
  231                  * Do it after the ptracestop() above is finished, to
  232                  * not block our debugger until child execs or exits
  233                  * to finish vfork wait.
  234                  */
  235                 td->td_pflags &= ~TDP_RFPPWAIT;
  236                 p2 = td->td_rfppwait_p;
  237 again:
  238                 PROC_LOCK(p2);
  239                 while (p2->p_flag & P_PPWAIT) {
  240                         PROC_LOCK(p);
  241                         if (thread_suspend_check_needed()) {
  242                                 PROC_UNLOCK(p2);
  243                                 thread_suspend_check(0);
  244                                 PROC_UNLOCK(p);
  245                                 goto again;
  246                         } else {
  247                                 PROC_UNLOCK(p);
  248                         }
  249                         cv_timedwait(&p2->p_pwait, &p2->p_mtx, hz);
  250                 }
  251                 PROC_UNLOCK(p2);
  252 
  253                 if (td->td_dbgflags & TDB_VFORK) {
  254                         PROC_LOCK(p);
  255                         if (p->p_ptevents & PTRACE_VFORK)
  256                                 ptracestop(td, SIGTRAP, NULL);
  257                         td->td_dbgflags &= ~TDB_VFORK;
  258                         PROC_UNLOCK(p);
  259                 }
  260         }
  261 }

Cache object: 4921826c17a2c117980b156ca970ce93


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