subr_syscall.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) 2010 Konstantin Belousov <kib@freebsd.org>
    8  *
    9  * This code is derived from software contributed to Berkeley by
   10  * the University of Utah, and William Jolitz.
   11  *
   12  * Redistribution and use in source and binary forms, with or without
   13  * modification, are permitted provided that the following conditions
   14  * are met:
   15  * 1. Redistributions of source code must retain the above copyright
   16  *    notice, this list of conditions and the following disclaimer.
   17  * 2. Redistributions in binary form must reproduce the above copyright
   18  *    notice, this list of conditions and the following disclaimer in the
   19  *    documentation and/or other materials provided with the distribution.
   20  * 3. All advertising materials mentioning features or use of this software
   21  *    must display the following acknowledgement:
   22  *      This product includes software developed by the University of
   23  *      California, Berkeley and its contributors.
   24  * 4. Neither the name of the University nor the names of its contributors
   25  *    may be used to endorse or promote products derived from this software
   26  *    without specific prior written permission.
   27  *
   28  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   29  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   30  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   31  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   32  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   33  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   34  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   35  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   36  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   37  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   38  * SUCH DAMAGE.
   39  *
   40  *      from: @(#)trap.c        7.4 (Berkeley) 5/13/91
   41  */
   42 
   43 #include "opt_capsicum.h"
   44 #include "opt_ktrace.h"
   45 
   46 __FBSDID("$FreeBSD$");
   47 
   48 #include <sys/capsicum.h>
   49 #include <sys/ktr.h>
   50 #include <sys/vmmeter.h>
   51 #ifdef KTRACE
   52 #include <sys/uio.h>
   53 #include <sys/ktrace.h>
   54 #endif
   55 #include <security/audit/audit.h>
   56 
   57 static inline void
   58 syscallenter(struct thread *td)
   59 {
   60         struct proc *p;
   61         struct syscall_args *sa;
   62         struct sysent *se;
   63         int error, traced;
   64         bool sy_thr_static;
   65 
   66         VM_CNT_INC(v_syscall);
   67         p = td->td_proc;
   68         sa = &td->td_sa;
   69 
   70         td->td_pticks = 0;
   71         if (__predict_false(td->td_cowgen != p->p_cowgen))
   72                 thread_cow_update(td);
   73         traced = (p->p_flag & P_TRACED) != 0;
   74         if (__predict_false(traced || td->td_dbgflags & TDB_USERWR)) {
   75                 PROC_LOCK(p);
   76                 MPASS((td->td_dbgflags & TDB_BOUNDARY) == 0);
   77                 td->td_dbgflags &= ~TDB_USERWR;
   78                 if (traced)
   79                         td->td_dbgflags |= TDB_SCE;
   80                 PROC_UNLOCK(p);
   81         }
   82         error = (p->p_sysent->sv_fetch_syscall_args)(td);
   83         se = sa->callp;
   84 #ifdef KTRACE
   85         if (KTRPOINT(td, KTR_SYSCALL))
   86                 ktrsyscall(sa->code, se->sy_narg, sa->args);
   87 #endif
   88         KTR_START4(KTR_SYSC, "syscall", syscallname(p, sa->code),
   89             (uintptr_t)td, "pid:%d", td->td_proc->p_pid, "arg0:%p", sa->args[0],
   90             "arg1:%p", sa->args[1], "arg2:%p", sa->args[2]);
   91 
   92         if (__predict_false(error != 0)) {
   93                 td->td_errno = error;
   94                 goto retval;
   95         }
   96 
   97         if (__predict_false(traced)) {
   98                 PROC_LOCK(p);
   99                 if (p->p_ptevents & PTRACE_SCE)
  100                         ptracestop((td), SIGTRAP, NULL);
  101                 PROC_UNLOCK(p);
  102 
  103                 if ((td->td_dbgflags & TDB_USERWR) != 0) {
  104                         /*
  105                          * Reread syscall number and arguments if debugger
  106                          * modified registers or memory.
  107                          */
  108                         error = (p->p_sysent->sv_fetch_syscall_args)(td);
  109                         se = sa->callp;
  110 #ifdef KTRACE
  111                         if (KTRPOINT(td, KTR_SYSCALL))
  112                                 ktrsyscall(sa->code, se->sy_narg, sa->args);
  113 #endif
  114                         if (error != 0) {
  115                                 td->td_errno = error;
  116                                 goto retval;
  117                         }
  118                 }
  119         }
  120 
  121 #ifdef CAPABILITY_MODE
  122         /*
  123          * In capability mode, we only allow access to system calls
  124          * flagged with SYF_CAPENABLED.
  125          */
  126         if (__predict_false(IN_CAPABILITY_MODE(td) &&
  127             (se->sy_flags & SYF_CAPENABLED) == 0)) {
  128                 td->td_errno = error = ECAPMODE;
  129                 goto retval;
  130         }
  131 #endif
  132 
  133         /*
  134          * Fetch fast sigblock value at the time of syscall entry to
  135          * handle sleepqueue primitives which might call cursig().
  136          */
  137         if (__predict_false(sigfastblock_fetch_always))
  138                 (void)sigfastblock_fetch(td);
  139 
  140         /* Let system calls set td_errno directly. */
  141         KASSERT((td->td_pflags & TDP_NERRNO) == 0,
  142             ("%s: TDP_NERRNO set", __func__));
  143 
  144         sy_thr_static = (se->sy_thrcnt & SY_THR_STATIC) != 0;
  145 
  146         if (__predict_false(SYSTRACE_ENABLED() ||
  147             AUDIT_SYSCALL_ENTER(sa->code, td) ||
  148             !sy_thr_static)) {
  149                 if (!sy_thr_static) {
  150                         error = syscall_thread_enter(td, se);
  151                         if (error != 0) {
  152                                 td->td_errno = error;
  153                                 goto retval;
  154                         }
  155                 }
  156 
  157 #ifdef KDTRACE_HOOKS
  158                 /* Give the syscall:::entry DTrace probe a chance to fire. */
  159                 if (__predict_false(se->sy_entry != 0))
  160                         (*systrace_probe_func)(sa, SYSTRACE_ENTRY, 0);
  161 #endif
  162                 error = (se->sy_call)(td, sa->args);
  163                 /* Save the latest error return value. */
  164                 if (__predict_false((td->td_pflags & TDP_NERRNO) != 0))
  165                         td->td_pflags &= ~TDP_NERRNO;
  166                 else
  167                         td->td_errno = error;
  168 
  169                 /*
  170                  * Note that some syscall implementations (e.g., sys_execve)
  171                  * will commit the audit record just before their final return.
  172                  * These were done under the assumption that nothing of interest
  173                  * would happen between their return and here, where we would
  174                  * normally commit the audit record.  These assumptions will
  175                  * need to be revisited should any substantial logic be added
  176                  * above.
  177                  */
  178                 AUDIT_SYSCALL_EXIT(error, td);
  179 
  180 #ifdef KDTRACE_HOOKS
  181                 /* Give the syscall:::return DTrace probe a chance to fire. */
  182                 if (__predict_false(se->sy_return != 0))
  183                         (*systrace_probe_func)(sa, SYSTRACE_RETURN,
  184                             error ? -1 : td->td_retval[0]);
  185 #endif
  186 
  187                 if (!sy_thr_static)
  188                         syscall_thread_exit(td, se);
  189         } else {
  190                 error = (se->sy_call)(td, sa->args);
  191                 /* Save the latest error return value. */
  192                 if (__predict_false((td->td_pflags & TDP_NERRNO) != 0))
  193                         td->td_pflags &= ~TDP_NERRNO;
  194                 else
  195                         td->td_errno = error;
  196         }
  197 
  198  retval:
  199         KTR_STOP4(KTR_SYSC, "syscall", syscallname(p, sa->code),
  200             (uintptr_t)td, "pid:%d", td->td_proc->p_pid, "error:%d", error,
  201             "retval0:%#lx", td->td_retval[0], "retval1:%#lx",
  202             td->td_retval[1]);
  203         if (__predict_false(traced)) {
  204                 PROC_LOCK(p);
  205                 td->td_dbgflags &= ~(TDB_SCE | TDB_BOUNDARY);
  206                 PROC_UNLOCK(p);
  207         }
  208         (p->p_sysent->sv_set_syscall_retval)(td, error);
  209 }
  210 
  211 static inline void
  212 syscallret(struct thread *td)
  213 {
  214         struct proc *p;
  215         struct syscall_args *sa;
  216         ksiginfo_t ksi;
  217         int traced;
  218 
  219         KASSERT((td->td_pflags & TDP_FORKING) == 0,
  220             ("fork() did not clear TDP_FORKING upon completion"));
  221         KASSERT(td->td_errno != ERELOOKUP,
  222             ("ERELOOKUP not consumed syscall %d", td->td_sa.code));
  223 
  224         p = td->td_proc;
  225         sa = &td->td_sa;
  226         if (__predict_false(td->td_errno == ENOTCAPABLE ||
  227             td->td_errno == ECAPMODE)) {
  228                 if ((trap_enotcap ||
  229                     (p->p_flag2 & P2_TRAPCAP) != 0) && IN_CAPABILITY_MODE(td)) {
  230                         ksiginfo_init_trap(&ksi);
  231                         ksi.ksi_signo = SIGTRAP;
  232                         ksi.ksi_errno = td->td_errno;
  233                         ksi.ksi_code = TRAP_CAP;
  234                         trapsignal(td, &ksi);
  235                 }
  236         }
  237 
  238         /*
  239          * Handle reschedule and other end-of-syscall issues
  240          */
  241         userret(td, td->td_frame);
  242 
  243 #ifdef KTRACE
  244         if (KTRPOINT(td, KTR_SYSRET)) {
  245                 ktrsysret(sa->code, td->td_errno, td->td_retval[0]);
  246         }
  247 #endif
  248 
  249         traced = 0;
  250         if (__predict_false(p->p_flag & P_TRACED)) {
  251                 traced = 1;
  252                 PROC_LOCK(p);
  253                 td->td_dbgflags |= TDB_SCX;
  254                 PROC_UNLOCK(p);
  255         }
  256         if (__predict_false(traced ||
  257             (td->td_dbgflags & (TDB_EXEC | TDB_FORK)) != 0)) {
  258                 PROC_LOCK(p);
  259                 /*
  260                  * Linux debuggers expect an additional stop for exec,
  261                  * between the usual syscall entry and exit.  Raise
  262                  * the exec event now and then clear TDB_EXEC so that
  263                  * the next stop is reported as a syscall exit by
  264                  * linux_ptrace_status().
  265                  *
  266                  * We are accessing p->p_pptr without any additional
  267                  * locks here: it cannot change while p is kept locked;
  268                  * while the debugger could in theory change its ABI
  269                  * while tracing another process, the outcome of such
  270                  * a race wouln't be deterministic anyway.
  271                  */
  272                 if (traced && (td->td_dbgflags & TDB_EXEC) != 0 &&
  273                     SV_PROC_ABI(p->p_pptr) == SV_ABI_LINUX) {
  274                         ptracestop(td, SIGTRAP, NULL);
  275                         td->td_dbgflags &= ~TDB_EXEC;
  276                 }
  277                 /*
  278                  * If tracing the execed process, trap to the debugger
  279                  * so that breakpoints can be set before the program
  280                  * executes.  If debugger requested tracing of syscall
  281                  * returns, do it now too.
  282                  */
  283                 if (traced &&
  284                     ((td->td_dbgflags & (TDB_FORK | TDB_EXEC)) != 0 ||
  285                     (p->p_ptevents & PTRACE_SCX) != 0)) {
  286                         MPASS((td->td_dbgflags & TDB_BOUNDARY) == 0);
  287                         td->td_dbgflags |= TDB_BOUNDARY;
  288                         ptracestop(td, SIGTRAP, NULL);
  289                 }
  290                 td->td_dbgflags &= ~(TDB_SCX | TDB_EXEC | TDB_FORK |
  291                     TDB_BOUNDARY);
  292                 PROC_UNLOCK(p);
  293         }
  294 
  295         if (__predict_false(td->td_pflags & TDP_RFPPWAIT))
  296                 fork_rfppwait(td);
  297 }
Cache object: 8477e8a793cb1e777318320ae2c2d657
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FreeBSD/Linux Kernel Cross Reference sys/kern/subr_syscall.c

FreeBSD/Linux Kernel Cross Reference
sys/kern/subr_syscall.c
