subr_syscall.c

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/*-
 * Copyright (C) 1994, David Greenman
 * Copyright (c) 1990, 1993
 *      The Regents of the University of California.  All rights reserved.
 * Copyright (C) 2010 Konstantin Belousov <kib@freebsd.org>
 *
 * This code is derived from software contributed to Berkeley by
 * the University of Utah, and William Jolitz.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      from: @(#)trap.c        7.4 (Berkeley) 5/13/91
 */

#include "opt_capsicum.h"
#include "opt_ktrace.h"
#include "opt_kdtrace.h"

__FBSDID("$BSDSUniX$");

#include <sys/capability.h>
#include <sys/ktr.h>
#ifdef KTRACE
#include <sys/uio.h>
#include <sys/ktrace.h>
#endif
#include <security/audit/audit.h>

static inline int
syscallenter(struct thread *td, struct syscall_args *sa)
{
        struct proc *p;
        int error, traced;

        PCPU_INC(cnt.v_syscall);
        p = td->td_proc;

        td->td_pticks = 0;
        if (td->td_ucred != p->p_ucred)
                cred_update_thread(td);
        traced = (p->p_flag & P_TRACED) != 0;
        if (traced || td->td_dbgflags & TDB_USERWR) {
                PROC_LOCK(p);
                td->td_dbgflags &= ~TDB_USERWR;
                if (traced)
                        td->td_dbgflags |= TDB_SCE;
                PROC_UNLOCK(p);
        }
        error = (p->p_sysent->sv_fetch_syscall_args)(td, sa);
#ifdef KTRACE
        if (KTRPOINT(td, KTR_SYSCALL))
                ktrsyscall(sa->code, sa->narg, sa->args);
#endif

        CTR6(KTR_SYSC,
"syscall: td=%p pid %d %s (%#lx, %#lx, %#lx)",
            td, td->td_proc->p_pid, syscallname(p, sa->code),
            sa->args[0], sa->args[1], sa->args[2]);

        if (error == 0) {
                STOPEVENT(p, S_SCE, sa->narg);
                if (p->p_flag & P_TRACED) {
                        PROC_LOCK(p);
                        td->td_dbg_sc_code = sa->code;
                        td->td_dbg_sc_narg = sa->narg;
                        if (p->p_stops & S_PT_SCE)
                                ptracestop((td), SIGTRAP);
                        PROC_UNLOCK(p);
                }
                if (td->td_dbgflags & TDB_USERWR) {
                        /*
                         * Reread syscall number and arguments if
                         * debugger modified registers or memory.
                         */
                        error = (p->p_sysent->sv_fetch_syscall_args)(td, sa);
                        PROC_LOCK(p);
                        td->td_dbg_sc_code = sa->code;
                        td->td_dbg_sc_narg = sa->narg;
                        PROC_UNLOCK(p);
#ifdef KTRACE
                        if (KTRPOINT(td, KTR_SYSCALL))
                                ktrsyscall(sa->code, sa->narg, sa->args);
#endif
                        if (error != 0)
                                goto retval;
                }

#ifdef CAPABILITY_MODE
                /*
                 * In capability mode, we only allow access to system calls
                 * flagged with SYF_CAPENABLED.
                 */
                if (IN_CAPABILITY_MODE(td) &&
                    !(sa->callp->sy_flags & SYF_CAPENABLED)) {
                        error = ECAPMODE;
                        goto retval;
                }
#endif

                error = syscall_thread_enter(td, sa->callp);
                if (error != 0)
                        goto retval;

#ifdef KDTRACE_HOOKS
                /*
                 * If the systrace module has registered it's probe
                 * callback and if there is a probe active for the
                 * syscall 'entry', process the probe.
                 */
                if (systrace_probe_func != NULL && sa->callp->sy_entry != 0)
                        (*systrace_probe_func)(sa->callp->sy_entry, sa->code,
                            sa->callp, sa->args, 0);
#endif

                AUDIT_SYSCALL_ENTER(sa->code, td);
                error = (sa->callp->sy_call)(td, sa->args);
                AUDIT_SYSCALL_EXIT(error, td);

                /* Save the latest error return value. */
                if ((td->td_pflags & TDP_NERRNO) == 0)
                        td->td_errno = error;

#ifdef KDTRACE_HOOKS
                /*
                 * If the systrace module has registered it's probe
                 * callback and if there is a probe active for the
                 * syscall 'return', process the probe.
                 */
                if (systrace_probe_func != NULL && sa->callp->sy_return != 0)
                        (*systrace_probe_func)(sa->callp->sy_return, sa->code,
                            sa->callp, NULL, (error) ? -1 : td->td_retval[0]);
#endif
                syscall_thread_exit(td, sa->callp);
                CTR4(KTR_SYSC, "syscall: p=%p error=%d return %#lx %#lx",
                    p, error, td->td_retval[0], td->td_retval[1]);
        }
 retval:
        if (traced) {
                PROC_LOCK(p);
                td->td_dbgflags &= ~TDB_SCE;
                PROC_UNLOCK(p);
        }
        (p->p_sysent->sv_set_syscall_retval)(td, error);
        return (error);
}

static inline void
syscallret(struct thread *td, int error, struct syscall_args *sa __unused)
{
        struct proc *p, *p2;
        int traced;

        p = td->td_proc;

        /*
         * Check for misbehavior.
         */
        WITNESS_WARN(WARN_PANIC, NULL, "System call %s returning",
            syscallname(p, sa->code));
        KASSERT(td->td_critnest == 0,
            ("System call %s returning in a critical section",
            syscallname(p, sa->code)));
        KASSERT(td->td_locks == 0,
            ("System call %s returning with %d locks held",
             syscallname(p, sa->code), td->td_locks));
        KASSERT((td->td_pflags & TDP_NOFAULTING) == 0,
            ("System call %s returning with pagefaults disabled",
             syscallname(p, sa->code)));
        KASSERT((td->td_pflags & TDP_NOSLEEPING) == 0,
            ("System call %s returning with sleep disabled",
             syscallname(p, sa->code)));

        /*
         * Handle reschedule and other end-of-syscall issues
         */
        userret(td, td->td_frame);

        CTR4(KTR_SYSC, "syscall %s exit thread %p pid %d proc %s",
            syscallname(p, sa->code), td, td->td_proc->p_pid, td->td_name);

#ifdef KTRACE
        if (KTRPOINT(td, KTR_SYSRET)) {
                ktrsysret(sa->code, (td->td_pflags & TDP_NERRNO) == 0 ?
                    error : td->td_errno, td->td_retval[0]);
        }
#endif
        td->td_pflags &= ~TDP_NERRNO;

        if (p->p_flag & P_TRACED) {
                traced = 1;
                PROC_LOCK(p);
                td->td_dbgflags |= TDB_SCX;
                PROC_UNLOCK(p);
        } else
                traced = 0;
        /*
         * This works because errno is findable through the
         * register set.  If we ever support an emulation where this
         * is not the case, this code will need to be revisited.
         */
        STOPEVENT(p, S_SCX, sa->code);
        if (traced || (td->td_dbgflags & (TDB_EXEC | TDB_FORK)) != 0) {
                PROC_LOCK(p);
                /*
                 * If tracing the execed process, trap to the debugger
                 * so that breakpoints can be set before the program
                 * executes.  If debugger requested tracing of syscall
                 * returns, do it now too.
                 */
                if (traced &&
                    ((td->td_dbgflags & (TDB_FORK | TDB_EXEC)) != 0 ||
                    (p->p_stops & S_PT_SCX) != 0))
                        ptracestop(td, SIGTRAP);
                td->td_dbgflags &= ~(TDB_SCX | TDB_EXEC | TDB_FORK);
                PROC_UNLOCK(p);
        }

        if (td->td_pflags & TDP_RFPPWAIT) {
                /*
                 * Preserve synchronization semantics of vfork.  If
                 * waiting for child to exec or exit, fork set
                 * P_PPWAIT on child, and there we sleep on our proc
                 * (in case of exit).
                 *
                 * Do it after the ptracestop() above is finished, to
                 * not block our debugger until child execs or exits
                 * to finish vfork wait.
                 */
                td->td_pflags &= ~TDP_RFPPWAIT;
                p2 = td->td_rfppwait_p;
                PROC_LOCK(p2);
                while (p2->p_flag & P_PPWAIT)
                        cv_wait(&p2->p_pwait, &p2->p_mtx);
                PROC_UNLOCK(p2);
        }
}