zfs: merge openzfs/zfs@a94860a6d

[FreeBSD/FreeBSD.git] / sys / kern / kern_sig.c

/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1982, 1986, 1989, 1991, 1993
 *      The Regents of the University of California.  All rights reserved.
 * (c) UNIX System Laboratories, Inc.
 * All or some portions of this file are derived from material licensed
 * to the University of California by American Telephone and Telegraph
 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
 * the permission of UNIX System Laboratories, Inc.
 *
 * 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. 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.
 *
 *      @(#)kern_sig.c  8.7 (Berkeley) 4/18/94
 */

#include <sys/cdefs.h>
#include "opt_capsicum.h"
#include "opt_ktrace.h"

#include <sys/param.h>
#include <sys/capsicum.h>
#include <sys/ctype.h>
#include <sys/systm.h>
#include <sys/signalvar.h>
#include <sys/vnode.h>
#include <sys/acct.h>
#include <sys/capsicum.h>
#include <sys/compressor.h>
#include <sys/condvar.h>
#include <sys/devctl.h>
#include <sys/event.h>
#include <sys/fcntl.h>
#include <sys/imgact.h>
#include <sys/jail.h>
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <sys/ktrace.h>
#include <sys/limits.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/refcount.h>
#include <sys/namei.h>
#include <sys/proc.h>
#include <sys/procdesc.h>
#include <sys/ptrace.h>
#include <sys/posix4.h>
#include <sys/racct.h>
#include <sys/resourcevar.h>
#include <sys/sdt.h>
#include <sys/sbuf.h>
#include <sys/sleepqueue.h>
#include <sys/smp.h>
#include <sys/stat.h>
#include <sys/sx.h>
#include <sys/syscall.h>
#include <sys/syscallsubr.h>
#include <sys/sysctl.h>
#include <sys/sysent.h>
#include <sys/syslog.h>
#include <sys/sysproto.h>
#include <sys/timers.h>
#include <sys/unistd.h>
#include <sys/vmmeter.h>
#include <sys/wait.h>
#include <vm/vm.h>
#include <vm/vm_extern.h>
#include <vm/uma.h>

#include <machine/cpu.h>

#include <security/audit/audit.h>

#define ONSIG   32              /* NSIG for osig* syscalls.  XXX. */

SDT_PROVIDER_DECLARE(proc);
SDT_PROBE_DEFINE3(proc, , , signal__send,
    "struct thread *", "struct proc *", "int");
SDT_PROBE_DEFINE2(proc, , , signal__clear,
    "int", "ksiginfo_t *");
SDT_PROBE_DEFINE3(proc, , , signal__discard,
    "struct thread *", "struct proc *", "int");

static int      coredump(struct thread *);
static int      killpg1(struct thread *td, int sig, int pgid, int all,
                    ksiginfo_t *ksi);
static int      issignal(struct thread *td);
static void     reschedule_signals(struct proc *p, sigset_t block, int flags);
static int      sigprop(int sig);
static void     tdsigwakeup(struct thread *, int, sig_t, int);
static int      sig_suspend_threads(struct thread *, struct proc *);
static int      filt_sigattach(struct knote *kn);
static void     filt_sigdetach(struct knote *kn);
static int      filt_signal(struct knote *kn, long hint);
static struct thread *sigtd(struct proc *p, int sig, bool fast_sigblock);
static void     sigqueue_start(void);
static void     sigfastblock_setpend(struct thread *td, bool resched);

static uma_zone_t       ksiginfo_zone = NULL;
struct filterops sig_filtops = {
        .f_isfd = 0,
        .f_attach = filt_sigattach,
        .f_detach = filt_sigdetach,
        .f_event = filt_signal,
};

static int      kern_logsigexit = 1;
SYSCTL_INT(_kern, KERN_LOGSIGEXIT, logsigexit, CTLFLAG_RW,
    &kern_logsigexit, 0,
    "Log processes quitting on abnormal signals to syslog(3)");

static int      kern_forcesigexit = 1;
SYSCTL_INT(_kern, OID_AUTO, forcesigexit, CTLFLAG_RW,
    &kern_forcesigexit, 0, "Force trap signal to be handled");

static SYSCTL_NODE(_kern, OID_AUTO, sigqueue, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
    "POSIX real time signal");

static int      max_pending_per_proc = 128;
SYSCTL_INT(_kern_sigqueue, OID_AUTO, max_pending_per_proc, CTLFLAG_RW,
    &max_pending_per_proc, 0, "Max pending signals per proc");

static int      preallocate_siginfo = 1024;
SYSCTL_INT(_kern_sigqueue, OID_AUTO, preallocate, CTLFLAG_RDTUN,
    &preallocate_siginfo, 0, "Preallocated signal memory size");

static int      signal_overflow = 0;
SYSCTL_INT(_kern_sigqueue, OID_AUTO, overflow, CTLFLAG_RD,
    &signal_overflow, 0, "Number of signals overflew");

static int      signal_alloc_fail = 0;
SYSCTL_INT(_kern_sigqueue, OID_AUTO, alloc_fail, CTLFLAG_RD,
    &signal_alloc_fail, 0, "signals failed to be allocated");

static int      kern_lognosys = 0;
SYSCTL_INT(_kern, OID_AUTO, lognosys, CTLFLAG_RWTUN, &kern_lognosys, 0,
    "Log invalid syscalls");

static int      kern_signosys = 1;
SYSCTL_INT(_kern, OID_AUTO, signosys, CTLFLAG_RWTUN, &kern_signosys, 0,
    "Send SIGSYS on return from invalid syscall");

__read_frequently bool sigfastblock_fetch_always = false;
SYSCTL_BOOL(_kern, OID_AUTO, sigfastblock_fetch_always, CTLFLAG_RWTUN,
    &sigfastblock_fetch_always, 0,
    "Fetch sigfastblock word on each syscall entry for proper "
    "blocking semantic");

static bool     kern_sig_discard_ign = true;
SYSCTL_BOOL(_kern, OID_AUTO, sig_discard_ign, CTLFLAG_RWTUN,
    &kern_sig_discard_ign, 0,
    "Discard ignored signals on delivery, otherwise queue them to "
    "the target queue");

SYSINIT(signal, SI_SUB_P1003_1B, SI_ORDER_FIRST+3, sigqueue_start, NULL);

/*
 * Policy -- Can ucred cr1 send SIGIO to process cr2?
 * Should use cr_cansignal() once cr_cansignal() allows SIGIO and SIGURG
 * in the right situations.
 */
#define CANSIGIO(cr1, cr2) \
        ((cr1)->cr_uid == 0 || \
            (cr1)->cr_ruid == (cr2)->cr_ruid || \
            (cr1)->cr_uid == (cr2)->cr_ruid || \
            (cr1)->cr_ruid == (cr2)->cr_uid || \
            (cr1)->cr_uid == (cr2)->cr_uid)

static int      sugid_coredump;
SYSCTL_INT(_kern, OID_AUTO, sugid_coredump, CTLFLAG_RWTUN,
    &sugid_coredump, 0, "Allow setuid and setgid processes to dump core");

static int      capmode_coredump;
SYSCTL_INT(_kern, OID_AUTO, capmode_coredump, CTLFLAG_RWTUN,
    &capmode_coredump, 0, "Allow processes in capability mode to dump core");

static int      do_coredump = 1;
SYSCTL_INT(_kern, OID_AUTO, coredump, CTLFLAG_RW,
        &do_coredump, 0, "Enable/Disable coredumps");

static int      set_core_nodump_flag = 0;
SYSCTL_INT(_kern, OID_AUTO, nodump_coredump, CTLFLAG_RW, &set_core_nodump_flag,
        0, "Enable setting the NODUMP flag on coredump files");

static int      coredump_devctl = 0;
SYSCTL_INT(_kern, OID_AUTO, coredump_devctl, CTLFLAG_RW, &coredump_devctl,
        0, "Generate a devctl notification when processes coredump");

/*
 * Signal properties and actions.
 * The array below categorizes the signals and their default actions
 * according to the following properties:
 */
#define SIGPROP_KILL            0x01    /* terminates process by default */
#define SIGPROP_CORE            0x02    /* ditto and coredumps */
#define SIGPROP_STOP            0x04    /* suspend process */
#define SIGPROP_TTYSTOP         0x08    /* ditto, from tty */
#define SIGPROP_IGNORE          0x10    /* ignore by default */
#define SIGPROP_CONT            0x20    /* continue if suspended */

static const int sigproptbl[NSIG] = {
        [SIGHUP] =      SIGPROP_KILL,
        [SIGINT] =      SIGPROP_KILL,
        [SIGQUIT] =     SIGPROP_KILL | SIGPROP_CORE,
        [SIGILL] =      SIGPROP_KILL | SIGPROP_CORE,
        [SIGTRAP] =     SIGPROP_KILL | SIGPROP_CORE,
        [SIGABRT] =     SIGPROP_KILL | SIGPROP_CORE,
        [SIGEMT] =      SIGPROP_KILL | SIGPROP_CORE,
        [SIGFPE] =      SIGPROP_KILL | SIGPROP_CORE,
        [SIGKILL] =     SIGPROP_KILL,
        [SIGBUS] =      SIGPROP_KILL | SIGPROP_CORE,
        [SIGSEGV] =     SIGPROP_KILL | SIGPROP_CORE,
        [SIGSYS] =      SIGPROP_KILL | SIGPROP_CORE,
        [SIGPIPE] =     SIGPROP_KILL,
        [SIGALRM] =     SIGPROP_KILL,
        [SIGTERM] =     SIGPROP_KILL,
        [SIGURG] =      SIGPROP_IGNORE,
        [SIGSTOP] =     SIGPROP_STOP,
        [SIGTSTP] =     SIGPROP_STOP | SIGPROP_TTYSTOP,
        [SIGCONT] =     SIGPROP_IGNORE | SIGPROP_CONT,
        [SIGCHLD] =     SIGPROP_IGNORE,
        [SIGTTIN] =     SIGPROP_STOP | SIGPROP_TTYSTOP,
        [SIGTTOU] =     SIGPROP_STOP | SIGPROP_TTYSTOP,
        [SIGIO] =       SIGPROP_IGNORE,
        [SIGXCPU] =     SIGPROP_KILL,
        [SIGXFSZ] =     SIGPROP_KILL,
        [SIGVTALRM] =   SIGPROP_KILL,
        [SIGPROF] =     SIGPROP_KILL,
        [SIGWINCH] =    SIGPROP_IGNORE,
        [SIGINFO] =     SIGPROP_IGNORE,
        [SIGUSR1] =     SIGPROP_KILL,
        [SIGUSR2] =     SIGPROP_KILL,
};

#define _SIG_FOREACH_ADVANCE(i, set) ({                                 \
        int __found;                                                    \
        for (;;) {                                                      \
                if (__bits != 0) {                                      \
                        int __sig = ffs(__bits);                        \
                        __bits &= ~(1u << (__sig - 1));                 \
                        sig = __i * sizeof((set)->__bits[0]) * NBBY + __sig; \
                        __found = 1;                                    \
                        break;                                          \
                }                                                       \
                if (++__i == _SIG_WORDS) {                              \
                        __found = 0;                                    \
                        break;                                          \
                }                                                       \
                __bits = (set)->__bits[__i];                            \
        }                                                               \
        __found != 0;                                                   \
})

#define SIG_FOREACH(i, set)                                             \
        for (int32_t __i = -1, __bits = 0;                              \
            _SIG_FOREACH_ADVANCE(i, set); )                             \

static sigset_t fastblock_mask;

static void
ast_sig(struct thread *td, int tda)
{
        struct proc *p;
        int old_boundary, sig;
        bool resched_sigs;

        p = td->td_proc;

#ifdef DIAGNOSTIC
        if (p->p_numthreads == 1 && (tda & (TDAI(TDA_SIG) |
            TDAI(TDA_AST))) == 0) {
                PROC_LOCK(p);
                thread_lock(td);
                /*
                 * Note that TDA_SIG should be re-read from
                 * td_ast, since signal might have been delivered
                 * after we cleared td_flags above.  This is one of
                 * the reason for looping check for AST condition.
                 * See comment in userret() about P_PPWAIT.
                 */
                if ((p->p_flag & P_PPWAIT) == 0 &&
                    (td->td_pflags & TDP_SIGFASTBLOCK) == 0) {
                        if (SIGPENDING(td) && ((tda | td->td_ast) &
                            (TDAI(TDA_SIG) | TDAI(TDA_AST))) == 0) {
                                thread_unlock(td); /* fix dumps */
                                panic(
                                    "failed2 to set signal flags for ast p %p "
                                    "td %p tda %#x td_ast %#x fl %#x",
                                    p, td, tda, td->td_ast, td->td_flags);
                        }
                }
                thread_unlock(td);
                PROC_UNLOCK(p);
        }
#endif

        /*
         * Check for signals. Unlocked reads of p_pendingcnt or
         * p_siglist might cause process-directed signal to be handled
         * later.
         */
        if ((tda & TDAI(TDA_SIG)) != 0 || p->p_pendingcnt > 0 ||
            !SIGISEMPTY(p->p_siglist)) {
                sigfastblock_fetch(td);
                PROC_LOCK(p);
                old_boundary = ~TDB_BOUNDARY | (td->td_dbgflags & TDB_BOUNDARY);
                td->td_dbgflags |= TDB_BOUNDARY;
                mtx_lock(&p->p_sigacts->ps_mtx);
                while ((sig = cursig(td)) != 0) {
                        KASSERT(sig >= 0, ("sig %d", sig));
                        postsig(sig);
                }
                mtx_unlock(&p->p_sigacts->ps_mtx);
                td->td_dbgflags &= old_boundary;
                PROC_UNLOCK(p);
                resched_sigs = true;
        } else {
                resched_sigs = false;
        }

        /*
         * Handle deferred update of the fast sigblock value, after
         * the postsig() loop was performed.
         */
        sigfastblock_setpend(td, resched_sigs);
}

static void
ast_sigsuspend(struct thread *td, int tda __unused)
{
        MPASS((td->td_pflags & TDP_OLDMASK) != 0);
        td->td_pflags &= ~TDP_OLDMASK;
        kern_sigprocmask(td, SIG_SETMASK, &td->td_oldsigmask, NULL, 0);
}

static void
sigqueue_start(void)
{
        ksiginfo_zone = uma_zcreate("ksiginfo", sizeof(ksiginfo_t),
                NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
        uma_prealloc(ksiginfo_zone, preallocate_siginfo);
        p31b_setcfg(CTL_P1003_1B_REALTIME_SIGNALS, _POSIX_REALTIME_SIGNALS);
        p31b_setcfg(CTL_P1003_1B_RTSIG_MAX, SIGRTMAX - SIGRTMIN + 1);
        p31b_setcfg(CTL_P1003_1B_SIGQUEUE_MAX, max_pending_per_proc);
        SIGFILLSET(fastblock_mask);
        SIG_CANTMASK(fastblock_mask);
        ast_register(TDA_SIG, ASTR_UNCOND, 0, ast_sig);
        ast_register(TDA_SIGSUSPEND, ASTR_ASTF_REQUIRED | ASTR_TDP,
            TDP_OLDMASK, ast_sigsuspend);
}

ksiginfo_t *
ksiginfo_alloc(int mwait)
{
        MPASS(mwait == M_WAITOK || mwait == M_NOWAIT);

        if (ksiginfo_zone == NULL)
                return (NULL);
        return (uma_zalloc(ksiginfo_zone, mwait | M_ZERO));
}

void
ksiginfo_free(ksiginfo_t *ksi)
{
        uma_zfree(ksiginfo_zone, ksi);
}

static __inline bool
ksiginfo_tryfree(ksiginfo_t *ksi)
{
        if ((ksi->ksi_flags & KSI_EXT) == 0) {
                uma_zfree(ksiginfo_zone, ksi);
                return (true);
        }
        return (false);
}

void
sigqueue_init(sigqueue_t *list, struct proc *p)
{
        SIGEMPTYSET(list->sq_signals);
        SIGEMPTYSET(list->sq_kill);
        SIGEMPTYSET(list->sq_ptrace);
        TAILQ_INIT(&list->sq_list);
        list->sq_proc = p;
        list->sq_flags = SQ_INIT;
}

/*
 * Get a signal's ksiginfo.
 * Return:
 *      0       -       signal not found
 *      others  -       signal number
 */
static int
sigqueue_get(sigqueue_t *sq, int signo, ksiginfo_t *si)
{
        struct proc *p = sq->sq_proc;
        struct ksiginfo *ksi, *next;
        int count = 0;

        KASSERT(sq->sq_flags & SQ_INIT, ("sigqueue not inited"));

        if (!SIGISMEMBER(sq->sq_signals, signo))
                return (0);

        if (SIGISMEMBER(sq->sq_ptrace, signo)) {
                count++;
                SIGDELSET(sq->sq_ptrace, signo);
                si->ksi_flags |= KSI_PTRACE;
        }
        if (SIGISMEMBER(sq->sq_kill, signo)) {
                count++;
                if (count == 1)
                        SIGDELSET(sq->sq_kill, signo);
        }

        TAILQ_FOREACH_SAFE(ksi, &sq->sq_list, ksi_link, next) {
                if (ksi->ksi_signo == signo) {
                        if (count == 0) {
                                TAILQ_REMOVE(&sq->sq_list, ksi, ksi_link);
                                ksi->ksi_sigq = NULL;
                                ksiginfo_copy(ksi, si);
                                if (ksiginfo_tryfree(ksi) && p != NULL)
                                        p->p_pendingcnt--;
                        }
                        if (++count > 1)
                                break;
                }
        }

        if (count <= 1)
                SIGDELSET(sq->sq_signals, signo);
        si->ksi_signo = signo;
        return (signo);
}

void
sigqueue_take(ksiginfo_t *ksi)
{
        struct ksiginfo *kp;
        struct proc     *p;
        sigqueue_t      *sq;

        if (ksi == NULL || (sq = ksi->ksi_sigq) == NULL)
                return;

        p = sq->sq_proc;
        TAILQ_REMOVE(&sq->sq_list, ksi, ksi_link);
        ksi->ksi_sigq = NULL;
        if (!(ksi->ksi_flags & KSI_EXT) && p != NULL)
                p->p_pendingcnt--;

        for (kp = TAILQ_FIRST(&sq->sq_list); kp != NULL;
             kp = TAILQ_NEXT(kp, ksi_link)) {
                if (kp->ksi_signo == ksi->ksi_signo)
                        break;
        }
        if (kp == NULL && !SIGISMEMBER(sq->sq_kill, ksi->ksi_signo) &&
            !SIGISMEMBER(sq->sq_ptrace, ksi->ksi_signo))
                SIGDELSET(sq->sq_signals, ksi->ksi_signo);
}

static int
sigqueue_add(sigqueue_t *sq, int signo, ksiginfo_t *si)
{
        struct proc *p = sq->sq_proc;
        struct ksiginfo *ksi;
        int ret = 0;

        KASSERT(sq->sq_flags & SQ_INIT, ("sigqueue not inited"));

        /*
         * SIGKILL/SIGSTOP cannot be caught or masked, so take the fast path
         * for these signals.
         */
        if (signo == SIGKILL || signo == SIGSTOP || si == NULL) {
                SIGADDSET(sq->sq_kill, signo);
                goto out_set_bit;
        }

        /* directly insert the ksi, don't copy it */
        if (si->ksi_flags & KSI_INS) {
                if (si->ksi_flags & KSI_HEAD)
                        TAILQ_INSERT_HEAD(&sq->sq_list, si, ksi_link);
                else
                        TAILQ_INSERT_TAIL(&sq->sq_list, si, ksi_link);
                si->ksi_sigq = sq;
                goto out_set_bit;
        }

        if (__predict_false(ksiginfo_zone == NULL)) {
                SIGADDSET(sq->sq_kill, signo);
                goto out_set_bit;
        }

        if (p != NULL && p->p_pendingcnt >= max_pending_per_proc) {
                signal_overflow++;
                ret = EAGAIN;
        } else if ((ksi = ksiginfo_alloc(M_NOWAIT)) == NULL) {
                signal_alloc_fail++;
                ret = EAGAIN;
        } else {
                if (p != NULL)
                        p->p_pendingcnt++;
                ksiginfo_copy(si, ksi);
                ksi->ksi_signo = signo;
                if (si->ksi_flags & KSI_HEAD)
                        TAILQ_INSERT_HEAD(&sq->sq_list, ksi, ksi_link);
                else
                        TAILQ_INSERT_TAIL(&sq->sq_list, ksi, ksi_link);
                ksi->ksi_sigq = sq;
        }

        if (ret != 0) {
                if ((si->ksi_flags & KSI_PTRACE) != 0) {
                        SIGADDSET(sq->sq_ptrace, signo);
                        ret = 0;
                        goto out_set_bit;
                } else if ((si->ksi_flags & KSI_TRAP) != 0 ||
                    (si->ksi_flags & KSI_SIGQ) == 0) {
                        SIGADDSET(sq->sq_kill, signo);
                        ret = 0;
                        goto out_set_bit;
                }
                return (ret);
        }

out_set_bit:
        SIGADDSET(sq->sq_signals, signo);
        return (ret);
}

void
sigqueue_flush(sigqueue_t *sq)
{
        struct proc *p = sq->sq_proc;
        ksiginfo_t *ksi;

        KASSERT(sq->sq_flags & SQ_INIT, ("sigqueue not inited"));

        if (p != NULL)
                PROC_LOCK_ASSERT(p, MA_OWNED);

        while ((ksi = TAILQ_FIRST(&sq->sq_list)) != NULL) {
                TAILQ_REMOVE(&sq->sq_list, ksi, ksi_link);
                ksi->ksi_sigq = NULL;
                if (ksiginfo_tryfree(ksi) && p != NULL)
                        p->p_pendingcnt--;
        }

        SIGEMPTYSET(sq->sq_signals);
        SIGEMPTYSET(sq->sq_kill);
        SIGEMPTYSET(sq->sq_ptrace);
}

static void
sigqueue_move_set(sigqueue_t *src, sigqueue_t *dst, const sigset_t *set)
{
        sigset_t tmp;
        struct proc *p1, *p2;
        ksiginfo_t *ksi, *next;

        KASSERT(src->sq_flags & SQ_INIT, ("src sigqueue not inited"));
        KASSERT(dst->sq_flags & SQ_INIT, ("dst sigqueue not inited"));
        p1 = src->sq_proc;
        p2 = dst->sq_proc;
        /* Move siginfo to target list */
        TAILQ_FOREACH_SAFE(ksi, &src->sq_list, ksi_link, next) {
                if (SIGISMEMBER(*set, ksi->ksi_signo)) {
                        TAILQ_REMOVE(&src->sq_list, ksi, ksi_link);
                        if (p1 != NULL)
                                p1->p_pendingcnt--;
                        TAILQ_INSERT_TAIL(&dst->sq_list, ksi, ksi_link);
                        ksi->ksi_sigq = dst;
                        if (p2 != NULL)
                                p2->p_pendingcnt++;
                }
        }

        /* Move pending bits to target list */
        tmp = src->sq_kill;
        SIGSETAND(tmp, *set);
        SIGSETOR(dst->sq_kill, tmp);
        SIGSETNAND(src->sq_kill, tmp);

        tmp = src->sq_ptrace;
        SIGSETAND(tmp, *set);
        SIGSETOR(dst->sq_ptrace, tmp);
        SIGSETNAND(src->sq_ptrace, tmp);

        tmp = src->sq_signals;
        SIGSETAND(tmp, *set);
        SIGSETOR(dst->sq_signals, tmp);
        SIGSETNAND(src->sq_signals, tmp);
}

#if 0
static void
sigqueue_move(sigqueue_t *src, sigqueue_t *dst, int signo)
{
        sigset_t set;

        SIGEMPTYSET(set);
        SIGADDSET(set, signo);
        sigqueue_move_set(src, dst, &set);
}
#endif

static void
sigqueue_delete_set(sigqueue_t *sq, const sigset_t *set)
{
        struct proc *p = sq->sq_proc;
        ksiginfo_t *ksi, *next;

        KASSERT(sq->sq_flags & SQ_INIT, ("src sigqueue not inited"));

        /* Remove siginfo queue */
        TAILQ_FOREACH_SAFE(ksi, &sq->sq_list, ksi_link, next) {
                if (SIGISMEMBER(*set, ksi->ksi_signo)) {
                        TAILQ_REMOVE(&sq->sq_list, ksi, ksi_link);
                        ksi->ksi_sigq = NULL;
                        if (ksiginfo_tryfree(ksi) && p != NULL)
                                p->p_pendingcnt--;
                }
        }
        SIGSETNAND(sq->sq_kill, *set);
        SIGSETNAND(sq->sq_ptrace, *set);
        SIGSETNAND(sq->sq_signals, *set);
}

void
sigqueue_delete(sigqueue_t *sq, int signo)
{
        sigset_t set;

        SIGEMPTYSET(set);
        SIGADDSET(set, signo);
        sigqueue_delete_set(sq, &set);
}

/* Remove a set of signals for a process */
static void
sigqueue_delete_set_proc(struct proc *p, const sigset_t *set)
{
        sigqueue_t worklist;
        struct thread *td0;

        PROC_LOCK_ASSERT(p, MA_OWNED);

        sigqueue_init(&worklist, NULL);
        sigqueue_move_set(&p->p_sigqueue, &worklist, set);

        FOREACH_THREAD_IN_PROC(p, td0)
                sigqueue_move_set(&td0->td_sigqueue, &worklist, set);

        sigqueue_flush(&worklist);
}

void
sigqueue_delete_proc(struct proc *p, int signo)
{
        sigset_t set;

        SIGEMPTYSET(set);
        SIGADDSET(set, signo);
        sigqueue_delete_set_proc(p, &set);
}

static void
sigqueue_delete_stopmask_proc(struct proc *p)
{
        sigset_t set;

        SIGEMPTYSET(set);
        SIGADDSET(set, SIGSTOP);
        SIGADDSET(set, SIGTSTP);
        SIGADDSET(set, SIGTTIN);
        SIGADDSET(set, SIGTTOU);
        sigqueue_delete_set_proc(p, &set);
}

/*
 * Determine signal that should be delivered to thread td, the current
 * thread, 0 if none.  If there is a pending stop signal with default
 * action, the process stops in issignal().
 */
int
cursig(struct thread *td)
{
        PROC_LOCK_ASSERT(td->td_proc, MA_OWNED);
        mtx_assert(&td->td_proc->p_sigacts->ps_mtx, MA_OWNED);
        THREAD_LOCK_ASSERT(td, MA_NOTOWNED);
        return (SIGPENDING(td) ? issignal(td) : 0);
}

/*
 * Arrange for ast() to handle unmasked pending signals on return to user
 * mode.  This must be called whenever a signal is added to td_sigqueue or
 * unmasked in td_sigmask.
 */
void
signotify(struct thread *td)
{

        PROC_LOCK_ASSERT(td->td_proc, MA_OWNED);

        if (SIGPENDING(td))
                ast_sched(td, TDA_SIG);
}

/*
 * Returns 1 (true) if altstack is configured for the thread, and the
 * passed stack bottom address falls into the altstack range.  Handles
 * the 43 compat special case where the alt stack size is zero.
 */
int
sigonstack(size_t sp)
{
        struct thread *td;

        td = curthread;
        if ((td->td_pflags & TDP_ALTSTACK) == 0)
                return (0);
#if defined(COMPAT_43)
        if (SV_PROC_FLAG(td->td_proc, SV_AOUT) && td->td_sigstk.ss_size == 0)
                return ((td->td_sigstk.ss_flags & SS_ONSTACK) != 0);
#endif
        return (sp >= (size_t)td->td_sigstk.ss_sp &&
            sp < td->td_sigstk.ss_size + (size_t)td->td_sigstk.ss_sp);
}

static __inline int
sigprop(int sig)
{

        if (sig > 0 && sig < nitems(sigproptbl))
                return (sigproptbl[sig]);
        return (0);
}

static bool
sigact_flag_test(const struct sigaction *act, int flag)
{

        /*
         * SA_SIGINFO is reset when signal disposition is set to
         * ignore or default.  Other flags are kept according to user
         * settings.
         */
        return ((act->sa_flags & flag) != 0 && (flag != SA_SIGINFO ||
            ((__sighandler_t *)act->sa_sigaction != SIG_IGN &&
            (__sighandler_t *)act->sa_sigaction != SIG_DFL)));
}

/*
 * kern_sigaction
 * sigaction
 * freebsd4_sigaction
 * osigaction
 */
int
kern_sigaction(struct thread *td, int sig, const struct sigaction *act,
    struct sigaction *oact, int flags)
{
        struct sigacts *ps;
        struct proc *p = td->td_proc;

        if (!_SIG_VALID(sig))
                return (EINVAL);
        if (act != NULL && act->sa_handler != SIG_DFL &&
            act->sa_handler != SIG_IGN && (act->sa_flags & ~(SA_ONSTACK |
            SA_RESTART | SA_RESETHAND | SA_NOCLDSTOP | SA_NODEFER |
            SA_NOCLDWAIT | SA_SIGINFO)) != 0)
                return (EINVAL);

        PROC_LOCK(p);
        ps = p->p_sigacts;
        mtx_lock(&ps->ps_mtx);
        if (oact) {
                memset(oact, 0, sizeof(*oact));
                oact->sa_mask = ps->ps_catchmask[_SIG_IDX(sig)];
                if (SIGISMEMBER(ps->ps_sigonstack, sig))
                        oact->sa_flags |= SA_ONSTACK;
                if (!SIGISMEMBER(ps->ps_sigintr, sig))
                        oact->sa_flags |= SA_RESTART;
                if (SIGISMEMBER(ps->ps_sigreset, sig))
                        oact->sa_flags |= SA_RESETHAND;
                if (SIGISMEMBER(ps->ps_signodefer, sig))
                        oact->sa_flags |= SA_NODEFER;
                if (SIGISMEMBER(ps->ps_siginfo, sig)) {
                        oact->sa_flags |= SA_SIGINFO;
                        oact->sa_sigaction =
                            (__siginfohandler_t *)ps->ps_sigact[_SIG_IDX(sig)];
                } else
                        oact->sa_handler = ps->ps_sigact[_SIG_IDX(sig)];
                if (sig == SIGCHLD && ps->ps_flag & PS_NOCLDSTOP)
                        oact->sa_flags |= SA_NOCLDSTOP;
                if (sig == SIGCHLD && ps->ps_flag & PS_NOCLDWAIT)
                        oact->sa_flags |= SA_NOCLDWAIT;
        }
        if (act) {
                if ((sig == SIGKILL || sig == SIGSTOP) &&
                    act->sa_handler != SIG_DFL) {
                        mtx_unlock(&ps->ps_mtx);
                        PROC_UNLOCK(p);
                        return (EINVAL);
                }

                /*
                 * Change setting atomically.
                 */

                ps->ps_catchmask[_SIG_IDX(sig)] = act->sa_mask;
                SIG_CANTMASK(ps->ps_catchmask[_SIG_IDX(sig)]);
                if (sigact_flag_test(act, SA_SIGINFO)) {
                        ps->ps_sigact[_SIG_IDX(sig)] =
                            (__sighandler_t *)act->sa_sigaction;
                        SIGADDSET(ps->ps_siginfo, sig);
                } else {
                        ps->ps_sigact[_SIG_IDX(sig)] = act->sa_handler;
                        SIGDELSET(ps->ps_siginfo, sig);
                }
                if (!sigact_flag_test(act, SA_RESTART))
                        SIGADDSET(ps->ps_sigintr, sig);
                else
                        SIGDELSET(ps->ps_sigintr, sig);
                if (sigact_flag_test(act, SA_ONSTACK))
                        SIGADDSET(ps->ps_sigonstack, sig);
                else
                        SIGDELSET(ps->ps_sigonstack, sig);
                if (sigact_flag_test(act, SA_RESETHAND))
                        SIGADDSET(ps->ps_sigreset, sig);
                else
                        SIGDELSET(ps->ps_sigreset, sig);
                if (sigact_flag_test(act, SA_NODEFER))
                        SIGADDSET(ps->ps_signodefer, sig);
                else
                        SIGDELSET(ps->ps_signodefer, sig);
                if (sig == SIGCHLD) {
                        if (act->sa_flags & SA_NOCLDSTOP)
                                ps->ps_flag |= PS_NOCLDSTOP;
                        else
                                ps->ps_flag &= ~PS_NOCLDSTOP;
                        if (act->sa_flags & SA_NOCLDWAIT) {
                                /*
                                 * Paranoia: since SA_NOCLDWAIT is implemented
                                 * by reparenting the dying child to PID 1 (and
                                 * trust it to reap the zombie), PID 1 itself
                                 * is forbidden to set SA_NOCLDWAIT.
                                 */
                                if (p->p_pid == 1)
                                        ps->ps_flag &= ~PS_NOCLDWAIT;
                                else
                                        ps->ps_flag |= PS_NOCLDWAIT;
                        } else
                                ps->ps_flag &= ~PS_NOCLDWAIT;
                        if (ps->ps_sigact[_SIG_IDX(SIGCHLD)] == SIG_IGN)
                                ps->ps_flag |= PS_CLDSIGIGN;
                        else
                                ps->ps_flag &= ~PS_CLDSIGIGN;
                }
                /*
                 * Set bit in ps_sigignore for signals that are set to SIG_IGN,
                 * and for signals set to SIG_DFL where the default is to
                 * ignore. However, don't put SIGCONT in ps_sigignore, as we
                 * have to restart the process.
                 */
                if (ps->ps_sigact[_SIG_IDX(sig)] == SIG_IGN ||
                    (sigprop(sig) & SIGPROP_IGNORE &&
                     ps->ps_sigact[_SIG_IDX(sig)] == SIG_DFL)) {
                        /* never to be seen again */
                        sigqueue_delete_proc(p, sig);
                        if (sig != SIGCONT)
                                /* easier in psignal */
                                SIGADDSET(ps->ps_sigignore, sig);
                        SIGDELSET(ps->ps_sigcatch, sig);
                } else {
                        SIGDELSET(ps->ps_sigignore, sig);
                        if (ps->ps_sigact[_SIG_IDX(sig)] == SIG_DFL)
                                SIGDELSET(ps->ps_sigcatch, sig);
                        else
                                SIGADDSET(ps->ps_sigcatch, sig);
                }
#ifdef COMPAT_FREEBSD4
                if (ps->ps_sigact[_SIG_IDX(sig)] == SIG_IGN ||
                    ps->ps_sigact[_SIG_IDX(sig)] == SIG_DFL ||
                    (flags & KSA_FREEBSD4) == 0)
                        SIGDELSET(ps->ps_freebsd4, sig);
                else
                        SIGADDSET(ps->ps_freebsd4, sig);
#endif
#ifdef COMPAT_43
                if (ps->ps_sigact[_SIG_IDX(sig)] == SIG_IGN ||
                    ps->ps_sigact[_SIG_IDX(sig)] == SIG_DFL ||
                    (flags & KSA_OSIGSET) == 0)
                        SIGDELSET(ps->ps_osigset, sig);
                else
                        SIGADDSET(ps->ps_osigset, sig);
#endif
        }
        mtx_unlock(&ps->ps_mtx);
        PROC_UNLOCK(p);
        return (0);
}

#ifndef _SYS_SYSPROTO_H_
struct sigaction_args {
        int     sig;
        struct  sigaction *act;
        struct  sigaction *oact;
};
#endif
int
sys_sigaction(struct thread *td, struct sigaction_args *uap)
{
        struct sigaction act, oact;
        struct sigaction *actp, *oactp;
        int error;

        actp = (uap->act != NULL) ? &act : NULL;
        oactp = (uap->oact != NULL) ? &oact : NULL;
        if (actp) {
                error = copyin(uap->act, actp, sizeof(act));
                if (error)
                        return (error);
        }
        error = kern_sigaction(td, uap->sig, actp, oactp, 0);
        if (oactp && !error)
                error = copyout(oactp, uap->oact, sizeof(oact));
        return (error);
}

#ifdef COMPAT_FREEBSD4
#ifndef _SYS_SYSPROTO_H_
struct freebsd4_sigaction_args {
        int     sig;
        struct  sigaction *act;
        struct  sigaction *oact;
};
#endif
int
freebsd4_sigaction(struct thread *td, struct freebsd4_sigaction_args *uap)
{
        struct sigaction act, oact;
        struct sigaction *actp, *oactp;
        int error;

        actp = (uap->act != NULL) ? &act : NULL;
        oactp = (uap->oact != NULL) ? &oact : NULL;
        if (actp) {
                error = copyin(uap->act, actp, sizeof(act));
                if (error)
                        return (error);
        }
        error = kern_sigaction(td, uap->sig, actp, oactp, KSA_FREEBSD4);
        if (oactp && !error)
                error = copyout(oactp, uap->oact, sizeof(oact));
        return (error);
}
#endif  /* COMAPT_FREEBSD4 */

#ifdef COMPAT_43        /* XXX - COMPAT_FBSD3 */
#ifndef _SYS_SYSPROTO_H_
struct osigaction_args {
        int     signum;
        struct  osigaction *nsa;
        struct  osigaction *osa;
};
#endif
int
osigaction(struct thread *td, struct osigaction_args *uap)
{
        struct osigaction sa;
        struct sigaction nsa, osa;
        struct sigaction *nsap, *osap;
        int error;

        if (uap->signum <= 0 || uap->signum >= ONSIG)
                return (EINVAL);

        nsap = (uap->nsa != NULL) ? &nsa : NULL;
        osap = (uap->osa != NULL) ? &osa : NULL;

        if (nsap) {
                error = copyin(uap->nsa, &sa, sizeof(sa));
                if (error)
                        return (error);
                nsap->sa_handler = sa.sa_handler;
                nsap->sa_flags = sa.sa_flags;
                OSIG2SIG(sa.sa_mask, nsap->sa_mask);
        }
        error = kern_sigaction(td, uap->signum, nsap, osap, KSA_OSIGSET);
        if (osap && !error) {
                sa.sa_handler = osap->sa_handler;
                sa.sa_flags = osap->sa_flags;
                SIG2OSIG(osap->sa_mask, sa.sa_mask);
                error = copyout(&sa, uap->osa, sizeof(sa));
        }
        return (error);
}

#if !defined(__i386__)
/* Avoid replicating the same stub everywhere */
int
osigreturn(struct thread *td, struct osigreturn_args *uap)
{

        return (nosys(td, (struct nosys_args *)uap));
}
#endif
#endif /* COMPAT_43 */

/*
 * Initialize signal state for process 0;
 * set to ignore signals that are ignored by default.
 */
void
siginit(struct proc *p)
{
        int i;
        struct sigacts *ps;

        PROC_LOCK(p);
        ps = p->p_sigacts;
        mtx_lock(&ps->ps_mtx);
        for (i = 1; i <= NSIG; i++) {
                if (sigprop(i) & SIGPROP_IGNORE && i != SIGCONT) {
                        SIGADDSET(ps->ps_sigignore, i);
                }
        }
        mtx_unlock(&ps->ps_mtx);
        PROC_UNLOCK(p);
}

/*
 * Reset specified signal to the default disposition.
 */
static void
sigdflt(struct sigacts *ps, int sig)
{

        mtx_assert(&ps->ps_mtx, MA_OWNED);
        SIGDELSET(ps->ps_sigcatch, sig);
        if ((sigprop(sig) & SIGPROP_IGNORE) != 0 && sig != SIGCONT)
                SIGADDSET(ps->ps_sigignore, sig);
        ps->ps_sigact[_SIG_IDX(sig)] = SIG_DFL;
        SIGDELSET(ps->ps_siginfo, sig);
}

/*
 * Reset signals for an exec of the specified process.
 */
void
execsigs(struct proc *p)
{
        struct sigacts *ps;
        struct thread *td;

        /*
         * Reset caught signals.  Held signals remain held
         * through td_sigmask (unless they were caught,
         * and are now ignored by default).
         */
        PROC_LOCK_ASSERT(p, MA_OWNED);
        ps = p->p_sigacts;
        mtx_lock(&ps->ps_mtx);
        sig_drop_caught(p);

        /*
         * Reset stack state to the user stack.
         * Clear set of signals caught on the signal stack.
         */
        td = curthread;
        MPASS(td->td_proc == p);
        td->td_sigstk.ss_flags = SS_DISABLE;
        td->td_sigstk.ss_size = 0;
        td->td_sigstk.ss_sp = 0;
        td->td_pflags &= ~TDP_ALTSTACK;
        /*
         * Reset no zombies if child dies flag as Solaris does.
         */
        ps->ps_flag &= ~(PS_NOCLDWAIT | PS_CLDSIGIGN);
        if (ps->ps_sigact[_SIG_IDX(SIGCHLD)] == SIG_IGN)
                ps->ps_sigact[_SIG_IDX(SIGCHLD)] = SIG_DFL;
        mtx_unlock(&ps->ps_mtx);
}

/*
 * kern_sigprocmask()
 *
 *      Manipulate signal mask.
 */
int
kern_sigprocmask(struct thread *td, int how, sigset_t *set, sigset_t *oset,
    int flags)
{
        sigset_t new_block, oset1;
        struct proc *p;
        int error;

        p = td->td_proc;
        if ((flags & SIGPROCMASK_PROC_LOCKED) != 0)
                PROC_LOCK_ASSERT(p, MA_OWNED);
        else
                PROC_LOCK(p);
        mtx_assert(&p->p_sigacts->ps_mtx, (flags & SIGPROCMASK_PS_LOCKED) != 0
            ? MA_OWNED : MA_NOTOWNED);
        if (oset != NULL)
                *oset = td->td_sigmask;

        error = 0;
        if (set != NULL) {
                switch (how) {
                case SIG_BLOCK:
                        SIG_CANTMASK(*set);
                        oset1 = td->td_sigmask;
                        SIGSETOR(td->td_sigmask, *set);
                        new_block = td->td_sigmask;
                        SIGSETNAND(new_block, oset1);
                        break;
                case SIG_UNBLOCK:
                        SIGSETNAND(td->td_sigmask, *set);
                        signotify(td);
                        goto out;
                case SIG_SETMASK:
                        SIG_CANTMASK(*set);
                        oset1 = td->td_sigmask;
                        if (flags & SIGPROCMASK_OLD)
                                SIGSETLO(td->td_sigmask, *set);
                        else
                                td->td_sigmask = *set;
                        new_block = td->td_sigmask;
                        SIGSETNAND(new_block, oset1);
                        signotify(td);
                        break;
                default:
                        error = EINVAL;
                        goto out;
                }

                /*
                 * The new_block set contains signals that were not previously
                 * blocked, but are blocked now.
                 *
                 * In case we block any signal that was not previously blocked
                 * for td, and process has the signal pending, try to schedule
                 * signal delivery to some thread that does not block the
                 * signal, possibly waking it up.
                 */
                if (p->p_numthreads != 1)
                        reschedule_signals(p, new_block, flags);
        }

out:
        if (!(flags & SIGPROCMASK_PROC_LOCKED))
                PROC_UNLOCK(p);
        return (error);
}

#ifndef _SYS_SYSPROTO_H_
struct sigprocmask_args {
        int     how;
        const sigset_t *set;
        sigset_t *oset;
};
#endif
int
sys_sigprocmask(struct thread *td, struct sigprocmask_args *uap)
{
        sigset_t set, oset;
        sigset_t *setp, *osetp;
        int error;

        setp = (uap->set != NULL) ? &set : NULL;
        osetp = (uap->oset != NULL) ? &oset : NULL;
        if (setp) {
                error = copyin(uap->set, setp, sizeof(set));
                if (error)
                        return (error);
        }
        error = kern_sigprocmask(td, uap->how, setp, osetp, 0);
        if (osetp && !error) {
                error = copyout(osetp, uap->oset, sizeof(oset));
        }
        return (error);
}

#ifdef COMPAT_43        /* XXX - COMPAT_FBSD3 */
#ifndef _SYS_SYSPROTO_H_
struct osigprocmask_args {
        int     how;
        osigset_t mask;
};
#endif
int
osigprocmask(struct thread *td, struct osigprocmask_args *uap)
{
        sigset_t set, oset;
        int error;

        OSIG2SIG(uap->mask, set);
        error = kern_sigprocmask(td, uap->how, &set, &oset, 1);
        SIG2OSIG(oset, td->td_retval[0]);
        return (error);
}
#endif /* COMPAT_43 */

int
sys_sigwait(struct thread *td, struct sigwait_args *uap)
{
        ksiginfo_t ksi;
        sigset_t set;
        int error;

        error = copyin(uap->set, &set, sizeof(set));
        if (error) {
                td->td_retval[0] = error;
                return (0);
        }

        error = kern_sigtimedwait(td, set, &ksi, NULL);
        if (error) {
                /*
                 * sigwait() function shall not return EINTR, but
                 * the syscall does.  Non-ancient libc provides the
                 * wrapper which hides EINTR.  Otherwise, EINTR return
                 * is used by libthr to handle required cancellation
                 * point in the sigwait().
                 */
                if (error == EINTR && td->td_proc->p_osrel < P_OSREL_SIGWAIT)
                        return (ERESTART);
                td->td_retval[0] = error;
                return (0);
        }

        error = copyout(&ksi.ksi_signo, uap->sig, sizeof(ksi.ksi_signo));
        td->td_retval[0] = error;
        return (0);
}

int
sys_sigtimedwait(struct thread *td, struct sigtimedwait_args *uap)
{
        struct timespec ts;
        struct timespec *timeout;
        sigset_t set;
        ksiginfo_t ksi;
        int error;

        if (uap->timeout) {
                error = copyin(uap->timeout, &ts, sizeof(ts));
                if (error)
                        return (error);

                timeout = &ts;
        } else
                timeout = NULL;

        error = copyin(uap->set, &set, sizeof(set));
        if (error)
                return (error);

        error = kern_sigtimedwait(td, set, &ksi, timeout);
        if (error)
                return (error);

        if (uap->info)
                error = copyout(&ksi.ksi_info, uap->info, sizeof(siginfo_t));

        if (error == 0)
                td->td_retval[0] = ksi.ksi_signo;
        return (error);
}

int
sys_sigwaitinfo(struct thread *td, struct sigwaitinfo_args *uap)
{
        ksiginfo_t ksi;
        sigset_t set;
        int error;

        error = copyin(uap->set, &set, sizeof(set));
        if (error)
                return (error);

        error = kern_sigtimedwait(td, set, &ksi, NULL);
        if (error)
                return (error);

        if (uap->info)
                error = copyout(&ksi.ksi_info, uap->info, sizeof(siginfo_t));

        if (error == 0)
                td->td_retval[0] = ksi.ksi_signo;
        return (error);
}

static void
proc_td_siginfo_capture(struct thread *td, siginfo_t *si)
{
        struct thread *thr;

        FOREACH_THREAD_IN_PROC(td->td_proc, thr) {
                if (thr == td)
                        thr->td_si = *si;
                else
                        thr->td_si.si_signo = 0;
        }
}

int
kern_sigtimedwait(struct thread *td, sigset_t waitset, ksiginfo_t *ksi,
        struct timespec *timeout)
{
        struct sigacts *ps;
        sigset_t saved_mask, new_block;
        struct proc *p;
        int error, sig, timevalid = 0;
        sbintime_t sbt, precision, tsbt;
        struct timespec ts;
        bool traced;

        p = td->td_proc;
        error = 0;
        traced = false;

        /* Ensure the sigfastblock value is up to date. */
        sigfastblock_fetch(td);

        if (timeout != NULL) {
                if (timeout->tv_nsec >= 0 && timeout->tv_nsec < 1000000000) {
                        timevalid = 1;
                        ts = *timeout;
                        if (ts.tv_sec < INT32_MAX / 2) {
                                tsbt = tstosbt(ts);
                                precision = tsbt;
                                precision >>= tc_precexp;
                                if (TIMESEL(&sbt, tsbt))
                                        sbt += tc_tick_sbt;
                                sbt += tsbt;
                        } else
                                precision = sbt = 0;
                }
        } else
                precision = sbt = 0;
        ksiginfo_init(ksi);
        /* Some signals can not be waited for. */
        SIG_CANTMASK(waitset);
        ps = p->p_sigacts;
        PROC_LOCK(p);
        saved_mask = td->td_sigmask;
        SIGSETNAND(td->td_sigmask, waitset);
        if ((p->p_sysent->sv_flags & SV_SIG_DISCIGN) != 0 ||
            !kern_sig_discard_ign) {
                thread_lock(td);
                td->td_flags |= TDF_SIGWAIT;
                thread_unlock(td);
        }
        for (;;) {
                mtx_lock(&ps->ps_mtx);
                sig = cursig(td);
                mtx_unlock(&ps->ps_mtx);
                KASSERT(sig >= 0, ("sig %d", sig));
                if (sig != 0 && SIGISMEMBER(waitset, sig)) {
                        if (sigqueue_get(&td->td_sigqueue, sig, ksi) != 0 ||
                            sigqueue_get(&p->p_sigqueue, sig, ksi) != 0) {
                                error = 0;
                                break;
                        }
                }

                if (error != 0)
                        break;

                /*
                 * POSIX says this must be checked after looking for pending
                 * signals.
                 */
                if (timeout != NULL && !timevalid) {
                        error = EINVAL;
                        break;
                }

                if (traced) {
                        error = EINTR;
                        break;
                }

                error = msleep_sbt(&p->p_sigacts, &p->p_mtx, PPAUSE | PCATCH,
                    "sigwait", sbt, precision, C_ABSOLUTE);

                /* The syscalls can not be restarted. */
                if (error == ERESTART)
                        error = EINTR;

                /*
                 * If PTRACE_SCE or PTRACE_SCX were set after
                 * userspace entered the syscall, return spurious
                 * EINTR after wait was done.  Only do this as last
                 * resort after rechecking for possible queued signals
                 * and expired timeouts.
                 */
                if (error == 0 && (p->p_ptevents & PTRACE_SYSCALL) != 0)
                        traced = true;
        }
        thread_lock(td);
        td->td_flags &= ~TDF_SIGWAIT;
        thread_unlock(td);

        new_block = saved_mask;
        SIGSETNAND(new_block, td->td_sigmask);
        td->td_sigmask = saved_mask;
        /*
         * Fewer signals can be delivered to us, reschedule signal
         * notification.
         */
        if (p->p_numthreads != 1)
                reschedule_signals(p, new_block, 0);

        if (error == 0) {
                SDT_PROBE2(proc, , , signal__clear, sig, ksi);

                if (ksi->ksi_code == SI_TIMER)
                        itimer_accept(p, ksi->ksi_timerid, ksi);

#ifdef KTRACE
                if (KTRPOINT(td, KTR_PSIG)) {
                        sig_t action;

                        mtx_lock(&ps->ps_mtx);
                        action = ps->ps_sigact[_SIG_IDX(sig)];
                        mtx_unlock(&ps->ps_mtx);
                        ktrpsig(sig, action, &td->td_sigmask, ksi->ksi_code);
                }
#endif
                if (sig == SIGKILL) {
                        proc_td_siginfo_capture(td, &ksi->ksi_info);
                        sigexit(td, sig);
                }
        }
        PROC_UNLOCK(p);
        return (error);
}

#ifndef _SYS_SYSPROTO_H_
struct sigpending_args {
        sigset_t        *set;
};
#endif
int
sys_sigpending(struct thread *td, struct sigpending_args *uap)
{
        struct proc *p = td->td_proc;
        sigset_t pending;

        PROC_LOCK(p);
        pending = p->p_sigqueue.sq_signals;
        SIGSETOR(pending, td->td_sigqueue.sq_signals);
        PROC_UNLOCK(p);
        return (copyout(&pending, uap->set, sizeof(sigset_t)));
}

#ifdef COMPAT_43        /* XXX - COMPAT_FBSD3 */
#ifndef _SYS_SYSPROTO_H_
struct osigpending_args {
        int     dummy;
};
#endif
int
osigpending(struct thread *td, struct osigpending_args *uap)
{
        struct proc *p = td->td_proc;
        sigset_t pending;

        PROC_LOCK(p);
        pending = p->p_sigqueue.sq_signals;
        SIGSETOR(pending, td->td_sigqueue.sq_signals);
        PROC_UNLOCK(p);
        SIG2OSIG(pending, td->td_retval[0]);
        return (0);
}
#endif /* COMPAT_43 */

#if defined(COMPAT_43)
/*
 * Generalized interface signal handler, 4.3-compatible.
 */
#ifndef _SYS_SYSPROTO_H_
struct osigvec_args {
        int     signum;
        struct  sigvec *nsv;
        struct  sigvec *osv;
};
#endif
/* ARGSUSED */
int
osigvec(struct thread *td, struct osigvec_args *uap)
{
        struct sigvec vec;
        struct sigaction nsa, osa;
        struct sigaction *nsap, *osap;
        int error;

        if (uap->signum <= 0 || uap->signum >= ONSIG)
                return (EINVAL);
        nsap = (uap->nsv != NULL) ? &nsa : NULL;
        osap = (uap->osv != NULL) ? &osa : NULL;
        if (nsap) {
                error = copyin(uap->nsv, &vec, sizeof(vec));
                if (error)
                        return (error);
                nsap->sa_handler = vec.sv_handler;
                OSIG2SIG(vec.sv_mask, nsap->sa_mask);
                nsap->sa_flags = vec.sv_flags;
                nsap->sa_flags ^= SA_RESTART;   /* opposite of SV_INTERRUPT */
        }
        error = kern_sigaction(td, uap->signum, nsap, osap, KSA_OSIGSET);
        if (osap && !error) {
                vec.sv_handler = osap->sa_handler;
                SIG2OSIG(osap->sa_mask, vec.sv_mask);
                vec.sv_flags = osap->sa_flags;
                vec.sv_flags &= ~SA_NOCLDWAIT;
                vec.sv_flags ^= SA_RESTART;
                error = copyout(&vec, uap->osv, sizeof(vec));
        }
        return (error);
}

#ifndef _SYS_SYSPROTO_H_
struct osigblock_args {
        int     mask;
};
#endif
int
osigblock(struct thread *td, struct osigblock_args *uap)
{
        sigset_t set, oset;

        OSIG2SIG(uap->mask, set);
        kern_sigprocmask(td, SIG_BLOCK, &set, &oset, 0);
        SIG2OSIG(oset, td->td_retval[0]);
        return (0);
}

#ifndef _SYS_SYSPROTO_H_
struct osigsetmask_args {
        int     mask;
};
#endif
int
osigsetmask(struct thread *td, struct osigsetmask_args *uap)
{
        sigset_t set, oset;

        OSIG2SIG(uap->mask, set);
        kern_sigprocmask(td, SIG_SETMASK, &set, &oset, 0);
        SIG2OSIG(oset, td->td_retval[0]);
        return (0);
}
#endif /* COMPAT_43 */

/*
 * Suspend calling thread until signal, providing mask to be set in the
 * meantime.
 */
#ifndef _SYS_SYSPROTO_H_
struct sigsuspend_args {
        const sigset_t *sigmask;
};
#endif
/* ARGSUSED */
int
sys_sigsuspend(struct thread *td, struct sigsuspend_args *uap)
{
        sigset_t mask;
        int error;

        error = copyin(uap->sigmask, &mask, sizeof(mask));
        if (error)
                return (error);
        return (kern_sigsuspend(td, mask));
}

int
kern_sigsuspend(struct thread *td, sigset_t mask)
{
        struct proc *p = td->td_proc;
        int has_sig, sig;

        /* Ensure the sigfastblock value is up to date. */
        sigfastblock_fetch(td);

        /*
         * When returning from sigsuspend, we want
         * the old mask to be restored after the
         * signal handler has finished.  Thus, we
         * save it here and mark the sigacts structure
         * to indicate this.
         */
        PROC_LOCK(p);
        kern_sigprocmask(td, SIG_SETMASK, &mask, &td->td_oldsigmask,
            SIGPROCMASK_PROC_LOCKED);
        td->td_pflags |= TDP_OLDMASK;
        ast_sched(td, TDA_SIGSUSPEND);

        /*
         * Process signals now. Otherwise, we can get spurious wakeup
         * due to signal entered process queue, but delivered to other
         * thread. But sigsuspend should return only on signal
         * delivery.
         */
        (p->p_sysent->sv_set_syscall_retval)(td, EINTR);
        for (has_sig = 0; !has_sig;) {
                while (msleep(&p->p_sigacts, &p->p_mtx, PPAUSE|PCATCH, "pause",
                        0) == 0)
                        /* void */;
                thread_suspend_check(0);
                mtx_lock(&p->p_sigacts->ps_mtx);
                while ((sig = cursig(td)) != 0) {
                        KASSERT(sig >= 0, ("sig %d", sig));
                        has_sig += postsig(sig);
                }
                mtx_unlock(&p->p_sigacts->ps_mtx);

                /*
                 * If PTRACE_SCE or PTRACE_SCX were set after
                 * userspace entered the syscall, return spurious
                 * EINTR.
                 */
                if ((p->p_ptevents & PTRACE_SYSCALL) != 0)
                        has_sig += 1;
        }
        PROC_UNLOCK(p);
        td->td_errno = EINTR;
        td->td_pflags |= TDP_NERRNO;
        return (EJUSTRETURN);
}

#ifdef COMPAT_43        /* XXX - COMPAT_FBSD3 */
/*
 * Compatibility sigsuspend call for old binaries.  Note nonstandard calling
 * convention: libc stub passes mask, not pointer, to save a copyin.
 */
#ifndef _SYS_SYSPROTO_H_
struct osigsuspend_args {
        osigset_t mask;
};
#endif
/* ARGSUSED */
int
osigsuspend(struct thread *td, struct osigsuspend_args *uap)
{
        sigset_t mask;

        OSIG2SIG(uap->mask, mask);
        return (kern_sigsuspend(td, mask));
}
#endif /* COMPAT_43 */

#if defined(COMPAT_43)
#ifndef _SYS_SYSPROTO_H_
struct osigstack_args {
        struct  sigstack *nss;
        struct  sigstack *oss;
};
#endif
/* ARGSUSED */
int
osigstack(struct thread *td, struct osigstack_args *uap)
{
        struct sigstack nss, oss;
        int error = 0;

        if (uap->nss != NULL) {
                error = copyin(uap->nss, &nss, sizeof(nss));
                if (error)
                        return (error);
        }
        oss.ss_sp = td->td_sigstk.ss_sp;
        oss.ss_onstack = sigonstack(cpu_getstack(td));
        if (uap->nss != NULL) {
                td->td_sigstk.ss_sp = nss.ss_sp;
                td->td_sigstk.ss_size = 0;
                td->td_sigstk.ss_flags |= nss.ss_onstack & SS_ONSTACK;
                td->td_pflags |= TDP_ALTSTACK;
        }
        if (uap->oss != NULL)
                error = copyout(&oss, uap->oss, sizeof(oss));

        return (error);
}
#endif /* COMPAT_43 */

#ifndef _SYS_SYSPROTO_H_
struct sigaltstack_args {
        stack_t *ss;
        stack_t *oss;
};
#endif
/* ARGSUSED */
int
sys_sigaltstack(struct thread *td, struct sigaltstack_args *uap)
{
        stack_t ss, oss;
        int error;

        if (uap->ss != NULL) {
                error = copyin(uap->ss, &ss, sizeof(ss));
                if (error)
                        return (error);
        }
        error = kern_sigaltstack(td, (uap->ss != NULL) ? &ss : NULL,
            (uap->oss != NULL) ? &oss : NULL);
        if (error)
                return (error);
        if (uap->oss != NULL)
                error = copyout(&oss, uap->oss, sizeof(stack_t));
        return (error);
}

int
kern_sigaltstack(struct thread *td, stack_t *ss, stack_t *oss)
{
        struct proc *p = td->td_proc;
        int oonstack;

        oonstack = sigonstack(cpu_getstack(td));

        if (oss != NULL) {
                *oss = td->td_sigstk;
                oss->ss_flags = (td->td_pflags & TDP_ALTSTACK)
                    ? ((oonstack) ? SS_ONSTACK : 0) : SS_DISABLE;
        }

        if (ss != NULL) {
                if (oonstack)
                        return (EPERM);
                if ((ss->ss_flags & ~SS_DISABLE) != 0)
                        return (EINVAL);
                if (!(ss->ss_flags & SS_DISABLE)) {
                        if (ss->ss_size < p->p_sysent->sv_minsigstksz)
                                return (ENOMEM);

                        td->td_sigstk = *ss;
                        td->td_pflags |= TDP_ALTSTACK;
                } else {
                        td->td_pflags &= ~TDP_ALTSTACK;
                }
        }
        return (0);
}

struct killpg1_ctx {
        struct thread *td;
        ksiginfo_t *ksi;
        int sig;
        bool sent;
        bool found;
        int ret;
};

static void
killpg1_sendsig_locked(struct proc *p, struct killpg1_ctx *arg)
{
        int err;

        err = p_cansignal(arg->td, p, arg->sig);
        if (err == 0 && arg->sig != 0)
                pksignal(p, arg->sig, arg->ksi);
        if (err != ESRCH)
                arg->found = true;
        if (err == 0)
                arg->sent = true;
        else if (arg->ret == 0 && err != ESRCH && err != EPERM)
                arg->ret = err;
}

static void
killpg1_sendsig(struct proc *p, bool notself, struct killpg1_ctx *arg)
{

        if (p->p_pid <= 1 || (p->p_flag & P_SYSTEM) != 0 ||
            (notself && p == arg->td->td_proc) || p->p_state == PRS_NEW)
                return;

        PROC_LOCK(p);
        killpg1_sendsig_locked(p, arg);
        PROC_UNLOCK(p);
}

static void
kill_processes_prison_cb(struct proc *p, void *arg)
{
        struct killpg1_ctx *ctx = arg;

        if (p->p_pid <= 1 || (p->p_flag & P_SYSTEM) != 0 ||
            (p == ctx->td->td_proc) || p->p_state == PRS_NEW)
                return;

        killpg1_sendsig_locked(p, ctx);
}

/*
 * Common code for kill process group/broadcast kill.
 * td is the calling thread, as usual.
 */
static int
killpg1(struct thread *td, int sig, int pgid, int all, ksiginfo_t *ksi)
{
        struct proc *p;
        struct pgrp *pgrp;
        struct killpg1_ctx arg;

        arg.td = td;
        arg.ksi = ksi;
        arg.sig = sig;
        arg.sent = false;
        arg.found = false;
        arg.ret = 0;
        if (all) {
                /*
                 * broadcast
                 */
                prison_proc_iterate(td->td_ucred->cr_prison,
                    kill_processes_prison_cb, &arg);
        } else {
again:
                sx_slock(&proctree_lock);
                if (pgid == 0) {
                        /*
                         * zero pgid means send to my process group.
                         */
                        pgrp = td->td_proc->p_pgrp;
                        PGRP_LOCK(pgrp);
                } else {
                        pgrp = pgfind(pgid);
                        if (pgrp == NULL) {
                                sx_sunlock(&proctree_lock);
                                return (ESRCH);
                        }
                }
                sx_sunlock(&proctree_lock);
                if (!sx_try_xlock(&pgrp->pg_killsx)) {
                        PGRP_UNLOCK(pgrp);
                        sx_xlock(&pgrp->pg_killsx);
                        sx_xunlock(&pgrp->pg_killsx);
                        goto again;
                }
                LIST_FOREACH(p, &pgrp->pg_members, p_pglist) {
                        killpg1_sendsig(p, false, &arg);
                }
                PGRP_UNLOCK(pgrp);
                sx_xunlock(&pgrp->pg_killsx);
        }
        MPASS(arg.ret != 0 || arg.found || !arg.sent);
        if (arg.ret == 0 && !arg.sent)
                arg.ret = arg.found ? EPERM : ESRCH;
        return (arg.ret);
}

#ifndef _SYS_SYSPROTO_H_
struct kill_args {
        int     pid;
        int     signum;
};
#endif
/* ARGSUSED */
int
sys_kill(struct thread *td, struct kill_args *uap)
{

        return (kern_kill(td, uap->pid, uap->signum));
}

int
kern_kill(struct thread *td, pid_t pid, int signum)
{
        ksiginfo_t ksi;
        struct proc *p;
        int error;

        /*
         * A process in capability mode can send signals only to himself.
         * The main rationale behind this is that abort(3) is implemented as
         * kill(getpid(), SIGABRT).
         */
        if (IN_CAPABILITY_MODE(td) && pid != td->td_proc->p_pid)
                return (ECAPMODE);

        AUDIT_ARG_SIGNUM(signum);
        AUDIT_ARG_PID(pid);
        if ((u_int)signum > _SIG_MAXSIG)
                return (EINVAL);

        ksiginfo_init(&ksi);
        ksi.ksi_signo = signum;
        ksi.ksi_code = SI_USER;
        ksi.ksi_pid = td->td_proc->p_pid;
        ksi.ksi_uid = td->td_ucred->cr_ruid;

        if (pid > 0) {
                /* kill single process */
                if ((p = pfind_any(pid)) == NULL)
                        return (ESRCH);
                AUDIT_ARG_PROCESS(p);
                error = p_cansignal(td, p, signum);
                if (error == 0 && signum)
                        pksignal(p, signum, &ksi);
                PROC_UNLOCK(p);
                return (error);
        }
        switch (pid) {
        case -1:                /* broadcast signal */
                return (killpg1(td, signum, 0, 1, &ksi));
        case 0:                 /* signal own process group */
                return (killpg1(td, signum, 0, 0, &ksi));
        default:                /* negative explicit process group */
                return (killpg1(td, signum, -pid, 0, &ksi));
        }
        /* NOTREACHED */
}

int
sys_pdkill(struct thread *td, struct pdkill_args *uap)
{
        struct proc *p;
        int error;

        AUDIT_ARG_SIGNUM(uap->signum);
        AUDIT_ARG_FD(uap->fd);
        if ((u_int)uap->signum > _SIG_MAXSIG)
                return (EINVAL);

        error = procdesc_find(td, uap->fd, &cap_pdkill_rights, &p);
        if (error)
                return (error);
        AUDIT_ARG_PROCESS(p);
        error = p_cansignal(td, p, uap->signum);
        if (error == 0 && uap->signum)
                kern_psignal(p, uap->signum);
        PROC_UNLOCK(p);
        return (error);
}

#if defined(COMPAT_43)
#ifndef _SYS_SYSPROTO_H_
struct okillpg_args {
        int     pgid;
        int     signum;
};
#endif
/* ARGSUSED */
int
okillpg(struct thread *td, struct okillpg_args *uap)
{
        ksiginfo_t ksi;

        AUDIT_ARG_SIGNUM(uap->signum);
        AUDIT_ARG_PID(uap->pgid);
        if ((u_int)uap->signum > _SIG_MAXSIG)
                return (EINVAL);

        ksiginfo_init(&ksi);
        ksi.ksi_signo = uap->signum;
        ksi.ksi_code = SI_USER;
        ksi.ksi_pid = td->td_proc->p_pid;
        ksi.ksi_uid = td->td_ucred->cr_ruid;
        return (killpg1(td, uap->signum, uap->pgid, 0, &ksi));
}
#endif /* COMPAT_43 */

#ifndef _SYS_SYSPROTO_H_
struct sigqueue_args {
        pid_t pid;
        int signum;
        /* union sigval */ void *value;
};
#endif
int
sys_sigqueue(struct thread *td, struct sigqueue_args *uap)
{
        union sigval sv;

        sv.sival_ptr = uap->value;

        return (kern_sigqueue(td, uap->pid, uap->signum, &sv));
}

int
kern_sigqueue(struct thread *td, pid_t pid, int signum, union sigval *value)
{
        ksiginfo_t ksi;
        struct proc *p;
        int error;

        if ((u_int)signum > _SIG_MAXSIG)
                return (EINVAL);

        /*
         * Specification says sigqueue can only send signal to
         * single process.
         */
        if (pid <= 0)
                return (EINVAL);

        if ((p = pfind_any(pid)) == NULL)
                return (ESRCH);
        error = p_cansignal(td, p, signum);
        if (error == 0 && signum != 0) {
                ksiginfo_init(&ksi);
                ksi.ksi_flags = KSI_SIGQ;
                ksi.ksi_signo = signum;
                ksi.ksi_code = SI_QUEUE;
                ksi.ksi_pid = td->td_proc->p_pid;
                ksi.ksi_uid = td->td_ucred->cr_ruid;
                ksi.ksi_value = *value;
                error = pksignal(p, ksi.ksi_signo, &ksi);
        }
        PROC_UNLOCK(p);
        return (error);
}

/*
 * Send a signal to a process group.  If checktty is 1,
 * limit to members which have a controlling terminal.
 */
void
pgsignal(struct pgrp *pgrp, int sig, int checkctty, ksiginfo_t *ksi)
{
        struct proc *p;

        if (pgrp) {
                PGRP_LOCK_ASSERT(pgrp, MA_OWNED);
                LIST_FOREACH(p, &pgrp->pg_members, p_pglist) {
                        PROC_LOCK(p);
                        if (p->p_state == PRS_NORMAL &&
                            (checkctty == 0 || p->p_flag & P_CONTROLT))
                                pksignal(p, sig, ksi);
                        PROC_UNLOCK(p);
                }
        }
}

/*
 * Recalculate the signal mask and reset the signal disposition after
 * usermode frame for delivery is formed.  Should be called after
 * mach-specific routine, because sysent->sv_sendsig() needs correct
 * ps_siginfo and signal mask.
 */
static void
postsig_done(int sig, struct thread *td, struct sigacts *ps)
{
        sigset_t mask;

        mtx_assert(&ps->ps_mtx, MA_OWNED);
        td->td_ru.ru_nsignals++;
        mask = ps->ps_catchmask[_SIG_IDX(sig)];
        if (!SIGISMEMBER(ps->ps_signodefer, sig))
                SIGADDSET(mask, sig);
        kern_sigprocmask(td, SIG_BLOCK, &mask, NULL,
            SIGPROCMASK_PROC_LOCKED | SIGPROCMASK_PS_LOCKED);
        if (SIGISMEMBER(ps->ps_sigreset, sig))
                sigdflt(ps, sig);
}

/*
 * Send a signal caused by a trap to the current thread.  If it will be
 * caught immediately, deliver it with correct code.  Otherwise, post it
 * normally.
 */
void
trapsignal(struct thread *td, ksiginfo_t *ksi)
{
        struct sigacts *ps;
        struct proc *p;
        sigset_t sigmask;
        int sig;

        p = td->td_proc;
        sig = ksi->ksi_signo;
        KASSERT(_SIG_VALID(sig), ("invalid signal"));

        sigfastblock_fetch(td);
        PROC_LOCK(p);
        ps = p->p_sigacts;
        mtx_lock(&ps->ps_mtx);
        sigmask = td->td_sigmask;
        if (td->td_sigblock_val != 0)
                SIGSETOR(sigmask, fastblock_mask);
        if ((p->p_flag & P_TRACED) == 0 && SIGISMEMBER(ps->ps_sigcatch, sig) &&
            !SIGISMEMBER(sigmask, sig)) {
#ifdef KTRACE
                if (KTRPOINT(curthread, KTR_PSIG))
                        ktrpsig(sig, ps->ps_sigact[_SIG_IDX(sig)],
                            &td->td_sigmask, ksi->ksi_code);
#endif
                (*p->p_sysent->sv_sendsig)(ps->ps_sigact[_SIG_IDX(sig)],
                    ksi, &td->td_sigmask);
                postsig_done(sig, td, ps);
                mtx_unlock(&ps->ps_mtx);
        } else {
                /*
                 * Avoid a possible infinite loop if the thread
                 * masking the signal or process is ignoring the
                 * signal.
                 */
                if (kern_forcesigexit && (SIGISMEMBER(sigmask, sig) ||
                    ps->ps_sigact[_SIG_IDX(sig)] == SIG_IGN)) {
                        SIGDELSET(td->td_sigmask, sig);
                        SIGDELSET(ps->ps_sigcatch, sig);
                        SIGDELSET(ps->ps_sigignore, sig);
                        ps->ps_sigact[_SIG_IDX(sig)] = SIG_DFL;
                        td->td_pflags &= ~TDP_SIGFASTBLOCK;
                        td->td_sigblock_val = 0;
                }
                mtx_unlock(&ps->ps_mtx);
                p->p_sig = sig;         /* XXX to verify code */
                tdsendsignal(p, td, sig, ksi);
        }
        PROC_UNLOCK(p);
}

static struct thread *
sigtd(struct proc *p, int sig, bool fast_sigblock)
{
        struct thread *td, *signal_td;

        PROC_LOCK_ASSERT(p, MA_OWNED);
        MPASS(!fast_sigblock || p == curproc);

        /*
         * Check if current thread can handle the signal without
         * switching context to another thread.
         */
        if (curproc == p && !SIGISMEMBER(curthread->td_sigmask, sig) &&
            (!fast_sigblock || curthread->td_sigblock_val == 0))
                return (curthread);

        /* Find a non-stopped thread that does not mask the signal. */
        signal_td = NULL;
        FOREACH_THREAD_IN_PROC(p, td) {
                if (!SIGISMEMBER(td->td_sigmask, sig) && (!fast_sigblock ||
                    td != curthread || td->td_sigblock_val == 0) &&
                    (td->td_flags & TDF_BOUNDARY) == 0) {
                        signal_td = td;
                        break;
                }
        }
        /* Select random (first) thread if no better match was found. */
        if (signal_td == NULL)
                signal_td = FIRST_THREAD_IN_PROC(p);
        return (signal_td);
}

/*
 * Send the signal to the process.  If the signal has an action, the action
 * is usually performed by the target process rather than the caller; we add
 * the signal to the set of pending signals for the process.
 *
 * Exceptions:
 *   o When a stop signal is sent to a sleeping process that takes the
 *     default action, the process is stopped without awakening it.
 *   o SIGCONT restarts stopped processes (or puts them back to sleep)
 *     regardless of the signal action (eg, blocked or ignored).
 *
 * Other ignored signals are discarded immediately.
 *
 * NB: This function may be entered from the debugger via the "kill" DDB
 * command.  There is little that can be done to mitigate the possibly messy
 * side effects of this unwise possibility.
 */
void
kern_psignal(struct proc *p, int sig)
{
        ksiginfo_t ksi;

        ksiginfo_init(&ksi);
        ksi.ksi_signo = sig;
        ksi.ksi_code = SI_KERNEL;
        (void) tdsendsignal(p, NULL, sig, &ksi);
}

int
pksignal(struct proc *p, int sig, ksiginfo_t *ksi)
{

        return (tdsendsignal(p, NULL, sig, ksi));
}

/* Utility function for finding a thread to send signal event to. */
int
sigev_findtd(struct proc *p, struct sigevent *sigev, struct thread **ttd)
{
        struct thread *td;

        if (sigev->sigev_notify == SIGEV_THREAD_ID) {
                td = tdfind(sigev->sigev_notify_thread_id, p->p_pid);
                if (td == NULL)
                        return (ESRCH);
                *ttd = td;
        } else {
                *ttd = NULL;
                PROC_LOCK(p);
        }
        return (0);
}

void
tdsignal(struct thread *td, int sig)
{
        ksiginfo_t ksi;

        ksiginfo_init(&ksi);
        ksi.ksi_signo = sig;
        ksi.ksi_code = SI_KERNEL;
        (void) tdsendsignal(td->td_proc, td, sig, &ksi);
}

void
tdksignal(struct thread *td, int sig, ksiginfo_t *ksi)
{

        (void) tdsendsignal(td->td_proc, td, sig, ksi);
}

static int
sig_sleepq_abort(struct thread *td, int intrval)
{
        THREAD_LOCK_ASSERT(td, MA_OWNED);

        if (intrval == 0 && (td->td_flags & TDF_SIGWAIT) == 0) {
                thread_unlock(td);
                return (0);
        }
        return (sleepq_abort(td, intrval));
}

int
tdsendsignal(struct proc *p, struct thread *td, int sig, ksiginfo_t *ksi)
{
        sig_t action;
        sigqueue_t *sigqueue;
        int prop;
        struct sigacts *ps;
        int intrval;
        int ret = 0;
        int wakeup_swapper;

        MPASS(td == NULL || p == td->td_proc);
        PROC_LOCK_ASSERT(p, MA_OWNED);

        if (!_SIG_VALID(sig))
                panic("%s(): invalid signal %d", __func__, sig);

        KASSERT(ksi == NULL || !KSI_ONQ(ksi), ("%s: ksi on queue", __func__));

        /*
         * IEEE Std 1003.1-2001: return success when killing a zombie.
         */
        if (p->p_state == PRS_ZOMBIE) {
                if (ksi != NULL && (ksi->ksi_flags & KSI_INS) != 0)
                        ksiginfo_tryfree(ksi);
                return (ret);
        }

        ps = p->p_sigacts;
        KNOTE_LOCKED(p->p_klist, NOTE_SIGNAL | sig);
        prop = sigprop(sig);

        if (td == NULL) {
                td = sigtd(p, sig, false);
                sigqueue = &p->p_sigqueue;
        } else
                sigqueue = &td->td_sigqueue;

        SDT_PROBE3(proc, , , signal__send, td, p, sig);

        /*
         * If the signal is being ignored, then we forget about it
         * immediately, except when the target process executes
         * sigwait().  (Note: we don't set SIGCONT in ps_sigignore,
         * and if it is set to SIG_IGN, action will be SIG_DFL here.)
         */
        mtx_lock(&ps->ps_mtx);
        if (SIGISMEMBER(ps->ps_sigignore, sig)) {
                if (kern_sig_discard_ign &&
                    (p->p_sysent->sv_flags & SV_SIG_DISCIGN) == 0) {
                        SDT_PROBE3(proc, , , signal__discard, td, p, sig);

                        mtx_unlock(&ps->ps_mtx);
                        if (ksi != NULL && (ksi->ksi_flags & KSI_INS) != 0)
                                ksiginfo_tryfree(ksi);
                        return (ret);
                } else {
                        action = SIG_CATCH;
                        intrval = 0;
                }
        } else {
                if (SIGISMEMBER(td->td_sigmask, sig))
                        action = SIG_HOLD;
                else if (SIGISMEMBER(ps->ps_sigcatch, sig))
                        action = SIG_CATCH;
                else
                        action = SIG_DFL;
                if (SIGISMEMBER(ps->ps_sigintr, sig))
                        intrval = EINTR;
                else
                        intrval = ERESTART;
        }
        mtx_unlock(&ps->ps_mtx);

        if (prop & SIGPROP_CONT)
                sigqueue_delete_stopmask_proc(p);
        else if (prop & SIGPROP_STOP) {
                /*
                 * If sending a tty stop signal to a member of an orphaned
                 * process group, discard the signal here if the action
                 * is default; don't stop the process below if sleeping,
                 * and don't clear any pending SIGCONT.
                 */
                if ((prop & SIGPROP_TTYSTOP) != 0 &&
                    (p->p_pgrp->pg_flags & PGRP_ORPHANED) != 0 &&
                    action == SIG_DFL) {
                        if (ksi != NULL && (ksi->ksi_flags & KSI_INS) != 0)
                                ksiginfo_tryfree(ksi);
                        return (ret);
                }
                sigqueue_delete_proc(p, SIGCONT);
                if (p->p_flag & P_CONTINUED) {
                        p->p_flag &= ~P_CONTINUED;
                        PROC_LOCK(p->p_pptr);
                        sigqueue_take(p->p_ksi);
                        PROC_UNLOCK(p->p_pptr);
                }
        }

        ret = sigqueue_add(sigqueue, sig, ksi);
        if (ret != 0)
                return (ret);
        signotify(td);
        /*
         * Defer further processing for signals which are held,
         * except that stopped processes must be continued by SIGCONT.
         */
        if (action == SIG_HOLD &&
            !((prop & SIGPROP_CONT) && (p->p_flag & P_STOPPED_SIG)))
                return (ret);

        wakeup_swapper = 0;

        /*
         * Some signals have a process-wide effect and a per-thread
         * component.  Most processing occurs when the process next
         * tries to cross the user boundary, however there are some
         * times when processing needs to be done immediately, such as
         * waking up threads so that they can cross the user boundary.
         * We try to do the per-process part here.
         */
        if (P_SHOULDSTOP(p)) {
                KASSERT(!(p->p_flag & P_WEXIT),
                    ("signal to stopped but exiting process"));
                if (sig == SIGKILL) {
                        /*
                         * If traced process is already stopped,
                         * then no further action is necessary.
                         */
                        if (p->p_flag & P_TRACED)
                                goto out;
                        /*
                         * SIGKILL sets process running.
                         * It will die elsewhere.
                         * All threads must be restarted.
                         */
                        p->p_flag &= ~P_STOPPED_SIG;
                        goto runfast;
                }

                if (prop & SIGPROP_CONT) {
                        /*
                         * If traced process is already stopped,
                         * then no further action is necessary.
                         */
                        if (p->p_flag & P_TRACED)
                                goto out;
                        /*
                         * If SIGCONT is default (or ignored), we continue the
                         * process but don't leave the signal in sigqueue as
                         * it has no further action.  If SIGCONT is held, we
                         * continue the process and leave the signal in
                         * sigqueue.  If the process catches SIGCONT, let it
                         * handle the signal itself.  If it isn't waiting on
                         * an event, it goes back to run state.
                         * Otherwise, process goes back to sleep state.
                         */
                        p->p_flag &= ~P_STOPPED_SIG;
                        PROC_SLOCK(p);
                        if (p->p_numthreads == p->p_suspcount) {
                                PROC_SUNLOCK(p);
                                p->p_flag |= P_CONTINUED;
                                p->p_xsig = SIGCONT;
                                PROC_LOCK(p->p_pptr);
                                childproc_continued(p);
                                PROC_UNLOCK(p->p_pptr);
                                PROC_SLOCK(p);
                        }
                        if (action == SIG_DFL) {
                                thread_unsuspend(p);
                                PROC_SUNLOCK(p);
                                sigqueue_delete(sigqueue, sig);
                                goto out_cont;
                        }
                        if (action == SIG_CATCH) {
                                /*
                                 * The process wants to catch it so it needs
                                 * to run at least one thread, but which one?
                                 */
                                PROC_SUNLOCK(p);
                                goto runfast;
                        }
                        /*
                         * The signal is not ignored or caught.
                         */
                        thread_unsuspend(p);
                        PROC_SUNLOCK(p);
                        goto out_cont;
                }

                if (prop & SIGPROP_STOP) {
                        /*
                         * If traced process is already stopped,
                         * then no further action is necessary.
                         */
                        if (p->p_flag & P_TRACED)
                                goto out;
                        /*
                         * Already stopped, don't need to stop again
                         * (If we did the shell could get confused).
                         * Just make sure the signal STOP bit set.
                         */
                        p->p_flag |= P_STOPPED_SIG;
                        sigqueue_delete(sigqueue, sig);
                        goto out;
                }

                /*
                 * All other kinds of signals:
                 * If a thread is sleeping interruptibly, simulate a
                 * wakeup so that when it is continued it will be made
                 * runnable and can look at the signal.  However, don't make
                 * the PROCESS runnable, leave it stopped.
                 * It may run a bit until it hits a thread_suspend_check().
                 */
                PROC_SLOCK(p);
                thread_lock(td);
                if (TD_CAN_ABORT(td))
                        wakeup_swapper = sig_sleepq_abort(td, intrval);
                else
                        thread_unlock(td);
                PROC_SUNLOCK(p);
                goto out;
                /*
                 * Mutexes are short lived. Threads waiting on them will
                 * hit thread_suspend_check() soon.
                 */
        } else if (p->p_state == PRS_NORMAL) {
                if (p->p_flag & P_TRACED || action == SIG_CATCH) {
                        tdsigwakeup(td, sig, action, intrval);
                        goto out;
                }

                MPASS(action == SIG_DFL);

                if (prop & SIGPROP_STOP) {
                        if (p->p_flag & (P_PPWAIT|P_WEXIT))
                                goto out;
                        p->p_flag |= P_STOPPED_SIG;
                        p->p_xsig = sig;
                        PROC_SLOCK(p);
                        wakeup_swapper = sig_suspend_threads(td, p);
                        if (p->p_numthreads == p->p_suspcount) {
                                /*
                                 * only thread sending signal to another
                                 * process can reach here, if thread is sending
                                 * signal to its process, because thread does
                                 * not suspend itself here, p_numthreads
                                 * should never be equal to p_suspcount.
                                 */
                                thread_stopped(p);
                                PROC_SUNLOCK(p);
                                sigqueue_delete_proc(p, p->p_xsig);
                        } else
                                PROC_SUNLOCK(p);
                        goto out;
                }
        } else {
                /* Not in "NORMAL" state. discard the signal. */
                sigqueue_delete(sigqueue, sig);
                goto out;
        }

        /*
         * The process is not stopped so we need to apply the signal to all the
         * running threads.
         */
runfast:
        tdsigwakeup(td, sig, action, intrval);
        PROC_SLOCK(p);
        thread_unsuspend(p);
        PROC_SUNLOCK(p);
out_cont:
        itimer_proc_continue(p);
        kqtimer_proc_continue(p);
out:
        /* If we jump here, proc slock should not be owned. */
        PROC_SLOCK_ASSERT(p, MA_NOTOWNED);
        if (wakeup_swapper)
                kick_proc0();

        return (ret);
}

/*
 * The force of a signal has been directed against a single
 * thread.  We need to see what we can do about knocking it
 * out of any sleep it may be in etc.
 */
static void
tdsigwakeup(struct thread *td, int sig, sig_t action, int intrval)
{
        struct proc *p = td->td_proc;
        int prop, wakeup_swapper;

        PROC_LOCK_ASSERT(p, MA_OWNED);
        prop = sigprop(sig);

        PROC_SLOCK(p);
        thread_lock(td);
        /*
         * Bring the priority of a thread up if we want it to get
         * killed in this lifetime.  Be careful to avoid bumping the
         * priority of the idle thread, since we still allow to signal
         * kernel processes.
         */
        if (action == SIG_DFL && (prop & SIGPROP_KILL) != 0 &&
            td->td_priority > PUSER && !TD_IS_IDLETHREAD(td))
                sched_prio(td, PUSER);
        if (TD_ON_SLEEPQ(td)) {
                /*
                 * If thread is sleeping uninterruptibly
                 * we can't interrupt the sleep... the signal will
                 * be noticed when the process returns through
                 * trap() or syscall().
                 */
                if ((td->td_flags & TDF_SINTR) == 0)
                        goto out;
                /*
                 * If SIGCONT is default (or ignored) and process is
                 * asleep, we are finished; the process should not
                 * be awakened.
                 */
                if ((prop & SIGPROP_CONT) && action == SIG_DFL) {
                        thread_unlock(td);
                        PROC_SUNLOCK(p);
                        sigqueue_delete(&p->p_sigqueue, sig);
                        /*
                         * It may be on either list in this state.
                         * Remove from both for now.
                         */
                        sigqueue_delete(&td->td_sigqueue, sig);
                        return;
                }

                /*
                 * Don't awaken a sleeping thread for SIGSTOP if the
                 * STOP signal is deferred.
                 */
                if ((prop & SIGPROP_STOP) != 0 && (td->td_flags & (TDF_SBDRY |
                    TDF_SERESTART | TDF_SEINTR)) == TDF_SBDRY)
                        goto out;

                /*
                 * Give low priority threads a better chance to run.
                 */
                if (td->td_priority > PUSER && !TD_IS_IDLETHREAD(td))
                        sched_prio(td, PUSER);

                wakeup_swapper = sig_sleepq_abort(td, intrval);
                PROC_SUNLOCK(p);
                if (wakeup_swapper)
                        kick_proc0();
                return;
        }

        /*
         * Other states do nothing with the signal immediately,
         * other than kicking ourselves if we are running.
         * It will either never be noticed, or noticed very soon.
         */
#ifdef SMP
        if (TD_IS_RUNNING(td) && td != curthread)
                forward_signal(td);
#endif

out:
        PROC_SUNLOCK(p);
        thread_unlock(td);
}

static void
ptrace_coredumpreq(struct thread *td, struct proc *p,
    struct thr_coredump_req *tcq)
{
        void *rl_cookie;

        if (p->p_sysent->sv_coredump == NULL) {
                tcq->tc_error = ENOSYS;
                return;
        }

        rl_cookie = vn_rangelock_wlock(tcq->tc_vp, 0, OFF_MAX);
        tcq->tc_error = p->p_sysent->sv_coredump(td, tcq->tc_vp,
            tcq->tc_limit, tcq->tc_flags);
        vn_rangelock_unlock(tcq->tc_vp, rl_cookie);
}

static void
ptrace_syscallreq(struct thread *td, struct proc *p,
    struct thr_syscall_req *tsr)
{
        struct sysentvec *sv;
        struct sysent *se;
        register_t rv_saved[2];
        int error, nerror;
        int sc;
        bool audited, sy_thr_static;

        sv = p->p_sysent;
        if (sv->sv_table == NULL || sv->sv_size < tsr->ts_sa.code) {
                tsr->ts_ret.sr_error = ENOSYS;
                return;
        }

        sc = tsr->ts_sa.code;
        if (sc == SYS_syscall || sc == SYS___syscall) {
                sc = tsr->ts_sa.args[0];
                memmove(&tsr->ts_sa.args[0], &tsr->ts_sa.args[1],
                    sizeof(register_t) * (tsr->ts_nargs - 1));
        }

        tsr->ts_sa.callp = se = &sv->sv_table[sc];

        VM_CNT_INC(v_syscall);
        td->td_pticks = 0;
        if (__predict_false(td->td_cowgen != atomic_load_int(
            &td->td_proc->p_cowgen)))
                thread_cow_update(td);

#ifdef CAPABILITY_MODE
        if (IN_CAPABILITY_MODE(td) && (se->sy_flags & SYF_CAPENABLED) == 0) {
                tsr->ts_ret.sr_error = ECAPMODE;
                return;
        }
#endif

        sy_thr_static = (se->sy_thrcnt & SY_THR_STATIC) != 0;
        audited = AUDIT_SYSCALL_ENTER(sc, td) != 0;

        if (!sy_thr_static) {
                error = syscall_thread_enter(td, &se);
                sy_thr_static = (se->sy_thrcnt & SY_THR_STATIC) != 0;
                if (error != 0) {
                        tsr->ts_ret.sr_error = error;
                        return;
                }
        }

        rv_saved[0] = td->td_retval[0];
        rv_saved[1] = td->td_retval[1];
        nerror = td->td_errno;
        td->td_retval[0] = 0;
        td->td_retval[1] = 0;

#ifdef KDTRACE_HOOKS
        if (se->sy_entry != 0)
                (*systrace_probe_func)(&tsr->ts_sa, SYSTRACE_ENTRY, 0);
#endif
        tsr->ts_ret.sr_error = se->sy_call(td, tsr->ts_sa.args);
#ifdef KDTRACE_HOOKS
        if (se->sy_return != 0)
                (*systrace_probe_func)(&tsr->ts_sa, SYSTRACE_RETURN,
                    tsr->ts_ret.sr_error != 0 ? -1 : td->td_retval[0]);
#endif

        tsr->ts_ret.sr_retval[0] = td->td_retval[0];
        tsr->ts_ret.sr_retval[1] = td->td_retval[1];
        td->td_retval[0] = rv_saved[0];
        td->td_retval[1] = rv_saved[1];
        td->td_errno = nerror;

        if (audited)
                AUDIT_SYSCALL_EXIT(error, td);
        if (!sy_thr_static)
                syscall_thread_exit(td, se);
}

static void
ptrace_remotereq(struct thread *td, int flag)
{
        struct proc *p;

        MPASS(td == curthread);
        p = td->td_proc;
        PROC_LOCK_ASSERT(p, MA_OWNED);
        if ((td->td_dbgflags & flag) == 0)
                return;
        KASSERT((p->p_flag & P_STOPPED_TRACE) != 0, ("not stopped"));
        KASSERT(td->td_remotereq != NULL, ("td_remotereq is NULL"));

        PROC_UNLOCK(p);
        switch (flag) {
        case TDB_COREDUMPREQ:
                ptrace_coredumpreq(td, p, td->td_remotereq);
                break;
        case TDB_SCREMOTEREQ:
                ptrace_syscallreq(td, p, td->td_remotereq);
                break;
        default:
                __unreachable();
        }
        PROC_LOCK(p);

        MPASS((td->td_dbgflags & flag) != 0);
        td->td_dbgflags &= ~flag;
        td->td_remotereq = NULL;
        wakeup(p);
}

static int
sig_suspend_threads(struct thread *td, struct proc *p)
{
        struct thread *td2;
        int wakeup_swapper;

        PROC_LOCK_ASSERT(p, MA_OWNED);
        PROC_SLOCK_ASSERT(p, MA_OWNED);

        wakeup_swapper = 0;
        FOREACH_THREAD_IN_PROC(p, td2) {
                thread_lock(td2);
                ast_sched_locked(td2, TDA_SUSPEND);
                if ((TD_IS_SLEEPING(td2) || TD_IS_SWAPPED(td2)) &&
                    (td2->td_flags & TDF_SINTR)) {
                        if (td2->td_flags & TDF_SBDRY) {
                                /*
                                 * Once a thread is asleep with
                                 * TDF_SBDRY and without TDF_SERESTART
                                 * or TDF_SEINTR set, it should never
                                 * become suspended due to this check.
                                 */
                                KASSERT(!TD_IS_SUSPENDED(td2),
                                    ("thread with deferred stops suspended"));
                                if (TD_SBDRY_INTR(td2)) {
                                        wakeup_swapper |= sleepq_abort(td2,
                                            TD_SBDRY_ERRNO(td2));
                                        continue;
                                }
                        } else if (!TD_IS_SUSPENDED(td2))
                                thread_suspend_one(td2);
                } else if (!TD_IS_SUSPENDED(td2)) {
#ifdef SMP
                        if (TD_IS_RUNNING(td2) && td2 != td)
                                forward_signal(td2);
#endif
                }
                thread_unlock(td2);
        }
        return (wakeup_swapper);
}

/*
 * Stop the process for an event deemed interesting to the debugger. If si is
 * non-NULL, this is a signal exchange; the new signal requested by the
 * debugger will be returned for handling. If si is NULL, this is some other
 * type of interesting event. The debugger may request a signal be delivered in
 * that case as well, however it will be deferred until it can be handled.
 */
int
ptracestop(struct thread *td, int sig, ksiginfo_t *si)
{
        struct proc *p = td->td_proc;
        struct thread *td2;
        ksiginfo_t ksi;

        PROC_LOCK_ASSERT(p, MA_OWNED);
        KASSERT(!(p->p_flag & P_WEXIT), ("Stopping exiting process"));
        WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK,
            &p->p_mtx.lock_object, "Stopping for traced signal");

        td->td_xsig = sig;

        if (si == NULL || (si->ksi_flags & KSI_PTRACE) == 0) {
                td->td_dbgflags |= TDB_XSIG;
                CTR4(KTR_PTRACE, "ptracestop: tid %d (pid %d) flags %#x sig %d",
                    td->td_tid, p->p_pid, td->td_dbgflags, sig);
                PROC_SLOCK(p);
                while ((p->p_flag & P_TRACED) && (td->td_dbgflags & TDB_XSIG)) {
                        if (P_KILLED(p)) {
                                /*
                                 * Ensure that, if we've been PT_KILLed, the
                                 * exit status reflects that. Another thread
                                 * may also be in ptracestop(), having just
                                 * received the SIGKILL, but this thread was
                                 * unsuspended first.
                                 */
                                td->td_dbgflags &= ~TDB_XSIG;
                                td->td_xsig = SIGKILL;
                                p->p_ptevents = 0;
                                break;
                        }
                        if (p->p_flag & P_SINGLE_EXIT &&
                            !(td->td_dbgflags & TDB_EXIT)) {
                                /*
                                 * Ignore ptrace stops except for thread exit
                                 * events when the process exits.
                                 */
                                td->td_dbgflags &= ~TDB_XSIG;
                                PROC_SUNLOCK(p);
                                return (0);
                        }

                        /*
                         * Make wait(2) work.  Ensure that right after the
                         * attach, the thread which was decided to become the
                         * leader of attach gets reported to the waiter.
                         * Otherwise, just avoid overwriting another thread's
                         * assignment to p_xthread.  If another thread has
                         * already set p_xthread, the current thread will get
                         * a chance to report itself upon the next iteration.
                         */
                        if ((td->td_dbgflags & TDB_FSTP) != 0 ||
                            ((p->p_flag2 & P2_PTRACE_FSTP) == 0 &&
                            p->p_xthread == NULL)) {
                                p->p_xsig = sig;
                                p->p_xthread = td;

                                /*
                                 * If we are on sleepqueue already,
                                 * let sleepqueue code decide if it
                                 * needs to go sleep after attach.
                                 */
                                if (td->td_wchan == NULL)
                                        td->td_dbgflags &= ~TDB_FSTP;

                                p->p_flag2 &= ~P2_PTRACE_FSTP;
                                p->p_flag |= P_STOPPED_SIG | P_STOPPED_TRACE;
                                sig_suspend_threads(td, p);
                        }
                        if ((td->td_dbgflags & TDB_STOPATFORK) != 0) {
                                td->td_dbgflags &= ~TDB_STOPATFORK;
                        }
stopme:
                        td->td_dbgflags |= TDB_SSWITCH;
                        thread_suspend_switch(td, p);
                        td->td_dbgflags &= ~TDB_SSWITCH;
                        if ((td->td_dbgflags & (TDB_COREDUMPREQ |
                            TDB_SCREMOTEREQ)) != 0) {
                                MPASS((td->td_dbgflags & (TDB_COREDUMPREQ |
                                    TDB_SCREMOTEREQ)) !=
                                    (TDB_COREDUMPREQ | TDB_SCREMOTEREQ));
                                PROC_SUNLOCK(p);
                                ptrace_remotereq(td, td->td_dbgflags &
                                    (TDB_COREDUMPREQ | TDB_SCREMOTEREQ));
                                PROC_SLOCK(p);
                                goto stopme;
                        }
                        if (p->p_xthread == td)
                                p->p_xthread = NULL;
                        if (!(p->p_flag & P_TRACED))
                                break;
                        if (td->td_dbgflags & TDB_SUSPEND) {
                                if (p->p_flag & P_SINGLE_EXIT)
                                        break;
                                goto stopme;
                        }
                }
                PROC_SUNLOCK(p);
        }

        if (si != NULL && sig == td->td_xsig) {
                /* Parent wants us to take the original signal unchanged. */
                si->ksi_flags |= KSI_HEAD;
                if (sigqueue_add(&td->td_sigqueue, sig, si) != 0)
                        si->ksi_signo = 0;
        } else if (td->td_xsig != 0) {
                /*
                 * If parent wants us to take a new signal, then it will leave
                 * it in td->td_xsig; otherwise we just look for signals again.
                 */
                ksiginfo_init(&ksi);
                ksi.ksi_signo = td->td_xsig;
                ksi.ksi_flags |= KSI_PTRACE;
                td2 = sigtd(p, td->td_xsig, false);
                tdsendsignal(p, td2, td->td_xsig, &ksi);
                if (td != td2)
                        return (0);
        }

        return (td->td_xsig);
}

static void
reschedule_signals(struct proc *p, sigset_t block, int flags)
{
        struct sigacts *ps;
        struct thread *td;
        int sig;
        bool fastblk, pslocked;

        PROC_LOCK_ASSERT(p, MA_OWNED);
        ps = p->p_sigacts;
        pslocked = (flags & SIGPROCMASK_PS_LOCKED) != 0;
        mtx_assert(&ps->ps_mtx, pslocked ? MA_OWNED : MA_NOTOWNED);
        if (SIGISEMPTY(p->p_siglist))
                return;
        SIGSETAND(block, p->p_siglist);
        fastblk = (flags & SIGPROCMASK_FASTBLK) != 0;
        SIG_FOREACH(sig, &block) {
                td = sigtd(p, sig, fastblk);

                /*
                 * If sigtd() selected us despite sigfastblock is
                 * blocking, do not activate AST or wake us, to avoid
                 * loop in AST handler.
                 */
                if (fastblk && td == curthread)
                        continue;

                signotify(td);
                if (!pslocked)
                        mtx_lock(&ps->ps_mtx);
                if (p->p_flag & P_TRACED ||
                    (SIGISMEMBER(ps->ps_sigcatch, sig) &&
                    !SIGISMEMBER(td->td_sigmask, sig))) {
                        tdsigwakeup(td, sig, SIG_CATCH,
                            (SIGISMEMBER(ps->ps_sigintr, sig) ? EINTR :
                            ERESTART));
                }
                if (!pslocked)
                        mtx_unlock(&ps->ps_mtx);
        }
}

void
tdsigcleanup(struct thread *td)
{
        struct proc *p;
        sigset_t unblocked;

        p = td->td_proc;
        PROC_LOCK_ASSERT(p, MA_OWNED);

        sigqueue_flush(&td->td_sigqueue);
        if (p->p_numthreads == 1)
                return;

        /*
         * Since we cannot handle signals, notify signal post code
         * about this by filling the sigmask.
         *
         * Also, if needed, wake up thread(s) that do not block the
         * same signals as the exiting thread, since the thread might
         * have been selected for delivery and woken up.
         */
        SIGFILLSET(unblocked);
        SIGSETNAND(unblocked, td->td_sigmask);
        SIGFILLSET(td->td_sigmask);
        reschedule_signals(p, unblocked, 0);

}

static int
sigdeferstop_curr_flags(int cflags)
{

        MPASS((cflags & (TDF_SEINTR | TDF_SERESTART)) == 0 ||
            (cflags & TDF_SBDRY) != 0);
        return (cflags & (TDF_SBDRY | TDF_SEINTR | TDF_SERESTART));
}

/*
 * Defer the delivery of SIGSTOP for the current thread, according to
 * the requested mode.  Returns previous flags, which must be restored
 * by sigallowstop().
 *
 * TDF_SBDRY, TDF_SEINTR, and TDF_SERESTART flags are only set and
 * cleared by the current thread, which allow the lock-less read-only
 * accesses below.
 */
int
sigdeferstop_impl(int mode)
{
        struct thread *td;
        int cflags, nflags;

        td = curthread;
        cflags = sigdeferstop_curr_flags(td->td_flags);
        switch (mode) {
        case SIGDEFERSTOP_NOP:
                nflags = cflags;
                break;
        case SIGDEFERSTOP_OFF:
                nflags = 0;
                break;
        case SIGDEFERSTOP_SILENT:
                nflags = (cflags | TDF_SBDRY) & ~(TDF_SEINTR | TDF_SERESTART);
                break;
        case SIGDEFERSTOP_EINTR:
                nflags = (cflags | TDF_SBDRY | TDF_SEINTR) & ~TDF_SERESTART;
                break;
        case SIGDEFERSTOP_ERESTART:
                nflags = (cflags | TDF_SBDRY | TDF_SERESTART) & ~TDF_SEINTR;
                break;
        default:
                panic("sigdeferstop: invalid mode %x", mode);
                break;
        }
        if (cflags == nflags)
                return (SIGDEFERSTOP_VAL_NCHG);
        thread_lock(td);
        td->td_flags = (td->td_flags & ~cflags) | nflags;
        thread_unlock(td);
        return (cflags);
}

/*
 * Restores the STOP handling mode, typically permitting the delivery
 * of SIGSTOP for the current thread.  This does not immediately
 * suspend if a stop was posted.  Instead, the thread will suspend
 * either via ast() or a subsequent interruptible sleep.
 */
void
sigallowstop_impl(int prev)
{
        struct thread *td;
        int cflags;

        KASSERT(prev != SIGDEFERSTOP_VAL_NCHG, ("failed sigallowstop"));
        KASSERT((prev & ~(TDF_SBDRY | TDF_SEINTR | TDF_SERESTART)) == 0,
            ("sigallowstop: incorrect previous mode %x", prev));
        td = curthread;
        cflags = sigdeferstop_curr_flags(td->td_flags);
        if (cflags != prev) {
                thread_lock(td);
                td->td_flags = (td->td_flags & ~cflags) | prev;
                thread_unlock(td);
        }
}

enum sigstatus {
        SIGSTATUS_HANDLE,
        SIGSTATUS_HANDLED,
        SIGSTATUS_IGNORE,
        SIGSTATUS_SBDRY_STOP,
};

/*
 * The thread has signal "sig" pending.  Figure out what to do with it:
 *
 * _HANDLE     -> the caller should handle the signal
 * _HANDLED    -> handled internally, reload pending signal set
 * _IGNORE     -> ignored, remove from the set of pending signals and try the
 *                next pending signal
 * _SBDRY_STOP -> the signal should stop the thread but this is not
 *                permitted in the current context
 */
static enum sigstatus
sigprocess(struct thread *td, int sig)
{
        struct proc *p;
        struct sigacts *ps;
        struct sigqueue *queue;
        ksiginfo_t ksi;
        int prop;

        KASSERT(_SIG_VALID(sig), ("%s: invalid signal %d", __func__, sig));

        p = td->td_proc;
        ps = p->p_sigacts;
        mtx_assert(&ps->ps_mtx, MA_OWNED);
        PROC_LOCK_ASSERT(p, MA_OWNED);

        /*
         * We should allow pending but ignored signals below
         * if there is sigwait() active, or P_TRACED was
         * on when they were posted.
         */
        if (SIGISMEMBER(ps->ps_sigignore, sig) &&
            (p->p_flag & P_TRACED) == 0 &&
            (td->td_flags & TDF_SIGWAIT) == 0) {
                return (SIGSTATUS_IGNORE);
        }

        /*
         * If the process is going to single-thread mode to prepare
         * for exit, there is no sense in delivering any signal
         * to usermode.  Another important consequence is that
         * msleep(..., PCATCH, ...) now is only interruptible by a
         * suspend request.
         */
        if ((p->p_flag2 & P2_WEXIT) != 0)
                return (SIGSTATUS_IGNORE);

        if ((p->p_flag & (P_TRACED | P_PPTRACE)) == P_TRACED) {
                /*
                 * If traced, always stop.
                 * Remove old signal from queue before the stop.
                 * XXX shrug off debugger, it causes siginfo to
                 * be thrown away.
                 */
                queue = &td->td_sigqueue;
                ksiginfo_init(&ksi);
                if (sigqueue_get(queue, sig, &ksi) == 0) {
                        queue = &p->p_sigqueue;
                        sigqueue_get(queue, sig, &ksi);
                }
                td->td_si = ksi.ksi_info;

                mtx_unlock(&ps->ps_mtx);
                sig = ptracestop(td, sig, &ksi);
                mtx_lock(&ps->ps_mtx);

                td->td_si.si_signo = 0;

                /*
                 * Keep looking if the debugger discarded or
                 * replaced the signal.
                 */
                if (sig == 0)
                        return (SIGSTATUS_HANDLED);

                /*
                 * If the signal became masked, re-queue it.
                 */
                if (SIGISMEMBER(td->td_sigmask, sig)) {
                        ksi.ksi_flags |= KSI_HEAD;
                        sigqueue_add(&p->p_sigqueue, sig, &ksi);
                        return (SIGSTATUS_HANDLED);
                }

                /*
                 * If the traced bit got turned off, requeue the signal and
                 * reload the set of pending signals.  This ensures that p_sig*
                 * and p_sigact are consistent.
                 */
                if ((p->p_flag & P_TRACED) == 0) {
                        if ((ksi.ksi_flags & KSI_PTRACE) == 0) {
                                ksi.ksi_flags |= KSI_HEAD;
                                sigqueue_add(queue, sig, &ksi);
                        }
                        return (SIGSTATUS_HANDLED);
                }
        }

        /*
         * Decide whether the signal should be returned.
         * Return the signal's number, or fall through
         * to clear it from the pending mask.
         */
        switch ((intptr_t)p->p_sigacts->ps_sigact[_SIG_IDX(sig)]) {
        case (intptr_t)SIG_DFL:
                /*
                 * Don't take default actions on system processes.
                 */
                if (p->p_pid <= 1) {
#ifdef DIAGNOSTIC
                        /*
                         * Are you sure you want to ignore SIGSEGV
                         * in init? XXX
                         */
                        printf("Process (pid %lu) got signal %d\n",
                                (u_long)p->p_pid, sig);
#endif
                        return (SIGSTATUS_IGNORE);
                }

                /*
                 * If there is a pending stop signal to process with
                 * default action, stop here, then clear the signal.
                 * Traced or exiting processes should ignore stops.
                 * Additionally, a member of an orphaned process group
                 * should ignore tty stops.
                 */
                prop = sigprop(sig);
                if (prop & SIGPROP_STOP) {
                        mtx_unlock(&ps->ps_mtx);
                        if ((p->p_flag & (P_TRACED | P_WEXIT |
                            P_SINGLE_EXIT)) != 0 || ((p->p_pgrp->
                            pg_flags & PGRP_ORPHANED) != 0 &&
                            (prop & SIGPROP_TTYSTOP) != 0)) {
                                mtx_lock(&ps->ps_mtx);
                                return (SIGSTATUS_IGNORE);
                        }
                        if (TD_SBDRY_INTR(td)) {
                                KASSERT((td->td_flags & TDF_SBDRY) != 0,
                                    ("lost TDF_SBDRY"));
                                mtx_lock(&ps->ps_mtx);
                                return (SIGSTATUS_SBDRY_STOP);
                        }
                        WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK,
                            &p->p_mtx.lock_object, "Catching SIGSTOP");
                        sigqueue_delete(&td->td_sigqueue, sig);
                        sigqueue_delete(&p->p_sigqueue, sig);
                        p->p_flag |= P_STOPPED_SIG;
                        p->p_xsig = sig;
                        PROC_SLOCK(p);
                        sig_suspend_threads(td, p);
                        thread_suspend_switch(td, p);
                        PROC_SUNLOCK(p);
                        mtx_lock(&ps->ps_mtx);
                        return (SIGSTATUS_HANDLED);
                } else if ((prop & SIGPROP_IGNORE) != 0 &&
                    (td->td_flags & TDF_SIGWAIT) == 0) {
                        /*
                         * Default action is to ignore; drop it if
                         * not in kern_sigtimedwait().
                         */
                        return (SIGSTATUS_IGNORE);
                } else {
                        return (SIGSTATUS_HANDLE);
                }

        case (intptr_t)SIG_IGN:
                if ((td->td_flags & TDF_SIGWAIT) == 0)
                        return (SIGSTATUS_IGNORE);
                else
                        return (SIGSTATUS_HANDLE);

        default:
                /*
                 * This signal has an action, let postsig() process it.
                 */
                return (SIGSTATUS_HANDLE);
        }
}

/*
 * If the current process has received a signal (should be caught or cause
 * termination, should interrupt current syscall), return the signal number.
 * Stop signals with default action are processed immediately, then cleared;
 * they aren't returned.  This is checked after each entry to the system for
 * a syscall or trap (though this can usually be done without calling
 * issignal by checking the pending signal masks in cursig.) The normal call
 * sequence is
 *
 *      while (sig = cursig(curthread))
 *              postsig(sig);
 */
static int
issignal(struct thread *td)
{
        struct proc *p;
        sigset_t sigpending;
        int sig;

        p = td->td_proc;
        PROC_LOCK_ASSERT(p, MA_OWNED);

        for (;;) {
                sigpending = td->td_sigqueue.sq_signals;
                SIGSETOR(sigpending, p->p_sigqueue.sq_signals);
                SIGSETNAND(sigpending, td->td_sigmask);

                if ((p->p_flag & P_PPWAIT) != 0 || (td->td_flags &
                    (TDF_SBDRY | TDF_SERESTART | TDF_SEINTR)) == TDF_SBDRY)
                        SIG_STOPSIGMASK(sigpending);
                if (SIGISEMPTY(sigpending))     /* no signal to send */
                        return (0);

                /*
                 * Do fast sigblock if requested by usermode.  Since
                 * we do know that there was a signal pending at this
                 * point, set the FAST_SIGBLOCK_PEND as indicator for
                 * usermode to perform a dummy call to
                 * FAST_SIGBLOCK_UNBLOCK, which causes immediate
                 * delivery of postponed pending signal.
                 */
                if ((td->td_pflags & TDP_SIGFASTBLOCK) != 0) {
                        if (td->td_sigblock_val != 0)
                                SIGSETNAND(sigpending, fastblock_mask);
                        if (SIGISEMPTY(sigpending)) {
                                td->td_pflags |= TDP_SIGFASTPENDING;
                                return (0);
                        }
                }

                if ((p->p_flag & (P_TRACED | P_PPTRACE)) == P_TRACED &&
                    (p->p_flag2 & P2_PTRACE_FSTP) != 0 &&
                    SIGISMEMBER(sigpending, SIGSTOP)) {
                        /*
                         * If debugger just attached, always consume
                         * SIGSTOP from ptrace(PT_ATTACH) first, to
                         * execute the debugger attach ritual in
                         * order.
                         */
                        td->td_dbgflags |= TDB_FSTP;
                        SIGEMPTYSET(sigpending);
                        SIGADDSET(sigpending, SIGSTOP);
                }

                SIG_FOREACH(sig, &sigpending) {
                        switch (sigprocess(td, sig)) {
                        case SIGSTATUS_HANDLE:
                                return (sig);
                        case SIGSTATUS_HANDLED:
                                goto next;
                        case SIGSTATUS_IGNORE:
                                sigqueue_delete(&td->td_sigqueue, sig);
                                sigqueue_delete(&p->p_sigqueue, sig);
                                break;
                        case SIGSTATUS_SBDRY_STOP:
                                return (-1);
                        }
                }
next:;
        }
}

void
thread_stopped(struct proc *p)
{
        int n;

        PROC_LOCK_ASSERT(p, MA_OWNED);
        PROC_SLOCK_ASSERT(p, MA_OWNED);
        n = p->p_suspcount;
        if (p == curproc)
                n++;
        if ((p->p_flag & P_STOPPED_SIG) && (n == p->p_numthreads)) {
                PROC_SUNLOCK(p);
                p->p_flag &= ~P_WAITED;
                PROC_LOCK(p->p_pptr);
                childproc_stopped(p, (p->p_flag & P_TRACED) ?
                        CLD_TRAPPED : CLD_STOPPED);
                PROC_UNLOCK(p->p_pptr);
                PROC_SLOCK(p);
        }
}

/*
 * Take the action for the specified signal
 * from the current set of pending signals.
 */
int
postsig(int sig)
{
        struct thread *td;
        struct proc *p;
        struct sigacts *ps;
        sig_t action;
        ksiginfo_t ksi;
        sigset_t returnmask;

        KASSERT(sig != 0, ("postsig"));

        td = curthread;
        p = td->td_proc;
        PROC_LOCK_ASSERT(p, MA_OWNED);
        ps = p->p_sigacts;
        mtx_assert(&ps->ps_mtx, MA_OWNED);
        ksiginfo_init(&ksi);
        if (sigqueue_get(&td->td_sigqueue, sig, &ksi) == 0 &&
            sigqueue_get(&p->p_sigqueue, sig, &ksi) == 0)
                return (0);
        ksi.ksi_signo = sig;
        if (ksi.ksi_code == SI_TIMER)
                itimer_accept(p, ksi.ksi_timerid, &ksi);
        action = ps->ps_sigact[_SIG_IDX(sig)];
#ifdef KTRACE
        if (KTRPOINT(td, KTR_PSIG))
                ktrpsig(sig, action, td->td_pflags & TDP_OLDMASK ?
                    &td->td_oldsigmask : &td->td_sigmask, ksi.ksi_code);
#endif

        if (action == SIG_DFL) {
                /*
                 * Default action, where the default is to kill
                 * the process.  (Other cases were ignored above.)
                 */
                mtx_unlock(&ps->ps_mtx);
                proc_td_siginfo_capture(td, &ksi.ksi_info);
                sigexit(td, sig);
                /* NOTREACHED */
        } else {
                /*
                 * If we get here, the signal must be caught.
                 */
                KASSERT(action != SIG_IGN, ("postsig action %p", action));
                KASSERT(!SIGISMEMBER(td->td_sigmask, sig),
                    ("postsig action: blocked sig %d", sig));

                /*
                 * Set the new mask value and also defer further
                 * occurrences of this signal.
                 *
                 * Special case: user has done a sigsuspend.  Here the
                 * current mask is not of interest, but rather the
                 * mask from before the sigsuspend is what we want
                 * restored after the signal processing is completed.
                 */
                if (td->td_pflags & TDP_OLDMASK) {
                        returnmask = td->td_oldsigmask;
                        td->td_pflags &= ~TDP_OLDMASK;
                } else
                        returnmask = td->td_sigmask;

                if (p->p_sig == sig) {
                        p->p_sig = 0;
                }
                (*p->p_sysent->sv_sendsig)(action, &ksi, &returnmask);
                postsig_done(sig, td, ps);
        }
        return (1);
}

int
sig_ast_checksusp(struct thread *td)
{
        struct proc *p __diagused;
        int ret;

        p = td->td_proc;
        PROC_LOCK_ASSERT(p, MA_OWNED);

        if (!td_ast_pending(td, TDA_SUSPEND))
                return (0);

        ret = thread_suspend_check(1);
        MPASS(ret == 0 || ret == EINTR || ret == ERESTART);
        return (ret);
}

int
sig_ast_needsigchk(struct thread *td)
{
        struct proc *p;
        struct sigacts *ps;
        int ret, sig;

        p = td->td_proc;
        PROC_LOCK_ASSERT(p, MA_OWNED);

        if (!td_ast_pending(td, TDA_SIG))
                return (0);

        ps = p->p_sigacts;
        mtx_lock(&ps->ps_mtx);
        sig = cursig(td);
        if (sig == -1) {
                mtx_unlock(&ps->ps_mtx);
                KASSERT((td->td_flags & TDF_SBDRY) != 0, ("lost TDF_SBDRY"));
                KASSERT(TD_SBDRY_INTR(td),
                    ("lost TDF_SERESTART of TDF_SEINTR"));
                KASSERT((td->td_flags & (TDF_SEINTR | TDF_SERESTART)) !=
                    (TDF_SEINTR | TDF_SERESTART),
                    ("both TDF_SEINTR and TDF_SERESTART"));
                ret = TD_SBDRY_ERRNO(td);
        } else if (sig != 0) {
                ret = SIGISMEMBER(ps->ps_sigintr, sig) ? EINTR : ERESTART;
                mtx_unlock(&ps->ps_mtx);
        } else {
                mtx_unlock(&ps->ps_mtx);
                ret = 0;
        }

        /*
         * Do not go into sleep if this thread was the ptrace(2)
         * attach leader.  cursig() consumed SIGSTOP from PT_ATTACH,
         * but we usually act on the signal by interrupting sleep, and
         * should do that here as well.
         */
        if ((td->td_dbgflags & TDB_FSTP) != 0) {
                if (ret == 0)
                        ret = EINTR;
                td->td_dbgflags &= ~TDB_FSTP;
        }

        return (ret);
}

int
sig_intr(void)
{
        struct thread *td;
        struct proc *p;
        int ret;

        td = curthread;
        if (!td_ast_pending(td, TDA_SIG) && !td_ast_pending(td, TDA_SUSPEND))
                return (0);

        p = td->td_proc;

        PROC_LOCK(p);
        ret = sig_ast_checksusp(td);
        if (ret == 0)
                ret = sig_ast_needsigchk(td);
        PROC_UNLOCK(p);
        return (ret);
}

bool
curproc_sigkilled(void)
{
        struct thread *td;
        struct proc *p;
        struct sigacts *ps;
        bool res;

        td = curthread;
        if (!td_ast_pending(td, TDA_SIG))
                return (false);

        p = td->td_proc;
        PROC_LOCK(p);
        ps = p->p_sigacts;
        mtx_lock(&ps->ps_mtx);
        res = SIGISMEMBER(td->td_sigqueue.sq_signals, SIGKILL) ||
            SIGISMEMBER(p->p_sigqueue.sq_signals, SIGKILL);
        mtx_unlock(&ps->ps_mtx);
        PROC_UNLOCK(p);
        return (res);
}

void
proc_wkilled(struct proc *p)
{

        PROC_LOCK_ASSERT(p, MA_OWNED);
        if ((p->p_flag & P_WKILLED) == 0) {
                p->p_flag |= P_WKILLED;
                /*
                 * Notify swapper that there is a process to swap in.
                 * The notification is racy, at worst it would take 10
                 * seconds for the swapper process to notice.
                 */
                if ((p->p_flag & (P_INMEM | P_SWAPPINGIN)) == 0)
                        wakeup(&proc0);
        }
}

/*
 * Kill the current process for stated reason.
 */
void
killproc(struct proc *p, const char *why)
{

        PROC_LOCK_ASSERT(p, MA_OWNED);
        CTR3(KTR_PROC, "killproc: proc %p (pid %d, %s)", p, p->p_pid,
            p->p_comm);
        log(LOG_ERR, "pid %d (%s), jid %d, uid %d, was killed: %s\n",
            p->p_pid, p->p_comm, p->p_ucred->cr_prison->pr_id,
            p->p_ucred->cr_uid, why);
        proc_wkilled(p);
        kern_psignal(p, SIGKILL);
}

/*
 * Force the current process to exit with the specified signal, dumping core
 * if appropriate.  We bypass the normal tests for masked and caught signals,
 * allowing unrecoverable failures to terminate the process without changing
 * signal state.  Mark the accounting record with the signal termination.
 * If dumping core, save the signal number for the debugger.  Calls exit and
 * does not return.
 */
void
sigexit(struct thread *td, int sig)
{
        struct proc *p = td->td_proc;
        const char *coreinfo;
        int rv;

        PROC_LOCK_ASSERT(p, MA_OWNED);
        proc_set_p2_wexit(p);

        p->p_acflag |= AXSIG;
        /*
         * We must be single-threading to generate a core dump.  This
         * ensures that the registers in the core file are up-to-date.
         * Also, the ELF dump handler assumes that the thread list doesn't
         * change out from under it.
         *
         * XXX If another thread attempts to single-thread before us
         *     (e.g. via fork()), we won't get a dump at all.
         */
        if ((sigprop(sig) & SIGPROP_CORE) &&
            thread_single(p, SINGLE_NO_EXIT) == 0) {
                p->p_sig = sig;
                /*
                 * Log signals which would cause core dumps
                 * (Log as LOG_INFO to appease those who don't want
                 * these messages.)
                 * XXX : Todo, as well as euid, write out ruid too
                 * Note that coredump() drops proc lock.
                 */
                rv = coredump(td);
                switch (rv) {
                case 0:
                        sig |= WCOREFLAG;
                        coreinfo = " (core dumped)";
                        break;
                case EFAULT:
                        coreinfo = " (no core dump - bad address)";
                        break;
                case EINVAL:
                        coreinfo = " (no core dump - invalid argument)";
                        break;
                case EFBIG:
                        coreinfo = " (no core dump - too large)";
                        break;
                default:
                        coreinfo = " (no core dump - other error)";
                        break;
                }
                if (kern_logsigexit)
                        log(LOG_INFO,
                            "pid %d (%s), jid %d, uid %d: exited on "
                            "signal %d%s\n", p->p_pid, p->p_comm,
                            p->p_ucred->cr_prison->pr_id,
                            td->td_ucred->cr_uid,
                            sig &~ WCOREFLAG, coreinfo);
        } else
                PROC_UNLOCK(p);
        exit1(td, 0, sig);
        /* NOTREACHED */
}

/*
 * Send queued SIGCHLD to parent when child process's state
 * is changed.
 */
static void
sigparent(struct proc *p, int reason, int status)
{
        PROC_LOCK_ASSERT(p, MA_OWNED);
        PROC_LOCK_ASSERT(p->p_pptr, MA_OWNED);

        if (p->p_ksi != NULL) {
                p->p_ksi->ksi_signo  = SIGCHLD;
                p->p_ksi->ksi_code   = reason;
                p->p_ksi->ksi_status = status;
                p->p_ksi->ksi_pid    = p->p_pid;
                p->p_ksi->ksi_uid    = p->p_ucred->cr_ruid;
                if (KSI_ONQ(p->p_ksi))
                        return;
        }
        pksignal(p->p_pptr, SIGCHLD, p->p_ksi);
}

static void
childproc_jobstate(struct proc *p, int reason, int sig)
{
        struct sigacts *ps;

        PROC_LOCK_ASSERT(p, MA_OWNED);
        PROC_LOCK_ASSERT(p->p_pptr, MA_OWNED);

        /*
         * Wake up parent sleeping in kern_wait(), also send
         * SIGCHLD to parent, but SIGCHLD does not guarantee
         * that parent will awake, because parent may masked
         * the signal.
         */
        p->p_pptr->p_flag |= P_STATCHILD;
        wakeup(p->p_pptr);

        ps = p->p_pptr->p_sigacts;
        mtx_lock(&ps->ps_mtx);
        if ((ps->ps_flag & PS_NOCLDSTOP) == 0) {
                mtx_unlock(&ps->ps_mtx);
                sigparent(p, reason, sig);
        } else
                mtx_unlock(&ps->ps_mtx);
}

void
childproc_stopped(struct proc *p, int reason)
{

        childproc_jobstate(p, reason, p->p_xsig);
}

void
childproc_continued(struct proc *p)
{
        childproc_jobstate(p, CLD_CONTINUED, SIGCONT);
}

void
childproc_exited(struct proc *p)
{
        int reason, status;

        if (WCOREDUMP(p->p_xsig)) {
                reason = CLD_DUMPED;
                status = WTERMSIG(p->p_xsig);
        } else if (WIFSIGNALED(p->p_xsig)) {
                reason = CLD_KILLED;
                status = WTERMSIG(p->p_xsig);
        } else {
                reason = CLD_EXITED;
                status = p->p_xexit;
        }
        /*
         * XXX avoid calling wakeup(p->p_pptr), the work is
         * done in exit1().
         */
        sigparent(p, reason, status);
}

#define MAX_NUM_CORE_FILES 100000
#ifndef NUM_CORE_FILES
#define NUM_CORE_FILES 5
#endif
CTASSERT(NUM_CORE_FILES >= 0 && NUM_CORE_FILES <= MAX_NUM_CORE_FILES);
static int num_cores = NUM_CORE_FILES;

static int
sysctl_debug_num_cores_check (SYSCTL_HANDLER_ARGS)
{
        int error;
        int new_val;

        new_val = num_cores;
        error = sysctl_handle_int(oidp, &new_val, 0, req);
        if (error != 0 || req->newptr == NULL)
                return (error);
        if (new_val > MAX_NUM_CORE_FILES)
                new_val = MAX_NUM_CORE_FILES;
        if (new_val < 0)
                new_val = 0;
        num_cores = new_val;
        return (0);
}
SYSCTL_PROC(_debug, OID_AUTO, ncores,
    CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE, 0, sizeof(int),
    sysctl_debug_num_cores_check, "I",
    "Maximum number of generated process corefiles while using index format");

#define GZIP_SUFFIX     ".gz"
#define ZSTD_SUFFIX     ".zst"

int compress_user_cores = 0;

static int
sysctl_compress_user_cores(SYSCTL_HANDLER_ARGS)
{
        int error, val;

        val = compress_user_cores;
        error = sysctl_handle_int(oidp, &val, 0, req);
        if (error != 0 || req->newptr == NULL)
                return (error);
        if (val != 0 && !compressor_avail(val))
                return (EINVAL);
        compress_user_cores = val;
        return (error);
}
SYSCTL_PROC(_kern, OID_AUTO, compress_user_cores,
    CTLTYPE_INT | CTLFLAG_RWTUN | CTLFLAG_NEEDGIANT, 0, sizeof(int),
    sysctl_compress_user_cores, "I",
    "Enable compression of user corefiles ("
    __XSTRING(COMPRESS_GZIP) " = gzip, "
    __XSTRING(COMPRESS_ZSTD) " = zstd)");

int compress_user_cores_level = 6;
SYSCTL_INT(_kern, OID_AUTO, compress_user_cores_level, CTLFLAG_RWTUN,
    &compress_user_cores_level, 0,
    "Corefile compression level");

/*
 * Protect the access to corefilename[] by allproc_lock.
 */
#define corefilename_lock       allproc_lock

static char corefilename[MAXPATHLEN] = {"%N.core"};
TUNABLE_STR("kern.corefile", corefilename, sizeof(corefilename));

static int
sysctl_kern_corefile(SYSCTL_HANDLER_ARGS)
{
        int error;

        sx_xlock(&corefilename_lock);
        error = sysctl_handle_string(oidp, corefilename, sizeof(corefilename),
            req);
        sx_xunlock(&corefilename_lock);

        return (error);
}
SYSCTL_PROC(_kern, OID_AUTO, corefile, CTLTYPE_STRING | CTLFLAG_RW |
    CTLFLAG_MPSAFE, 0, 0, sysctl_kern_corefile, "A",
    "Process corefile name format string");

static void
vnode_close_locked(struct thread *td, struct vnode *vp)
{

        VOP_UNLOCK(vp);
        vn_close(vp, FWRITE, td->td_ucred, td);
}

/*
 * If the core format has a %I in it, then we need to check
 * for existing corefiles before defining a name.
 * To do this we iterate over 0..ncores to find a
 * non-existing core file name to use. If all core files are
 * already used we choose the oldest one.
 */
static int
corefile_open_last(struct thread *td, char *name, int indexpos,
    int indexlen, int ncores, struct vnode **vpp)
{
        struct vnode *oldvp, *nextvp, *vp;
        struct vattr vattr;
        struct nameidata nd;
        int error, i, flags, oflags, cmode;
        char ch;
        struct timespec lasttime;

        nextvp = oldvp = NULL;
        cmode = S_IRUSR | S_IWUSR;
        oflags = VN_OPEN_NOAUDIT | VN_OPEN_NAMECACHE |
            (capmode_coredump ? VN_OPEN_NOCAPCHECK : 0);

        for (i = 0; i < ncores; i++) {
                flags = O_CREAT | FWRITE | O_NOFOLLOW;

                ch = name[indexpos + indexlen];
                (void)snprintf(name + indexpos, indexlen + 1, "%.*u", indexlen,
                    i);
                name[indexpos + indexlen] = ch;

                NDINIT(&nd, LOOKUP, NOFOLLOW, UIO_SYSSPACE, name);
                error = vn_open_cred(&nd, &flags, cmode, oflags, td->td_ucred,
                    NULL);
                if (error != 0)
                        break;

                vp = nd.ni_vp;
                NDFREE_PNBUF(&nd);
                if ((flags & O_CREAT) == O_CREAT) {
                        nextvp = vp;
                        break;
                }

                error = VOP_GETATTR(vp, &vattr, td->td_ucred);
                if (error != 0) {
                        vnode_close_locked(td, vp);
                        break;
                }

                if (oldvp == NULL ||
                    lasttime.tv_sec > vattr.va_mtime.tv_sec ||
                    (lasttime.tv_sec == vattr.va_mtime.tv_sec &&
                    lasttime.tv_nsec >= vattr.va_mtime.tv_nsec)) {
                        if (oldvp != NULL)
                                vn_close(oldvp, FWRITE, td->td_ucred, td);
                        oldvp = vp;
                        VOP_UNLOCK(oldvp);
                        lasttime = vattr.va_mtime;
                } else {
                        vnode_close_locked(td, vp);
                }
        }

        if (oldvp != NULL) {
                if (nextvp == NULL) {
                        if ((td->td_proc->p_flag & P_SUGID) != 0) {
                                error = EFAULT;
                                vn_close(oldvp, FWRITE, td->td_ucred, td);
                        } else {
                                nextvp = oldvp;
                                error = vn_lock(nextvp, LK_EXCLUSIVE);
                                if (error != 0) {
                                        vn_close(nextvp, FWRITE, td->td_ucred,
                                            td);
                                        nextvp = NULL;
                                }
                        }
                } else {
                        vn_close(oldvp, FWRITE, td->td_ucred, td);
                }
        }
        if (error != 0) {
                if (nextvp != NULL)
                        vnode_close_locked(td, oldvp);
        } else {
                *vpp = nextvp;
        }

        return (error);
}

/*
 * corefile_open(comm, uid, pid, td, compress, vpp, namep)
 * Expand the name described in corefilename, using name, uid, and pid
 * and open/create core file.
 * corefilename is a printf-like string, with three format specifiers:
 *      %N      name of process ("name")
 *      %P      process id (pid)
 *      %U      user id (uid)
 * For example, "%N.core" is the default; they can be disabled completely
 * by using "/dev/null", or all core files can be stored in "/cores/%U/%N-%P".
 * This is controlled by the sysctl variable kern.corefile (see above).
 */
static int
corefile_open(const char *comm, uid_t uid, pid_t pid, struct thread *td,
    int compress, int signum, struct vnode **vpp, char **namep)
{
        struct sbuf sb;
        struct nameidata nd;
        const char *format;
        char *hostname, *name;
        int cmode, error, flags, i, indexpos, indexlen, oflags, ncores;

        hostname = NULL;
        format = corefilename;
        name = malloc(MAXPATHLEN, M_TEMP, M_WAITOK | M_ZERO);
        indexlen = 0;
        indexpos = -1;
        ncores = num_cores;
        (void)sbuf_new(&sb, name, MAXPATHLEN, SBUF_FIXEDLEN);
        sx_slock(&corefilename_lock);
        for (i = 0; format[i] != '\0'; i++) {
                switch (format[i]) {
                case '%':       /* Format character */
                        i++;
                        switch (format[i]) {
                        case '%':
                                sbuf_putc(&sb, '%');
                                break;
                        case 'H':       /* hostname */
                                if (hostname == NULL) {
                                        hostname = malloc(MAXHOSTNAMELEN,
                                            M_TEMP, M_WAITOK);
                                }
                                getcredhostname(td->td_ucred, hostname,
                                    MAXHOSTNAMELEN);
                                sbuf_printf(&sb, "%s", hostname);
                                break;
                        case 'I':       /* autoincrementing index */
                                if (indexpos != -1) {
                                        sbuf_printf(&sb, "%%I");
                                        break;
                                }

                                indexpos = sbuf_len(&sb);
                                sbuf_printf(&sb, "%u", ncores - 1);
                                indexlen = sbuf_len(&sb) - indexpos;
                                break;
                        case 'N':       /* process name */
                                sbuf_printf(&sb, "%s", comm);
                                break;
                        case 'P':       /* process id */
                                sbuf_printf(&sb, "%u", pid);
                                break;
                        case 'S':       /* signal number */
                                sbuf_printf(&sb, "%i", signum);
                                break;
                        case 'U':       /* user id */
                                sbuf_printf(&sb, "%u", uid);
                                break;
                        default:
                                log(LOG_ERR,
                                    "Unknown format character %c in "
                                    "corename `%s'\n", format[i], format);
                                break;
                        }
                        break;
                default:
                        sbuf_putc(&sb, format[i]);
                        break;
                }
        }
        sx_sunlock(&corefilename_lock);
        free(hostname, M_TEMP);
        if (compress == COMPRESS_GZIP)
                sbuf_printf(&sb, GZIP_SUFFIX);
        else if (compress == COMPRESS_ZSTD)
                sbuf_printf(&sb, ZSTD_SUFFIX);
        if (sbuf_error(&sb) != 0) {
                log(LOG_ERR, "pid %ld (%s), uid (%lu): corename is too "
                    "long\n", (long)pid, comm, (u_long)uid);
                sbuf_delete(&sb);
                free(name, M_TEMP);
                return (ENOMEM);
        }
        sbuf_finish(&sb);
        sbuf_delete(&sb);

        if (indexpos != -1) {
                error = corefile_open_last(td, name, indexpos, indexlen, ncores,
                    vpp);
                if (error != 0) {
                        log(LOG_ERR,
                            "pid %d (%s), uid (%u):  Path `%s' failed "
                            "on initial open test, error = %d\n",
                            pid, comm, uid, name, error);
                }
        } else {
                cmode = S_IRUSR | S_IWUSR;
                oflags = VN_OPEN_NOAUDIT | VN_OPEN_NAMECACHE |
                    (capmode_coredump ? VN_OPEN_NOCAPCHECK : 0);
                flags = O_CREAT | FWRITE | O_NOFOLLOW;
                if ((td->td_proc->p_flag & P_SUGID) != 0)
                        flags |= O_EXCL;

                NDINIT(&nd, LOOKUP, NOFOLLOW, UIO_SYSSPACE, name);
                error = vn_open_cred(&nd, &flags, cmode, oflags, td->td_ucred,
                    NULL);
                if (error == 0) {
                        *vpp = nd.ni_vp;
                        NDFREE_PNBUF(&nd);
                }
        }

        if (error != 0) {
#ifdef AUDIT
                audit_proc_coredump(td, name, error);
#endif
                free(name, M_TEMP);
                return (error);
        }
        *namep = name;
        return (0);
}

/*
 * Dump a process' core.  The main routine does some
 * policy checking, and creates the name of the coredump;
 * then it passes on a vnode and a size limit to the process-specific
 * coredump routine if there is one; if there _is not_ one, it returns
 * ENOSYS; otherwise it returns the error from the process-specific routine.
 */

static int
coredump(struct thread *td)
{
        struct proc *p = td->td_proc;
        struct ucred *cred = td->td_ucred;
        struct vnode *vp;
        struct flock lf;
        struct vattr vattr;
        size_t fullpathsize;
        int error, error1, locked;
        char *name;                     /* name of corefile */
        void *rl_cookie;
        off_t limit;
        char *fullpath, *freepath = NULL;
        struct sbuf *sb;

        PROC_LOCK_ASSERT(p, MA_OWNED);
        MPASS((p->p_flag & P_HADTHREADS) == 0 || p->p_singlethread == td);

        if (!do_coredump || (!sugid_coredump && (p->p_flag & P_SUGID) != 0) ||
            (p->p_flag2 & P2_NOTRACE) != 0) {
                PROC_UNLOCK(p);
                return (EFAULT);
        }

        /*
         * Note that the bulk of limit checking is done after
         * the corefile is created.  The exception is if the limit
         * for corefiles is 0, in which case we don't bother
         * creating the corefile at all.  This layout means that
         * a corefile is truncated instead of not being created,
         * if it is larger than the limit.
         */
        limit = (off_t)lim_cur(td, RLIMIT_CORE);
        if (limit == 0 || racct_get_available(p, RACCT_CORE) == 0) {
                PROC_UNLOCK(p);
                return (EFBIG);
        }
        PROC_UNLOCK(p);

        error = corefile_open(p->p_comm, cred->cr_uid, p->p_pid, td,
            compress_user_cores, p->p_sig, &vp, &name);
        if (error != 0)
                return (error);

        /*
         * Don't dump to non-regular files or files with links.
         * Do not dump into system files. Effective user must own the corefile.
         */
        if (vp->v_type != VREG || VOP_GETATTR(vp, &vattr, cred) != 0 ||
            vattr.va_nlink != 1 || (vp->v_vflag & VV_SYSTEM) != 0 ||
            vattr.va_uid != cred->cr_uid) {
                VOP_UNLOCK(vp);
                error = EFAULT;
                goto out;
        }

        VOP_UNLOCK(vp);

        /* Postpone other writers, including core dumps of other processes. */
        rl_cookie = vn_rangelock_wlock(vp, 0, OFF_MAX);

        lf.l_whence = SEEK_SET;
        lf.l_start = 0;
        lf.l_len = 0;
        lf.l_type = F_WRLCK;
        locked = (VOP_ADVLOCK(vp, (caddr_t)p, F_SETLK, &lf, F_FLOCK) == 0);

        VATTR_NULL(&vattr);
        vattr.va_size = 0;
        if (set_core_nodump_flag)
                vattr.va_flags = UF_NODUMP;
        vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
        VOP_SETATTR(vp, &vattr, cred);
        VOP_UNLOCK(vp);
        PROC_LOCK(p);
        p->p_acflag |= ACORE;
        PROC_UNLOCK(p);

        if (p->p_sysent->sv_coredump != NULL) {
                error = p->p_sysent->sv_coredump(td, vp, limit, 0);
        } else {
                error = ENOSYS;
        }

        if (locked) {
                lf.l_type = F_UNLCK;
                VOP_ADVLOCK(vp, (caddr_t)p, F_UNLCK, &lf, F_FLOCK);
        }
        vn_rangelock_unlock(vp, rl_cookie);

        /*
         * Notify the userland helper that a process triggered a core dump.
         * This allows the helper to run an automated debugging session.
         */
        if (error != 0 || coredump_devctl == 0)
                goto out;
        sb = sbuf_new_auto();
        if (vn_fullpath_global(p->p_textvp, &fullpath, &freepath) != 0)
                goto out2;
        sbuf_printf(sb, "comm=\"");
        devctl_safe_quote_sb(sb, fullpath);
        free(freepath, M_TEMP);
        sbuf_printf(sb, "\" core=\"");

        /*
         * We can't lookup core file vp directly. When we're replacing a core, and
         * other random times, we flush the name cache, so it will fail. Instead,
         * if the path of the core is relative, add the current dir in front if it.
         */
        if (name[0] != '/') {
                fullpathsize = MAXPATHLEN;
                freepath = malloc(fullpathsize, M_TEMP, M_WAITOK);
                if (vn_getcwd(freepath, &fullpath, &fullpathsize) != 0) {
                        free(freepath, M_TEMP);
                        goto out2;
                }
                devctl_safe_quote_sb(sb, fullpath);
                free(freepath, M_TEMP);
                sbuf_putc(sb, '/');
        }
        devctl_safe_quote_sb(sb, name);
        sbuf_printf(sb, "\"");
        if (sbuf_finish(sb) == 0)
                devctl_notify("kernel", "signal", "coredump", sbuf_data(sb));
out2:
        sbuf_delete(sb);
out:
        error1 = vn_close(vp, FWRITE, cred, td);
        if (error == 0)
                error = error1;
#ifdef AUDIT
        audit_proc_coredump(td, name, error);
#endif
        free(name, M_TEMP);
        return (error);
}

/*
 * Nonexistent system call-- signal process (may want to handle it).  Flag
 * error in case process won't see signal immediately (blocked or ignored).
 */
#ifndef _SYS_SYSPROTO_H_
struct nosys_args {
        int     dummy;
};
#endif
/* ARGSUSED */
int
nosys(struct thread *td, struct nosys_args *args)
{
        struct proc *p;

        p = td->td_proc;

        if (SV_PROC_FLAG(p, SV_SIGSYS) != 0 && kern_signosys) {
                PROC_LOCK(p);
                tdsignal(td, SIGSYS);
                PROC_UNLOCK(p);
        }
        if (kern_lognosys == 1 || kern_lognosys == 3) {
                uprintf("pid %d comm %s: nosys %d\n", p->p_pid, p->p_comm,
                    td->td_sa.code);
        }
        if (kern_lognosys == 2 || kern_lognosys == 3 ||
            (p->p_pid == 1 && (kern_lognosys & 3) == 0)) {
                printf("pid %d comm %s: nosys %d\n", p->p_pid, p->p_comm,
                    td->td_sa.code);
        }
        return (ENOSYS);
}

/*
 * Send a SIGIO or SIGURG signal to a process or process group using stored
 * credentials rather than those of the current process.
 */
void
pgsigio(struct sigio **sigiop, int sig, int checkctty)
{
        ksiginfo_t ksi;
        struct sigio *sigio;

        ksiginfo_init(&ksi);
        ksi.ksi_signo = sig;
        ksi.ksi_code = SI_KERNEL;

        SIGIO_LOCK();
        sigio = *sigiop;
        if (sigio == NULL) {
                SIGIO_UNLOCK();
                return;
        }
        if (sigio->sio_pgid > 0) {
                PROC_LOCK(sigio->sio_proc);
                if (CANSIGIO(sigio->sio_ucred, sigio->sio_proc->p_ucred))
                        kern_psignal(sigio->sio_proc, sig);
                PROC_UNLOCK(sigio->sio_proc);
        } else if (sigio->sio_pgid < 0) {
                struct proc *p;

                PGRP_LOCK(sigio->sio_pgrp);
                LIST_FOREACH(p, &sigio->sio_pgrp->pg_members, p_pglist) {
                        PROC_LOCK(p);
                        if (p->p_state == PRS_NORMAL &&
                            CANSIGIO(sigio->sio_ucred, p->p_ucred) &&
                            (checkctty == 0 || (p->p_flag & P_CONTROLT)))
                                kern_psignal(p, sig);
                        PROC_UNLOCK(p);
                }
                PGRP_UNLOCK(sigio->sio_pgrp);
        }
        SIGIO_UNLOCK();
}

static int
filt_sigattach(struct knote *kn)
{
        struct proc *p = curproc;

        kn->kn_ptr.p_proc = p;
        kn->kn_flags |= EV_CLEAR;               /* automatically set */

        knlist_add(p->p_klist, kn, 0);

        return (0);
}

static void
filt_sigdetach(struct knote *kn)
{
        struct proc *p = kn->kn_ptr.p_proc;

        knlist_remove(p->p_klist, kn, 0);
}

/*
 * signal knotes are shared with proc knotes, so we apply a mask to
 * the hint in order to differentiate them from process hints.  This
 * could be avoided by using a signal-specific knote list, but probably
 * isn't worth the trouble.
 */
static int
filt_signal(struct knote *kn, long hint)
{

        if (hint & NOTE_SIGNAL) {
                hint &= ~NOTE_SIGNAL;

                if (kn->kn_id == hint)
                        kn->kn_data++;
        }
        return (kn->kn_data != 0);
}

struct sigacts *
sigacts_alloc(void)
{
        struct sigacts *ps;

        ps = malloc(sizeof(struct sigacts), M_SUBPROC, M_WAITOK | M_ZERO);
        refcount_init(&ps->ps_refcnt, 1);
        mtx_init(&ps->ps_mtx, "sigacts", NULL, MTX_DEF);
        return (ps);
}

void
sigacts_free(struct sigacts *ps)
{

        if (refcount_release(&ps->ps_refcnt) == 0)
                return;
        mtx_destroy(&ps->ps_mtx);
        free(ps, M_SUBPROC);
}

struct sigacts *
sigacts_hold(struct sigacts *ps)
{

        refcount_acquire(&ps->ps_refcnt);
        return (ps);
}

void
sigacts_copy(struct sigacts *dest, struct sigacts *src)
{

        KASSERT(dest->ps_refcnt == 1, ("sigacts_copy to shared dest"));
        mtx_lock(&src->ps_mtx);
        bcopy(src, dest, offsetof(struct sigacts, ps_refcnt));
        mtx_unlock(&src->ps_mtx);
}

int
sigacts_shared(struct sigacts *ps)
{

        return (ps->ps_refcnt > 1);
}

void
sig_drop_caught(struct proc *p)
{
        int sig;
        struct sigacts *ps;

        ps = p->p_sigacts;
        PROC_LOCK_ASSERT(p, MA_OWNED);
        mtx_assert(&ps->ps_mtx, MA_OWNED);
        SIG_FOREACH(sig, &ps->ps_sigcatch) {
                sigdflt(ps, sig);
                if ((sigprop(sig) & SIGPROP_IGNORE) != 0)
                        sigqueue_delete_proc(p, sig);
        }
}

static void
sigfastblock_failed(struct thread *td, bool sendsig, bool write)
{
        ksiginfo_t ksi;

        /*
         * Prevent further fetches and SIGSEGVs, allowing thread to
         * issue syscalls despite corruption.
         */
        sigfastblock_clear(td);

        if (!sendsig)
                return;
        ksiginfo_init_trap(&ksi);
        ksi.ksi_signo = SIGSEGV;
        ksi.ksi_code = write ? SEGV_ACCERR : SEGV_MAPERR;
        ksi.ksi_addr = td->td_sigblock_ptr;
        trapsignal(td, &ksi);
}

static bool
sigfastblock_fetch_sig(struct thread *td, bool sendsig, uint32_t *valp)
{
        uint32_t res;

        if ((td->td_pflags & TDP_SIGFASTBLOCK) == 0)
                return (true);
        if (fueword32((void *)td->td_sigblock_ptr, &res) == -1) {
                sigfastblock_failed(td, sendsig, false);
                return (false);
        }
        *valp = res;
        td->td_sigblock_val = res & ~SIGFASTBLOCK_FLAGS;
        return (true);
}

static void
sigfastblock_resched(struct thread *td, bool resched)
{
        struct proc *p;

        if (resched) {
                p = td->td_proc;
                PROC_LOCK(p);
                reschedule_signals(p, td->td_sigmask, 0);
                PROC_UNLOCK(p);
        }
        ast_sched(td, TDA_SIG);
}

int
sys_sigfastblock(struct thread *td, struct sigfastblock_args *uap)
{
        struct proc *p;
        int error, res;
        uint32_t oldval;

        error = 0;
        p = td->td_proc;
        switch (uap->cmd) {
        case SIGFASTBLOCK_SETPTR:
                if ((td->td_pflags & TDP_SIGFASTBLOCK) != 0) {
                        error = EBUSY;
                        break;
                }
                if (((uintptr_t)(uap->ptr) & (sizeof(uint32_t) - 1)) != 0) {
                        error = EINVAL;
                        break;
                }
                td->td_pflags |= TDP_SIGFASTBLOCK;
                td->td_sigblock_ptr = uap->ptr;
                break;

        case SIGFASTBLOCK_UNBLOCK:
                if ((td->td_pflags & TDP_SIGFASTBLOCK) == 0) {
                        error = EINVAL;
                        break;
                }

                for (;;) {
                        res = casueword32(td->td_sigblock_ptr,
                            SIGFASTBLOCK_PEND, &oldval, 0);
                        if (res == -1) {
                                error = EFAULT;
                                sigfastblock_failed(td, false, true);
                                break;
                        }
                        if (res == 0)
                                break;
                        MPASS(res == 1);
                        if (oldval != SIGFASTBLOCK_PEND) {
                                error = EBUSY;
                                break;
                        }
                        error = thread_check_susp(td, false);
                        if (error != 0)
                                break;
                }
                if (error != 0)
                        break;

                /*
                 * td_sigblock_val is cleared there, but not on a
                 * syscall exit.  The end effect is that a single
                 * interruptible sleep, while user sigblock word is
                 * set, might return EINTR or ERESTART to usermode
                 * without delivering signal.  All further sleeps,
                 * until userspace clears the word and does
                 * sigfastblock(UNBLOCK), observe current word and no
                 * longer get interrupted.  It is slight
                 * non-conformance, with alternative to have read the
                 * sigblock word on each syscall entry.
                 */
                td->td_sigblock_val = 0;

                /*
                 * Rely on normal ast mechanism to deliver pending
                 * signals to current thread.  But notify others about
                 * fake unblock.
                 */
                sigfastblock_resched(td, error == 0 && p->p_numthreads != 1);

                break;

        case SIGFASTBLOCK_UNSETPTR:
                if ((td->td_pflags & TDP_SIGFASTBLOCK) == 0) {
                        error = EINVAL;
                        break;
                }
                if (!sigfastblock_fetch_sig(td, false, &oldval)) {
                        error = EFAULT;
                        break;
                }
                if (oldval != 0 && oldval != SIGFASTBLOCK_PEND) {
                        error = EBUSY;
                        break;
                }
                sigfastblock_clear(td);
                break;

        default:
                error = EINVAL;
                break;
        }
        return (error);
}

void
sigfastblock_clear(struct thread *td)
{
        bool resched;

        if ((td->td_pflags & TDP_SIGFASTBLOCK) == 0)
                return;
        td->td_sigblock_val = 0;
        resched = (td->td_pflags & TDP_SIGFASTPENDING) != 0 ||
            SIGPENDING(td);
        td->td_pflags &= ~(TDP_SIGFASTBLOCK | TDP_SIGFASTPENDING);
        sigfastblock_resched(td, resched);
}

void
sigfastblock_fetch(struct thread *td)
{
        uint32_t val;

        (void)sigfastblock_fetch_sig(td, true, &val);
}

static void
sigfastblock_setpend1(struct thread *td)
{
        int res;
        uint32_t oldval;

        if ((td->td_pflags & TDP_SIGFASTPENDING) == 0)
                return;
        res = fueword32((void *)td->td_sigblock_ptr, &oldval);
        if (res == -1) {
                sigfastblock_failed(td, true, false);
                return;
        }
        for (;;) {
                res = casueword32(td->td_sigblock_ptr, oldval, &oldval,
                    oldval | SIGFASTBLOCK_PEND);
                if (res == -1) {
                        sigfastblock_failed(td, true, true);
                        return;
                }
                if (res == 0) {
                        td->td_sigblock_val = oldval & ~SIGFASTBLOCK_FLAGS;
                        td->td_pflags &= ~TDP_SIGFASTPENDING;
                        break;
                }
                MPASS(res == 1);
                if (thread_check_susp(td, false) != 0)
                        break;
        }
}

static void
sigfastblock_setpend(struct thread *td, bool resched)
{
        struct proc *p;

        sigfastblock_setpend1(td);
        if (resched) {
                p = td->td_proc;
                PROC_LOCK(p);
                reschedule_signals(p, fastblock_mask, SIGPROCMASK_FASTBLK);
                PROC_UNLOCK(p);
        }
}