FreeBSD/Linux Kernel Cross Reference
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>
    __FBSDID("$FreeBSD$");
    
    #include "opt_ktrace.h"
    
    #include <sys/param.h>
    #include <sys/ctype.h>
    #include <sys/systm.h>
    #include <sys/signalvar.h>
    #include <sys/vnode.h>
    #include <sys/acct.h>
    #include <sys/bus.h>
    #include <sys/capsicum.h>
    #include <sys/compressor.h>
    #include <sys/condvar.h>
    #include <sys/event.h>
    #include <sys/fcntl.h>
    #include <sys/imgact.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/pioctl.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/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/wait.h>
    #include <vm/vm.h>
    #include <vm/vm_extern.h>
    #include <vm/uma.h>
    
    #include <sys/jail.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 int      sigprop(int sig);
   static void     tdsigwakeup(struct thread *, int, sig_t, int);
   static int      sig_suspend_threads(struct thread *, struct proc *, int);
   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, int prop);
   static void     sigqueue_start(void);
   
   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, 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");
   
   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 */
   #define SIGPROP_CANTMASK        0x40    /* non-maskable, catchable */
   
   static 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,
   };
   
   static void reschedule_signals(struct proc *p, sigset_t block, int flags);
   
   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);
   }
   
   ksiginfo_t *
   ksiginfo_alloc(int wait)
   {
           int flags;
   
           flags = M_ZERO;
           if (! wait)
                   flags |= M_NOWAIT;
           if (ksiginfo_zone != NULL)
                   return ((ksiginfo_t *)uma_zalloc(ksiginfo_zone, flags));
           return (NULL);
   }
   
   void
   ksiginfo_free(ksiginfo_t *ksi)
   {
           uma_zfree(ksiginfo_zone, ksi);
   }
   
   static __inline int
   ksiginfo_tryfree(ksiginfo_t *ksi)
   {
           if (!(ksi->ksi_flags & KSI_EXT)) {
                   uma_zfree(ksiginfo_zone, ksi);
                   return (1);
           }
           return (0);
   }
   
   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(0)) == 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)) {
                   thread_lock(td);
                   td->td_flags |= TDF_NEEDSIGCHK | TDF_ASTPENDING;
                   thread_unlock(td);
           }
   }
   
   /*
    * 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);
   }
   
   int
   sig_ffs(sigset_t *set)
   {
           int i;
   
           for (i = 0; i < _SIG_WORDS; i++)
                   if (set->__bits[i])
                           return (ffs(set->__bits[i]) + (i * 32));
           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)
   {
           sigset_t osigignore;
           struct sigacts *ps;
           int sig;
           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);
   
           /*
            * As CloudABI processes cannot modify signal handlers, fully
            * reset all signals to their default behavior. Do ignore
            * SIGPIPE, as it would otherwise be impossible to recover from
            * writes to broken pipes and sockets.
            */
           if (SV_PROC_ABI(p) == SV_ABI_CLOUDABI) {
                   osigignore = ps->ps_sigignore;
                  while (SIGNOTEMPTY(osigignore)) {
                          sig = sig_ffs(&osigignore);
                          SIGDELSET(osigignore, sig);
                          if (sig != SIGPIPE)
                                  sigdflt(ps, sig);
                  }
                  SIGADDSET(ps->ps_sigignore, SIGPIPE);
          }
  
          /*
           * 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) {
                  if (error == EINTR && td->td_proc->p_osrel < P_OSREL_SIGWAIT)
                          error = ERESTART;
                  if (error == ERESTART)
                          return (error);
                  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, timo, timevalid = 0;
          struct timespec rts, ets, ts;
          struct timeval tv;
          bool traced;
  
          p = td->td_proc;
          error = 0;
          ets.tv_sec = 0;
          ets.tv_nsec = 0;
          traced = false;
  
          if (timeout != NULL) {
                  if (timeout->tv_nsec >= 0 && timeout->tv_nsec < 1000000000) {
                          timevalid = 1;
                          getnanouptime(&rts);
                          timespecadd(&rts, timeout, &ets);
                  }
          }
          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);
          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) {
                          if (!timevalid) {
                                  error = EINVAL;
                                  break;
                          }
                          getnanouptime(&rts);
                          if (timespeccmp(&rts, &ets, >=)) {
                                  error = EAGAIN;
                                  break;
                          }
                          timespecsub(&ets, &rts, &ts);
                          TIMESPEC_TO_TIMEVAL(&tv, &ts);
                          timo = tvtohz(&tv);
                  } else {
                          timo = 0;
                  }
  
                  if (traced) {
                          error = EINTR;
                          break;
                  }
  
                  error = msleep(&p->p_sigacts, &p->p_mtx, PPAUSE | PCATCH,
                      "sigwait", timo);
  
                  if (timeout != NULL) {
                          if (error == ERESTART) {
                                  /* Timeout can not be restarted. */
                                  error = EINTR;
                          } else if (error == EAGAIN) {
                                  /* We will calculate timeout by ourself. */
                                  error = 0;
                          }
                  }
  
                  /*
                   * 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;
          }
  
          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;
  
          /*
           * 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;
  
          /*
           * 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(struct proc *p, bool notself, struct killpg1_ctx *arg)
  {
          int err;
  
          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);
          err = p_cansignal(arg->td, p, arg->sig);
          if (err == 0 && arg->sig != 0)
                  pksignal(p, arg->sig, arg->ksi);
          PROC_UNLOCK(p);
          if (err != ESRCH)
                  arg->found = true;
          if (err == 0)
                  arg->sent = true;
          else if (arg->ret == 0 && err != ESRCH && err != EPERM)
                  arg->ret = err;
  }
  
  /*
   * Common code for kill process group/broadcast kill.
   * cp is calling process.
   */
  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
                   */
                  sx_slock(&allproc_lock);
                  FOREACH_PROC_IN_SYSTEM(p) {
                          killpg1_sendsig(p, true, &arg);
                  }
                  sx_sunlock(&allproc_lock);
          } else {
                  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);
                  LIST_FOREACH(p, &pgrp->pg_members, p_pglist) {
                          killpg1_sendsig(p, false, &arg);
                  }
                  PGRP_UNLOCK(pgrp);
          }
          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)
  {
          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) && uap->pid != td->td_proc->p_pid)
                  return (ECAPMODE);
  
          AUDIT_ARG_SIGNUM(uap->signum);
          AUDIT_ARG_PID(uap->pid);
          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;
  
          if (uap->pid > 0) {
                  /* kill single process */
                  if ((p = pfind_any(uap->pid)) == NULL)
                          return (ESRCH);
                  AUDIT_ARG_PROCESS(p);
                  error = p_cansignal(td, p, uap->signum);
                  if (error == 0 && uap->signum)
                          pksignal(p, uap->signum, &ksi);
                  PROC_UNLOCK(p);
                  return (error);
          }
          switch (uap->pid) {
          case -1:                /* broadcast signal */
                  return (killpg1(td, uap->signum, 0, 1, &ksi));
          case 0:                 /* signal own process group */
                  return (killpg1(td, uap->signum, 0, 0, &ksi));
          default:                /* negative explicit process group */
                  return (killpg1(td, uap->signum, -uap->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.
   */
  void
  gsignal(int pgid, int sig, ksiginfo_t *ksi)
  {
          struct pgrp *pgrp;
  
          if (pgid != 0) {
                  sx_slock(&proctree_lock);
                  pgrp = pgfind(pgid);
                  sx_sunlock(&proctree_lock);
                  if (pgrp != NULL) {
                          pgsignal(pgrp, sig, 0, ksi);
                          PGRP_UNLOCK(pgrp);
                  }
          }
  }
  
  /*
   * 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;
          int sig;
          int code;
  
          p = td->td_proc;
          sig = ksi->ksi_signo;
          code = ksi->ksi_code;
          KASSERT(_SIG_VALID(sig), ("invalid signal"));
  
          PROC_LOCK(p);
          ps = p->p_sigacts;
          mtx_lock(&ps->ps_mtx);
          if ((p->p_flag & P_TRACED) == 0 && SIGISMEMBER(ps->ps_sigcatch, sig) &&
              !SIGISMEMBER(td->td_sigmask, sig)) {
  #ifdef KTRACE
                  if (KTRPOINT(curthread, KTR_PSIG))
                          ktrpsig(sig, ps->ps_sigact[_SIG_IDX(sig)],
                              &td->td_sigmask, 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(td->td_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;
                  }
                  mtx_unlock(&ps->ps_mtx);
                  p->p_code = code;       /* XXX for core dump/debugger */
                  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, int prop)
  {
          struct thread *td, *signal_td;
  
          PROC_LOCK_ASSERT(p, MA_OWNED);
  
          /*
           * Check if current thread can handle the signal without
           * switching context to another thread.
           */
          if (curproc == p && !SIGISMEMBER(curthread->td_sigmask, sig))
                  return (curthread);
          signal_td = NULL;
          FOREACH_THREAD_IN_PROC(p, td) {
                  if (!SIGISMEMBER(td->td_sigmask, sig)) {
                          signal_td = td;
                          break;
                  }
          }
          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);
  }
  
  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 && (ksi->ksi_flags & KSI_INS))
                          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, prop);
                  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.
           * (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)) {
                  SDT_PROBE3(proc, , , signal__discard, td, p, sig);
  
                  mtx_unlock(&ps->ps_mtx);
                  if (ksi && (ksi->ksi_flags & KSI_INS))
                          ksiginfo_tryfree(ksi);
                  return (ret);
          }
          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 && (ksi->ksi_flags & KSI_INS))
                                  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);
  
          /* SIGKILL: Remove procfs STOPEVENTs. */
          if (sig == SIGKILL) {
                  /* from procfs_ioctl.c: PIOCBIC */
                  p->p_stops = 0;
                  /* from procfs_ioctl.c: PIOCCONT */
                  p->p_step = 0;
                  wakeup(&p->p_step);
          }
          /*
           * 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;
                          }
                          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;
                  }
  
                  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().
                   */
                  wakeup_swapper = 0;
                  PROC_SLOCK(p);
                  thread_lock(td);
                  if (TD_ON_SLEEPQ(td) && (td->td_flags & TDF_SINTR))
                          wakeup_swapper = sleepq_abort(td, intrval);
                  thread_unlock(td);
                  PROC_SUNLOCK(p);
                  if (wakeup_swapper)
                          kick_proc0();
                  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, 1);
                          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);
                          if (wakeup_swapper)
                                  kick_proc0();
                          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:
          /* If we jump here, proc slock should not be owned. */
          PROC_SLOCK_ASSERT(p, MA_NOTOWNED);
          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;
          int wakeup_swapper;
  
          wakeup_swapper = 0;
          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 = sleepq_abort(td, intrval);
          } else {
                  /*
                   * 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);
          if (wakeup_swapper)
                  kick_proc0();
  }
  
  static int
  sig_suspend_threads(struct thread *td, struct proc *p, int sending)
  {
          struct thread *td2;
          int wakeup_swapper;
  
          PROC_LOCK_ASSERT(p, MA_OWNED);
          PROC_SLOCK_ASSERT(p, MA_OWNED);
          MPASS(sending || td == curthread);
  
          wakeup_swapper = 0;
          FOREACH_THREAD_IN_PROC(p, td2) {
                  thread_lock(td2);
                  td2->td_flags |= TDF_ASTPENDING | TDF_NEEDSUSPCHK;
                  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));
                          } else if (!TD_IS_SUSPENDED(td2)) {
                                  thread_suspend_one(td2);
                          }
                  } else if (!TD_IS_SUSPENDED(td2)) {
                          if (sending || td != td2)
                                  td2->td_flags |= TDF_ASTPENDING;
  #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;
          int prop;
  
          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, 0);
                          }
                          if ((td->td_dbgflags & TDB_STOPATFORK) != 0) {
                                  td->td_dbgflags &= ~TDB_STOPATFORK;
                          }
  stopme:
                          thread_suspend_switch(td, p);
                          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;
                  prop = sigprop(td->td_xsig);
                  td2 = sigtd(p, td->td_xsig, prop);
                  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;
  
          PROC_LOCK_ASSERT(p, MA_OWNED);
          ps = p->p_sigacts;
          mtx_assert(&ps->ps_mtx, (flags & SIGPROCMASK_PS_LOCKED) != 0 ?
              MA_OWNED : MA_NOTOWNED);
          if (SIGISEMPTY(p->p_siglist))
                  return;
          SIGSETAND(block, p->p_siglist);
          while ((sig = sig_ffs(&block)) != 0) {
                  SIGDELSET(block, sig);
                  td = sigtd(p, sig, 0);
                  signotify(td);
                  if (!(flags & SIGPROCMASK_PS_LOCKED))
                          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 (!(flags & SIGPROCMASK_PS_LOCKED))
                          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);
          }
  }
  
  /*
   * 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;
          struct sigacts *ps;
          struct sigqueue *queue;
          sigset_t sigpending;
          ksiginfo_t ksi;
          int prop, sig, traced;
  
          p = td->td_proc;
          ps = p->p_sigacts;
          mtx_assert(&ps->ps_mtx, MA_OWNED);
          PROC_LOCK_ASSERT(p, MA_OWNED);
          for (;;) {
                  traced = (p->p_flag & P_TRACED) || (p->p_stops & S_SIG);
  
                  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);
                  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.
                           */
                          sig = SIGSTOP;
                          td->td_dbgflags |= TDB_FSTP;
                  } else {
                          sig = sig_ffs(&sigpending);
                  }
  
                  if (p->p_stops & S_SIG) {
                          mtx_unlock(&ps->ps_mtx);
                          stopevent(p, S_SIG, sig);
                          mtx_lock(&ps->ps_mtx);
                  }
  
                  /*
                   * We should see pending but ignored signals
                   * only if P_TRACED was on when they were posted.
                   */
                  if (SIGISMEMBER(ps->ps_sigignore, sig) && (traced == 0)) {
                          sigqueue_delete(&td->td_sigqueue, sig);
                          sigqueue_delete(&p->p_sigqueue, sig);
                          continue;
                  }
                  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)
                                  continue;
  
                          /*
                           * 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);
                                  continue;
                          }
  
                          /*
                           * If the traced bit got turned off, requeue
                           * the signal and go back up to the top to
                           * rescan signals.  This ensures that p_sig*
                           * and p_sigact are consistent.
                           */
                          if ((p->p_flag & P_TRACED) == 0) {
                                  ksi.ksi_flags |= KSI_HEAD;
                                  sigqueue_add(queue, sig, &ksi);
                                  continue;
                          }
                  }
  
                  prop = sigprop(sig);
  
                  /*
                   * 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
                                  break;          /* == 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.
                           */
                          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);
                                          break;  /* == ignore */
                                  }
                                  if (TD_SBDRY_INTR(td)) {
                                          KASSERT((td->td_flags & TDF_SBDRY) != 0,
                                              ("lost TDF_SBDRY"));
                                          mtx_lock(&ps->ps_mtx);
                                          return (-1);
                                  }
                                  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, 0);
                                  thread_suspend_switch(td, p);
                                  PROC_SUNLOCK(p);
                                  mtx_lock(&ps->ps_mtx);
                                  goto next;
                          } else if (prop & SIGPROP_IGNORE) {
                                  /*
                                   * Except for SIGCONT, shouldn't get here.
                                   * Default action is to ignore; drop it.
                                   */
                                  break;          /* == ignore */
                          } else
                                  return (sig);
                          /*NOTREACHED*/
  
                  case (intptr_t)SIG_IGN:
                          /*
                           * Masking above should prevent us ever trying
                           * to take action on an ignored signal other
                           * than SIGCONT, unless process is traced.
                           */
                          if ((prop & SIGPROP_CONT) == 0 &&
                              (p->p_flag & P_TRACED) == 0)
                                  printf("issignal\n");
                          break;          /* == ignore */
  
                  default:
                          /*
                           * This signal has an action, let
                           * postsig() process it.
                           */
                          return (sig);
                  }
                  sigqueue_delete(&td->td_sigqueue, sig); /* take the signal! */
                  sigqueue_delete(&p->p_sigqueue, sig);
  next:;
          }
          /* NOTREACHED */
  }
  
  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 ((p->p_stops & S_SIG) != 0) {
                  mtx_unlock(&ps->ps_mtx);
                  stopevent(p, S_SIG, sig);
                  mtx_lock(&ps->ps_mtx);
          }
  
          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_code = 0;
                          p->p_sig = 0;
                  }
                  (*p->p_sysent->sv_sendsig)(action, &ksi, &returnmask);
                  postsig_done(sig, td, ps);
          }
          return (1);
  }
  
  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, 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 ? p->p_ucred->cr_uid : -1, 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;
  
          PROC_LOCK_ASSERT(p, MA_OWNED);
          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.
                   */
                  if (coredump(td) == 0)
                          sig |= WCOREFLAG;
                  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 ? td->td_ucred->cr_uid : -1,
                              sig &~ WCOREFLAG,
                              sig & WCOREFLAG ? " (core dumped)" : "");
          } 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,
              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,
      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, 0);
          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, td);
                  error = vn_open_cred(&nd, &flags, cmode, oflags, td->td_ucred,
                      NULL);
                  if (error != 0)
                          break;
  
                  vp = nd.ni_vp;
                  NDFREE(&nd, NDF_ONLY_PNBUF);
                  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, 0);
                          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, 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 '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, td);
                  error = vn_open_cred(&nd, &flags, cmode, oflags, td->td_ucred,
                      NULL);
                  if (error == 0) {
                          *vpp = nd.ni_vp;
                          NDFREE(&nd, NDF_ONLY_PNBUF);
                  }
          }
  
          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;
          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);
          _STOPEVENT(p, S_CORE, 0);
  
          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, &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, 0);
                  error = EFAULT;
                  goto out;
          }
  
          VOP_UNLOCK(vp, 0);
  
          /* 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, 0);
          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(td, 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] != '/') {
                  fullpath = malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
                  if (kern___getcwd(td, fullpath, UIO_SYSSPACE, MAXPATHLEN, MAXPATHLEN) != 0) {
                          free(fullpath, M_TEMP);
                          goto out2;
                  }
                  devctl_safe_quote_sb(sb, fullpath);
                  free(fullpath, 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;
  
          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);
          while (SIGNOTEMPTY(ps->ps_sigcatch)) {
                  sig = sig_ffs(&ps->ps_sigcatch);
                  sigdflt(ps, sig);
                  if ((sigprop(sig) & SIGPROP_IGNORE) != 0)
                          sigqueue_delete_proc(p, sig);
          }
  }