kernel - kqueue - major refactoring

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

/*
 * 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      @(#)kern_sig.c  8.7 (Berkeley) 4/18/94
 * $FreeBSD: src/sys/kern/kern_sig.c,v 1.72.2.17 2003/05/16 16:34:34 obrien Exp $
 * $DragonFly: src/sys/kern/kern_sig.c,v 1.90 2008/06/09 04:33:08 dillon Exp $
 */

#include "opt_ktrace.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/sysproto.h>
#include <sys/signalvar.h>
#include <sys/resourcevar.h>
#include <sys/vnode.h>
#include <sys/event.h>
#include <sys/proc.h>
#include <sys/nlookup.h>
#include <sys/pioctl.h>
#include <sys/systm.h>
#include <sys/acct.h>
#include <sys/fcntl.h>
#include <sys/lock.h>
#include <sys/wait.h>
#include <sys/ktrace.h>
#include <sys/syslog.h>
#include <sys/stat.h>
#include <sys/sysent.h>
#include <sys/sysctl.h>
#include <sys/malloc.h>
#include <sys/interrupt.h>
#include <sys/unistd.h>
#include <sys/kern_syscall.h>
#include <sys/vkernel.h>

#include <sys/signal2.h>
#include <sys/thread2.h>
#include <sys/mplock2.h>

#include <machine/cpu.h>
#include <machine/smp.h>

static int      coredump(struct lwp *, int);
static char     *expand_name(const char *, uid_t, pid_t);
static int      dokillpg(int sig, int pgid, int all);
static int      sig_ffs(sigset_t *set);
static int      sigprop(int sig);
#ifdef SMP
static void     signotify_remote(void *arg);
#endif
static int      kern_sigtimedwait(sigset_t set, siginfo_t *info,
                    struct timespec *timeout);

static int      filt_sigattach(struct knote *kn);
static void     filt_sigdetach(struct knote *kn);
static int      filt_signal(struct knote *kn, long hint);

struct filterops sig_filtops =
        { 0, filt_sigattach, filt_sigdetach, 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)");

/*
 * Can process p, with pcred pc, send the signal sig to process q?
 */
#define CANSIGNAL(q, sig) \
        (!p_trespass(curproc->p_ucred, (q)->p_ucred) || \
        ((sig) == SIGCONT && (q)->p_session == curproc->p_session))

/*
 * Policy -- Can real uid ruid with ucred uc send a signal to process q?
 */
#define CANSIGIO(ruid, uc, q) \
        ((uc)->cr_uid == 0 || \
            (ruid) == (q)->p_ucred->cr_ruid || \
            (uc)->cr_uid == (q)->p_ucred->cr_ruid || \
            (ruid) == (q)->p_ucred->cr_uid || \
            (uc)->cr_uid == (q)->p_ucred->cr_uid)

int sugid_coredump;
SYSCTL_INT(_kern, OID_AUTO, sugid_coredump, CTLFLAG_RW, 
        &sugid_coredump, 0, "Enable coredumping set user/group ID processes");

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

/*
 * Signal properties and actions.
 * The array below categorizes the signals and their default actions
 * according to the following properties:
 */
#define SA_KILL         0x01            /* terminates process by default */
#define SA_CORE         0x02            /* ditto and coredumps */
#define SA_STOP         0x04            /* suspend process */
#define SA_TTYSTOP      0x08            /* ditto, from tty */
#define SA_IGNORE       0x10            /* ignore by default */
#define SA_CONT         0x20            /* continue if suspended */
#define SA_CANTMASK     0x40            /* non-maskable, catchable */
#define SA_CKPT         0x80            /* checkpoint process */


static int sigproptbl[NSIG] = {
        SA_KILL,                /* SIGHUP */
        SA_KILL,                /* SIGINT */
        SA_KILL|SA_CORE,        /* SIGQUIT */
        SA_KILL|SA_CORE,        /* SIGILL */
        SA_KILL|SA_CORE,        /* SIGTRAP */
        SA_KILL|SA_CORE,        /* SIGABRT */
        SA_KILL|SA_CORE,        /* SIGEMT */
        SA_KILL|SA_CORE,        /* SIGFPE */
        SA_KILL,                /* SIGKILL */
        SA_KILL|SA_CORE,        /* SIGBUS */
        SA_KILL|SA_CORE,        /* SIGSEGV */
        SA_KILL|SA_CORE,        /* SIGSYS */
        SA_KILL,                /* SIGPIPE */
        SA_KILL,                /* SIGALRM */
        SA_KILL,                /* SIGTERM */
        SA_IGNORE,              /* SIGURG */
        SA_STOP,                /* SIGSTOP */
        SA_STOP|SA_TTYSTOP,     /* SIGTSTP */
        SA_IGNORE|SA_CONT,      /* SIGCONT */
        SA_IGNORE,              /* SIGCHLD */
        SA_STOP|SA_TTYSTOP,     /* SIGTTIN */
        SA_STOP|SA_TTYSTOP,     /* SIGTTOU */
        SA_IGNORE,              /* SIGIO */
        SA_KILL,                /* SIGXCPU */
        SA_KILL,                /* SIGXFSZ */
        SA_KILL,                /* SIGVTALRM */
        SA_KILL,                /* SIGPROF */
        SA_IGNORE,              /* SIGWINCH  */
        SA_IGNORE,              /* SIGINFO */
        SA_KILL,                /* SIGUSR1 */
        SA_KILL,                /* SIGUSR2 */
        SA_IGNORE,              /* SIGTHR */
        SA_CKPT,                /* SIGCKPT */ 
        SA_KILL|SA_CKPT,        /* SIGCKPTEXIT */  
        SA_IGNORE,
        SA_IGNORE,
        SA_IGNORE,
        SA_IGNORE,
        SA_IGNORE,
        SA_IGNORE,
        SA_IGNORE,
        SA_IGNORE,
        SA_IGNORE,
        SA_IGNORE,
        SA_IGNORE,
        SA_IGNORE,
        SA_IGNORE,
        SA_IGNORE,
        SA_IGNORE,
        SA_IGNORE,
        SA_IGNORE,
        SA_IGNORE,
        SA_IGNORE,
        SA_IGNORE,
        SA_IGNORE,
        SA_IGNORE,
        SA_IGNORE,
        SA_IGNORE,
        SA_IGNORE,
        SA_IGNORE,
        SA_IGNORE,
        SA_IGNORE,
        SA_IGNORE,
        SA_IGNORE,

};

static __inline int
sigprop(int sig)
{

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

static __inline 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);
}

int
kern_sigaction(int sig, struct sigaction *act, struct sigaction *oact)
{
        struct thread *td = curthread;
        struct proc *p = td->td_proc;
        struct lwp *lp;
        struct sigacts *ps = p->p_sigacts;

        if (sig <= 0 || sig > _SIG_MAXSIG)
                return (EINVAL);

        if (oact) {
                oact->sa_handler = ps->ps_sigact[_SIG_IDX(sig)];
                oact->sa_mask = ps->ps_catchmask[_SIG_IDX(sig)];
                oact->sa_flags = 0;
                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;
                if (SIGISMEMBER(ps->ps_sigmailbox, sig))
                        oact->sa_flags |= SA_MAILBOX;
                if (sig == SIGCHLD && p->p_sigacts->ps_flag & PS_NOCLDSTOP)
                        oact->sa_flags |= SA_NOCLDSTOP;
                if (sig == SIGCHLD && p->p_sigacts->ps_flag & PS_NOCLDWAIT)
                        oact->sa_flags |= SA_NOCLDWAIT;
        }
        if (act) {
                /*
                 * Check for invalid requests.  KILL and STOP cannot be
                 * caught.
                 */
                if (sig == SIGKILL || sig == SIGSTOP) {
                        if (act->sa_handler != SIG_DFL)
                                return (EINVAL);
#if 0
                        /* (not needed, SIG_DFL forces action to occur) */
                        if (act->sa_flags & SA_MAILBOX)
                                return (EINVAL);
#endif
                }

                /*
                 * Change setting atomically.
                 */
                crit_enter();

                ps->ps_catchmask[_SIG_IDX(sig)] = act->sa_mask;
                SIG_CANTMASK(ps->ps_catchmask[_SIG_IDX(sig)]);
                if (act->sa_flags & 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 (!(act->sa_flags & SA_RESTART))
                        SIGADDSET(ps->ps_sigintr, sig);
                else
                        SIGDELSET(ps->ps_sigintr, sig);
                if (act->sa_flags & SA_ONSTACK)
                        SIGADDSET(ps->ps_sigonstack, sig);
                else
                        SIGDELSET(ps->ps_sigonstack, sig);
                if (act->sa_flags & SA_RESETHAND)
                        SIGADDSET(ps->ps_sigreset, sig);
                else
                        SIGDELSET(ps->ps_sigreset, sig);
                if (act->sa_flags & SA_NODEFER)
                        SIGADDSET(ps->ps_signodefer, sig);
                else
                        SIGDELSET(ps->ps_signodefer, sig);
                if (act->sa_flags & SA_MAILBOX)
                        SIGADDSET(ps->ps_sigmailbox, sig);
                else
                        SIGDELSET(ps->ps_sigmailbox, sig);
                if (sig == SIGCHLD) {
                        if (act->sa_flags & SA_NOCLDSTOP)
                                p->p_sigacts->ps_flag |= PS_NOCLDSTOP;
                        else
                                p->p_sigacts->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)
                                        p->p_sigacts->ps_flag &= ~PS_NOCLDWAIT;
                                else
                                        p->p_sigacts->ps_flag |= PS_NOCLDWAIT;
                        } else {
                                p->p_sigacts->ps_flag &= ~PS_NOCLDWAIT;
                        }
                }
                /*
                 * Set bit in p_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 p_sigignore, as we
                 * have to restart the process.
                 */
                if (ps->ps_sigact[_SIG_IDX(sig)] == SIG_IGN ||
                    (sigprop(sig) & SA_IGNORE &&
                     ps->ps_sigact[_SIG_IDX(sig)] == SIG_DFL)) {
                        /* never to be seen again */
                        SIGDELSET(p->p_siglist, sig);
                        /*
                         * Remove the signal also from the thread lists.
                         */
                        FOREACH_LWP_IN_PROC(lp, p) {
                                SIGDELSET(lp->lwp_siglist, sig);
                        }
                        if (sig != SIGCONT)
                                /* easier in ksignal */
                                SIGADDSET(p->p_sigignore, sig);
                        SIGDELSET(p->p_sigcatch, sig);
                } else {
                        SIGDELSET(p->p_sigignore, sig);
                        if (ps->ps_sigact[_SIG_IDX(sig)] == SIG_DFL)
                                SIGDELSET(p->p_sigcatch, sig);
                        else
                                SIGADDSET(p->p_sigcatch, sig);
                }

                crit_exit();
        }
        return (0);
}

/*
 * MPALMOSTSAFE
 */
int
sys_sigaction(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);
        }
        get_mplock();
        error = kern_sigaction(uap->sig, actp, oactp);
        rel_mplock();
        if (oactp && !error) {
                error = copyout(oactp, uap->oact, sizeof(oact));
        }
        return (error);
}

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

        for (i = 1; i <= NSIG; i++)
                if (sigprop(i) & SA_IGNORE && i != SIGCONT)
                        SIGADDSET(p->p_sigignore, i);
}

/*
 * Reset signals for an exec of the specified process.
 */
void
execsigs(struct proc *p)
{
        struct sigacts *ps = p->p_sigacts;
        struct lwp *lp;
        int sig;

        lp = ONLY_LWP_IN_PROC(p);

        /*
         * Reset caught signals.  Held signals remain held
         * through p_sigmask (unless they were caught,
         * and are now ignored by default).
         */
        while (SIGNOTEMPTY(p->p_sigcatch)) {
                sig = sig_ffs(&p->p_sigcatch);
                SIGDELSET(p->p_sigcatch, sig);
                if (sigprop(sig) & SA_IGNORE) {
                        if (sig != SIGCONT)
                                SIGADDSET(p->p_sigignore, sig);
                        SIGDELSET(p->p_siglist, sig);
                        SIGDELSET(lp->lwp_siglist, sig);
                }
                ps->ps_sigact[_SIG_IDX(sig)] = SIG_DFL;
        }

        /*
         * Reset stack state to the user stack.
         * Clear set of signals caught on the signal stack.
         */
        lp->lwp_sigstk.ss_flags = SS_DISABLE;
        lp->lwp_sigstk.ss_size = 0;
        lp->lwp_sigstk.ss_sp = 0;
        lp->lwp_flag &= ~LWP_ALTSTACK;
        /*
         * Reset no zombies if child dies flag as Solaris does.
         */
        p->p_sigacts->ps_flag &= ~PS_NOCLDWAIT;
}

/*
 * kern_sigprocmask() - MP SAFE ONLY IF p == curproc
 *
 *      Manipulate signal mask.  This routine is MP SAFE *ONLY* if
 *      p == curproc.
 */
int
kern_sigprocmask(int how, sigset_t *set, sigset_t *oset)
{
        struct thread *td = curthread;
        struct lwp *lp = td->td_lwp;
        int error;

        if (oset != NULL)
                *oset = lp->lwp_sigmask;

        error = 0;
        if (set != NULL) {
                switch (how) {
                case SIG_BLOCK:
                        SIG_CANTMASK(*set);
                        SIGSETOR(lp->lwp_sigmask, *set);
                        break;
                case SIG_UNBLOCK:
                        SIGSETNAND(lp->lwp_sigmask, *set);
                        break;
                case SIG_SETMASK:
                        SIG_CANTMASK(*set);
                        lp->lwp_sigmask = *set;
                        break;
                default:
                        error = EINVAL;
                        break;
                }
        }
        return (error);
}

/*
 * sigprocmask()
 *
 * MPSAFE
 */
int
sys_sigprocmask(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(uap->how, setp, osetp);
        if (osetp && !error) {
                error = copyout(osetp, uap->oset, sizeof(oset));
        }
        return (error);
}

/*
 * MPSAFE
 */
int
kern_sigpending(struct __sigset *set)
{
        struct lwp *lp = curthread->td_lwp;

        *set = lwp_sigpend(lp);

        return (0);
}

/*
 * MPSAFE
 */
int
sys_sigpending(struct sigpending_args *uap)
{
        sigset_t set;
        int error;

        error = kern_sigpending(&set);

        if (error == 0)
                error = copyout(&set, uap->set, sizeof(set));
        return (error);
}

/*
 * Suspend process until signal, providing mask to be set
 * in the meantime.
 *
 * MPSAFE
 */
int
kern_sigsuspend(struct __sigset *set)
{
        struct thread *td = curthread;
        struct lwp *lp = td->td_lwp;
        struct proc *p = td->td_proc;
        struct sigacts *ps = p->p_sigacts;

        /*
         * 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.
         */
        lp->lwp_oldsigmask = lp->lwp_sigmask;
        lp->lwp_flag |= LWP_OLDMASK;

        SIG_CANTMASK(*set);
        lp->lwp_sigmask = *set;
        while (tsleep(ps, PCATCH, "pause", 0) == 0)
                /* void */;
        /* always return EINTR rather than ERESTART... */
        return (EINTR);
}

/*
 * Note nonstandard calling convention: libc stub passes mask, not
 * pointer, to save a copyin.
 *
 * MPSAFE
 */
int
sys_sigsuspend(struct sigsuspend_args *uap)
{
        sigset_t mask;
        int error;

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

        error = kern_sigsuspend(&mask);

        return (error);
}

/*
 * MPSAFE
 */
int
kern_sigaltstack(struct sigaltstack *ss, struct sigaltstack *oss)
{
        struct thread *td = curthread;
        struct lwp *lp = td->td_lwp;
        struct proc *p = td->td_proc;

        if ((lp->lwp_flag & LWP_ALTSTACK) == 0)
                lp->lwp_sigstk.ss_flags |= SS_DISABLE;

        if (oss)
                *oss = lp->lwp_sigstk;

        if (ss) {
                if (ss->ss_flags & SS_DISABLE) {
                        if (lp->lwp_sigstk.ss_flags & SS_ONSTACK)
                                return (EINVAL);
                        lp->lwp_flag &= ~LWP_ALTSTACK;
                        lp->lwp_sigstk.ss_flags = ss->ss_flags;
                } else {
                        if (ss->ss_size < p->p_sysent->sv_minsigstksz)
                                return (ENOMEM);
                        lp->lwp_flag |= LWP_ALTSTACK;
                        lp->lwp_sigstk = *ss;
                }
        }

        return (0);
}

/*
 * MPSAFE
 */
int
sys_sigaltstack(struct sigaltstack_args *uap)
{
        stack_t ss, oss;
        int error;

        if (uap->ss) {
                error = copyin(uap->ss, &ss, sizeof(ss));
                if (error)
                        return (error);
        }

        error = kern_sigaltstack(uap->ss ? &ss : NULL,
            uap->oss ? &oss : NULL);

        if (error == 0 && uap->oss)
                error = copyout(&oss, uap->oss, sizeof(*uap->oss));
        return (error);
}

/*
 * Common code for kill process group/broadcast kill.
 * cp is calling process.
 */
struct killpg_info {
        int nfound;
        int sig;
};

static int killpg_all_callback(struct proc *p, void *data);

static int
dokillpg(int sig, int pgid, int all)
{
        struct killpg_info info;
        struct proc *cp = curproc;
        struct proc *p;
        struct pgrp *pgrp;

        info.nfound = 0;
        info.sig = sig;

        if (all) {
                /*
                 * broadcast
                 */
                allproc_scan(killpg_all_callback, &info);
        } else {
                if (pgid == 0) {
                        /*
                         * zero pgid means send to my process group.
                         */
                        pgrp = cp->p_pgrp;
                } else {
                        pgrp = pgfind(pgid);
                        if (pgrp == NULL)
                                return (ESRCH);
                }
                lockmgr(&pgrp->pg_lock, LK_EXCLUSIVE);
                LIST_FOREACH(p, &pgrp->pg_members, p_pglist) {
                        if (p->p_pid <= 1 || 
                            p->p_stat == SZOMB ||
                            (p->p_flag & P_SYSTEM) ||
                            !CANSIGNAL(p, sig)) {
                                continue;
                        }
                        ++info.nfound;
                        if (sig)
                                ksignal(p, sig);
                }
                lockmgr(&pgrp->pg_lock, LK_RELEASE);
        }
        return (info.nfound ? 0 : ESRCH);
}

static int
killpg_all_callback(struct proc *p, void *data)
{
        struct killpg_info *info = data;

        if (p->p_pid <= 1 || (p->p_flag & P_SYSTEM) ||
            p == curproc || !CANSIGNAL(p, info->sig)) {
                return (0);
        }
        ++info->nfound;
        if (info->sig)
                ksignal(p, info->sig);
        return(0);
}

/*
 * Send a general signal to a process or LWPs within that process.  Note
 * that new signals cannot be sent if a process is exiting.
 */
int
kern_kill(int sig, pid_t pid, lwpid_t tid)
{
        if ((u_int)sig > _SIG_MAXSIG)
                return (EINVAL);
        if (pid > 0) {
                struct proc *p;
                struct lwp *lp = NULL;

                /* kill single process */
                if ((p = pfind(pid)) == NULL)
                        return (ESRCH);
                if (!CANSIGNAL(p, sig))
                        return (EPERM);

                /*
                 * NOP if the process is exiting.  Note that lwpsignal() is
                 * called directly with P_WEXIT set to kill individual LWPs
                 * during exit, which is allowed.
                 */
                if (p->p_flag & P_WEXIT)
                        return (0);
                if (tid != -1) {
                        lp = lwp_rb_tree_RB_LOOKUP(&p->p_lwp_tree, tid);
                        if (lp == NULL)
                                return (ESRCH);
                }
                if (sig)
                        lwpsignal(p, lp, sig);
                return (0);
        }
        /*
         * If we come here, pid is a special broadcast pid.
         * This doesn't mix with a tid.
         */
        if (tid != -1)
                return (EINVAL);
        switch (pid) {
        case -1:                /* broadcast signal */
                return (dokillpg(sig, 0, 1));
        case 0:                 /* signal own process group */
                return (dokillpg(sig, 0, 0));
        default:                /* negative explicit process group */
                return (dokillpg(sig, -pid, 0));
        }
        /* NOTREACHED */
}

/*
 * MPALMOSTSAFE
 */
int
sys_kill(struct kill_args *uap)
{
        int error;

        get_mplock();
        error = kern_kill(uap->signum, uap->pid, -1);
        rel_mplock();
        return (error);
}

/*
 * MPALMOSTSAFE
 */
int
sys_lwp_kill(struct lwp_kill_args *uap)
{
        int error;
        pid_t pid = uap->pid;

        /*
         * A tid is mandatory for lwp_kill(), otherwise
         * you could simply use kill().
         */
        if (uap->tid == -1)
                return (EINVAL);

        /*
         * To save on a getpid() function call for intra-process
         * signals, pid == -1 means current process.
         */
        if (pid == -1)
                pid = curproc->p_pid;

        get_mplock();
        error = kern_kill(uap->signum, pid, uap->tid);
        rel_mplock();
        return (error);
}

/*
 * Send a signal to a process group.
 */
void
gsignal(int pgid, int sig)
{
        struct pgrp *pgrp;

        if (pgid && (pgrp = pgfind(pgid)))
                pgsignal(pgrp, sig, 0);
}

/*
 * Send a signal to a process group.  If checktty is 1,
 * limit to members which have a controlling terminal.
 *
 * pg_lock interlocks against a fork that might be in progress, to
 * ensure that the new child process picks up the signal.
 */
void
pgsignal(struct pgrp *pgrp, int sig, int checkctty)
{
        struct proc *p;

        if (pgrp) {
                lockmgr(&pgrp->pg_lock, LK_EXCLUSIVE);
                LIST_FOREACH(p, &pgrp->pg_members, p_pglist) {
                        if (checkctty == 0 || p->p_flag & P_CONTROLT)
                                ksignal(p, sig);
                }
                lockmgr(&pgrp->pg_lock, LK_RELEASE);
        }
}

/*
 * Send a signal caused by a trap to the current lwp.  If it will be caught
 * immediately, deliver it with correct code.  Otherwise, post it normally.
 *
 * These signals may ONLY be delivered to the specified lwp and may never
 * be delivered to the process generically.
 */
void
trapsignal(struct lwp *lp, int sig, u_long code)
{
        struct proc *p = lp->lwp_proc;
        struct sigacts *ps = p->p_sigacts;

        /*
         * If we are a virtual kernel running an emulated user process
         * context, switch back to the virtual kernel context before
         * trying to post the signal.
         */
        if (lp->lwp_vkernel && lp->lwp_vkernel->ve) {
                struct trapframe *tf = lp->lwp_md.md_regs;
                tf->tf_trapno = 0;
                vkernel_trap(lp, tf);
        }


        if ((p->p_flag & P_TRACED) == 0 && SIGISMEMBER(p->p_sigcatch, sig) &&
            !SIGISMEMBER(lp->lwp_sigmask, sig)) {
                lp->lwp_ru.ru_nsignals++;
#ifdef KTRACE
                if (KTRPOINT(lp->lwp_thread, KTR_PSIG))
                        ktrpsig(lp, sig, ps->ps_sigact[_SIG_IDX(sig)],
                                &lp->lwp_sigmask, code);
#endif
                (*p->p_sysent->sv_sendsig)(ps->ps_sigact[_SIG_IDX(sig)], sig,
                                                &lp->lwp_sigmask, code);
                SIGSETOR(lp->lwp_sigmask, ps->ps_catchmask[_SIG_IDX(sig)]);
                if (!SIGISMEMBER(ps->ps_signodefer, sig))
                        SIGADDSET(lp->lwp_sigmask, sig);
                if (SIGISMEMBER(ps->ps_sigreset, sig)) {
                        /*
                         * See kern_sigaction() for origin of this code.
                         */
                        SIGDELSET(p->p_sigcatch, sig);
                        if (sig != SIGCONT &&
                            sigprop(sig) & SA_IGNORE)
                                SIGADDSET(p->p_sigignore, sig);
                        ps->ps_sigact[_SIG_IDX(sig)] = SIG_DFL;
                }
        } else {
                lp->lwp_code = code;    /* XXX for core dump/debugger */
                lp->lwp_sig = sig;      /* XXX to verify code */
                lwpsignal(p, lp, sig);
        }
}

/*
 * Find a suitable lwp to deliver the signal to.
 *
 * Returns NULL if all lwps hold the signal blocked.
 */
static struct lwp *
find_lwp_for_signal(struct proc *p, int sig)
{
        struct lwp *lp;
        struct lwp *run, *sleep, *stop;

        /*
         * If the running/preempted thread belongs to the proc to which
         * the signal is being delivered and this thread does not block
         * the signal, then we can avoid a context switch by delivering
         * the signal to this thread, because it will return to userland
         * soon anyways.
         */
        lp = lwkt_preempted_proc();
        if (lp != NULL && lp->lwp_proc == p && !SIGISMEMBER(lp->lwp_sigmask, sig))
                return (lp);

        run = sleep = stop = NULL;
        FOREACH_LWP_IN_PROC(lp, p) {
                /*
                 * If the signal is being blocked by the lwp, then this
                 * lwp is not eligible for receiving the signal.
                 */
                if (SIGISMEMBER(lp->lwp_sigmask, sig))
                        continue;

                switch (lp->lwp_stat) {
                case LSRUN:
                        run = lp;
                        break;

                case LSSTOP:
                        stop = lp;
                        break;

                case LSSLEEP:
                        if (lp->lwp_flag & LWP_SINTR)
                                sleep = lp;
                        break;
                }
        }

        if (run != NULL)
                return (run);
        else if (sleep != NULL)
                return (sleep);
        else
                return (stop);
}

/*
 * 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.
 */
void
ksignal(struct proc *p, int sig)
{
        lwpsignal(p, NULL, sig);
}

/*
 * The core for ksignal.  lp may be NULL, then a suitable thread
 * will be chosen.  If not, lp MUST be a member of p.
 */
void
lwpsignal(struct proc *p, struct lwp *lp, int sig)
{
        int prop;
        sig_t action;

        if (sig > _SIG_MAXSIG || sig <= 0) {
                kprintf("lwpsignal: signal %d\n", sig);
                panic("lwpsignal signal number");
        }

        KKASSERT(lp == NULL || lp->lwp_proc == p);

        crit_enter();
        KNOTE(&p->p_klist, NOTE_SIGNAL | sig);
        crit_exit();

        prop = sigprop(sig);

        /*
         * If proc is traced, always give parent a chance;
         * if signal event is tracked by procfs, give *that*
         * a chance, as well.
         */
        if ((p->p_flag & P_TRACED) || (p->p_stops & S_SIG)) {
                action = SIG_DFL;
        } else {
                /*
                 * Do not try to deliver signals to an exiting lwp.  Note
                 * that we must still deliver the signal if P_WEXIT is set
                 * in the process flags.
                 */
                if (lp && (lp->lwp_flag & LWP_WEXIT))
                        return;

                /*
                 * If the signal is being ignored, then we forget about
                 * it immediately.  NOTE: We don't set SIGCONT in p_sigignore,
                 * and if it is set to SIG_IGN, action will be SIG_DFL here.
                 */
                if (SIGISMEMBER(p->p_sigignore, sig))
                        return;
                if (SIGISMEMBER(p->p_sigcatch, sig))
                        action = SIG_CATCH;
                else
                        action = SIG_DFL;
        }

        /*
         * If continuing, clear any pending STOP signals.
         */
        if (prop & SA_CONT)
                SIG_STOPSIGMASK(p->p_siglist);
        
        if (prop & SA_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 & SA_TTYSTOP && p->p_pgrp->pg_jobc == 0 &&
                    action == SIG_DFL) {
                        return;
                }
                SIG_CONTSIGMASK(p->p_siglist);
                p->p_flag &= ~P_CONTINUED;
        }

        crit_enter();

        if (p->p_stat == SSTOP) {
                /*
                 * Nobody can handle this signal, add it to the lwp or
                 * process pending list 
                 */
                if (lp)
                        SIGADDSET(lp->lwp_siglist, sig);
                else
                        SIGADDSET(p->p_siglist, sig);

                /*
                 * If the process is stopped and is being traced, then no
                 * further action is necessary.
                 */
                if (p->p_flag & P_TRACED)
                        goto out;

                /*
                 * If the process is stopped and receives a KILL signal,
                 * make the process runnable.
                 */
                if (sig == SIGKILL) {
                        proc_unstop(p);
                        goto active_process;
                }

                /*
                 * If the process is stopped and receives a CONT signal,
                 * then try to make the process runnable again.
                 */
                if (prop & SA_CONT) {
                        /*
                         * If SIGCONT is default (or ignored), we continue the
                         * process but don't leave the signal in p_siglist, as
                         * it has no further action.  If SIGCONT is held, we
                         * continue the process and leave the signal in
                         * p_siglist.  If the process catches SIGCONT, let it
                         * handle the signal itself.
                         */
                        /* XXX what if the signal is being held blocked? */
                        p->p_flag |= P_CONTINUED;
                        wakeup(p->p_pptr);
                        if (action == SIG_DFL)
                                SIGDELSET(p->p_siglist, sig);
                        proc_unstop(p);
                        if (action == SIG_CATCH)
                                goto active_process;
                        goto out;
                }

                /*
                 * If the process is stopped and receives another STOP
                 * signal, we do not need to stop it again.  If we did
                 * the shell could get confused.
                 *
                 * However, if the current/preempted lwp is part of the
                 * process receiving the signal, we need to keep it,
                 * so that this lwp can stop in issignal() later, as
                 * we don't want to wait until it reaches userret!
                 */
                if (prop & SA_STOP) {
                        if (lwkt_preempted_proc() == NULL ||
                            lwkt_preempted_proc()->lwp_proc != p)
                                SIGDELSET(p->p_siglist, sig);
                }

                /*
                 * Otherwise the process is stopped and it received some
                 * signal, which does not change its stopped state.
                 *
                 * We have to select one thread to set LWP_BREAKTSLEEP,
                 * so that the current signal will break the sleep
                 * as soon as a SA_CONT signal will unstop the process.
                 */
                if (lp == NULL)
                        lp = find_lwp_for_signal(p, sig);
                if (lp != NULL &&
                    (lp->lwp_stat == LSSLEEP || lp->lwp_stat == LSSTOP))
                        lp->lwp_flag |= LWP_BREAKTSLEEP;
                goto out;

                /* NOTREACHED */
        }
        /* else not stopped */
active_process:

        /*
         * Never deliver a lwp-specific signal to a random lwp.
         */
        if (lp == NULL) {
                lp = find_lwp_for_signal(p, sig);
                if (lp && SIGISMEMBER(lp->lwp_sigmask, sig))
                        lp = NULL;
        }

        /*
         * Deliver to the process generically if (1) the signal is being
         * sent to any thread or (2) we could not find a thread to deliver
         * it to.
         */
        if (lp == NULL) {
                SIGADDSET(p->p_siglist, sig);
                goto out;
        }

        /*
         * Deliver to a specific LWP whether it masks it or not.  It will
         * not be dispatched if masked but we must still deliver it.
         */
        if (p->p_nice > NZERO && action == SIG_DFL && (prop & SA_KILL) &&
            (p->p_flag & P_TRACED) == 0) {
                p->p_nice = NZERO;
        }

        /*
         * If the process receives a STOP signal which indeed needs to
         * stop the process, do so.  If the process chose to catch the
         * signal, it will be treated like any other signal.
         */
        if ((prop & SA_STOP) && action == SIG_DFL) {
                /*
                 * If a child holding parent blocked, stopping
                 * could cause deadlock.  Take no action at this
                 * time.
                 */
                if (p->p_flag & P_PPWAIT) {
                        SIGADDSET(p->p_siglist, sig);
                        goto out;
                }

                /*
                 * Do not actually try to manipulate the process, but simply
                 * stop it.  Lwps will stop as soon as they safely can.
                 */
                p->p_xstat = sig;
                proc_stop(p);
                goto out;
        }

        /*
         * If it is a CONT signal with default action, just ignore it.
         */
        if ((prop & SA_CONT) && action == SIG_DFL)
                goto out;

        /*
         * Mark signal pending at this specific thread.
         */
        SIGADDSET(lp->lwp_siglist, sig);

        lwp_signotify(lp);

out:
        crit_exit();
}

void
lwp_signotify(struct lwp *lp)
{
        crit_enter();
        if (lp->lwp_stat == LSSLEEP || lp->lwp_stat == LSSTOP) {
                /*
                 * Thread is in tsleep.
                 */

                /*
                 * If the thread is sleeping uninterruptibly
                 * we can't interrupt the sleep... the signal will
                 * be noticed when the lwp returns through
                 * trap() or syscall().
                 *
                 * Otherwise the signal can interrupt the sleep.
                 *
                 * If the process is traced, the lwp will handle the
                 * tracing in issignal() when it returns to userland.
                 */
                if (lp->lwp_flag & LWP_SINTR) {
                        /*
                         * Make runnable and break out of any tsleep as well.
                         */
                        lp->lwp_flag |= LWP_BREAKTSLEEP;
                        setrunnable(lp);
                }
        } else {
                /*
                 * Otherwise the thread is running
                 *
                 * LSRUN does nothing with the signal, other than kicking
                 * ourselves if we are running.
                 * SZOMB and SIDL mean that it will either never be noticed,
                 * or noticed very soon.
                 *
                 * Note that lwp_thread may be NULL or may not be completely
                 * initialized if the process is in the SIDL or SZOMB state.
                 *
                 * For SMP we may have to forward the request to another cpu.
                 * YYY the MP lock prevents the target process from moving
                 * to another cpu, see kern/kern_switch.c
                 *
                 * If the target thread is waiting on its message port,
                 * wakeup the target thread so it can check (or ignore)
                 * the new signal.  YYY needs cleanup.
                 */
                if (lp == lwkt_preempted_proc()) {
                        signotify();
                } else if (lp->lwp_stat == LSRUN) {
                        struct thread *td = lp->lwp_thread;
                        struct proc *p __debugvar = lp->lwp_proc;

                        KASSERT(td != NULL,
                            ("pid %d/%d NULL lwp_thread stat %d flags %08x/%08x",
                            p->p_pid, lp->lwp_tid, lp->lwp_stat,
                            p->p_flag, lp->lwp_flag));

                        /*
                         * To prevent a MP race with TDF_SINTR we must
                         * schedule the thread on the correct cpu.
                         */
#ifdef SMP
                        if (td->td_gd != mycpu) {
                                LWPHOLD(lp);
                                lwkt_send_ipiq(td->td_gd, signotify_remote, lp);
                        } else
#endif
                        if (td->td_flags & TDF_SINTR)
                                lwkt_schedule(td);
                }
        }
        crit_exit();
}

#ifdef SMP

/*
 * This function is called via an IPI.  We will be in a critical section but
 * the MP lock will NOT be held.  Also note that by the time the ipi message
 * gets to us the process 'p' (arg) may no longer be scheduled or even valid.
 */
static void
signotify_remote(void *arg)
{
        struct lwp *lp = arg;

        if (lp == lwkt_preempted_proc()) {
                signotify();
        } else {
                struct thread *td = lp->lwp_thread;
                if (td->td_flags & TDF_SINTR)
                        lwkt_schedule(td);
        }
        LWPRELE(lp);
}

#endif

void
proc_stop(struct proc *p)
{
        struct lwp *lp;

        /* If somebody raced us, be happy with it */
        if (p->p_stat == SSTOP || p->p_stat == SZOMB)
                return;

        crit_enter();
        p->p_stat = SSTOP;

        FOREACH_LWP_IN_PROC(lp, p) {
                switch (lp->lwp_stat) {
                case LSSTOP:
                        /*
                         * Do nothing, we are already counted in
                         * p_nstopped.
                         */
                        break;

                case LSSLEEP:
                        /*
                         * We're sleeping, but we will stop before
                         * returning to userspace, so count us
                         * as stopped as well.  We set LWP_WSTOP
                         * to signal the lwp that it should not
                         * increase p_nstopped when reaching tstop().
                         */
                        if ((lp->lwp_flag & LWP_WSTOP) == 0) {
                                lp->lwp_flag |= LWP_WSTOP;
                                ++p->p_nstopped;
                        }
                        break;

                case LSRUN:
                        /*
                         * We might notify ourself, but that's not
                         * a problem.
                         */
                        lwp_signotify(lp);
                        break;
                }
        }

        if (p->p_nstopped == p->p_nthreads) {
                p->p_flag &= ~P_WAITED;
                wakeup(p->p_pptr);
                if ((p->p_pptr->p_sigacts->ps_flag & PS_NOCLDSTOP) == 0)
                        ksignal(p->p_pptr, SIGCHLD);
        }
        crit_exit();
}

void
proc_unstop(struct proc *p)
{
        struct lwp *lp;

        if (p->p_stat != SSTOP)
                return;

        crit_enter();
        p->p_stat = SACTIVE;

        FOREACH_LWP_IN_PROC(lp, p) {
                switch (lp->lwp_stat) {
                case LSRUN:
                        /*
                         * Uh?  Not stopped?  Well, I guess that's okay.
                         */
                        if (bootverbose)
                                kprintf("proc_unstop: lwp %d/%d not sleeping\n",
                                        p->p_pid, lp->lwp_tid);
                        break;

                case LSSLEEP:
                        /*
                         * Still sleeping.  Don't bother waking it up.
                         * However, if this thread was counted as
                         * stopped, undo this.
                         *
                         * Nevertheless we call setrunnable() so that it
                         * will wake up in case a signal or timeout arrived
                         * in the meantime.
                         */
                        if (lp->lwp_flag & LWP_WSTOP) {
                                lp->lwp_flag &= ~LWP_WSTOP;
                                --p->p_nstopped;
                        } else {
                                if (bootverbose)
                                        kprintf("proc_unstop: lwp %d/%d sleeping, not stopped\n",
                                                p->p_pid, lp->lwp_tid);
                        }
                        /* FALLTHROUGH */

                case LSSTOP:
                        setrunnable(lp);
                        break;

                }
        }
        crit_exit();
}

static int
kern_sigtimedwait(sigset_t waitset, siginfo_t *info, struct timespec *timeout)
{
        sigset_t savedmask, set;
        struct proc *p = curproc;
        struct lwp *lp = curthread->td_lwp;
        int error, sig, hz, timevalid = 0;
        struct timespec rts, ets, ts;
        struct timeval tv;

        error = 0;
        sig = 0;
        ets.tv_sec = 0;         /* silence compiler warning */
        ets.tv_nsec = 0;        /* silence compiler warning */
        SIG_CANTMASK(waitset);
        savedmask = lp->lwp_sigmask;

        if (timeout) {
                if (timeout->tv_sec >= 0 && timeout->tv_nsec >= 0 &&
                    timeout->tv_nsec < 1000000000) {
                        timevalid = 1;
                        getnanouptime(&rts);
                        ets = rts;
                        timespecadd(&ets, timeout);
                }
        }

        for (;;) {
                set = lwp_sigpend(lp);
                SIGSETAND(set, waitset);
                if ((sig = sig_ffs(&set)) != 0) {
                        SIGFILLSET(lp->lwp_sigmask);
                        SIGDELSET(lp->lwp_sigmask, sig);
                        SIG_CANTMASK(lp->lwp_sigmask);
                        sig = issignal(lp, 1);
                        /*
                         * It may be a STOP signal, in the case, issignal
                         * returns 0, because we may stop there, and new
                         * signal can come in, we should restart if we got
                         * nothing.
                         */
                        if (sig == 0)
                                continue;
                        else
                                break;
                }

                /*
                 * Previous checking got nothing, and we retried but still
                 * got nothing, we should return the error status.
                 */
                if (error)
                        break;

                /*
                 * POSIX says this must be checked after looking for pending
                 * signals.
                 */
                if (timeout) {
                        if (timevalid == 0) {
                                error = EINVAL;
                                break;
                        }
                        getnanouptime(&rts);
                        if (timespeccmp(&rts, &ets, >=)) {
                                error = EAGAIN;
                                break;
                        }
                        ts = ets;
                        timespecsub(&ts, &rts);
                        TIMESPEC_TO_TIMEVAL(&tv, &ts);
                        hz = tvtohz_high(&tv);
                } else
                        hz = 0;

                lp->lwp_sigmask = savedmask;
                SIGSETNAND(lp->lwp_sigmask, waitset);
                /*
                 * We won't ever be woken up.  Instead, our sleep will
                 * be broken in lwpsignal().
                 */
                error = tsleep(&p->p_sigacts, PCATCH, "sigwt", hz);
                if (timeout) {
                        if (error == ERESTART) {
                                /* can not restart a timeout wait. */
                                error = EINTR;
                        } else if (error == EAGAIN) {
                                /* will calculate timeout by ourself. */
                                error = 0;
                        }
                }
                /* Retry ... */
        }

        lp->lwp_sigmask = savedmask;
        if (sig) {
                error = 0;
                bzero(info, sizeof(*info));
                info->si_signo = sig;
                lwp_delsig(lp, sig);    /* take the signal! */

                if (sig == SIGKILL)
                        sigexit(lp, sig);
        }
        return (error);
}

/*
 * MPALMOSTSAFE
 */
int
sys_sigtimedwait(struct sigtimedwait_args *uap)
{
        struct timespec ts;
        struct timespec *timeout;
        sigset_t set;
        siginfo_t info;
        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);
        get_mplock();
        error = kern_sigtimedwait(set, &info, timeout);
        rel_mplock();
        if (error)
                return (error);
        if (uap->info)
                error = copyout(&info, uap->info, sizeof(info));
        /* Repost if we got an error. */
        /*
         * XXX lwp
         *
         * This could transform a thread-specific signal to another
         * thread / process pending signal.
         */
        if (error) {
                get_mplock();
                ksignal(curproc, info.si_signo);
                rel_mplock();
        } else {
                uap->sysmsg_result = info.si_signo;
        }
        return (error);
}

/*
 * MPALMOSTSAFE
 */
int
sys_sigwaitinfo(struct sigwaitinfo_args *uap)
{
        siginfo_t info;
        sigset_t set;
        int error;

        error = copyin(uap->set, &set, sizeof(set));
        if (error)
                return (error);
        get_mplock();
        error = kern_sigtimedwait(set, &info, NULL);
        rel_mplock();
        if (error)
                return (error);
        if (uap->info)
                error = copyout(&info, uap->info, sizeof(info));
        /* Repost if we got an error. */
        /*
         * XXX lwp
         *
         * This could transform a thread-specific signal to another
         * thread / process pending signal.
         */
        if (error) {
                get_mplock();
                ksignal(curproc, info.si_signo);
                rel_mplock();
        } else {
                uap->sysmsg_result = info.si_signo;
        }
        return (error);
}

/*
 * If the current process has received a signal that would interrupt a
 * system call, return EINTR or ERESTART as appropriate.
 */
int
iscaught(struct lwp *lp)
{
        struct proc *p = lp->lwp_proc;
        int sig;

        if (p) {
                if ((sig = CURSIG(lp)) != 0) {
                        if (SIGISMEMBER(p->p_sigacts->ps_sigintr, sig))
                                return (EINTR);                        
                        return (ERESTART);     
                }                         
        }
        return(EWOULDBLOCK);
}

/*
 * 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 the CURSIG macro.) The normal call
 * sequence is
 *
 * This routine is called via CURSIG/__cursig and the MP lock might not be
 * held.  Obtain the MP lock for the duration of the operation.
 *
 *      while (sig = CURSIG(curproc))
 *              postsig(sig);
 */
int
issignal(struct lwp *lp, int maytrace)
{
        struct proc *p = lp->lwp_proc;
        sigset_t mask;
        int sig, prop;

        get_mplock();
        for (;;) {
                int traced = (p->p_flag & P_TRACED) || (p->p_stops & S_SIG);

                /*
                 * If this process is supposed to stop, stop this thread.
                 */
                if (p->p_stat == SSTOP)
                        tstop();

                mask = lwp_sigpend(lp);
                SIGSETNAND(mask, lp->lwp_sigmask);
                if (p->p_flag & P_PPWAIT)
                        SIG_STOPSIGMASK(mask);
                if (SIGISEMPTY(mask)) {         /* no signal to send */
                        rel_mplock();
                        return (0);
                }
                sig = sig_ffs(&mask);

                STOPEVENT(p, S_SIG, sig);

                /*
                 * We should see pending but ignored signals
                 * only if P_TRACED was on when they were posted.
                 */
                if (SIGISMEMBER(p->p_sigignore, sig) && (traced == 0)) {
                        lwp_delsig(lp, sig);
                        continue;
                }
                if (maytrace && (p->p_flag & P_TRACED) && (p->p_flag & P_PPWAIT) == 0) {
                        /*
                         * If traced, always stop, and stay stopped until
                         * released by the parent.
                         *
                         * NOTE: SSTOP may get cleared during the loop,
                         * but we do not re-notify the parent if we have 
                         * to loop several times waiting for the parent
                         * to let us continue.
                         *
                         * XXX not sure if this is still true
                         */
                        p->p_xstat = sig;
                        proc_stop(p);
                        do {
                                tstop();
                        } while (!trace_req(p) && (p->p_flag & P_TRACED));

                        /*
                         * If parent wants us to take the signal,
                         * then it will leave it in p->p_xstat;
                         * otherwise we just look for signals again.
                         */
                        lwp_delsig(lp, sig);    /* clear old signal */
                        sig = p->p_xstat;
                        if (sig == 0)
                                continue;

                        /*
                         * Put the new signal into p_siglist.  If the
                         * signal is being masked, look for other signals.
                         *
                         * XXX lwp might need a call to ksignal()
                         */
                        SIGADDSET(p->p_siglist, sig);
                        if (SIGISMEMBER(lp->lwp_sigmask, sig))
                                continue;

                        /*
                         * If the traced bit got turned off, go back up
                         * to the top to rescan signals.  This ensures
                         * that p_sig* and ps_sigact are consistent.
                         */
                        if ((p->p_flag & P_TRACED) == 0)
                                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
                                 */
                                kprintf("Process (pid %lu) got signal %d\n",
                                        (u_long)p->p_pid, sig);
#endif
                                break;          /* == ignore */
                        }

                        /*
                         * Handle the in-kernel checkpoint action
                         */
                        if (prop & SA_CKPT) {
                                checkpoint_signal_handler(lp);
                                break;
                        }

                        /*
                         * If there is a pending stop signal to process
                         * with default action, stop here,
                         * then clear the signal.  However,
                         * if process is member of an orphaned
                         * process group, ignore tty stop signals.
                         */
                        if (prop & SA_STOP) {
                                if (p->p_flag & P_TRACED ||
                                    (p->p_pgrp->pg_jobc == 0 &&
                                    prop & SA_TTYSTOP))
                                        break;  /* == ignore */
                                p->p_xstat = sig;
                                proc_stop(p);
                                tstop();
                                break;
                        } else if (prop & SA_IGNORE) {
                                /*
                                 * Except for SIGCONT, shouldn't get here.
                                 * Default action is to ignore; drop it.
                                 */
                                break;          /* == ignore */
                        } else {
                                rel_mplock();
                                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 & SA_CONT) == 0 &&
                            (p->p_flag & P_TRACED) == 0)
                                kprintf("issignal\n");
                        break;          /* == ignore */

                default:
                        /*
                         * This signal has an action, let
                         * postsig() process it.
                         */
                        rel_mplock();
                        return (sig);
                }
                lwp_delsig(lp, sig);            /* take the signal! */
        }
        /* NOTREACHED */
}

/*
 * Take the action for the specified signal
 * from the current set of pending signals.
 */
void
postsig(int sig)
{
        struct lwp *lp = curthread->td_lwp;
        struct proc *p = lp->lwp_proc;
        struct sigacts *ps = p->p_sigacts;
        sig_t action;
        sigset_t returnmask;
        int code;

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

        /*
         * If we are a virtual kernel running an emulated user process
         * context, switch back to the virtual kernel context before
         * trying to post the signal.
         */
        if (lp->lwp_vkernel && lp->lwp_vkernel->ve) {
                struct trapframe *tf = lp->lwp_md.md_regs;
                tf->tf_trapno = 0;
                vkernel_trap(lp, tf);
        }

        lwp_delsig(lp, sig);
        action = ps->ps_sigact[_SIG_IDX(sig)];
#ifdef KTRACE
        if (KTRPOINT(lp->lwp_thread, KTR_PSIG))
                ktrpsig(lp, sig, action, lp->lwp_flag & LWP_OLDMASK ?
                        &lp->lwp_oldsigmask : &lp->lwp_sigmask, 0);
#endif
        STOPEVENT(p, S_SIG, sig);

        if (action == SIG_DFL) {
                /*
                 * Default action, where the default is to kill
                 * the process.  (Other cases were ignored above.)
                 */
                sigexit(lp, sig);
                /* NOTREACHED */
        } else {
                /*
                 * If we get here, the signal must be caught.
                 */
                KASSERT(action != SIG_IGN && !SIGISMEMBER(lp->lwp_sigmask, sig),
                    ("postsig action"));

                crit_enter();

                /*
                 * Reset the signal handler if asked to
                 */
                if (SIGISMEMBER(ps->ps_sigreset, sig)) {
                        /*
                         * See kern_sigaction() for origin of this code.
                         */
                        SIGDELSET(p->p_sigcatch, sig);
                        if (sig != SIGCONT &&
                            sigprop(sig) & SA_IGNORE)
                                SIGADDSET(p->p_sigignore, sig);
                        ps->ps_sigact[_SIG_IDX(sig)] = SIG_DFL;
                }

                /*
                 * Handle the mailbox case.  Copyout to the appropriate
                 * location but do not generate a signal frame.  The system
                 * call simply returns EINTR and the user is responsible for
                 * polling the mailbox.
                 */
                if (SIGISMEMBER(ps->ps_sigmailbox, sig)) {
                        int sig_copy = sig;
                        copyout(&sig_copy, (void *)action, sizeof(int));
                        curproc->p_flag |= P_MAILBOX;
                        crit_exit();
                        goto done;
                }

                /*
                 * Set the signal mask and calculate the mask to restore
                 * when the signal function returns.
                 *
                 * 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 (lp->lwp_flag & LWP_OLDMASK) {
                        returnmask = lp->lwp_oldsigmask;
                        lp->lwp_flag &= ~LWP_OLDMASK;
                } else {
                        returnmask = lp->lwp_sigmask;
                }

                SIGSETOR(lp->lwp_sigmask, ps->ps_catchmask[_SIG_IDX(sig)]);
                if (!SIGISMEMBER(ps->ps_signodefer, sig))
                        SIGADDSET(lp->lwp_sigmask, sig);

                crit_exit();
                lp->lwp_ru.ru_nsignals++;
                if (lp->lwp_sig != sig) {
                        code = 0;
                } else {
                        code = lp->lwp_code;
                        lp->lwp_code = 0;
                        lp->lwp_sig = 0;
                }
                (*p->p_sysent->sv_sendsig)(action, sig, &returnmask, code);
        }
done:
        ;
}

/*
 * Kill the current process for stated reason.
 */
void
killproc(struct proc *p, char *why)
{
        log(LOG_ERR, "pid %d (%s), uid %d, was killed: %s\n", 
                p->p_pid, p->p_comm,
                p->p_ucred ? p->p_ucred->cr_uid : -1, why);
        ksignal(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 lwp *lp, int sig)
{
        struct proc *p = lp->lwp_proc;

        p->p_acflag |= AXSIG;
        if (sigprop(sig) & SA_CORE) {
                lp->lwp_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
                 */
                if (coredump(lp, sig) == 0)
                        sig |= WCOREFLAG;
                if (kern_logsigexit)
                        log(LOG_INFO,
                            "pid %d (%s), uid %d: exited on signal %d%s\n",
                            p->p_pid, p->p_comm,
                            p->p_ucred ? p->p_ucred->cr_uid : -1,
                            sig &~ WCOREFLAG,
                            sig & WCOREFLAG ? " (core dumped)" : "");
        }
        exit1(W_EXITCODE(0, sig));
        /* NOTREACHED */
}

static char corefilename[MAXPATHLEN+1] = {"%N.core"};
SYSCTL_STRING(_kern, OID_AUTO, corefile, CTLFLAG_RW, corefilename,
              sizeof(corefilename), "process corefile name format string");

/*
 * expand_name(name, uid, pid)
 * Expand the name described in corefilename, using name, uid, and pid.
 * corefilename is a kprintf-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 char *
expand_name(const char *name, uid_t uid, pid_t pid)
{
        char *temp;
        char buf[11];           /* Buffer for pid/uid -- max 4B */
        int i, n;
        char *format = corefilename;
        size_t namelen;

        temp = kmalloc(MAXPATHLEN + 1, M_TEMP, M_NOWAIT);
        if (temp == NULL)
                return NULL;
        namelen = strlen(name);
        for (i = 0, n = 0; n < MAXPATHLEN && format[i]; i++) {
                int l;
                switch (format[i]) {
                case '%':       /* Format character */
                        i++;
                        switch (format[i]) {
                        case '%':
                                temp[n++] = '%';
                                break;
                        case 'N':       /* process name */
                                if ((n + namelen) > MAXPATHLEN) {
                                        log(LOG_ERR, "pid %d (%s), uid (%u):  Path `%s%s' is too long\n",
                                            pid, name, uid, temp, name);
                                        kfree(temp, M_TEMP);
                                        return NULL;
                                }
                                memcpy(temp+n, name, namelen);
                                n += namelen;
                                break;
                        case 'P':       /* process id */
                                l = ksprintf(buf, "%u", pid);
                                if ((n + l) > MAXPATHLEN) {
                                        log(LOG_ERR, "pid %d (%s), uid (%u):  Path `%s%s' is too long\n",
                                            pid, name, uid, temp, name);
                                        kfree(temp, M_TEMP);
                                        return NULL;
                                }
                                memcpy(temp+n, buf, l);
                                n += l;
                                break;
                        case 'U':       /* user id */
                                l = ksprintf(buf, "%u", uid);
                                if ((n + l) > MAXPATHLEN) {
                                        log(LOG_ERR, "pid %d (%s), uid (%u):  Path `%s%s' is too long\n",
                                            pid, name, uid, temp, name);
                                        kfree(temp, M_TEMP);
                                        return NULL;
                                }
                                memcpy(temp+n, buf, l);
                                n += l;
                                break;
                        default:
                                log(LOG_ERR, "Unknown format character %c in `%s'\n", format[i], format);
                        }
                        break;
                default:
                        temp[n++] = format[i];
                }
        }
        temp[n] = '\0';
        return temp;
}

/*
 * 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.
 *
 * The parameter `lp' is the lwp which triggered the coredump.
 */

static int
coredump(struct lwp *lp, int sig)
{
        struct proc *p = lp->lwp_proc;
        struct vnode *vp;
        struct ucred *cred = p->p_ucred;
        struct flock lf;
        struct nlookupdata nd;
        struct vattr vattr;
        int error, error1;
        char *name;                     /* name of corefile */
        off_t limit;
        
        STOPEVENT(p, S_CORE, 0);

        if (((sugid_coredump == 0) && p->p_flag & P_SUGID) || do_coredump == 0)
                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 = p->p_rlimit[RLIMIT_CORE].rlim_cur;
        if (limit == 0)
                return EFBIG;

        name = expand_name(p->p_comm, p->p_ucred->cr_uid, p->p_pid);
        if (name == NULL)
                return (EINVAL);
        error = nlookup_init(&nd, name, UIO_SYSSPACE, NLC_LOCKVP);
        if (error == 0)
                error = vn_open(&nd, NULL, O_CREAT | FWRITE | O_NOFOLLOW, S_IRUSR | S_IWUSR);
        kfree(name, M_TEMP);
        if (error) {
                nlookup_done(&nd);
                return (error);
        }
        vp = nd.nl_open_vp;
        nd.nl_open_vp = NULL;
        nlookup_done(&nd);

        vn_unlock(vp);
        lf.l_whence = SEEK_SET;
        lf.l_start = 0;
        lf.l_len = 0;
        lf.l_type = F_WRLCK;
        error = VOP_ADVLOCK(vp, (caddr_t)p, F_SETLK, &lf, 0);
        if (error)
                goto out2;

        /* Don't dump to non-regular files or files with links. */
        if (vp->v_type != VREG ||
            VOP_GETATTR(vp, &vattr) || vattr.va_nlink != 1) {
                error = EFAULT;
                goto out1;
        }

        /* Don't dump to files current user does not own */
        if (vattr.va_uid != p->p_ucred->cr_uid) {
                error = EFAULT;
                goto out1;
        }

        VATTR_NULL(&vattr);
        vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
        vattr.va_size = 0;
        VOP_SETATTR(vp, &vattr, cred);
        p->p_acflag |= ACORE;
        vn_unlock(vp);

        error = p->p_sysent->sv_coredump ?
                  p->p_sysent->sv_coredump(lp, sig, vp, limit) : ENOSYS;

out1:
        lf.l_type = F_UNLCK;
        VOP_ADVLOCK(vp, (caddr_t)p, F_UNLCK, &lf, 0);
out2:
        error1 = vn_close(vp, FWRITE);
        if (error == 0)
                error = error1;
        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).
 *
 * MPALMOSTSAFE
 */
/* ARGSUSED */
int
sys_nosys(struct nosys_args *args)
{
        get_mplock();
        lwpsignal(curproc, curthread->td_lwp, SIGSYS);
        rel_mplock();
        return (EINVAL);
}

/*
 * 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 *sigio, int sig, int checkctty)
{
        if (sigio == NULL)
                return;
                
        if (sigio->sio_pgid > 0) {
                if (CANSIGIO(sigio->sio_ruid, sigio->sio_ucred,
                             sigio->sio_proc))
                        ksignal(sigio->sio_proc, sig);
        } else if (sigio->sio_pgid < 0) {
                struct proc *p;

                lockmgr(&sigio->sio_pgrp->pg_lock, LK_EXCLUSIVE);
                LIST_FOREACH(p, &sigio->sio_pgrp->pg_members, p_pglist) {
                        if (CANSIGIO(sigio->sio_ruid, sigio->sio_ucred, p) &&
                            (checkctty == 0 || (p->p_flag & P_CONTROLT)))
                                ksignal(p, sig);
                }
                lockmgr(&sigio->sio_pgrp->pg_lock, LK_RELEASE);
        }
}

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

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

        /* XXX lock the proc here while adding to the list? */
        SLIST_INSERT_HEAD(&p->p_klist, kn, kn_selnext);

        return (0);
}

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

        SLIST_REMOVE(&p->p_klist, kn, knote, kn_selnext);
}

/*
 * 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);
}