port/sys/signal.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#pragma ident   "%Z%%M% %I% %E% SMI"

#pragma weak _signal = signal
#pragma weak _sighold = sighold
#pragma weak _sigrelse = sigrelse
#pragma weak _sigignore = sigignore
#pragma weak _sigset = sigset

#include "lint.h"
#include <sys/types.h>
#include <unistd.h>
#include <errno.h>
#include <signal.h>
#include <wait.h>

/*
 * Check for valid signal number as per SVID.
 */
#define CHECK_SIG(s, code) \
    if ((s) <= 0 || (s) >= NSIG || (s) == SIGKILL || (s) == SIGSTOP) { \
        errno = EINVAL; \
        return (code); \
    }

/*
 * Equivalent to stopdefault set in the kernel implementation (sig.c).
 */
#define STOPDEFAULT(s) \
    ((s) == SIGSTOP || (s) == SIGTSTP || (s) == SIGTTOU || (s) == SIGTTIN)


/*
 * SVr3.x signal compatibility routines. They are now
 * implemented as library routines instead of system
 * calls.
 */

void(*
signal(int sig, void(*func)(int)))(int)
{
    struct sigaction nact;
    struct sigaction oact;

    CHECK_SIG(sig, SIG_ERR);

    nact.sa_handler = func;
    nact.sa_flags = SA_RESETHAND|SA_NODEFER;
    (void) sigemptyset(&nact.sa_mask);

    /*
     * Pay special attention if sig is SIGCHLD and
     * the disposition is SIG_IGN, per sysV signal man page.
     */
    if (sig == SIGCHLD) {
        nact.sa_flags |= SA_NOCLDSTOP;
        if (func == SIG_IGN)
            nact.sa_flags |= SA_NOCLDWAIT;
    }

    if (STOPDEFAULT(sig))
        nact.sa_flags |= SA_RESTART;

    if (sigaction(sig, &nact, &oact) < 0)
        return (SIG_ERR);

    return (oact.sa_handler);
}

int
sighold(int sig)
{
    sigset_t set;

    CHECK_SIG(sig, -1);

    /*
     * errno set on failure by either sigaddset or sigprocmask.
     */
    (void) sigemptyset(&set);
    if (sigaddset(&set, sig) < 0)
        return (-1);
    return (sigprocmask(SIG_BLOCK, &set, (sigset_t *)0));
}

int
sigrelse(int sig)
{
    sigset_t set;

    CHECK_SIG(sig, -1);

    /*
     * errno set on failure by either sigaddset or sigprocmask.
     */
    (void) sigemptyset(&set);
    if (sigaddset(&set, sig) < 0)
        return (-1);
    return (sigprocmask(SIG_UNBLOCK, &set, (sigset_t *)0));
}

int
sigignore(int sig)
{
    struct sigaction act;
    sigset_t set;

    CHECK_SIG(sig, -1);

    act.sa_handler = SIG_IGN;
    act.sa_flags = 0;
    (void) sigemptyset(&act.sa_mask);

    /*
     * Pay special attention if sig is SIGCHLD and
     * the disposition is SIG_IGN, per sysV signal man page.
     */
    if (sig == SIGCHLD) {
        act.sa_flags |= SA_NOCLDSTOP;
        act.sa_flags |= SA_NOCLDWAIT;
    }

    if (STOPDEFAULT(sig))
        act.sa_flags |= SA_RESTART;

    if (sigaction(sig, &act, (struct sigaction *)0) < 0)
        return (-1);

    (void) sigemptyset(&set);
    if (sigaddset(&set, sig) < 0)
        return (-1);
    return (sigprocmask(SIG_UNBLOCK, &set, (sigset_t *)0));
}

int
__sigpause(int sig)
{
    sigset_t set;
    int rval;

    CHECK_SIG(sig, -1);

    /*
     * sigpause() is defined to unblock the signal
     * and not block it again on return.
     * sigsuspend() restores the original signal set,
     * so we have to unblock sig overtly.
     */
    (void) sigprocmask(0, (sigset_t *)0, &set);
    if (sigdelset(&set, sig) < 0)
        return (-1);
    rval = sigsuspend(&set);
    (void) sigrelse(sig);
    return (rval);
}

void(*
sigset(int sig, void(*func)(int)))(int)
{
    struct sigaction nact;
    struct sigaction oact;
    sigset_t nset;
    sigset_t oset;
    int code;

    CHECK_SIG(sig, SIG_ERR);

    (void) sigemptyset(&nset);
    if (sigaddset(&nset, sig) < 0)
        return (SIG_ERR);

    if (func == SIG_HOLD) {
        if (sigprocmask(SIG_BLOCK, &nset, &oset) < 0)
            return (SIG_ERR);
        if (sigaction(sig, (struct sigaction *)0, &oact) < 0)
            return (SIG_ERR);
    } else {
        nact.sa_handler = func;
        nact.sa_flags = 0;
        (void) sigemptyset(&nact.sa_mask);
        /*
         * Pay special attention if sig is SIGCHLD and
         * the disposition is SIG_IGN, per sysV signal man page.
         */
        if (sig == SIGCHLD) {
            nact.sa_flags |= SA_NOCLDSTOP;
            if (func == SIG_IGN)
                nact.sa_flags |= SA_NOCLDWAIT;
        }

        if (STOPDEFAULT(sig))
            nact.sa_flags |= SA_RESTART;

        if (sigaction(sig, &nact, &oact) < 0)
            return (SIG_ERR);

        if (sigprocmask(SIG_UNBLOCK, &nset, &oset) < 0)
            return (SIG_ERR);
    }

    if ((code = sigismember(&oset, sig)) < 0)
        return (SIG_ERR);
    else if (code == 1)
        return (SIG_HOLD);

    return (oact.sa_handler);
}