signals.c

/*
 * $Id: signals.c,v 2.24 1996/10/15 20:16:35 hzoli Exp $
 *
 * signals.c - signals handling code
 *
 * This file is part of zsh, the Z shell.
 *
 * Copyright (c) 1992-1996 Paul Falstad
 * All rights reserved.
 *
 * Permission is hereby granted, without written agreement and without
 * license or royalty fees, to use, copy, modify, and distribute this
 * software and to distribute modified versions of this software for any
 * purpose, provided that the above copyright notice and the following
 * two paragraphs appear in all copies of this software.
 *
 * In no event shall Paul Falstad or the Zsh Development Group be liable
 * to any party for direct, indirect, special, incidental, or consequential
 * damages arising out of the use of this software and its documentation,
 * even if Paul Falstad and the Zsh Development Group have been advised of
 * the possibility of such damage.
 *
 * Paul Falstad and the Zsh Development Group specifically disclaim any
 * warranties, including, but not limited to, the implied warranties of
 * merchantability and fitness for a particular purpose.  The software
 * provided hereunder is on an "as is" basis, and Paul Falstad and the
 * Zsh Development Group have no obligation to provide maintenance,
 * support, updates, enhancements, or modifications.
 *
 */

#include "zsh.h"
 
/* This is only used on machines that don't understand signal sets.  *
 * On SYSV machines this will represent the signals that are blocked *
 * (held) using sighold.  On machines which can't block signals at   *
 * all, we will simulate this by ignoring them and remembering them  *
 * in this variable.                                                 */
#if !defined(POSIX_SIGNALS) && !defined(BSD_SIGNALS)
static sigset_t blocked_set;
#endif

#ifdef POSIX_SIGNALS
# define signal_jmp_buf       sigjmp_buf
# define signal_setjmp(b)     sigsetjmp((b),1)
# define signal_longjmp(b,n)  siglongjmp((b),(n))
#else
# define signal_jmp_buf       jmp_buf
# define signal_setjmp(b)     setjmp(b)
# define signal_longjmp(b,n)  longjmp((b),(n))
#endif
 
#ifdef NO_SIGNAL_BLOCKING
# define signal_process(sig)  signal_ignore(sig)
# define signal_reset(sig)    install_handler(sig)
#else
# define signal_process(sig)  ;
# define signal_reset(sig)    ;
#endif

/* Install signal handler for given signal.           *
 * If possible, we want to make sure that interrupted *
 * system calls are not restarted.                    */

/**/
void
install_handler(int sig)
{
#ifdef POSIX_SIGNALS
    struct sigaction act;
 
    act.sa_handler = (SIGNAL_HANDTYPE) handler;
    sigemptyset(&act.sa_mask);        /* only block sig while in handler */
    act.sa_flags = 0;
# ifdef SA_INTERRUPT                  /* SunOS 4.x */
    if (interact)
        act.sa_flags |= SA_INTERRUPT; /* make sure system calls are not restarted */
# endif
    sigaction(sig, &act, (struct sigaction *)NULL);
#else
# ifdef BSD_SIGNALS
    struct sigvec vec;
 
    vec.sv_handler = (SIGNAL_HANDTYPE) handler;
    vec.sv_mask = sigmask(sig);    /* mask out this signal while in handler    */
#  ifdef SV_INTERRUPT
    vec.sv_flags = SV_INTERRUPT;   /* make sure system calls are not restarted */
#  endif
    sigvec(sig, &vec, (struct sigvec *)NULL);
# else
#  ifdef SYSV_SIGNALS
    /* we want sigset rather than signal because it will   *
     * block sig while in handler.  signal usually doesn't */
    sigset(sig, handler);
#  else  /* NO_SIGNAL_BLOCKING (bummer) */
    signal(sig, handler);

#  endif /* SYSV_SIGNALS  */
# endif  /* BSD_SIGNALS   */
#endif   /* POSIX_SIGNALS */
}

/* enable ^C interrupts */
 
/**/
void
intr(void)
{
    if (interact)
        install_handler(SIGINT);
}

/* disable ^C interrupts */
 
/**/
void
nointr(void)
{
    if (interact)
        signal_ignore(SIGINT);
}
 
/* temporarily block ^C interrupts */
 
/**/
void
holdintr(void)
{
    if (interact)
        signal_block(signal_mask(SIGINT));
}

/* release ^C interrupts */
 
/**/
void
noholdintr(void)
{
    if (interact)
        signal_unblock(signal_mask(SIGINT));
}
 
/* create a signal mask containing *
 * only the given signal           */
 
/**/
sigset_t
signal_mask(int sig)
{
    sigset_t set;
 
    sigemptyset(&set);
    if (sig)
        sigaddset(&set, sig);
    return set;
}

/* Block the signals in the given signal *
 * set. Return the old signal set.       */
 
/**/
sigset_t
signal_block(sigset_t set)
{
    sigset_t oset;
 
#ifdef POSIX_SIGNALS
    sigprocmask(SIG_BLOCK, &set, &oset);
#else
# ifdef BSD_SIGNALS
    oset = sigblock(set);
# else
#  ifdef SYSV_SIGNALS
    int i;
 
    oset = blocked_set;
    for (i = 1; i <= NSIG; ++i) {
        if (sigismember(&set, i) && !sigismember(&blocked_set, i)) {
            sigaddset(&blocked_set, i);
            sighold(i);
        }
    }
#  else  /* NO_SIGNAL_BLOCKING */
/* We will just ignore signals if the system doesn't have *
 * the ability to block them.                             */
    int i;

    oset = blocked_set;
    for (i = 1; i <= NSIG; ++i) {
        if (sigismember(&set, i) && !sigismember(&blocked_set, i)) {
            sigaddset(&blocked_set, i);
            signal_ignore(i);
        }
   }
#  endif /* SYSV_SIGNALS  */
# endif  /* BSD_SIGNALS   */
#endif   /* POSIX_SIGNALS */
 
    return oset;
}

/* Unblock the signals in the given signal *
 * set. Return the old signal set.         */

/**/
sigset_t
signal_unblock(sigset_t set)
{
    sigset_t oset;
 
#ifdef POSIX_SIGNALS
    sigprocmask(SIG_UNBLOCK, &set, &oset);
#else
# ifdef BSD_SIGNALS
    sigfillset(&oset);
    oset = sigsetmask(oset);
    sigsetmask(oset & ~set);
# else
#  ifdef SYSV_SIGNALS
    int i;
 
    oset = blocked_set;
    for (i = 1; i <= NSIG; ++i) {
        if (sigismember(&set, i) && sigismember(&blocked_set, i)) {
            sigdelset(&blocked_set, i);
            sigrelse(i);
        }
    }
#  else  /* NO_SIGNAL_BLOCKING */
/* On systems that can't block signals, we are just ignoring them.  So *
 * to unblock signals, we just reenable the signal handler for them.   */
    int i;

    oset = blocked_set;
    for (i = 1; i <= NSIG; ++i) {
        if (sigismember(&set, i) && sigismember(&blocked_set, i)) {
            sigdelset(&blocked_set, i);
            install_handler(i);
        }
   }
#  endif /* SYSV_SIGNALS  */
# endif  /* BSD_SIGNALS   */
#endif   /* POSIX_SIGNALS */
 
    return oset;
}

/* set the process signal mask to *
 * be the given signal mask       */

/**/
sigset_t
signal_setmask(sigset_t set)
{
    sigset_t oset;
 
#ifdef POSIX_SIGNALS
    sigprocmask(SIG_SETMASK, &set, &oset);
#else
# ifdef BSD_SIGNALS
    oset = sigsetmask(set);
# else
#  ifdef SYSV_SIGNALS
    int i;
 
    oset = blocked_set;
    for (i = 1; i <= NSIG; ++i) {
        if (sigismember(&set, i) && !sigismember(&blocked_set, i)) {
            sigaddset(&blocked_set, i);
            sighold(i);
        } else if (!sigismember(&set, i) && sigismember(&blocked_set, i)) {
            sigdelset(&blocked_set, i);
            sigrelse(i);
        }
    }
#  else  /* NO_SIGNAL_BLOCKING */
    int i;

    oset = blocked_set;
    for (i = 1; i < NSIG; ++i) {
        if (sigismember(&set, i) && !sigismember(&blocked_set, i)) {
            sigaddset(&blocked_set, i);
            signal_ignore(i);
        } else if (!sigismember(&set, i) && sigismember(&blocked_set, i)) {
            sigdelset(&blocked_set, i);
            install_handler(i);
        }
    }
#  endif /* SYSV_SIGNALS  */
# endif  /* BSD_SIGNALS   */
#endif   /* POSIX_SIGNALS */
 
    return oset;
}

#if defined(NO_SIGNAL_BLOCKING)
static int suspend_longjmp = 0;
static signal_jmp_buf suspend_jmp_buf;
#endif
 
/**/
int
signal_suspend(int sig, int sig2)
{
    int ret;
 
#ifdef POSIX_SIGNALS
    sigset_t set;

    sigfillset(&set);
    sigdelset(&set, sig);
    sigdelset(&set, SIGHUP);  /* still don't know why we add this? */
    if (sig2)
        sigdelset(&set, sig2);
    ret = sigsuspend(&set);
#else
# ifdef BSD_SIGNALS
    sigset_t set;

    sigfillset(&set);
    sigdelset(&set, sig);
    if (sig2)
      sigdelset(&set, sig2);
    ret = sigpause(set);
# else
#  ifdef SYSV_SIGNALS
    ret = sigpause(sig);

#  else  /* NO_SIGNAL_BLOCKING */
    /* need to use signal_longjmp to make this race-free *
     * between the child_unblock() and pause()           */
    if (signal_setjmp(suspend_jmp_buf) == 0) {
        suspend_longjmp = 1;   /* we want to signal_longjmp after catching signal */
        child_unblock();       /* do we need to unblock sig2 as well?             */
        ret = pause();
    }
    suspend_longjmp = 0;       /* turn off using signal_longjmp since we are past *
                                * the pause() function.                           */
#  endif /* SYSV_SIGNALS  */
# endif  /* BSD_SIGNALS   */
#endif   /* POSIX_SIGNALS */
 
    return ret;
}

/* What flavor of waitpid/wait3/wait shall we use? */
 
#ifdef HAVE_WAITPID
# define  WAIT(pid, statusp, options) waitpid(pid, statusp, options)
#else
# ifdef HAVE_WAIT3
#  define WAIT(pid, statusp, options) wait3((void *) statusp, options, NULL)
# else
#  define WAIT(pid, statusp, options) wait(statusp)
# endif
#endif

/* the signal handler */
 
/**/
RETSIGTYPE
handler(int sig)
{
    sigset_t newmask, oldmask;

#if defined(NO_SIGNAL_BLOCKING)
    int do_jump;
    signal_jmp_buf jump_to;
#endif
 
    signal_process(sig);
 
    sigfillset(&newmask);
    oldmask = signal_block(newmask);        /* Block all signals temporarily           */
 
#if defined(NO_SIGNAL_BLOCKING)
    do_jump = suspend_longjmp;              /* do we need to longjmp to signal_suspend */
    suspend_longjmp = 0;                    /* In case a SIGCHLD somehow arrives       */

    if (sig == SIGCHLD) {                   /* Traps can cause nested child_suspend()  */
        if (do_jump)
            jump_to = suspend_jmp_buf;      /* Copy suspend_jmp_buf                    */
    }
#endif

    if (queueing_enabled) {           /* Are we queueing signals now?      */
        int temp_rear = ++queue_rear % MAX_QUEUE_SIZE;

	DPUTS(temp_rear == queue_front, "BUG: signal queue full");
        if (temp_rear != queue_front) { /* Make sure it's not full (extremely unlikely) */
            queue_rear = temp_rear;                  /* ok, not full, so add to queue   */
            signal_queue[queue_rear] = sig;          /* save signal caught              */
            signal_mask_queue[queue_rear] = oldmask; /* save current signal mask        */
        }
        signal_reset(sig);
        return;
    }
 
    signal_setmask(oldmask);          /* Reset signal mask, signal traps ok now */
 
    switch (sig) {
    case SIGCHLD:

	/* keep WAITING until no more child processes to reap */
	for (;;)
	  cont: {
            int old_errno = errno; /* save the errno, since WAIT may change it */
	    int status;
	    Job jn;
	    Process pn;
            pid_t pid;
	    pid_t *procsubpid = &cmdoutpid;
	    int *procsubval = &cmdoutval;
	    struct execstack *es = exstack;

            pid = WAIT(-1, &status, WNOHANG|WUNTRACED);  /* reap the child process */

            if (!pid)  /* no more children to reap */
                break;

	    /* check if child returned was from process substitution */
	    for (;;) {
		if (pid == *procsubpid) {
		    *procsubpid = 0;
		    if (WIFSIGNALED(status))
			*procsubval = (0200 | WTERMSIG(status));
		    else
			*procsubval = WEXITSTATUS(status);
		    times(&shtms);
		    goto cont;
		}
		if (!es)
		    break;
		procsubpid = &es->cmdoutpid;
		procsubval = &es->cmdoutval;
		es = es->next;
	    }

	    /* check for WAIT error */
            if (pid == -1) {
                if (errno != ECHILD)
                    zerr("wait failed: %e", NULL, errno);
                errno = old_errno;    /* WAIT changed errno, so restore the original */
                break;
            }

	    /* Find the process and job containing this pid and update it. */
	    if (findproc(pid, &jn, &pn)) {
		update_process(pn, status);
		update_job(jn);
	    } else {
		/* If not found, update the shell record of time spent by
		 * children in sub processes anyway:  otherwise, this
		 * will get added on to the next found process that terminates.
		 */
		times(&shtms);
	    }
        }
        break;
 
    case SIGHUP:
        if (sigtrapped[SIGHUP])
            dotrap(SIGHUP);
        else {
            stopmsg = 1;
            zexit(SIGHUP, 1);
        }
        break;
 
    case SIGINT:
        if (sigtrapped[SIGINT])
            dotrap(SIGINT);
        else {
            extern int list_pipe, simple_pline;
 
	    if (isset(PRIVILEGED) && isset(INTERACTIVE) && noerrexit < 0)
		zexit(SIGINT, 1);
            if (list_pipe || chline || simple_pline) {
                breaks = loops;
                errflag = 1;
		inerrflush();
            }
        }
        break;

#ifdef SIGWINCH
    case SIGWINCH:
        adjustwinsize(1);  /* check window size and adjust */
	if (sigtrapped[SIGWINCH])
	    dotrap(SIGWINCH);
        break;
#endif

    case SIGALRM:
        if (sigtrapped[SIGALRM]) {
	    int tmout;
            dotrap(SIGALRM);
            if ((tmout = getiparam("TMOUT")))
                alarm(tmout);           /* reset the alarm */
        } else {
	    int idle = ttyidlegetfn(NULL);
	    int tmout = getiparam("TMOUT");
	    if (idle >= 0 && idle < tmout)
		alarm(tmout - idle);
	    else {
		errflag = noerrs = 0;
		zerr("timeout", NULL, 0);
		errflag = 0;
		stopmsg = 1;
		zexit(SIGALRM, 1);
	    }
        }
        break;
 
    default:
        dotrap(sig);
        break;
    }   /* end of switch(sig) */
 
    signal_reset(sig);

/* This is used to make signal_suspend() race-free */
#if defined(NO_SIGNAL_BLOCKING)
    if (do_jump)
        signal_longjmp(jump_to, 1);
#endif

} /* handler */

 
/* SIGHUP any jobs left running */
 
/**/
void
killrunjobs(int from_signal)
{
    int i, killed = 0;
 
    if (unset(HUP))
        return;
    for (i = 1; i < MAXJOB; i++)
        if ((from_signal || i != thisjob) && (jobtab[i].stat & STAT_LOCKED) &&
            !(jobtab[i].stat & STAT_NOPRINT) &&
            !(jobtab[i].stat & STAT_STOPPED)) {
            if (killpg(jobtab[i].gleader, SIGHUP) != -1)
                killed++;
        }
    if (killed)
        zerr("warning: %d jobs SIGHUPed", NULL, killed);
}


/* send a signal to a job (simply involves kill if monitoring is on) */
 
/**/
int
killjb(Job jn, int sig)
{
    Process pn;
    int err = 0;
 
    if (jobbing) {
        if (jn->stat & STAT_SUPERJOB) {
            if (sig == SIGCONT) {
                for (pn = jobtab[jn->other].procs; pn; pn = pn->next)
                    kill(pn->pid, sig);
 
                for (pn = jn->procs; pn->next; pn = pn->next)
                    err = kill(pn->pid, sig);
 
                return err;
            }
 
            killpg(jobtab[jn->other].gleader, sig);
            return killpg(jn->gleader, sig);
        }
        else
            return (killpg(jn->gleader, sig));
    }
    for (pn = jn->procs; pn; pn = pn->next)
        if ((err = kill(pn->pid, sig)) == -1 && errno != ESRCH)
            return -1;
    return err;
}

/**/
int
settrap(int sig, List l)
{
    if (sig == -1)
        return 1;
    if (jobbing && (sig == SIGTTOU || sig == SIGTSTP || sig == SIGTTIN)) {
        zerr("can't trap SIG%s in interactive shells", sigs[sig], 0);
        return 1;
    }
    if (sigfuncs[sig])
	unsettrap(sig);
    sigfuncs[sig] = l;
    if (!l) {
	sigtrapped[sig] = ZSIG_IGNORED;
        if (sig && sig <= SIGCOUNT &&
#ifdef SIGWINCH
            sig != SIGWINCH &&
#endif
            sig != SIGCHLD)
            signal_ignore(sig);
    } else {
        sigtrapped[sig] = ZSIG_TRAPPED;
        if (sig && sig <= SIGCOUNT &&
#ifdef SIGWINCH
            sig != SIGWINCH &&
#endif
            sig != SIGCHLD)
            install_handler(sig);
    }
    return 0;
}

/**/
void
unsettrap(int sig)
{
    int trapped;

    if (sig == -1 || !(trapped = sigtrapped[sig]) ||
	(jobbing && (sig == SIGTTOU || sig == SIGTSTP || sig == SIGTTIN))) {
        return;
    }
    sigtrapped[sig] = 0;
    if (sig == SIGINT && interact) {
	/* PWS 1995/05/16:  added test for interactive, also noholdintr() *
	 * as subshells ignoring SIGINT have it blocked from delivery     */
        intr();
	noholdintr();
    } else if (sig == SIGHUP)
        install_handler(sig);
    else if (sig && sig <= SIGCOUNT &&
#ifdef SIGWINCH
             sig != SIGWINCH &&
#endif
             sig != SIGCHLD)
        signal_default(sig);
    if (trapped & ZSIG_FUNC) {
	char func[20];
	HashNode hn;

	sprintf(func, "TRAP%s", sigs[sig]);
	if ((hn = shfunctab->removenode(shfunctab, func)))
	    shfunctab->freenode(hn);
    } else if (sigfuncs[sig]) {
	freestruct(sigfuncs[sig]);
	sigfuncs[sig] = NULL;
    }
}

/* Execute a trap function for a given signal, possibly
 * with non-standard sigtrapped & sigfuncs values
 */

/**/
void
dotrapargs(int sig, int *sigtr, void *sigfn)
{
    LinkList args;
    char *name, num[4];
    int trapret = 0;
    int obreaks = breaks;
 
    /* if signal is being ignored or the trap function		      *
     * is NULL, then return					      *
     *								      *
     * Also return if errflag is set.  In fact, the code in the       *
     * function will test for this, but this way we keep status flags *
     * intact without working too hard.  Special cases (e.g. calling  *
     * a trap for SIGINT after the error flag was set) are handled    *
     * by the calling code.  (PWS 1995/06/08).			      */
    if ((*sigtr & ZSIG_IGNORED) || !sigfn || errflag)
        return;

    *sigtr |= ZSIG_IGNORED;

    lexsave();
    execsave();
    breaks = 0;
    if (*sigtr & ZSIG_FUNC) {
	PERMALLOC {
	    args = newlinklist();
	    name = (char *) zalloc(5 + strlen(sigs[sig]));
	    sprintf(name, "TRAP%s", sigs[sig]);
	    addlinknode(args, name);
	    sprintf(num, "%d", sig);
	    addlinknode(args, num);
	} LASTALLOC;
	trapreturn = -1;
	doshfunc(sigfn, args, 0, 1);
	freelinklist(args, (FreeFunc) NULL);
	zsfree(name);
    } else HEAPALLOC {
	execlist(dupstruct(sigfn), 1, 0);
    } LASTALLOC;
    if (trapreturn > 0)
	trapret = trapreturn;
    else if (errflag)
	trapret = 1;
    execrestore();
    lexrestore();

    if (trapret > 0) {
	breaks = loops;
	errflag = 1;
    } else {
	breaks += obreaks;
	if (breaks > loops)
	    breaks = loops;
    }

    if (*sigtr != ZSIG_IGNORED)
	*sigtr &= ~ZSIG_IGNORED;
}

/* Standard call to execute a trap for a given signal */

/**/
void
dotrap(int sig)
{
    dotrapargs(sig, sigtrapped+sig, sigfuncs[sig]);
}