cmd/sh/fault.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 2009 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*  Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
/*    All Rights Reserved   */


/*
 * UNIX shell
 */

#include    "defs.h"
#include    <sys/procset.h>
#include    <siginfo.h>
#include    <ucontext.h>
#include    <errno.h>
#include    <string.h>

extern void hupforegnd(void);

/* previous signal handler for signal 0 */
static  void (*psig0_func)() = SIG_ERR;
static  char sigsegv_stack[SIGSTKSZ];

static void sigsegv(int sig, siginfo_t *sip, ucontext_t *uap);
static void fault();
static BOOL sleeping = 0;
static unsigned char *trapcom[MAXTRAP]; /* array of actions, one per signal */
static BOOL trapflg[MAXTRAP] =
{
    0,
    0,  /* hangup */
    0,  /* interrupt */
    0,  /* quit */
    0,  /* illegal instr */
    0,  /* trace trap */
    0,  /* IOT */
    0,  /* EMT */
    0,  /* float pt. exp */
    0,  /* kill */
    0,  /* bus error */
    0,  /* memory faults */
    0,  /* bad sys call */
    0,  /* bad pipe call */
    0,  /* alarm */
    0,  /* software termination */
    0,  /* unassigned */
    0,  /* unassigned */
    0,  /* death of child */
    0,  /* power fail */
    0,  /* window size change */
    0,  /* urgent IO condition */
    0,  /* pollable event occured */
    0,  /* stopped by signal */
    0,  /* stopped by user */
    0,  /* continued */
    0,  /* stopped by tty input */
    0,  /* stopped by tty output */
    0,  /* virtual timer expired */
    0,  /* profiling timer expired */
    0,  /* exceeded cpu limit */
    0,  /* exceeded file size limit */
    0,  /* process's lwps are blocked */
    0,  /* special signal used by thread library */
    0,  /* check point freeze */
    0,  /* check point thaw */
};

static void (*(
sigval[MAXTRAP]))() =
{
    0,
    done,   /* hangup */
    fault,  /* interrupt */
    fault,  /* quit */
    done,   /* illegal instr */
    done,   /* trace trap */
    done,   /* IOT */
    done,   /* EMT */
    done,   /* floating pt. exp */
    0,  /* kill */
    done,   /* bus error */
    sigsegv,    /* memory faults */
    done,   /* bad sys call */
    done,   /* bad pipe call */
    done,   /* alarm */
    fault,  /* software termination */
    done,   /* unassigned */
    done,   /* unassigned */
    0,  /* death of child */
    done,   /* power fail */
    0,  /* window size change */
    done,   /* urgent IO condition */
    done,   /* pollable event occured */
    0,  /* uncatchable stop */
    0,  /* foreground stop */
    0,  /* stopped process continued */
    0,  /* background tty read */
    0,  /* background tty write */
    done,   /* virtual timer expired */
    done,   /* profiling timer expired */
    done,   /* exceeded cpu limit */
    done,   /* exceeded file size limit */
    0,  /* process's lwps are blocked */
    0,  /* special signal used by thread library */
    0,  /* check point freeze */
    0,  /* check point thaw */
};

static int
ignoring(int i)
{
    struct sigaction act;
    if (trapflg[i] & SIGIGN)
        return (1);
    sigaction(i, 0, &act);
    if (act.sa_handler == SIG_IGN) {
        trapflg[i] |= SIGIGN;
        return (1);
    }
    return (0);
}

static void
clrsig(i)
int i;
{
    if (trapcom[i] != 0) {
        free(trapcom[i]);
        trapcom[i] = 0;
    }


    if (trapflg[i] & SIGMOD) {
        /*
         * If the signal has been set to SIGIGN and we are now
         * clearing the disposition of the signal (restoring it
         * back to its default value) then we need to clear this
         * bit as well
         *
         */
        if (trapflg[i] & SIGIGN)
            trapflg[i] &= ~SIGIGN;

        trapflg[i] &= ~SIGMOD;
        handle(i, sigval[i]);
    }
}

void
done(sig)
{
    unsigned char   *t;
    int savxit;

    if (t = trapcom[0]) {
        trapcom[0] = 0;
        /* Save exit value so trap handler will not change its val */
        savxit = exitval;
        execexp(t, 0);
        exitval = savxit;       /* Restore exit value */
        free(t);
    }
    else
        chktrap();

    rmtemp(0);
    rmfunctmp();

#ifdef ACCT
    doacct();
#endif
    if (flags & subsh) {
        /* in a subshell, need to wait on foreground job */
        collect_fg_job();
    }

    (void) endjobs(0);
    if (sig) {
        sigset_t set;

        /*
         * If the signal is SIGHUP, then it should be delivered
         * to the process group leader of the foreground job.
         */
        if (sig == SIGHUP)
            hupforegnd();

        sigemptyset(&set);
        sigaddset(&set, sig);
        sigprocmask(SIG_UNBLOCK, &set, 0);
        handle(sig, SIG_DFL);
        kill(mypid, sig);
    }
    exit(exitval);
}

static void
fault(int sig)
{
    int flag;

    switch (sig) {
        case SIGALRM:
            if (sleeping)
                return;
            break;
    }

    if (trapcom[sig])
        flag = TRAPSET;
    else if (flags & subsh)
        done(sig);
    else
        flag = SIGSET;

    trapnote |= flag;
    trapflg[sig] |= flag;
}

int
handle(sig, func)
    int sig;
    void (*func)();
{
    int ret;
    struct sigaction act, oact;

    if (func == SIG_IGN && (trapflg[sig] & SIGIGN))
        return (0);

    /*
     * Ensure that sigaction is only called with valid signal numbers,
     * we can get random values back for oact.sa_handler if the signal
     * number is invalid
     *
     */
    if (sig > MINTRAP && sig < MAXTRAP) {
        sigemptyset(&act.sa_mask);
        act.sa_flags = (sig == SIGSEGV) ? (SA_ONSTACK | SA_SIGINFO) : 0;
        act.sa_handler = func;
        sigaction(sig, &act, &oact);
    }

    if (func == SIG_IGN)
        trapflg[sig] |= SIGIGN;

    /*
     * Special case for signal zero, we can not obtain the previos
     * action by calling sigaction, instead we save it in the variable
     * psig0_func, so we can test it next time through this code
     *
     */
    if (sig == 0) {
        ret = (psig0_func != func);
        psig0_func = func;
    } else {
        ret = (func != oact.sa_handler);
    }

    return (ret);
}

void
stdsigs()
{
    int i;
    stack_t ss;
    int rtmin = (int)SIGRTMIN;
    int rtmax = (int)SIGRTMAX;

    ss.ss_size = SIGSTKSZ;
    ss.ss_sp = sigsegv_stack;
    ss.ss_flags = 0;
    if (sigaltstack(&ss, NULL) == -1) {
        error("sigaltstack(2) failed");
    }

    for (i = 1; i < MAXTRAP; i++) {
        if (i == rtmin) {
            i = rtmax;
            continue;
        }
        if (sigval[i] == 0)
            continue;
        if (i != SIGSEGV && ignoring(i))
            continue;
        handle(i, sigval[i]);
    }

    /*
     * handle all the realtime signals
     *
     */
    for (i = rtmin; i <= rtmax; i++) {
        handle(i, done);
    }
}

void
oldsigs()
{
    int i;
    unsigned char   *t;

    i = MAXTRAP;
    while (i--) {
        t = trapcom[i];
        if (t == 0 || *t)
            clrsig(i);
        trapflg[i] = 0;
    }
    trapnote = 0;
}

/*
 * check for traps
 */

void
chktrap()
{
    int i = MAXTRAP;
    unsigned char   *t;

    trapnote &= ~TRAPSET;
    while (--i) {
        if (trapflg[i] & TRAPSET) {
            trapflg[i] &= ~TRAPSET;
            if (t = trapcom[i]) {
                int savxit = exitval;

                execexp(t, 0);
                exitval = savxit;
                exitset();
            }
        }
    }
}

void
systrap(int argc, char **argv)
{
    int sig;

    if (argc == 1) {
        /*
         * print out the current action associated with each signal
         * handled by the shell
         *
         */
        for (sig = 0; sig < MAXTRAP; sig++) {
            if (trapcom[sig]) {
                prn_buff(sig);
                prs_buff(colon);
                prs_buff(trapcom[sig]);
                prc_buff(NL);
            }
        }
    } else {
        /*
         * set the action for the list of signals
         *
         */
        char *cmd = *argv, *a1 = *(argv+1);
        BOOL noa1;
        noa1 = (str2sig(a1, &sig) == 0);
        if (noa1 == 0)
            ++argv;
        while (*++argv) {
            if (str2sig(*argv, &sig) < 0 ||
                sig >= MAXTRAP || sig < MINTRAP ||
                sig == SIGSEGV) {
                failure(cmd, badtrap);
            } else if (noa1) {
                /*
                 * no action specifed so reset the siganl
                 * to its default disposition
                 *
                 */
                clrsig(sig);
            } else if (*a1) {
                /*
                 * set the action associated with the signal
                 * to a1
                 *
                 */
                if (trapflg[sig] & SIGMOD || sig == 0 ||
                    !ignoring(sig)) {
                    handle(sig, fault);
                    trapflg[sig] |= SIGMOD;
                    replace(&trapcom[sig], a1);
                }
            } else if (handle(sig, SIG_IGN)) {
                /*
                 * set the action associated with the signal
                 * to SIG_IGN
                 *
                 */
                trapflg[sig] |= SIGMOD;
                replace(&trapcom[sig], a1);
            }
        }
    }
}

void
sh_sleep(unsigned int ticks)
{
    sigset_t set, oset;
    struct sigaction act, oact;


    /*
     * add SIGALRM to mask
     */

    sigemptyset(&set);
    sigaddset(&set, SIGALRM);
    sigprocmask(SIG_BLOCK, &set, &oset);

    /*
     * catch SIGALRM
     */

    sigemptyset(&act.sa_mask);
    act.sa_flags = 0;
    act.sa_handler = fault;
    sigaction(SIGALRM, &act, &oact);

    /*
     * start alarm and wait for signal
     */

    alarm(ticks);
    sleeping = 1;
    sigsuspend(&oset);
    sleeping = 0;

    /*
     * reset alarm, catcher and mask
     */

    alarm(0);
    sigaction(SIGALRM, &oact, NULL);
    sigprocmask(SIG_SETMASK, &oset, 0);

}

void
sigsegv(int sig, siginfo_t *sip, ucontext_t *uap)
{
    if (sip == (siginfo_t *)NULL) {
        /*
         * This should never happen, but if it does this is all we
         * can do. It can only happen if sigaction(2) for SIGSEGV
         * has been called without SA_SIGINFO being set.
         *
         */

        exit(ERROR);
    } else {
        if (sip->si_code <= 0) {
            /*
             * If we are here then SIGSEGV must have been sent to
             * us from a user process NOT as a result of an
             * internal error within the shell eg
             * kill -SEGV $$
             * will bring us here. So do the normal thing.
             *
             */
            fault(sig);
        } else {
            /*
             * If we are here then there must have been an internal
             * error within the shell to generate SIGSEGV eg
             * the stack is full and we cannot call any more
             * functions (Remeber this signal handler is running
             * on an alternate stack). So we just exit cleanly
             * with an error status (no core file).
             */
            exit(ERROR);
        }
    }
}