/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1991, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Kenneth Almquist.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <signal.h>
#include <unistd.h>
#include <stdlib.h>

#include "shell.h"
#include "main.h"
#include "nodes.h"      /* for other headers */
#include "eval.h"
#include "jobs.h"
#include "show.h"
#include "options.h"
#include "syntax.h"
#include "output.h"
#include "memalloc.h"
#include "error.h"
#include "trap.h"
#include "mystring.h"
#include "builtins.h"
#ifndef NO_HISTORY
#include "myhistedit.h"
#endif


/*
 * Sigmode records the current value of the signal handlers for the various
 * modes.  A value of zero means that the current handler is not known.
 * S_HARD_IGN indicates that the signal was ignored on entry to the shell,
 */

#define S_DFL 1                 /* default signal handling (SIG_DFL) */
#define S_CATCH 2               /* signal is caught */
#define S_IGN 3                 /* signal is ignored (SIG_IGN) */
#define S_HARD_IGN 4            /* signal is ignored permanently */
#define S_RESET 5               /* temporary - to reset a hard ignored sig */


static char sigmode[NSIG];      /* current value of signal */
volatile sig_atomic_t pendingsig;       /* indicates some signal received */
volatile sig_atomic_t pendingsig_waitcmd;       /* indicates wait builtin should be interrupted */
static int in_dotrap;                   /* do we execute in a trap handler? */
static char *volatile trap[NSIG];       /* trap handler commands */
static volatile sig_atomic_t gotsig[NSIG];
                                /* indicates specified signal received */
static int ignore_sigchld;      /* Used while handling SIGCHLD traps. */
static int last_trapsig;

static int exiting;             /* exitshell() has been called */
static int exiting_exitstatus;  /* value passed to exitshell() */

static int getsigaction(int, sig_t *);


/*
 * Map a string to a signal number.
 *
 * Note: the signal number may exceed NSIG.
 */
static int
sigstring_to_signum(char *sig)
{

        if (is_number(sig)) {
                int signo;

                signo = atoi(sig);
                return ((signo >= 0 && signo < NSIG) ? signo : (-1));
        } else if (strcasecmp(sig, "EXIT") == 0) {
                return (0);
        } else {
                int n;

                if (strncasecmp(sig, "SIG", 3) == 0)
                        sig += 3;
                for (n = 1; n < sys_nsig; n++)
                        if (sys_signame[n] &&
                            strcasecmp(sys_signame[n], sig) == 0)
                                return (n);
        }
        return (-1);
}


/*
 * Print a list of valid signal names.
 */
static void
printsignals(void)
{
        int n, outlen;

        outlen = 0;
        for (n = 1; n < sys_nsig; n++) {
                if (sys_signame[n]) {
                        out1fmt("%s", sys_signame[n]);
                        outlen += strlen(sys_signame[n]);
                } else {
                        out1fmt("%d", n);
                        outlen += 3;    /* good enough */
                }
                ++outlen;
                if (outlen > 71 || n == sys_nsig - 1) {
                        out1str("\n");
                        outlen = 0;
                } else {
                        out1c(' ');
                }
        }
}


/*
 * The trap builtin.
 */
int
trapcmd(int argc __unused, char **argv)
{
        char *action;
        int signo;
        int errors = 0;
        int i;

        while ((i = nextopt("l")) != '\0') {
                switch (i) {
                case 'l':
                        printsignals();
                        return (0);
                }
        }
        argv = argptr;

        if (*argv == NULL) {
                for (signo = 0 ; signo < sys_nsig ; signo++) {
                        if (signo < NSIG && trap[signo] != NULL) {
                                out1str("trap -- ");
                                out1qstr(trap[signo]);
                                if (signo == 0) {
                                        out1str(" EXIT\n");
                                } else if (sys_signame[signo]) {
                                        out1fmt(" %s\n", sys_signame[signo]);
                                } else {
                                        out1fmt(" %d\n", signo);
                                }
                        }
                }
                return 0;
        }
        action = NULL;
        if (*argv && !is_number(*argv)) {
                if (strcmp(*argv, "-") == 0)
                        argv++;
                else {
                        action = *argv;
                        argv++;
                }
        }
        for (; *argv; argv++) {
                if ((signo = sigstring_to_signum(*argv)) == -1) {
                        warning("bad signal %s", *argv);
                        errors = 1;
                        continue;
                }
                INTOFF;
                if (action)
                        action = savestr(action);
                if (trap[signo])
                        ckfree(trap[signo]);
                trap[signo] = action;
                if (signo != 0)
                        setsignal(signo);
                INTON;
        }
        return errors;
}


/*
 * Clear traps on a fork.
 */
void
clear_traps(void)
{
        char *volatile *tp;

        for (tp = trap ; tp <= &trap[NSIG - 1] ; tp++) {
                if (*tp && **tp) {      /* trap not NULL or SIG_IGN */
                        INTOFF;
                        ckfree(*tp);
                        *tp = NULL;
                        if (tp != &trap[0])
                                setsignal(tp - trap);
                        INTON;
                }
        }
}


/*
 * Check if we have any traps enabled.
 */
int
have_traps(void)
{
        char *volatile *tp;

        for (tp = trap ; tp <= &trap[NSIG - 1] ; tp++) {
                if (*tp && **tp)        /* trap not NULL or SIG_IGN */
                        return 1;
        }
        return 0;
}

/*
 * Set the signal handler for the specified signal.  The routine figures
 * out what it should be set to.
 */
void
setsignal(int signo)
{
        int action;
        sig_t sigact = SIG_DFL;
        struct sigaction sa;
        char *t;

        if ((t = trap[signo]) == NULL)
                action = S_DFL;
        else if (*t != '\0')
                action = S_CATCH;
        else
                action = S_IGN;
        if (action == S_DFL) {
                switch (signo) {
                case SIGINT:
                        action = S_CATCH;
                        break;
                case SIGQUIT:
#ifdef DEBUG
                        if (debug)
                                break;
#endif
                        action = S_CATCH;
                        break;
                case SIGTERM:
                        if (rootshell && iflag)
                                action = S_IGN;
                        break;
#if JOBS
                case SIGTSTP:
                case SIGTTOU:
                        if (rootshell && mflag)
                                action = S_IGN;
                        break;
#endif
                }
        }

        t = &sigmode[signo];
        if (*t == 0) {
                /*
                 * current setting unknown
                 */
                if (!getsigaction(signo, &sigact)) {
                        /*
                         * Pretend it worked; maybe we should give a warning
                         * here, but other shells don't. We don't alter
                         * sigmode, so that we retry every time.
                         */
                        return;
                }
                if (sigact == SIG_IGN) {
                        if (mflag && (signo == SIGTSTP ||
                             signo == SIGTTIN || signo == SIGTTOU)) {
                                *t = S_IGN;     /* don't hard ignore these */
                        } else
                                *t = S_HARD_IGN;
                } else {
                        *t = S_RESET;   /* force to be set */
                }
        }
        if (*t == S_HARD_IGN || *t == action)
                return;
        switch (action) {
                case S_DFL:     sigact = SIG_DFL;       break;
                case S_CATCH:   sigact = onsig;         break;
                case S_IGN:     sigact = SIG_IGN;       break;
        }
        *t = action;
        sa.sa_handler = sigact;
        sa.sa_flags = 0;
        sigemptyset(&sa.sa_mask);
        sigaction(signo, &sa, NULL);
}


/*
 * Return the current setting for sig w/o changing it.
 */
static int
getsigaction(int signo, sig_t *sigact)
{
        struct sigaction sa;

        if (sigaction(signo, (struct sigaction *)0, &sa) == -1)
                return 0;
        *sigact = (sig_t) sa.sa_handler;
        return 1;
}


/*
 * Ignore a signal.
 */
void
ignoresig(int signo)
{

        if (sigmode[signo] == 0)
                setsignal(signo);
        if (sigmode[signo] != S_IGN && sigmode[signo] != S_HARD_IGN) {
                signal(signo, SIG_IGN);
                sigmode[signo] = S_IGN;
        }
}


int
issigchldtrapped(void)
{

        return (trap[SIGCHLD] != NULL && *trap[SIGCHLD] != '\0');
}


/*
 * Signal handler.
 */
void
onsig(int signo)
{

        if (signo == SIGINT && trap[SIGINT] == NULL) {
                if (suppressint)
                        SET_PENDING_INT;
                else
                        onint();
                return;
        }

        /* If we are currently in a wait builtin, prepare to break it */
        if (signo == SIGINT || signo == SIGQUIT)
                pendingsig_waitcmd = signo;

        if (trap[signo] != NULL && trap[signo][0] != '\0' &&
            (signo != SIGCHLD || !ignore_sigchld)) {
                gotsig[signo] = 1;
                pendingsig = signo;
                pendingsig_waitcmd = signo;
        }
}


/*
 * Called to execute a trap.  Perhaps we should avoid entering new trap
 * handlers while we are executing a trap handler.
 */
void
dotrap(void)
{
        struct stackmark smark;
        int i;
        int savestatus, prev_evalskip, prev_skipcount;

        in_dotrap++;
        for (;;) {
                pendingsig = 0;
                pendingsig_waitcmd = 0;
                for (i = 1; i < NSIG; i++) {
                        if (gotsig[i]) {
                                gotsig[i] = 0;
                                if (trap[i]) {
                                        /*
                                         * Ignore SIGCHLD to avoid infinite
                                         * recursion if the trap action does
                                         * a fork.
                                         */
                                        if (i == SIGCHLD)
                                                ignore_sigchld++;

                                        /*
                                         * Backup current evalskip
                                         * state and reset it before
                                         * executing a trap, so that the
                                         * trap is not disturbed by an
                                         * ongoing break/continue/return
                                         * statement.
                                         */
                                        prev_evalskip  = evalskip;
                                        prev_skipcount = skipcount;
                                        evalskip = 0;

                                        last_trapsig = i;
                                        savestatus = exitstatus;
                                        setstackmark(&smark);
                                        evalstring(stsavestr(trap[i]), 0);
                                        popstackmark(&smark);

                                        /*
                                         * If such a command was not
                                         * already in progress, allow a
                                         * break/continue/return in the
                                         * trap action to have an effect
                                         * outside of it.
                                         */
                                        if (evalskip == 0 ||
                                            prev_evalskip != 0) {
                                                evalskip  = prev_evalskip;
                                                skipcount = prev_skipcount;
                                                exitstatus = savestatus;
                                        }

                                        if (i == SIGCHLD)
                                                ignore_sigchld--;
                                }
                                break;
                        }
                }
                if (i >= NSIG)
                        break;
        }
        in_dotrap--;
}


void
trap_init(void)
{
        setsignal(SIGINT);
        setsignal(SIGQUIT);
}


/*
 * Controls whether the shell is interactive or not based on iflag.
 */
void
setinteractive(void)
{
        setsignal(SIGTERM);
}


/*
 * Called to exit the shell.
 */
void
exitshell(int status)
{
        TRACE(("exitshell(%d) pid=%d\n", status, getpid()));
        exiting = 1;
        exiting_exitstatus = status;
        exitshell_savedstatus();
}

void
exitshell_savedstatus(void)
{
        struct jmploc loc1, loc2;
        char *p;
        int sig = 0;
        sigset_t sigs;

        if (!exiting) {
                if (in_dotrap && last_trapsig) {
                        sig = last_trapsig;
                        exiting_exitstatus = sig + 128;
                } else
                        exiting_exitstatus = oexitstatus;
        }
        exitstatus = oexitstatus = exiting_exitstatus;
        if (!setjmp(loc1.loc)) {
                handler = &loc1;
                if ((p = trap[0]) != NULL && *p != '\0') {
                        /*
                         * Reset evalskip, or the trap on EXIT could be
                         * interrupted if the last command was a "return".
                         */
                        evalskip = 0;
                        trap[0] = NULL;
                        FORCEINTON;
                        evalstring(p, 0);
                }
        }
        if (!setjmp(loc2.loc)) {
                handler = &loc2;                /* probably unnecessary */
                FORCEINTON;
                flushall();
#if JOBS
                setjobctl(0);
#endif
#ifndef NO_HISTORY
                histsave();
#endif
        }
        if (sig != 0 && sig != SIGSTOP && sig != SIGTSTP && sig != SIGTTIN &&
            sig != SIGTTOU) {
                signal(sig, SIG_DFL);
                sigemptyset(&sigs);
                sigaddset(&sigs, sig);
                sigprocmask(SIG_UNBLOCK, &sigs, NULL);
                kill(getpid(), sig);
                /* If the default action is to ignore, fall back to _exit(). */
        }
        _exit(exiting_exitstatus);
}