/*      $OpenBSD: trap.c,v 1.33 2018/12/08 21:03:51 jca Exp $   */

/*
 * signal handling
 */

#include <ctype.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>

#include "sh.h"

Trap sigtraps[NSIG + 1];

static struct sigaction Sigact_ign, Sigact_trap;

void
inittraps(void)
{
        int     i;

        /* Populate sigtraps based on sys_signame and sys_siglist. */
        for (i = 0; i <= NSIG; i++) {
                sigtraps[i].signal = i;
                if (i == SIGERR_) {
                        sigtraps[i].name = "ERR";
                        sigtraps[i].mess = "Error handler";
                } else {
                        sigtraps[i].name = sys_signame[i];
                        sigtraps[i].mess = sys_siglist[i];
                }
        }
        sigtraps[SIGEXIT_].name = "EXIT";       /* our name for signal 0 */

        sigemptyset(&Sigact_ign.sa_mask);
        Sigact_ign.sa_flags = 0; /* interruptible */
        Sigact_ign.sa_handler = SIG_IGN;
        Sigact_trap = Sigact_ign;
        Sigact_trap.sa_handler = trapsig;

        sigtraps[SIGINT].flags |= TF_DFL_INTR | TF_TTY_INTR;
        sigtraps[SIGQUIT].flags |= TF_DFL_INTR | TF_TTY_INTR;
        sigtraps[SIGTERM].flags |= TF_DFL_INTR;/* not fatal for interactive */
        sigtraps[SIGHUP].flags |= TF_FATAL;
        sigtraps[SIGCHLD].flags |= TF_SHELL_USES;

        /* these are always caught so we can clean up any temporary files. */
        setsig(&sigtraps[SIGINT], trapsig, SS_RESTORE_ORIG);
        setsig(&sigtraps[SIGQUIT], trapsig, SS_RESTORE_ORIG);
        setsig(&sigtraps[SIGTERM], trapsig, SS_RESTORE_ORIG);
        setsig(&sigtraps[SIGHUP], trapsig, SS_RESTORE_ORIG);
}

static void alarm_catcher(int sig);

void
alarm_init(void)
{
        sigtraps[SIGALRM].flags |= TF_SHELL_USES;
        setsig(&sigtraps[SIGALRM], alarm_catcher,
                SS_RESTORE_ORIG|SS_FORCE|SS_SHTRAP);
}

static void
alarm_catcher(int sig)
{
        int errno_ = errno;

        if (ksh_tmout_state == TMOUT_READING) {
                int left = alarm(0);

                if (left == 0) {
                        ksh_tmout_state = TMOUT_LEAVING;
                        intrsig = 1;
                } else
                        alarm(left);
        }
        errno = errno_;
}

Trap *
gettrap(const char *name, int igncase)
{
        int i;
        Trap *p;

        if (digit(*name)) {
                int n;

                if (getn(name, &n) && 0 <= n && n < NSIG)
                        return &sigtraps[n];
                return NULL;
        }

        if (igncase && strncasecmp(name, "SIG", 3) == 0)
                name += 3;
        if (!igncase && strncmp(name, "SIG", 3) == 0)
                name += 3;

        for (p = sigtraps, i = NSIG+1; --i >= 0; p++)
                if (p->name) {
                        if (igncase && strcasecmp(p->name, name) == 0)
                                return p;
                        if (!igncase && strcmp(p->name, name) == 0)
                                return p;
                }
        return NULL;
}

/*
 * trap signal handler
 */
void
trapsig(int i)
{
        Trap *p = &sigtraps[i];
        int errno_ = errno;

        trap = p->set = 1;
        if (p->flags & TF_DFL_INTR)
                intrsig = 1;
        if ((p->flags & TF_FATAL) && !p->trap) {
                fatal_trap = 1;
                intrsig = 1;
        }
        if (p->shtrap)
                (*p->shtrap)(i);
        errno = errno_;
}

/* called when we want to allow the user to ^C out of something - won't
 * work if user has trapped SIGINT.
 */
void
intrcheck(void)
{
        if (intrsig)
                runtraps(TF_DFL_INTR|TF_FATAL);
}

/* called after EINTR to check if a signal with normally causes process
 * termination has been received.
 */
int
fatal_trap_check(void)
{
        int i;
        Trap *p;

        /* todo: should check if signal is fatal, not the TF_DFL_INTR flag */
        for (p = sigtraps, i = NSIG+1; --i >= 0; p++)
                if (p->set && (p->flags & (TF_DFL_INTR|TF_FATAL)))
                        /* return value is used as an exit code */
                        return 128 + p->signal;
        return 0;
}

/* Returns the signal number of any pending traps: ie, a signal which has
 * occurred for which a trap has been set or for which the TF_DFL_INTR flag
 * is set.
 */
int
trap_pending(void)
{
        int i;
        Trap *p;

        for (p = sigtraps, i = NSIG+1; --i >= 0; p++)
                if (p->set && ((p->trap && p->trap[0]) ||
                    ((p->flags & (TF_DFL_INTR|TF_FATAL)) && !p->trap)))
                        return p->signal;
        return 0;
}

/*
 * run any pending traps.  If intr is set, only run traps that
 * can interrupt commands.
 */
void
runtraps(int flag)
{
        int i;
        Trap *p;

        if (ksh_tmout_state == TMOUT_LEAVING) {
                ksh_tmout_state = TMOUT_EXECUTING;
                warningf(false, "timed out waiting for input");
                unwind(LEXIT);
        } else
                /* XXX: this means the alarm will have no effect if a trap
                 * is caught after the alarm() was started...not good.
                 */
                ksh_tmout_state = TMOUT_EXECUTING;
        if (!flag)
                trap = 0;
        if (flag & TF_DFL_INTR)
                intrsig = 0;
        if (flag & TF_FATAL)
                fatal_trap = 0;
        for (p = sigtraps, i = NSIG+1; --i >= 0; p++)
                if (p->set && (!flag ||
                    ((p->flags & flag) && p->trap == NULL)))
                        runtrap(p);
}

void
runtrap(Trap *p)
{
        int     i = p->signal;
        char    *trapstr = p->trap;
        int     oexstat;
        int     old_changed = 0;

        p->set = 0;
        if (trapstr == NULL) { /* SIG_DFL */
                if (p->flags & TF_FATAL) {
                        /* eg, SIGHUP */
                        exstat = 128 + i;
                        unwind(LLEAVE);
                }
                if (p->flags & TF_DFL_INTR) {
                        /* eg, SIGINT, SIGQUIT, SIGTERM, etc. */
                        exstat = 128 + i;
                        unwind(LINTR);
                }
                return;
        }
        if (trapstr[0] == '\0') /* SIG_IGN */
                return;
        if (i == SIGEXIT_ || i == SIGERR_) {    /* avoid recursion on these */
                old_changed = p->flags & TF_CHANGED;
                p->flags &= ~TF_CHANGED;
                p->trap = NULL;
        }
        oexstat = exstat;
        /* Note: trapstr is fully parsed before anything is executed, thus
         * no problem with afree(p->trap) in settrap() while still in use.
         */
        command(trapstr, current_lineno);
        exstat = oexstat;
        if (i == SIGEXIT_ || i == SIGERR_) {
                if (p->flags & TF_CHANGED)
                        /* don't clear TF_CHANGED */
                        afree(trapstr, APERM);
                else
                        p->trap = trapstr;
                p->flags |= old_changed;
        }
}

/* clear pending traps and reset user's trap handlers; used after fork(2) */
void
cleartraps(void)
{
        int i;
        Trap *p;

        trap = 0;
        intrsig = 0;
        fatal_trap = 0;
        for (i = NSIG+1, p = sigtraps; --i >= 0; p++) {
                p->set = 0;
                if ((p->flags & TF_USER_SET) && (p->trap && p->trap[0]))
                        settrap(p, NULL);
        }
}

/* restore signals just before an exec(2) */
void
restoresigs(void)
{
        int i;
        Trap *p;

        for (i = NSIG+1, p = sigtraps; --i >= 0; p++)
                if (p->flags & (TF_EXEC_IGN|TF_EXEC_DFL))
                        setsig(p, (p->flags & TF_EXEC_IGN) ? SIG_IGN : SIG_DFL,
                            SS_RESTORE_CURR|SS_FORCE);
}

void
settrap(Trap *p, char *s)
{
        sig_t f;

        afree(p->trap, APERM);
        p->trap = str_save(s, APERM); /* handles s == 0 */
        p->flags |= TF_CHANGED;
        f = !s ? SIG_DFL : s[0] ? trapsig : SIG_IGN;

        p->flags |= TF_USER_SET;
        if ((p->flags & (TF_DFL_INTR|TF_FATAL)) && f == SIG_DFL)
                f = trapsig;
        else if (p->flags & TF_SHELL_USES) {
                if (!(p->flags & TF_ORIG_IGN) || Flag(FTALKING)) {
                        /* do what user wants at exec time */
                        p->flags &= ~(TF_EXEC_IGN|TF_EXEC_DFL);
                        if (f == SIG_IGN)
                                p->flags |= TF_EXEC_IGN;
                        else
                                p->flags |= TF_EXEC_DFL;
                }

                /* assumes handler already set to what shell wants it
                 * (normally trapsig, but could be j_sigchld() or SIG_IGN)
                 */
                return;
        }

        /* todo: should we let user know signal is ignored? how? */
        setsig(p, f, SS_RESTORE_CURR|SS_USER);
}

/* Called by c_print() when writing to a co-process to ensure SIGPIPE won't
 * kill shell (unless user catches it and exits)
 */
int
block_pipe(void)
{
        int restore_dfl = 0;
        Trap *p = &sigtraps[SIGPIPE];

        if (!(p->flags & (TF_ORIG_IGN|TF_ORIG_DFL))) {
                setsig(p, SIG_IGN, SS_RESTORE_CURR);
                if (p->flags & TF_ORIG_DFL)
                        restore_dfl = 1;
        } else if (p->cursig == SIG_DFL) {
                setsig(p, SIG_IGN, SS_RESTORE_CURR);
                restore_dfl = 1; /* restore to SIG_DFL */
        }
        return restore_dfl;
}

/* Called by c_print() to undo whatever block_pipe() did */
void
restore_pipe(int restore_dfl)
{
        if (restore_dfl)
                setsig(&sigtraps[SIGPIPE], SIG_DFL, SS_RESTORE_CURR);
}

/* Set action for a signal.  Action may not be set if original
 * action was SIG_IGN, depending on the value of flags and
 * FTALKING.
 */
int
setsig(Trap *p, sig_t f, int flags)
{
        struct sigaction sigact;

        if (p->signal == SIGEXIT_ || p->signal == SIGERR_)
                return 1;

        /* First time setting this signal?  If so, get and note the current
         * setting.
         */
        if (!(p->flags & (TF_ORIG_IGN|TF_ORIG_DFL))) {
                sigaction(p->signal, &Sigact_ign, &sigact);
                p->flags |= sigact.sa_handler == SIG_IGN ?
                    TF_ORIG_IGN : TF_ORIG_DFL;
                p->cursig = SIG_IGN;
        }

        /* Generally, an ignored signal stays ignored, except if
         *      - the user of an interactive shell wants to change it
         *      - the shell wants for force a change
         */
        if ((p->flags & TF_ORIG_IGN) && !(flags & SS_FORCE) &&
            (!(flags & SS_USER) || !Flag(FTALKING)))
                return 0;

        setexecsig(p, flags & SS_RESTORE_MASK);

        /* This is here 'cause there should be a way of clearing shtraps, but
         * don't know if this is a sane way of doing it.  At the moment,
         * all users of shtrap are lifetime users (SIGCHLD, SIGALRM, SIGWINCH).
         */
        if (!(flags & SS_USER))
                p->shtrap = NULL;
        if (flags & SS_SHTRAP) {
                p->shtrap = f;
                f = trapsig;
        }

        if (p->cursig != f) {
                p->cursig = f;
                sigemptyset(&sigact.sa_mask);
                sigact.sa_flags = 0 /* interruptible */;
                sigact.sa_handler = f;
                sigaction(p->signal, &sigact, NULL);
        }

        return 1;
}

/* control what signal is set to before an exec() */
void
setexecsig(Trap *p, int restore)
{
        /* XXX debugging */
        if (!(p->flags & (TF_ORIG_IGN|TF_ORIG_DFL)))
                internal_errorf("%s: unset signal %d(%s)",
                    __func__, p->signal, p->name);

        /* restore original value for exec'd kids */
        p->flags &= ~(TF_EXEC_IGN|TF_EXEC_DFL);
        switch (restore & SS_RESTORE_MASK) {
        case SS_RESTORE_CURR: /* leave things as they currently are */
                break;
        case SS_RESTORE_ORIG:
                p->flags |= p->flags & TF_ORIG_IGN ? TF_EXEC_IGN : TF_EXEC_DFL;
                break;
        case SS_RESTORE_DFL:
                p->flags |= TF_EXEC_DFL;
                break;
        case SS_RESTORE_IGN:
                p->flags |= TF_EXEC_IGN;
                break;
        }
}