/* $NetBSD: trap.c,v 1.56 2021/11/10 15:26:34 kre Exp $ */
/*-
* 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 <sys/cdefs.h>
#ifndef lint
#if 0
static char sccsid[] = "@(#)trap.c 8.5 (Berkeley) 6/5/95";
#else
__RCSID("$NetBSD: trap.c,v 1.56 2021/11/10 15:26:34 kre Exp $");
#endif
#endif /* not lint */
#include <signal.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <limits.h>
#include <termios.h>
#undef CEOF /* from <termios.h> but concflicts with sh use */
#include <sys/ioctl.h>
#include <sys/resource.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 "builtins.h"
#include "syntax.h"
#include "output.h"
#include "memalloc.h"
#include "error.h"
#include "trap.h"
#include "mystring.h"
#include "var.h"
/*
* 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 permenantly */
#define S_RESET 5 /* temporary - to reset a hard ignored sig */
MKINIT char sigmode[NSIG]; /* current value of signal */
static volatile sig_atomic_t gotsig[NSIG];/* indicates specified signal received */
volatile sig_atomic_t pendingsigs; /* indicates some signal received */
int traps_invalid; /* in a subshell, but trap[] not yet cleared */
static char * volatile trap[NSIG]; /* trap handler commands */
static int in_dotrap;
static int last_trapsig;
static int exiting; /* exitshell() has been done */
static int exiting_status; /* the status to use for exit() */
static int getsigaction(int, sig_t *);
STATIC const char *trap_signame(int);
void printsignals(struct output *, int);
/*
* return the signal number described by `p' (as a number or a name)
* or -1 if it isn't one
*/
static int
signame_to_signum(const char *p)
{
int i;
if (is_number(p))
return number(p);
if (strcasecmp(p, "exit") == 0 )
return 0;
i = signalnumber(p);
if (i == 0)
i = -1;
return i;
}
/*
* return the name of a signal used by the "trap" command
*/
STATIC const char *
trap_signame(int signo)
{
static char nbuf[12];
const char *p;
if (signo == 0)
return "EXIT";
p = signalname(signo);
if (p != NULL)
return p;
(void)snprintf(nbuf, sizeof nbuf, "%d", signo);
return nbuf;
}
#ifdef SMALL
/*
* Print a list of valid signal names
*/
void
printsignals(struct output *out, int len)
{
int n;
if (len != 0)
outc(' ', out);
for (n = 1; n < NSIG; n++) {
outfmt(out, "%s", trap_signame(n));
if ((n == NSIG/2) || n == (NSIG - 1))
outstr("\n", out);
else
outc(' ', out);
}
}
#else /* !SMALL */
/*
* Print the names of all the signals (neatly) to fp
* "len" gives the number of chars already printed to
* the current output line (in kill.c, always 0)
*/
void
printsignals(struct output *out, int len)
{
int sig;
int nl, pad;
const char *name;
int termwidth = 80;
if ((name = bltinlookup("COLUMNS", 1)) != NULL)
termwidth = (int)strtol(name, NULL, 10);
else if (isatty(1)) {
struct winsize win;
if (ioctl(1, TIOCGWINSZ, &win) == 0 && win.ws_col > 0)
termwidth = win.ws_col;
}
if (posix)
pad = 1;
else
pad = (len | 7) + 1 - len;
for (sig = 0; (sig = signalnext(sig)) != 0; ) {
name = signalname(sig);
if (name == NULL)
continue;
nl = strlen(name);
if (len > 0 && nl + len + pad >= termwidth) {
outc('\n', out);
len = 0;
pad = 0;
} else if (pad > 0 && len != 0)
outfmt(out, "%*s", pad, "");
else
pad = 0;
len += nl + pad;
if (!posix)
pad = (nl | 7) + 1 - nl;
else
pad = 1;
outstr(name, out);
}
if (len != 0)
outc('\n', out);
}
#endif /* SMALL */
/*
* The trap builtin.
*/
int
trapcmd(int argc, char **argv)
{
char *action;
char **ap;
int signo;
int errs = 0;
int printonly = 0;
ap = argv + 1;
CTRACE(DBG_TRAP, ("trapcmd: "));
if (argc == 3 && strcmp(ap[1], "--") == 0)
argc--;
if (argc == 2 && strcmp(*ap, "-l") == 0) {
CTRACE(DBG_TRAP, ("-l\n"));
out1str("EXIT");
printsignals(out1, 4);
return 0;
}
if (argc == 2 && strcmp(*ap, "-") == 0) {
CTRACE(DBG_TRAP, ("-\n"));
for (signo = 0; signo < NSIG; signo++) {
if (trap[signo] == NULL)
continue;
INTOFF;
ckfree(trap[signo]);
trap[signo] = NULL;
if (signo != 0)
setsignal(signo, 0);
INTON;
}
traps_invalid = 0;
return 0;
}
if (argc >= 2 && (strcmp(*ap, "-p") == 0 || strcmp(*ap, "-P") == 0)) {
CTRACE(DBG_TRAP, ("%s ", *ap));
printonly = 1 + (ap[0][1] == 'p');
ap++;
argc--;
}
if (argc > 1 && strcmp(*ap, "--") == 0) {
argc--;
ap++;
}
if (printonly == 1 && argc < 2)
goto usage;
if (argc <= 1) {
int count;
CTRACE(DBG_TRAP, ("*all*\n"));
if (printonly) {
for (count = 0, signo = 0 ; signo < NSIG ; signo++) {
if (signo == SIGKILL || signo == SIGSTOP)
continue;
if (trap[signo] == NULL) {
if (count == 0)
out1str("trap -- -");
out1fmt(" %s", trap_signame(signo));
/* oh! unlucky 13 */
if (++count >= 13) {
out1str("\n");
count = 0;
}
}
}
if (count)
out1str("\n");
}
/*
* We don't need do deal with SIGSTOP or SIGKILL as a
* special case anywhere here, as they cannot be
* ignored or caught - the only possibility is default
*/
for (count = 0, signo = 0 ; signo < NSIG ; signo++)
if (trap[signo] != NULL && trap[signo][0] == '\0') {
if (count == 0)
out1str("trap -- ''");
out1fmt(" %s", trap_signame(signo));
/*
* the prefix is 10 bytes, with 4 byte
* signal names (common) we have room in
* the 70 bytes left on a normal line for
* 70/(4+1) signals, that's 14, but to
* allow for the occasional longer sig name
* we output one less...
*/
if (++count >= 13) {
out1str("\n");
count = 0;
}
}
if (count)
out1str("\n");
for (signo = 0 ; signo < NSIG ; signo++)
if (trap[signo] != NULL && trap[signo][0] != '\0') {
out1str("trap -- ");
print_quoted(trap[signo]);
out1fmt(" %s\n", trap_signame(signo));
}
return 0;
}
CTRACE(DBG_TRAP, ("\n"));
action = NULL;
if (!printonly && traps_invalid)
free_traps();
if (!printonly && !is_number(*ap)) {
if ((*ap)[0] == '-' && (*ap)[1] == '\0')
ap++; /* reset to default */
else
action = *ap++; /* can be '' for "ignore" */
argc--;
}
if (argc < 2) { /* there must be at least 1 condition */
usage:
out2str("Usage: trap [-l]\n"
" trap -p [condition ...]\n"
" trap -P condition ...\n"
" trap action condition ...\n"
" trap N condition ...\n");
return 2;
}
while (*ap) {
signo = signame_to_signum(*ap);
if (signo < 0 || signo >= NSIG) {
/* This is not a fatal error, so sayeth posix */
outfmt(out2, "trap: '%s' bad condition\n", *ap);
errs = 1;
ap++;
continue;
}
ap++;
if (printonly) {
/*
* we allow SIGSTOP and SIGKILL to be obtained
* (action will always be "-") here, if someone
* really wants to get that particular output
*/
if (printonly == 1) {
if (trap[signo] != NULL)
out1fmt("%s\n", trap[signo]);
} else {
out1str("trap -- ");
if (trap[signo] == NULL)
out1str("-");
else
print_quoted(trap[signo]);
out1fmt(" %s\n", trap_signame(signo));
}
continue;
}
if ((signo == SIGKILL || signo == SIGSTOP) && action != NULL) {
#ifndef SMALL
/*
* Don't bother with the error message in a SMALL shell
* just ignore req and return error status silently
* (POSIX says this is an "undefined" operation so
* whatever we do is OK!)
*
* When we do generate an error, make it attempt match
* the user's operand, as best we can reasonably.
*/
outfmt(out2, "trap: '%s%s' cannot be %s\n",
(!is_alpha(ap[-1][0]) ||
strncasecmp(ap[-1], "sig", 3) == 0) ? "" :
is_upper(ap[-1][0]) ? "SIG" : "sig",
ap[-1], *action ? "caught" : "ignored");
#endif
errs = 1;
continue;
}
INTOFF;
if (action)
action = savestr(action);
VTRACE(DBG_TRAP, ("trap for %d from %s%s%s to %s%s%s\n", signo,
trap[signo] ? "'" : "", trap[signo] ? trap[signo] : "-",
trap[signo] ? "'" : "", action ? "'" : "",
action ? action : "-", action ? "'" : ""));
if (trap[signo])
ckfree(trap[signo]);
trap[signo] = action;
if (signo != 0)
setsignal(signo, 0);
INTON;
}
return errs;
}
/*
* Clear traps on a fork or vfork.
* Takes one arg vfork, to tell it to not be destructive of
* the parents variables.
*/
void
clear_traps(int vforked)
{
char * volatile *tp;
VTRACE(DBG_TRAP, ("clear_traps(%d)\n", vforked));
if (!vforked)
traps_invalid = 1;
for (tp = &trap[1] ; tp < &trap[NSIG] ; tp++) {
if (*tp && **tp) { /* trap not NULL or SIG_IGN */
INTOFF;
setsignal(tp - trap, vforked == 1);
INTON;
}
}
if (vforked == 2)
free_traps();
}
void
free_traps(void)
{
char * volatile *tp;
VTRACE(DBG_TRAP, ("free_traps%s\n", traps_invalid ? "(invalid)" : ""));
INTOFF;
for (tp = trap ; tp < &trap[NSIG] ; tp++)
if (*tp && **tp) {
ckfree(*tp);
*tp = NULL;
}
traps_invalid = 0;
INTON;
}
/*
* See if there are any defined traps
*/
int
have_traps(void)
{
char * volatile *tp;
if (traps_invalid)
return 0;
for (tp = trap ; tp < &trap[NSIG] ; 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 vforked)
{
int action;
sig_t sigact = SIG_DFL, sig;
char *t, tsig;
if (traps_invalid || (t = trap[signo]) == NULL)
action = S_DFL;
else if (*t != '\0')
action = S_CATCH;
else
action = S_IGN;
VTRACE(DBG_TRAP, ("setsignal(%d%s) -> %d", signo,
vforked ? ", VF" : "", action));
if (rootshell && !vforked && action == S_DFL) {
switch (signo) {
case SIGINT:
if (iflag || minusc || sflag == 0)
action = S_CATCH;
break;
case SIGQUIT:
#ifdef DEBUG
if (debug)
break;
#endif
/* FALLTHROUGH */
case SIGTERM:
if (rootshell && iflag)
action = S_IGN;
break;
#if JOBS
case SIGTSTP:
case SIGTTOU:
if (rootshell && mflag)
action = S_IGN;
break;
#endif
}
}
/*
* Never let users futz with SIGCHLD
* instead we will give them pseudo SIGCHLD's
* when background jobs complete.
*/
if (signo == SIGCHLD)
action = S_DFL;
VTRACE(DBG_TRAP, (" -> %d", action));
t = &sigmode[signo];
tsig = *t;
if (tsig == 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.
*/
VTRACE(DBG_TRAP, (" getsigaction (%d)\n", errno));
return;
}
VTRACE(DBG_TRAP, (" [%s]%s%s", sigact==SIG_IGN ? "IGN" :
sigact==SIG_DFL ? "DFL" : "caught",
iflag ? "i" : "", mflag ? "m" : ""));
if (sigact == SIG_IGN) {
/*
* POSIX 3.14.13 states that non-interactive shells
* should ignore trap commands for signals that were
* ignored upon entry, and leaves the behavior
* unspecified for interactive shells. On interactive
* shells, or if job control is on, and we have a job
* control related signal, we allow the trap to work.
*
* This change allows us to be POSIX compliant, and
* at the same time override the default behavior if
* we need to by setting the interactive flag.
*/
if ((mflag && (signo == SIGTSTP ||
signo == SIGTTIN || signo == SIGTTOU)) || iflag) {
tsig = S_IGN;
} else
tsig = S_HARD_IGN;
} else {
tsig = S_RESET; /* force to be set */
}
}
VTRACE(DBG_TRAP, (" tsig=%d\n", tsig));
if (tsig == S_HARD_IGN || tsig == action)
return;
switch (action) {
case S_DFL: sigact = SIG_DFL; break;
case S_CATCH: sigact = onsig; break;
case S_IGN: sigact = SIG_IGN; break;
}
sig = signal(signo, sigact);
if (sig != SIG_ERR) {
sigset_t ss;
if (!vforked)
*t = action;
if (action == S_CATCH)
(void)siginterrupt(signo, 1);
/*
* If our parent accidentally blocked signals for
* us make sure we unblock them
*/
(void)sigemptyset(&ss);
(void)sigaddset(&ss, signo);
(void)sigprocmask(SIG_UNBLOCK, &ss, NULL);
}
return;
}
/*
* 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, int vforked)
{
if (sigmode[signo] == 0)
setsignal(signo, vforked);
VTRACE(DBG_TRAP, ("ignoresig(%d%s)\n", signo, vforked ? ", VF" : ""));
if (sigmode[signo] != S_IGN && sigmode[signo] != S_HARD_IGN) {
signal(signo, SIG_IGN);
if (!vforked)
sigmode[signo] = S_IGN;
}
}
char *
child_trap(void)
{
char * p;
p = trap[SIGCHLD];
if (traps_invalid || (p != NULL && *p == '\0'))
p = NULL;
return p;
}
#ifdef mkinit
INCLUDE <signal.h>
INCLUDE "trap.h"
INCLUDE "shell.h"
INCLUDE "show.h"
SHELLPROC {
char *sm;
INTOFF;
clear_traps(2);
for (sm = sigmode ; sm < sigmode + NSIG ; sm++) {
if (*sm == S_IGN) {
*sm = S_HARD_IGN;
VTRACE(DBG_TRAP, ("SHELLPROC: %d -> hard_ign\n",
(sm - sigmode)));
}
}
INTON;
}
#endif
/*
* Signal handler.
*/
void
onsig(int signo)
{
int sav_err = errno;
CTRACE(DBG_SIG, ("onsig(%d), had: pendingsigs %d%s, gotsig[%d]=%d\n",
signo, pendingsigs, intpending ? " (SIGINT-pending)" : "",
signo, gotsig[signo]));
/* This should not be needed.
signal(signo, onsig);
*/
if (signo == SIGINT && (traps_invalid || trap[SIGINT] == NULL)) {
VTRACE(DBG_SIG, ("onsig(SIGINT), doing it now\n"));
if (suppressint && !in_dotrap)
intpending = 1;
else
onint();
errno = sav_err;
return;
}
/*
* if the signal will do nothing, no point reporting it
*/
if (!traps_invalid && trap[signo] != NULL && trap[signo][0] != '\0' &&
signo != SIGCHLD) {
gotsig[signo] = 1;
pendingsigs++;
if (iflag && signo == SIGINT) {
if (!suppressint) {
VTRACE(DBG_SIG,
("onsig: -i gotsig[INT]->%d pendingsigs->%d BANG\n",
gotsig[SIGINT], pendingsigs));
onint();
errno = sav_err;
return;
}
intpending = 1;
}
VTRACE(DBG_SIG, ("onsig: gotsig[%d]->%d pendingsigs->%d%s\n",
signo, gotsig[signo], pendingsigs,
intpending ? " (SIGINT pending)":""));
}
errno = sav_err;
}
/*
* Called to execute a trap. Perhaps we should avoid entering new trap
* handlers while we are executing a trap handler.
*/
void
dotrap(void)
{
int i;
char *tr;
int savestatus;
struct skipsave saveskip;
CTRACE(DBG_TRAP|DBG_SIG, ("dotrap[%d]: %d pending, traps %sinvalid\n",
in_dotrap, pendingsigs, traps_invalid ? "" : "not "));
in_dotrap++;
for (;;) {
pendingsigs = 0;
for (i = 1 ; ; i++) {
if (i >= NSIG) {
in_dotrap--;
VTRACE(DBG_TRAP|DBG_SIG, ("dotrap[%d] done\n",
in_dotrap));
return;
}
if (gotsig[i])
break;
}
gotsig[i] = 0;
if (traps_invalid)
continue;
tr = trap[i];
CTRACE(DBG_TRAP|DBG_SIG, ("dotrap %d: %s%s%s\n", i,
tr ? "\"" : "", tr ? tr : "NULL", tr ? "\"" : ""));
if (tr != NULL) {
last_trapsig = i;
save_skipstate(&saveskip);
savestatus = exitstatus;
tr = savestr(tr); /* trap code may free trap[i] */
evalstring(tr, 0);
ckfree(tr);
if (current_skipstate() == SKIPNONE ||
saveskip.state != SKIPNONE) {
restore_skipstate(&saveskip);
exitstatus = savestatus;
}
}
}
}
int
lastsig(void)
{
int i;
for (i = NSIG; --i > 0; )
if (gotsig[i])
return i;
return SIGINT; /* XXX */
}
/*
* Controls whether the shell is interactive or not.
*/
void
setinteractive(int on)
{
static int is_interactive;
if (on == is_interactive)
return;
setsignal(SIGINT, 0);
setsignal(SIGQUIT, 0);
setsignal(SIGTERM, 0);
is_interactive = on;
}
/*
* Called to exit the shell.
*/
void
exitshell(int status)
{
CTRACE(DBG_ERRS|DBG_PROCS|DBG_CMDS|DBG_TRAP,
("pid %d: exitshell(%d)\n", getpid(), status));
exiting = 1;
exiting_status = status;
exitshell_savedstatus();
}
void
exitshell_savedstatus(void)
{
struct jmploc loc;
char *p;
volatile int sig = 0;
int s;
sigset_t sigs;
CTRACE(DBG_ERRS|DBG_PROCS|DBG_CMDS|DBG_TRAP,
("pid %d: exitshell_savedstatus()%s $?=%d xs=%d dt=%d ts=%d\n",
getpid(), exiting ? " exiting" : "", exitstatus,
exiting_status, in_dotrap, last_trapsig));
if (!exiting) {
if (in_dotrap && last_trapsig) {
sig = last_trapsig;
exiting_status = sig + 128;
} else
exiting_status = exitstatus;
}
exitstatus = exiting_status;
if (pendingsigs && !setjmp(loc.loc)) {
handler = &loc;
dotrap();
}
if (!setjmp(loc.loc)) {
handler = &loc;
if (!traps_invalid && (p = trap[0]) != NULL && *p != '\0') {
reset_eval();
trap[0] = NULL;
VTRACE(DBG_TRAP, ("exit trap: \"%s\"\n", p));
evalstring(p, 0);
}
}
INTOFF; /* we're done, no more interrupts. */
if (!setjmp(loc.loc)) {
handler = &loc; /* probably unnecessary */
flushall();
#if JOBS
setjobctl(0);
#endif
}
if ((s = sig) != 0 && s != SIGSTOP && s != SIGTSTP && s != SIGTTIN &&
s != SIGTTOU) {
struct rlimit nocore;
/*
* if the signal is of the core dump variety, don't...
*/
nocore.rlim_cur = nocore.rlim_max = 0;
(void) setrlimit(RLIMIT_CORE, &nocore);
signal(s, SIG_DFL);
sigemptyset(&sigs);
sigaddset(&sigs, s);
sigprocmask(SIG_UNBLOCK, &sigs, NULL);
VTRACE(DBG_ERRS|DBG_PROCS|DBG_CMDS|DBG_TRAP,
("exitshell_savedstatus(): pid %d Death by signal %d\n",
getpid(), s));
kill(getpid(), s);
}
VTRACE(DBG_ERRS|DBG_PROCS|DBG_CMDS|DBG_TRAP,
("exitshell_savedstatus(): pid %d exiting(%d)\n",
getpid(), exiting_status));
_exit(exiting_status);
/* NOTREACHED */
}