1/*-
2 * Copyright (c) 1991, 1993
3 *	The Regents of the University of California.  All rights reserved.
4 *
5 * This code is derived from software contributed to Berkeley by
6 * Kenneth Almquist.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 * 4. Neither the name of the University nor the names of its contributors
17 *    may be used to endorse or promote products derived from this software
18 *    without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 */
32
33#ifndef lint
34#if 0
35static char sccsid[] = "@(#)trap.c	8.5 (Berkeley) 6/5/95";
36#endif
37#endif /* not lint */
38#include <sys/cdefs.h>
39__FBSDID("$FreeBSD$");
40
41#include <signal.h>
42#include <unistd.h>
43#include <stdlib.h>
44
45#include "shell.h"
46#include "main.h"
47#include "nodes.h"	/* for other headers */
48#include "eval.h"
49#include "jobs.h"
50#include "show.h"
51#include "options.h"
52#include "syntax.h"
53#include "output.h"
54#include "memalloc.h"
55#include "error.h"
56#include "trap.h"
57#include "mystring.h"
58#include "builtins.h"
59#include "myhistedit.h"
60
61
62/*
63 * Sigmode records the current value of the signal handlers for the various
64 * modes.  A value of zero means that the current handler is not known.
65 * S_HARD_IGN indicates that the signal was ignored on entry to the shell,
66 */
67
68#define S_DFL 1			/* default signal handling (SIG_DFL) */
69#define S_CATCH 2		/* signal is caught */
70#define S_IGN 3			/* signal is ignored (SIG_IGN) */
71#define S_HARD_IGN 4		/* signal is ignored permanently */
72#define S_RESET 5		/* temporary - to reset a hard ignored sig */
73
74
75static char sigmode[NSIG];	/* current value of signal */
76volatile sig_atomic_t pendingsig;	/* indicates some signal received */
77volatile sig_atomic_t pendingsig_waitcmd;	/* indicates SIGINT/SIGQUIT received */
78int in_dotrap;			/* do we execute in a trap handler? */
79static char *volatile trap[NSIG];	/* trap handler commands */
80static volatile sig_atomic_t gotsig[NSIG];
81				/* indicates specified signal received */
82static int ignore_sigchld;	/* Used while handling SIGCHLD traps. */
83volatile sig_atomic_t gotwinch;
84static int last_trapsig;
85
86static int exiting;		/* exitshell() has been called */
87static int exiting_exitstatus;	/* value passed to exitshell() */
88
89static int getsigaction(int, sig_t *);
90
91
92/*
93 * Map a string to a signal number.
94 *
95 * Note: the signal number may exceed NSIG.
96 */
97static int
98sigstring_to_signum(char *sig)
99{
100
101	if (is_number(sig)) {
102		int signo;
103
104		signo = atoi(sig);
105		return ((signo >= 0 && signo < NSIG) ? signo : (-1));
106	} else if (strcasecmp(sig, "EXIT") == 0) {
107		return (0);
108	} else {
109		int n;
110
111		if (strncasecmp(sig, "SIG", 3) == 0)
112			sig += 3;
113		for (n = 1; n < sys_nsig; n++)
114			if (sys_signame[n] &&
115			    strcasecmp(sys_signame[n], sig) == 0)
116				return (n);
117	}
118	return (-1);
119}
120
121
122/*
123 * Print a list of valid signal names.
124 */
125static void
126printsignals(void)
127{
128	int n, outlen;
129
130	outlen = 0;
131	for (n = 1; n < sys_nsig; n++) {
132		if (sys_signame[n]) {
133			out1fmt("%s", sys_signame[n]);
134			outlen += strlen(sys_signame[n]);
135		} else {
136			out1fmt("%d", n);
137			outlen += 3;	/* good enough */
138		}
139		++outlen;
140		if (outlen > 71 || n == sys_nsig - 1) {
141			out1str("\n");
142			outlen = 0;
143		} else {
144			out1c(' ');
145		}
146	}
147}
148
149
150/*
151 * The trap builtin.
152 */
153int
154trapcmd(int argc __unused, char **argv)
155{
156	char *action;
157	int signo;
158	int errors = 0;
159	int i;
160
161	while ((i = nextopt("l")) != '\0') {
162		switch (i) {
163		case 'l':
164			printsignals();
165			return (0);
166		}
167	}
168	argv = argptr;
169
170	if (*argv == NULL) {
171		for (signo = 0 ; signo < sys_nsig ; signo++) {
172			if (signo < NSIG && trap[signo] != NULL) {
173				out1str("trap -- ");
174				out1qstr(trap[signo]);
175				if (signo == 0) {
176					out1str(" EXIT\n");
177				} else if (sys_signame[signo]) {
178					out1fmt(" %s\n", sys_signame[signo]);
179				} else {
180					out1fmt(" %d\n", signo);
181				}
182			}
183		}
184		return 0;
185	}
186	action = NULL;
187	if (*argv && sigstring_to_signum(*argv) == -1) {
188		if (strcmp(*argv, "-") == 0)
189			argv++;
190		else {
191			action = *argv;
192			argv++;
193		}
194	}
195	for (; *argv; argv++) {
196		if ((signo = sigstring_to_signum(*argv)) == -1) {
197			warning("bad signal %s", *argv);
198			errors = 1;
199			continue;
200		}
201		INTOFF;
202		if (action)
203			action = savestr(action);
204		if (trap[signo])
205			ckfree(trap[signo]);
206		trap[signo] = action;
207		if (signo != 0)
208			setsignal(signo);
209		INTON;
210	}
211	return errors;
212}
213
214
215/*
216 * Clear traps on a fork.
217 */
218void
219clear_traps(void)
220{
221	char *volatile *tp;
222
223	for (tp = trap ; tp <= &trap[NSIG - 1] ; tp++) {
224		if (*tp && **tp) {	/* trap not NULL or SIG_IGN */
225			INTOFF;
226			ckfree(*tp);
227			*tp = NULL;
228			if (tp != &trap[0])
229				setsignal(tp - trap);
230			INTON;
231		}
232	}
233}
234
235
236/*
237 * Check if we have any traps enabled.
238 */
239int
240have_traps(void)
241{
242	char *volatile *tp;
243
244	for (tp = trap ; tp <= &trap[NSIG - 1] ; tp++) {
245		if (*tp && **tp)	/* trap not NULL or SIG_IGN */
246			return 1;
247	}
248	return 0;
249}
250
251/*
252 * Set the signal handler for the specified signal.  The routine figures
253 * out what it should be set to.
254 */
255void
256setsignal(int signo)
257{
258	int action;
259	sig_t sigact = SIG_DFL;
260	struct sigaction sa;
261	char *t;
262
263	if ((t = trap[signo]) == NULL)
264		action = S_DFL;
265	else if (*t != '\0')
266		action = S_CATCH;
267	else
268		action = S_IGN;
269	if (action == S_DFL) {
270		switch (signo) {
271		case SIGINT:
272			action = S_CATCH;
273			break;
274		case SIGQUIT:
275#ifdef DEBUG
276			{
277			extern int debug;
278
279			if (debug)
280				break;
281			}
282#endif
283			action = S_CATCH;
284			break;
285		case SIGTERM:
286			if (rootshell && iflag)
287				action = S_IGN;
288			break;
289#if JOBS
290		case SIGTSTP:
291		case SIGTTOU:
292			if (rootshell && mflag)
293				action = S_IGN;
294			break;
295#endif
296#ifndef NO_HISTORY
297		case SIGWINCH:
298			if (rootshell && iflag)
299				action = S_CATCH;
300			break;
301#endif
302		}
303	}
304
305	t = &sigmode[signo];
306	if (*t == 0) {
307		/*
308		 * current setting unknown
309		 */
310		if (!getsigaction(signo, &sigact)) {
311			/*
312			 * Pretend it worked; maybe we should give a warning
313			 * here, but other shells don't. We don't alter
314			 * sigmode, so that we retry every time.
315			 */
316			return;
317		}
318		if (sigact == SIG_IGN) {
319			if (mflag && (signo == SIGTSTP ||
320			     signo == SIGTTIN || signo == SIGTTOU)) {
321				*t = S_IGN;	/* don't hard ignore these */
322			} else
323				*t = S_HARD_IGN;
324		} else {
325			*t = S_RESET;	/* force to be set */
326		}
327	}
328	if (*t == S_HARD_IGN || *t == action)
329		return;
330	switch (action) {
331		case S_DFL:	sigact = SIG_DFL;	break;
332		case S_CATCH:  	sigact = onsig;		break;
333		case S_IGN:	sigact = SIG_IGN;	break;
334	}
335	*t = action;
336	sa.sa_handler = sigact;
337	sa.sa_flags = 0;
338	sigemptyset(&sa.sa_mask);
339	sigaction(signo, &sa, NULL);
340}
341
342
343/*
344 * Return the current setting for sig w/o changing it.
345 */
346static int
347getsigaction(int signo, sig_t *sigact)
348{
349	struct sigaction sa;
350
351	if (sigaction(signo, (struct sigaction *)0, &sa) == -1)
352		return 0;
353	*sigact = (sig_t) sa.sa_handler;
354	return 1;
355}
356
357
358/*
359 * Ignore a signal.
360 */
361void
362ignoresig(int signo)
363{
364
365	if (sigmode[signo] != S_IGN && sigmode[signo] != S_HARD_IGN) {
366		signal(signo, SIG_IGN);
367	}
368	sigmode[signo] = S_HARD_IGN;
369}
370
371
372int
373issigchldtrapped(void)
374{
375
376	return (trap[SIGCHLD] != NULL && *trap[SIGCHLD] != '\0');
377}
378
379
380/*
381 * Signal handler.
382 */
383void
384onsig(int signo)
385{
386
387	if (signo == SIGINT && trap[SIGINT] == NULL) {
388		onint();
389		return;
390	}
391
392	/* If we are currently in a wait builtin, prepare to break it */
393	if (signo == SIGINT || signo == SIGQUIT)
394		pendingsig_waitcmd = signo;
395
396	if (trap[signo] != NULL && trap[signo][0] != '\0' &&
397	    (signo != SIGCHLD || !ignore_sigchld)) {
398		gotsig[signo] = 1;
399		pendingsig = signo;
400	}
401
402#ifndef NO_HISTORY
403	if (signo == SIGWINCH)
404		gotwinch = 1;
405#endif
406}
407
408
409/*
410 * Called to execute a trap.  Perhaps we should avoid entering new trap
411 * handlers while we are executing a trap handler.
412 */
413void
414dotrap(void)
415{
416	int i;
417	int savestatus, prev_evalskip, prev_skipcount;
418
419	in_dotrap++;
420	for (;;) {
421		pendingsig = 0;
422		pendingsig_waitcmd = 0;
423		for (i = 1; i < NSIG; i++) {
424			if (gotsig[i]) {
425				gotsig[i] = 0;
426				if (trap[i]) {
427					/*
428					 * Ignore SIGCHLD to avoid infinite
429					 * recursion if the trap action does
430					 * a fork.
431					 */
432					if (i == SIGCHLD)
433						ignore_sigchld++;
434
435					/*
436					 * Backup current evalskip
437					 * state and reset it before
438					 * executing a trap, so that the
439					 * trap is not disturbed by an
440					 * ongoing break/continue/return
441					 * statement.
442					 */
443					prev_evalskip  = evalskip;
444					prev_skipcount = skipcount;
445					evalskip = 0;
446
447					last_trapsig = i;
448					savestatus = exitstatus;
449					evalstring(trap[i], 0);
450
451					/*
452					 * If such a command was not
453					 * already in progress, allow a
454					 * break/continue/return in the
455					 * trap action to have an effect
456					 * outside of it.
457					 */
458					if (evalskip == 0 ||
459					    prev_evalskip != 0) {
460						evalskip  = prev_evalskip;
461						skipcount = prev_skipcount;
462						exitstatus = savestatus;
463					}
464
465					if (i == SIGCHLD)
466						ignore_sigchld--;
467				}
468				break;
469			}
470		}
471		if (i >= NSIG)
472			break;
473	}
474	in_dotrap--;
475}
476
477
478/*
479 * Controls whether the shell is interactive or not.
480 */
481void
482setinteractive(int on)
483{
484	static int is_interactive = -1;
485
486	if (on == is_interactive)
487		return;
488	setsignal(SIGINT);
489	setsignal(SIGQUIT);
490	setsignal(SIGTERM);
491#ifndef NO_HISTORY
492	setsignal(SIGWINCH);
493#endif
494	is_interactive = on;
495}
496
497
498/*
499 * Called to exit the shell.
500 */
501void
502exitshell(int status)
503{
504	TRACE(("exitshell(%d) pid=%d\n", status, getpid()));
505	exiting = 1;
506	exiting_exitstatus = status;
507	exitshell_savedstatus();
508}
509
510void
511exitshell_savedstatus(void)
512{
513	struct jmploc loc1, loc2;
514	char *p;
515	int sig = 0;
516	sigset_t sigs;
517
518	if (!exiting) {
519		if (in_dotrap && last_trapsig) {
520			sig = last_trapsig;
521			exiting_exitstatus = sig + 128;
522		} else
523			exiting_exitstatus = oexitstatus;
524	}
525	exitstatus = oexitstatus = exiting_exitstatus;
526	if (setjmp(loc1.loc)) {
527		goto l1;
528	}
529	if (setjmp(loc2.loc)) {
530		goto l2;
531	}
532	handler = &loc1;
533	if ((p = trap[0]) != NULL && *p != '\0') {
534		/*
535		 * Reset evalskip, or the trap on EXIT could be
536		 * interrupted if the last command was a "return".
537		 */
538		evalskip = 0;
539		trap[0] = NULL;
540		evalstring(p, 0);
541	}
542l1:   handler = &loc2;			/* probably unnecessary */
543	flushall();
544#if JOBS
545	setjobctl(0);
546#endif
547l2:
548	if (sig != 0 && sig != SIGSTOP && sig != SIGTSTP && sig != SIGTTIN &&
549	    sig != SIGTTOU) {
550		signal(sig, SIG_DFL);
551		sigemptyset(&sigs);
552		sigaddset(&sigs, sig);
553		sigprocmask(SIG_UNBLOCK, &sigs, NULL);
554		kill(getpid(), sig);
555		/* If the default action is to ignore, fall back to _exit(). */
556	}
557	_exit(exiting_exitstatus);
558}
559