trap.c revision 193169 
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: head/bin/sh/trap.c 193169 2009-05-31 12:36:14Z stefanf $");
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 "myhistedit.h"
59
60
61/*
62 * Sigmode records the current value of the signal handlers for the various
63 * modes.  A value of zero means that the current handler is not known.
64 * S_HARD_IGN indicates that the signal was ignored on entry to the shell,
65 */
66
67#define S_DFL 1			/* default signal handling (SIG_DFL) */
68#define S_CATCH 2		/* signal is caught */
69#define S_IGN 3			/* signal is ignored (SIG_IGN) */
70#define S_HARD_IGN 4		/* signal is ignored permanently */
71#define S_RESET 5		/* temporary - to reset a hard ignored sig */
72
73
74MKINIT char sigmode[NSIG];	/* current value of signal */
75int pendingsigs;		/* indicates some signal received */
76int in_dotrap;			/* do we execute in a trap handler? */
77static char *volatile trap[NSIG];	/* trap handler commands */
78static volatile sig_atomic_t gotsig[NSIG];
79				/* indicates specified signal received */
80static int ignore_sigchld;	/* Used while handling SIGCHLD traps. */
81volatile sig_atomic_t gotwinch;
82
83static int getsigaction(int, sig_t *);
84
85
86/*
87 * Map a string to a signal number.
88 *
89 * Note: the signal number may exceed NSIG.
90 */
91static int
92sigstring_to_signum(char *sig)
93{
94
95	if (is_number(sig)) {
96		int signo;
97
98		signo = atoi(sig);
99		return ((signo >= 0 && signo < NSIG) ? signo : (-1));
100	} else if (strcasecmp(sig, "exit") == 0) {
101		return (0);
102	} else {
103		int n;
104
105		if (strncasecmp(sig, "sig", 3) == 0)
106			sig += 3;
107		for (n = 1; n < sys_nsig; n++)
108			if (sys_signame[n] &&
109			    strcasecmp(sys_signame[n], sig) == 0)
110				return (n);
111	}
112	return (-1);
113}
114
115
116/*
117 * Print a list of valid signal names.
118 */
119static void
120printsignals(void)
121{
122	int n, outlen;
123
124	outlen = 0;
125	for (n = 1; n < sys_nsig; n++) {
126		if (sys_signame[n]) {
127			out1fmt("%s", sys_signame[n]);
128			outlen += strlen(sys_signame[n]);
129		} else {
130			out1fmt("%d", n);
131			outlen += 3;	/* good enough */
132		}
133		++outlen;
134		if (outlen > 70 || n == sys_nsig - 1) {
135			out1str("\n");
136			outlen = 0;
137		} else {
138			out1c(' ');
139		}
140	}
141}
142
143
144/*
145 * The trap builtin.
146 */
147int
148trapcmd(int argc, char **argv)
149{
150	char *action;
151	int signo;
152
153	if (argc <= 1) {
154		for (signo = 0 ; signo < sys_nsig ; signo++) {
155			if (signo < NSIG && trap[signo] != NULL) {
156				out1str("trap -- ");
157				out1qstr(trap[signo]);
158				if (signo == 0) {
159					out1str(" exit\n");
160				} else if (sys_signame[signo]) {
161					out1fmt(" %s\n", sys_signame[signo]);
162				} else {
163					out1fmt(" %d\n", signo);
164				}
165			}
166		}
167		return 0;
168	}
169	action = NULL;
170	if (*++argv && strcmp(*argv, "--") == 0)
171		argv++;
172	if (*argv && sigstring_to_signum(*argv) == -1) {
173		if ((*argv)[0] != '-') {
174			action = *argv;
175			argv++;
176		} else if ((*argv)[1] == '\0') {
177			argv++;
178		} else if ((*argv)[1] == 'l' && (*argv)[2] == '\0') {
179			printsignals();
180			return 0;
181		} else {
182			error("bad option %s", *argv);
183		}
184	}
185	while (*argv) {
186		if ((signo = sigstring_to_signum(*argv)) == -1)
187			error("bad signal %s", *argv);
188		INTOFF;
189		if (action)
190			action = savestr(action);
191		if (trap[signo])
192			ckfree(trap[signo]);
193		trap[signo] = action;
194		if (signo != 0)
195			setsignal(signo);
196		INTON;
197		argv++;
198	}
199	return 0;
200}
201
202
203/*
204 * Clear traps on a fork.
205 */
206void
207clear_traps(void)
208{
209	char *volatile *tp;
210
211	for (tp = trap ; tp <= &trap[NSIG - 1] ; tp++) {
212		if (*tp && **tp) {	/* trap not NULL or SIG_IGN */
213			INTOFF;
214			ckfree(*tp);
215			*tp = NULL;
216			if (tp != &trap[0])
217				setsignal(tp - trap);
218			INTON;
219		}
220	}
221}
222
223
224/*
225 * Set the signal handler for the specified signal.  The routine figures
226 * out what it should be set to.
227 */
228void
229setsignal(int signo)
230{
231	int action;
232	sig_t sig, sigact = SIG_DFL;
233	char *t;
234
235	if ((t = trap[signo]) == NULL)
236		action = S_DFL;
237	else if (*t != '\0')
238		action = S_CATCH;
239	else
240		action = S_IGN;
241	if (action == S_DFL) {
242		switch (signo) {
243		case SIGINT:
244			action = S_CATCH;
245			break;
246		case SIGQUIT:
247#ifdef DEBUG
248			{
249			extern int debug;
250
251			if (debug)
252				break;
253			}
254#endif
255			action = S_CATCH;
256			break;
257		case SIGTERM:
258			if (rootshell && iflag)
259				action = S_IGN;
260			break;
261#if JOBS
262		case SIGTSTP:
263		case SIGTTOU:
264			if (rootshell && mflag)
265				action = S_IGN;
266			break;
267#endif
268#ifndef NO_HISTORY
269		case SIGWINCH:
270			if (rootshell && iflag)
271				action = S_CATCH;
272			break;
273#endif
274		}
275	}
276
277	t = &sigmode[signo];
278	if (*t == 0) {
279		/*
280		 * current setting unknown
281		 */
282		if (!getsigaction(signo, &sigact)) {
283			/*
284			 * Pretend it worked; maybe we should give a warning
285			 * here, but other shells don't. We don't alter
286			 * sigmode, so that we retry every time.
287			 */
288			return;
289		}
290		if (sigact == SIG_IGN) {
291			if (mflag && (signo == SIGTSTP ||
292			     signo == SIGTTIN || signo == SIGTTOU)) {
293				*t = S_IGN;	/* don't hard ignore these */
294			} else
295				*t = S_HARD_IGN;
296		} else {
297			*t = S_RESET;	/* force to be set */
298		}
299	}
300	if (*t == S_HARD_IGN || *t == action)
301		return;
302	switch (action) {
303		case S_DFL:	sigact = SIG_DFL;	break;
304		case S_CATCH:  	sigact = onsig;		break;
305		case S_IGN:	sigact = SIG_IGN;	break;
306	}
307	*t = action;
308	sig = signal(signo, sigact);
309	if (sig != SIG_ERR && action == S_CATCH)
310		siginterrupt(signo, 1);
311}
312
313
314/*
315 * Return the current setting for sig w/o changing it.
316 */
317static int
318getsigaction(int signo, sig_t *sigact)
319{
320	struct sigaction sa;
321
322	if (sigaction(signo, (struct sigaction *)0, &sa) == -1)
323		return 0;
324	*sigact = (sig_t) sa.sa_handler;
325	return 1;
326}
327
328
329/*
330 * Ignore a signal.
331 */
332void
333ignoresig(int signo)
334{
335
336	if (sigmode[signo] != S_IGN && sigmode[signo] != S_HARD_IGN) {
337		signal(signo, SIG_IGN);
338	}
339	sigmode[signo] = S_HARD_IGN;
340}
341
342
343#ifdef mkinit
344INCLUDE <signal.h>
345INCLUDE "trap.h"
346
347SHELLPROC {
348	char *sm;
349
350	clear_traps();
351	for (sm = sigmode ; sm < sigmode + NSIG ; sm++) {
352		if (*sm == S_IGN)
353			*sm = S_HARD_IGN;
354	}
355}
356#endif
357
358
359/*
360 * Signal handler.
361 */
362void
363onsig(int signo)
364{
365
366	if (signo == SIGINT && trap[SIGINT] == NULL) {
367		onint();
368		return;
369	}
370
371	if (signo != SIGCHLD || !ignore_sigchld)
372		gotsig[signo] = 1;
373	pendingsigs++;
374
375	/* If we are currently in a wait builtin, prepare to break it */
376	if ((signo == SIGINT || signo == SIGQUIT) && in_waitcmd != 0)
377		breakwaitcmd = 1;
378	/*
379	 * If a trap is set, not ignored and not the null command, we need
380	 * to make sure traps are executed even when a child blocks signals.
381	 */
382	if (Tflag &&
383	    trap[signo] != NULL &&
384	    ! (trap[signo][0] == '\0') &&
385	    ! (trap[signo][0] == ':' && trap[signo][1] == '\0'))
386		breakwaitcmd = 1;
387
388#ifndef NO_HISTORY
389	if (signo == SIGWINCH)
390		gotwinch = 1;
391#endif
392}
393
394
395/*
396 * Called to execute a trap.  Perhaps we should avoid entering new trap
397 * handlers while we are executing a trap handler.
398 */
399void
400dotrap(void)
401{
402	int i;
403	int savestatus;
404
405	in_dotrap++;
406	for (;;) {
407		for (i = 1; i < NSIG; i++) {
408			if (gotsig[i]) {
409				gotsig[i] = 0;
410				if (trap[i]) {
411					/*
412					 * Ignore SIGCHLD to avoid infinite
413					 * recursion if the trap action does
414					 * a fork.
415					 */
416					if (i == SIGCHLD)
417						ignore_sigchld++;
418					savestatus = exitstatus;
419					evalstring(trap[i], 0);
420					exitstatus = savestatus;
421					if (i == SIGCHLD)
422						ignore_sigchld--;
423				}
424				break;
425			}
426		}
427		if (i >= NSIG)
428			break;
429	}
430	in_dotrap--;
431	pendingsigs = 0;
432}
433
434
435/*
436 * Controls whether the shell is interactive or not.
437 */
438void
439setinteractive(int on)
440{
441	static int is_interactive = -1;
442
443	if (on == is_interactive)
444		return;
445	setsignal(SIGINT);
446	setsignal(SIGQUIT);
447	setsignal(SIGTERM);
448#ifndef NO_HISTORY
449	setsignal(SIGWINCH);
450#endif
451	is_interactive = on;
452}
453
454
455/*
456 * Called to exit the shell.
457 */
458void
459exitshell(int status)
460{
461	struct jmploc loc1, loc2;
462	char *p;
463
464	TRACE(("exitshell(%d) pid=%d\n", status, getpid()));
465	if (setjmp(loc1.loc)) {
466		goto l1;
467	}
468	if (setjmp(loc2.loc)) {
469		goto l2;
470	}
471	handler = &loc1;
472	if ((p = trap[0]) != NULL && *p != '\0') {
473		trap[0] = NULL;
474		evalstring(p, 0);
475	}
476l1:   handler = &loc2;			/* probably unnecessary */
477	flushall();
478#if JOBS
479	setjobctl(0);
480#endif
481l2:   _exit(status);
482}
483