trap.c revision 199205 
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 199205 2009-11-11 23:13:24Z jilles $");
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 * Check if we have any traps enabled.
226 */
227int
228have_traps(void)
229{
230	char *volatile *tp;
231
232	for (tp = trap ; tp <= &trap[NSIG - 1] ; tp++) {
233		if (*tp && **tp)	/* trap not NULL or SIG_IGN */
234			return 1;
235	}
236	return 0;
237}
238
239/*
240 * Set the signal handler for the specified signal.  The routine figures
241 * out what it should be set to.
242 */
243void
244setsignal(int signo)
245{
246	int action;
247	sig_t sigact = SIG_DFL;
248	struct sigaction sa;
249	char *t;
250
251	if ((t = trap[signo]) == NULL)
252		action = S_DFL;
253	else if (*t != '\0')
254		action = S_CATCH;
255	else
256		action = S_IGN;
257	if (action == S_DFL) {
258		switch (signo) {
259		case SIGINT:
260			action = S_CATCH;
261			break;
262		case SIGQUIT:
263#ifdef DEBUG
264			{
265			extern int debug;
266
267			if (debug)
268				break;
269			}
270#endif
271			action = S_CATCH;
272			break;
273		case SIGTERM:
274			if (rootshell && iflag)
275				action = S_IGN;
276			break;
277#if JOBS
278		case SIGTSTP:
279		case SIGTTOU:
280			if (rootshell && mflag)
281				action = S_IGN;
282			break;
283#endif
284#ifndef NO_HISTORY
285		case SIGWINCH:
286			if (rootshell && iflag)
287				action = S_CATCH;
288			break;
289#endif
290		}
291	}
292
293	t = &sigmode[signo];
294	if (*t == 0) {
295		/*
296		 * current setting unknown
297		 */
298		if (!getsigaction(signo, &sigact)) {
299			/*
300			 * Pretend it worked; maybe we should give a warning
301			 * here, but other shells don't. We don't alter
302			 * sigmode, so that we retry every time.
303			 */
304			return;
305		}
306		if (sigact == SIG_IGN) {
307			if (mflag && (signo == SIGTSTP ||
308			     signo == SIGTTIN || signo == SIGTTOU)) {
309				*t = S_IGN;	/* don't hard ignore these */
310			} else
311				*t = S_HARD_IGN;
312		} else {
313			*t = S_RESET;	/* force to be set */
314		}
315	}
316	if (*t == S_HARD_IGN || *t == action)
317		return;
318	switch (action) {
319		case S_DFL:	sigact = SIG_DFL;	break;
320		case S_CATCH:  	sigact = onsig;		break;
321		case S_IGN:	sigact = SIG_IGN;	break;
322	}
323	*t = action;
324	sa.sa_handler = sigact;
325	sa.sa_flags = 0;
326	sigemptyset(&sa.sa_mask);
327	sigaction(signo, &sa, NULL);
328}
329
330
331/*
332 * Return the current setting for sig w/o changing it.
333 */
334static int
335getsigaction(int signo, sig_t *sigact)
336{
337	struct sigaction sa;
338
339	if (sigaction(signo, (struct sigaction *)0, &sa) == -1)
340		return 0;
341	*sigact = (sig_t) sa.sa_handler;
342	return 1;
343}
344
345
346/*
347 * Ignore a signal.
348 */
349void
350ignoresig(int signo)
351{
352
353	if (sigmode[signo] != S_IGN && sigmode[signo] != S_HARD_IGN) {
354		signal(signo, SIG_IGN);
355	}
356	sigmode[signo] = S_HARD_IGN;
357}
358
359
360#ifdef mkinit
361INCLUDE <signal.h>
362INCLUDE "trap.h"
363
364SHELLPROC {
365	char *sm;
366
367	clear_traps();
368	for (sm = sigmode ; sm < sigmode + NSIG ; sm++) {
369		if (*sm == S_IGN)
370			*sm = S_HARD_IGN;
371	}
372}
373#endif
374
375
376/*
377 * Signal handler.
378 */
379void
380onsig(int signo)
381{
382
383	if (signo == SIGINT && trap[SIGINT] == NULL) {
384		onint();
385		return;
386	}
387
388	if (signo != SIGCHLD || !ignore_sigchld)
389		gotsig[signo] = 1;
390	pendingsigs++;
391
392	/* If we are currently in a wait builtin, prepare to break it */
393	if ((signo == SIGINT || signo == SIGQUIT) && in_waitcmd != 0)
394		breakwaitcmd = 1;
395	/*
396	 * If a trap is set, not ignored and not the null command, we need
397	 * to make sure traps are executed even when a child blocks signals.
398	 */
399	if (Tflag &&
400	    trap[signo] != NULL &&
401	    ! (trap[signo][0] == '\0') &&
402	    ! (trap[signo][0] == ':' && trap[signo][1] == '\0'))
403		breakwaitcmd = 1;
404
405#ifndef NO_HISTORY
406	if (signo == SIGWINCH)
407		gotwinch = 1;
408#endif
409}
410
411
412/*
413 * Called to execute a trap.  Perhaps we should avoid entering new trap
414 * handlers while we are executing a trap handler.
415 */
416void
417dotrap(void)
418{
419	int i;
420	int savestatus;
421
422	in_dotrap++;
423	for (;;) {
424		for (i = 1; i < NSIG; i++) {
425			if (gotsig[i]) {
426				gotsig[i] = 0;
427				if (trap[i]) {
428					/*
429					 * Ignore SIGCHLD to avoid infinite
430					 * recursion if the trap action does
431					 * a fork.
432					 */
433					if (i == SIGCHLD)
434						ignore_sigchld++;
435					savestatus = exitstatus;
436					evalstring(trap[i], 0);
437					exitstatus = savestatus;
438					if (i == SIGCHLD)
439						ignore_sigchld--;
440				}
441				break;
442			}
443		}
444		if (i >= NSIG)
445			break;
446	}
447	in_dotrap--;
448	pendingsigs = 0;
449}
450
451
452/*
453 * Controls whether the shell is interactive or not.
454 */
455void
456setinteractive(int on)
457{
458	static int is_interactive = -1;
459
460	if (on == is_interactive)
461		return;
462	setsignal(SIGINT);
463	setsignal(SIGQUIT);
464	setsignal(SIGTERM);
465#ifndef NO_HISTORY
466	setsignal(SIGWINCH);
467#endif
468	is_interactive = on;
469}
470
471
472/*
473 * Called to exit the shell.
474 */
475void
476exitshell(int status)
477{
478	struct jmploc loc1, loc2;
479	char *p;
480
481	TRACE(("exitshell(%d) pid=%d\n", status, getpid()));
482	if (setjmp(loc1.loc)) {
483		goto l1;
484	}
485	if (setjmp(loc2.loc)) {
486		goto l2;
487	}
488	handler = &loc1;
489	if ((p = trap[0]) != NULL && *p != '\0') {
490		trap[0] = NULL;
491		evalstring(p, 0);
492	}
493l1:   handler = &loc2;			/* probably unnecessary */
494	flushall();
495#if JOBS
496	setjobctl(0);
497#endif
498l2:   _exit(status);
499}
500