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
35 static 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
75 static char sigmode[NSIG]; /* current value of signal */
76 volatile sig_atomic_t pendingsig; /* indicates some signal received */
77 volatile sig_atomic_t pendingsig_waitcmd; /* indicates wait builtin should be interrupted */
78 static int in_dotrap; /* do we execute in a trap handler? */
79 static char *volatile trap[NSIG]; /* trap handler commands */
80 static volatile sig_atomic_t gotsig[NSIG];
81 /* indicates specified signal received */
82 static int ignore_sigchld; /* Used while handling SIGCHLD traps. */
83 static int last_trapsig;
84
85 static int exiting; /* exitshell() has been called */
86 static int exiting_exitstatus; /* value passed to exitshell() */
87
88 static int getsigaction(int, sig_t *);
89
90
91 /*
92 * Map a string to a signal number.
93 *
94 * Note: the signal number may exceed NSIG.
95 */
96 static int
sigstring_to_signum(char * sig)97 sigstring_to_signum(char *sig)
98 {
99
100 if (is_number(sig)) {
101 int signo;
102
103 signo = atoi(sig);
104 return ((signo >= 0 && signo < NSIG) ? signo : (-1));
105 } else if (strcasecmp(sig, "EXIT") == 0) {
106 return (0);
107 } else {
108 int n;
109
110 if (strncasecmp(sig, "SIG", 3) == 0)
111 sig += 3;
112 for (n = 1; n < sys_nsig; n++)
113 if (sys_signame[n] &&
114 strcasecmp(sys_signame[n], sig) == 0)
115 return (n);
116 }
117 return (-1);
118 }
119
120
121 /*
122 * Print a list of valid signal names.
123 */
124 static void
printsignals(void)125 printsignals(void)
126 {
127 int n, outlen;
128
129 outlen = 0;
130 for (n = 1; n < sys_nsig; n++) {
131 if (sys_signame[n]) {
132 out1fmt("%s", sys_signame[n]);
133 outlen += strlen(sys_signame[n]);
134 } else {
135 out1fmt("%d", n);
136 outlen += 3; /* good enough */
137 }
138 ++outlen;
139 if (outlen > 71 || n == sys_nsig - 1) {
140 out1str("\n");
141 outlen = 0;
142 } else {
143 out1c(' ');
144 }
145 }
146 }
147
148
149 /*
150 * The trap builtin.
151 */
152 int
trapcmd(int argc __unused,char ** argv)153 trapcmd(int argc __unused, char **argv)
154 {
155 char *action;
156 int signo;
157 int errors = 0;
158 int i;
159
160 while ((i = nextopt("l")) != '\0') {
161 switch (i) {
162 case 'l':
163 printsignals();
164 return (0);
165 }
166 }
167 argv = argptr;
168
169 if (*argv == NULL) {
170 for (signo = 0 ; signo < sys_nsig ; signo++) {
171 if (signo < NSIG && trap[signo] != NULL) {
172 out1str("trap -- ");
173 out1qstr(trap[signo]);
174 if (signo == 0) {
175 out1str(" EXIT\n");
176 } else if (sys_signame[signo]) {
177 out1fmt(" %s\n", sys_signame[signo]);
178 } else {
179 out1fmt(" %d\n", signo);
180 }
181 }
182 }
183 return 0;
184 }
185 action = NULL;
186 if (*argv && !is_number(*argv)) {
187 if (strcmp(*argv, "-") == 0)
188 argv++;
189 else {
190 action = *argv;
191 argv++;
192 }
193 }
194 for (; *argv; argv++) {
195 if ((signo = sigstring_to_signum(*argv)) == -1) {
196 warning("bad signal %s", *argv);
197 errors = 1;
198 continue;
199 }
200 INTOFF;
201 if (action)
202 action = savestr(action);
203 if (trap[signo])
204 ckfree(trap[signo]);
205 trap[signo] = action;
206 if (signo != 0)
207 setsignal(signo);
208 INTON;
209 }
210 return errors;
211 }
212
213
214 /*
215 * Clear traps on a fork.
216 */
217 void
clear_traps(void)218 clear_traps(void)
219 {
220 char *volatile *tp;
221
222 for (tp = trap ; tp <= &trap[NSIG - 1] ; tp++) {
223 if (*tp && **tp) { /* trap not NULL or SIG_IGN */
224 INTOFF;
225 ckfree(*tp);
226 *tp = NULL;
227 if (tp != &trap[0])
228 setsignal(tp - trap);
229 INTON;
230 }
231 }
232 }
233
234
235 /*
236 * Check if we have any traps enabled.
237 */
238 int
have_traps(void)239 have_traps(void)
240 {
241 char *volatile *tp;
242
243 for (tp = trap ; tp <= &trap[NSIG - 1] ; tp++) {
244 if (*tp && **tp) /* trap not NULL or SIG_IGN */
245 return 1;
246 }
247 return 0;
248 }
249
250 /*
251 * Set the signal handler for the specified signal. The routine figures
252 * out what it should be set to.
253 */
254 void
setsignal(int signo)255 setsignal(int signo)
256 {
257 int action;
258 sig_t sigact = SIG_DFL;
259 struct sigaction sa;
260 char *t;
261
262 if ((t = trap[signo]) == NULL)
263 action = S_DFL;
264 else if (*t != '\0')
265 action = S_CATCH;
266 else
267 action = S_IGN;
268 if (action == S_DFL) {
269 switch (signo) {
270 case SIGINT:
271 action = S_CATCH;
272 break;
273 case SIGQUIT:
274 #ifdef DEBUG
275 {
276 extern int debug;
277
278 if (debug)
279 break;
280 }
281 #endif
282 action = S_CATCH;
283 break;
284 case SIGTERM:
285 if (rootshell && iflag)
286 action = S_IGN;
287 break;
288 #if JOBS
289 case SIGTSTP:
290 case SIGTTOU:
291 if (rootshell && mflag)
292 action = S_IGN;
293 break;
294 #endif
295 }
296 }
297
298 t = &sigmode[signo];
299 if (*t == 0) {
300 /*
301 * current setting unknown
302 */
303 if (!getsigaction(signo, &sigact)) {
304 /*
305 * Pretend it worked; maybe we should give a warning
306 * here, but other shells don't. We don't alter
307 * sigmode, so that we retry every time.
308 */
309 return;
310 }
311 if (sigact == SIG_IGN) {
312 if (mflag && (signo == SIGTSTP ||
313 signo == SIGTTIN || signo == SIGTTOU)) {
314 *t = S_IGN; /* don't hard ignore these */
315 } else
316 *t = S_HARD_IGN;
317 } else {
318 *t = S_RESET; /* force to be set */
319 }
320 }
321 if (*t == S_HARD_IGN || *t == action)
322 return;
323 switch (action) {
324 case S_DFL: sigact = SIG_DFL; break;
325 case S_CATCH: sigact = onsig; break;
326 case S_IGN: sigact = SIG_IGN; break;
327 }
328 *t = action;
329 sa.sa_handler = sigact;
330 sa.sa_flags = 0;
331 sigemptyset(&sa.sa_mask);
332 sigaction(signo, &sa, NULL);
333 }
334
335
336 /*
337 * Return the current setting for sig w/o changing it.
338 */
339 static int
getsigaction(int signo,sig_t * sigact)340 getsigaction(int signo, sig_t *sigact)
341 {
342 struct sigaction sa;
343
344 if (sigaction(signo, (struct sigaction *)0, &sa) == -1)
345 return 0;
346 *sigact = (sig_t) sa.sa_handler;
347 return 1;
348 }
349
350
351 /*
352 * Ignore a signal.
353 */
354 void
ignoresig(int signo)355 ignoresig(int signo)
356 {
357
358 if (sigmode[signo] == 0)
359 setsignal(signo);
360 if (sigmode[signo] != S_IGN && sigmode[signo] != S_HARD_IGN) {
361 signal(signo, SIG_IGN);
362 sigmode[signo] = S_IGN;
363 }
364 }
365
366
367 int
issigchldtrapped(void)368 issigchldtrapped(void)
369 {
370
371 return (trap[SIGCHLD] != NULL && *trap[SIGCHLD] != '\0');
372 }
373
374
375 /*
376 * Signal handler.
377 */
378 void
onsig(int signo)379 onsig(int signo)
380 {
381
382 if (signo == SIGINT && trap[SIGINT] == NULL) {
383 /*
384 * The !in_dotrap here is safe. The only way we can arrive
385 * here with in_dotrap set is that a trap handler set SIGINT to
386 * SIG_DFL and killed itself.
387 */
388 if (suppressint && !in_dotrap)
389 SET_PENDING_INT;
390 else
391 onint();
392 return;
393 }
394
395 /* If we are currently in a wait builtin, prepare to break it */
396 if (signo == SIGINT || signo == SIGQUIT)
397 pendingsig_waitcmd = signo;
398
399 if (trap[signo] != NULL && trap[signo][0] != '\0' &&
400 (signo != SIGCHLD || !ignore_sigchld)) {
401 gotsig[signo] = 1;
402 pendingsig = signo;
403 pendingsig_waitcmd = signo;
404 }
405 }
406
407
408 /*
409 * Called to execute a trap. Perhaps we should avoid entering new trap
410 * handlers while we are executing a trap handler.
411 */
412 void
dotrap(void)413 dotrap(void)
414 {
415 int i;
416 int savestatus, prev_evalskip, prev_skipcount;
417
418 in_dotrap++;
419 for (;;) {
420 pendingsig = 0;
421 pendingsig_waitcmd = 0;
422 for (i = 1; i < NSIG; i++) {
423 if (gotsig[i]) {
424 gotsig[i] = 0;
425 if (trap[i]) {
426 /*
427 * Ignore SIGCHLD to avoid infinite
428 * recursion if the trap action does
429 * a fork.
430 */
431 if (i == SIGCHLD)
432 ignore_sigchld++;
433
434 /*
435 * Backup current evalskip
436 * state and reset it before
437 * executing a trap, so that the
438 * trap is not disturbed by an
439 * ongoing break/continue/return
440 * statement.
441 */
442 prev_evalskip = evalskip;
443 prev_skipcount = skipcount;
444 evalskip = 0;
445
446 last_trapsig = i;
447 savestatus = exitstatus;
448 evalstring(trap[i], 0);
449
450 /*
451 * If such a command was not
452 * already in progress, allow a
453 * break/continue/return in the
454 * trap action to have an effect
455 * outside of it.
456 */
457 if (evalskip == 0 ||
458 prev_evalskip != 0) {
459 evalskip = prev_evalskip;
460 skipcount = prev_skipcount;
461 exitstatus = savestatus;
462 }
463
464 if (i == SIGCHLD)
465 ignore_sigchld--;
466 }
467 break;
468 }
469 }
470 if (i >= NSIG)
471 break;
472 }
473 in_dotrap--;
474 }
475
476
477 /*
478 * Controls whether the shell is interactive or not.
479 */
480 void
setinteractive(int on)481 setinteractive(int on)
482 {
483 static int is_interactive = -1;
484
485 if (on == is_interactive)
486 return;
487 setsignal(SIGINT);
488 setsignal(SIGQUIT);
489 setsignal(SIGTERM);
490 is_interactive = on;
491 }
492
493
494 /*
495 * Called to exit the shell.
496 */
497 void
exitshell(int status)498 exitshell(int status)
499 {
500 TRACE(("exitshell(%d) pid=%d\n", status, getpid()));
501 exiting = 1;
502 exiting_exitstatus = status;
503 exitshell_savedstatus();
504 }
505
506 void
exitshell_savedstatus(void)507 exitshell_savedstatus(void)
508 {
509 struct jmploc loc1, loc2;
510 char *p;
511 int sig = 0;
512 sigset_t sigs;
513
514 if (!exiting) {
515 if (in_dotrap && last_trapsig) {
516 sig = last_trapsig;
517 exiting_exitstatus = sig + 128;
518 } else
519 exiting_exitstatus = oexitstatus;
520 }
521 exitstatus = oexitstatus = exiting_exitstatus;
522 if (!setjmp(loc1.loc)) {
523 handler = &loc1;
524 if ((p = trap[0]) != NULL && *p != '\0') {
525 /*
526 * Reset evalskip, or the trap on EXIT could be
527 * interrupted if the last command was a "return".
528 */
529 evalskip = 0;
530 trap[0] = NULL;
531 evalstring(p, 0);
532 }
533 }
534 if (!setjmp(loc2.loc)) {
535 handler = &loc2; /* probably unnecessary */
536 flushall();
537 #if JOBS
538 setjobctl(0);
539 #endif
540 }
541 if (sig != 0 && sig != SIGSTOP && sig != SIGTSTP && sig != SIGTTIN &&
542 sig != SIGTTOU) {
543 signal(sig, SIG_DFL);
544 sigemptyset(&sigs);
545 sigaddset(&sigs, sig);
546 sigprocmask(SIG_UNBLOCK, &sigs, NULL);
547 kill(getpid(), sig);
548 /* If the default action is to ignore, fall back to _exit(). */
549 }
550 _exit(exiting_exitstatus);
551 }
552