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