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 * 3. 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 * @(#)trap.c 8.5 (Berkeley) 6/5/95 33 * $FreeBSD: head/bin/sh/trap.c 253658 2013-07-25 19:48:15Z jilles $ 34 */ 35 36 #include <signal.h> 37 #include <unistd.h> 38 #include <stdlib.h> 39 40 #include "shell.h" 41 #include "main.h" 42 #include "nodes.h" /* for other headers */ 43 #include "eval.h" 44 #include "jobs.h" 45 #include "show.h" 46 #include "options.h" 47 #include "syntax.h" 48 #include "output.h" 49 #include "memalloc.h" 50 #include "error.h" 51 #include "trap.h" 52 #include "mystring.h" 53 #include "builtins.h" 54 #include "myhistedit.h" 55 56 57 /* 58 * Sigmode records the current value of the signal handlers for the various 59 * modes. A value of zero means that the current handler is not known. 60 * S_HARD_IGN indicates that the signal was ignored on entry to the shell, 61 */ 62 63 #define S_DFL 1 /* default signal handling (SIG_DFL) */ 64 #define S_CATCH 2 /* signal is caught */ 65 #define S_IGN 3 /* signal is ignored (SIG_IGN) */ 66 #define S_HARD_IGN 4 /* signal is ignored permanently */ 67 #define S_RESET 5 /* temporary - to reset a hard ignored sig */ 68 69 70 static char sigmode[NSIG]; /* current value of signal */ 71 volatile sig_atomic_t pendingsig; /* indicates some signal received */ 72 int in_dotrap; /* do we execute in a trap handler? */ 73 static char *volatile trap[NSIG]; /* trap handler commands */ 74 static volatile sig_atomic_t gotsig[NSIG]; 75 /* indicates specified signal received */ 76 static int ignore_sigchld; /* Used while handling SIGCHLD traps. */ 77 volatile sig_atomic_t gotwinch; 78 static int last_trapsig; 79 80 static int exiting; /* exitshell() has been called */ 81 static int exiting_exitstatus; /* value passed to exitshell() */ 82 83 static 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 */ 91 static int 92 sigstring_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 */ 119 static void 120 printsignals(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 > 71 || 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 */ 147 int 148 trapcmd(int argc __unused, char **argv) 149 { 150 char *action; 151 int signo; 152 int errors = 0; 153 int i; 154 155 while ((i = nextopt("l")) != '\0') { 156 switch (i) { 157 case 'l': 158 printsignals(); 159 return (0); 160 } 161 } 162 argv = argptr; 163 164 if (*argv == NULL) { 165 for (signo = 0 ; signo < sys_nsig ; signo++) { 166 if (signo < NSIG && trap[signo] != NULL) { 167 out1str("trap -- "); 168 out1qstr(trap[signo]); 169 if (signo == 0) { 170 out1str(" EXIT\n"); 171 } else if (sys_signame[signo]) { 172 out1fmt(" %s\n", sys_signame[signo]); 173 } else { 174 out1fmt(" %d\n", signo); 175 } 176 } 177 } 178 return 0; 179 } 180 action = NULL; 181 if (*argv && sigstring_to_signum(*argv) == -1) { 182 if (strcmp(*argv, "-") == 0) 183 argv++; 184 else { 185 action = *argv; 186 argv++; 187 } 188 } 189 for (; *argv; argv++) { 190 if ((signo = sigstring_to_signum(*argv)) == -1) { 191 warning("bad signal %s", *argv); 192 errors = 1; 193 continue; 194 } 195 INTOFF; 196 if (action) 197 action = savestr(action); 198 if (trap[signo]) 199 ckfree(trap[signo]); 200 trap[signo] = action; 201 if (signo != 0) 202 setsignal(signo); 203 INTON; 204 } 205 return errors; 206 } 207 208 209 /* 210 * Clear traps on a fork. 211 */ 212 void 213 clear_traps(void) 214 { 215 char *volatile *tp; 216 217 for (tp = trap ; tp <= &trap[NSIG - 1] ; tp++) { 218 if (*tp && **tp) { /* trap not NULL or SIG_IGN */ 219 INTOFF; 220 ckfree(*tp); 221 *tp = NULL; 222 if (tp != &trap[0]) 223 setsignal(tp - trap); 224 INTON; 225 } 226 } 227 } 228 229 230 /* 231 * Check if we have any traps enabled. 232 */ 233 int 234 have_traps(void) 235 { 236 char *volatile *tp; 237 238 for (tp = trap ; tp <= &trap[NSIG - 1] ; tp++) { 239 if (*tp && **tp) /* trap not NULL or SIG_IGN */ 240 return 1; 241 } 242 return 0; 243 } 244 245 /* 246 * Set the signal handler for the specified signal. The routine figures 247 * out what it should be set to. 248 */ 249 void 250 setsignal(int signo) 251 { 252 int action; 253 sig_t sigact = SIG_DFL; 254 struct sigaction sa; 255 char *t; 256 257 if ((t = trap[signo]) == NULL) 258 action = S_DFL; 259 else if (*t != '\0') 260 action = S_CATCH; 261 else 262 action = S_IGN; 263 if (action == S_DFL) { 264 switch (signo) { 265 case SIGINT: 266 action = S_CATCH; 267 break; 268 case SIGQUIT: 269 #ifdef DEBUG 270 { 271 extern int debug; 272 273 if (debug) 274 break; 275 } 276 #endif 277 action = S_CATCH; 278 break; 279 case SIGTERM: 280 if (rootshell && iflag) 281 action = S_IGN; 282 break; 283 #if JOBS 284 case SIGTSTP: 285 case SIGTTOU: 286 if (rootshell && mflag) 287 action = S_IGN; 288 break; 289 #endif 290 #ifndef NO_HISTORY 291 case SIGWINCH: 292 if (rootshell && iflag) 293 action = S_CATCH; 294 break; 295 #endif 296 } 297 } 298 299 t = &sigmode[signo]; 300 if (*t == 0) { 301 /* 302 * current setting unknown 303 */ 304 if (!getsigaction(signo, &sigact)) { 305 /* 306 * Pretend it worked; maybe we should give a warning 307 * here, but other shells don't. We don't alter 308 * sigmode, so that we retry every time. 309 */ 310 return; 311 } 312 if (sigact == SIG_IGN) { 313 if (mflag && (signo == SIGTSTP || 314 signo == SIGTTIN || signo == SIGTTOU)) { 315 *t = S_IGN; /* don't hard ignore these */ 316 } else 317 *t = S_HARD_IGN; 318 } else { 319 *t = S_RESET; /* force to be set */ 320 } 321 } 322 if (*t == S_HARD_IGN || *t == action) 323 return; 324 switch (action) { 325 case S_DFL: sigact = SIG_DFL; break; 326 case S_CATCH: sigact = onsig; break; 327 case S_IGN: sigact = SIG_IGN; break; 328 } 329 *t = action; 330 sa.sa_handler = sigact; 331 sa.sa_flags = 0; 332 sigemptyset(&sa.sa_mask); 333 sigaction(signo, &sa, NULL); 334 } 335 336 337 /* 338 * Return the current setting for sig w/o changing it. 339 */ 340 static int 341 getsigaction(int signo, sig_t *sigact) 342 { 343 struct sigaction sa; 344 345 if (sigaction(signo, NULL, &sa) == -1) 346 return 0; 347 *sigact = (sig_t) sa.sa_handler; 348 return 1; 349 } 350 351 352 /* 353 * Ignore a signal. 354 */ 355 void 356 ignoresig(int signo) 357 { 358 359 if (sigmode[signo] != S_IGN && sigmode[signo] != S_HARD_IGN) { 360 signal(signo, SIG_IGN); 361 } 362 sigmode[signo] = S_HARD_IGN; 363 } 364 365 366 int 367 issigchldtrapped(void) 368 { 369 370 return (trap[SIGCHLD] != NULL && *trap[SIGCHLD] != '\0'); 371 } 372 373 374 /* 375 * Signal handler. 376 */ 377 void 378 onsig(int signo) 379 { 380 381 if (signo == SIGINT && trap[SIGINT] == NULL) { 382 onint(); 383 return; 384 } 385 386 /* If we are currently in a wait builtin, prepare to break it */ 387 if ((signo == SIGINT || signo == SIGQUIT) && in_waitcmd != 0) { 388 breakwaitcmd = 1; 389 pendingsig = signo; 390 } 391 392 if (trap[signo] != NULL && trap[signo][0] != '\0' && 393 (signo != SIGCHLD || !ignore_sigchld)) { 394 gotsig[signo] = 1; 395 pendingsig = signo; 396 397 /* 398 * If a trap is set, not ignored and not the null command, we 399 * need to make sure traps are executed even when a child 400 * blocks signals. 401 */ 402 if (Tflag && !(trap[signo][0] == ':' && trap[signo][1] == '\0')) 403 breakwaitcmd = 1; 404 } 405 406 #ifndef NO_HISTORY 407 if (signo == SIGWINCH) 408 gotwinch = 1; 409 #endif 410 } 411 412 413 /* 414 * Called to execute a trap. Perhaps we should avoid entering new trap 415 * handlers while we are executing a trap handler. 416 */ 417 void 418 dotrap(void) 419 { 420 int i; 421 int savestatus, prev_evalskip, prev_skipcount; 422 423 in_dotrap++; 424 for (;;) { 425 pendingsig = 0; 426 for (i = 1; i < NSIG; i++) { 427 if (gotsig[i]) { 428 gotsig[i] = 0; 429 if (trap[i]) { 430 /* 431 * Ignore SIGCHLD to avoid infinite 432 * recursion if the trap action does 433 * a fork. 434 */ 435 if (i == SIGCHLD) 436 ignore_sigchld++; 437 438 /* 439 * Backup current evalskip 440 * state and reset it before 441 * executing a trap, so that the 442 * trap is not disturbed by an 443 * ongoing break/continue/return 444 * statement. 445 */ 446 prev_evalskip = evalskip; 447 prev_skipcount = skipcount; 448 evalskip = 0; 449 450 last_trapsig = i; 451 savestatus = exitstatus; 452 evalstring(trap[i], 0); 453 454 /* 455 * If such a command was not 456 * already in progress, allow a 457 * break/continue/return in the 458 * trap action to have an effect 459 * outside of it. 460 */ 461 if (evalskip == 0 || 462 prev_evalskip != 0) { 463 evalskip = prev_evalskip; 464 skipcount = prev_skipcount; 465 exitstatus = savestatus; 466 } 467 468 if (i == SIGCHLD) 469 ignore_sigchld--; 470 } 471 break; 472 } 473 } 474 if (i >= NSIG) 475 break; 476 } 477 in_dotrap--; 478 } 479 480 481 /* 482 * Controls whether the shell is interactive or not. 483 */ 484 void 485 setinteractive(int on) 486 { 487 static int is_interactive = -1; 488 489 if (on == is_interactive) 490 return; 491 setsignal(SIGINT); 492 setsignal(SIGQUIT); 493 setsignal(SIGTERM); 494 #ifndef NO_HISTORY 495 setsignal(SIGWINCH); 496 #endif 497 is_interactive = on; 498 } 499 500 501 /* 502 * Called to exit the shell. 503 */ 504 void 505 exitshell(int status) 506 { 507 TRACE(("exitshell(%d) pid=%d\n", status, getpid())); 508 exiting = 1; 509 exiting_exitstatus = status; 510 exitshell_savedstatus(); 511 } 512 513 void 514 exitshell_savedstatus(void) 515 { 516 struct jmploc loc1, loc2; 517 char *p; 518 volatile int sig = 0; 519 sigset_t sigs; 520 521 if (!exiting) { 522 if (in_dotrap && last_trapsig) { 523 sig = last_trapsig; 524 exiting_exitstatus = sig + 128; 525 } else 526 exiting_exitstatus = oexitstatus; 527 } 528 exitstatus = oexitstatus = exiting_exitstatus; 529 if (setjmp(loc1.loc)) { 530 goto l1; 531 } 532 if (setjmp(loc2.loc)) { 533 goto l2; 534 } 535 handler = &loc1; 536 if ((p = trap[0]) != NULL && *p != '\0') { 537 /* 538 * Reset evalskip, or the trap on EXIT could be 539 * interrupted if the last command was a "return". 540 */ 541 evalskip = 0; 542 trap[0] = NULL; 543 evalstring(p, 0); 544 } 545 l1: handler = &loc2; /* probably unnecessary */ 546 flushall(); 547 #if JOBS 548 setjobctl(0); 549 #endif 550 l2: 551 if (sig != 0 && sig != SIGSTOP && sig != SIGTSTP && sig != SIGTTIN && 552 sig != SIGTTOU) { 553 signal(sig, SIG_DFL); 554 sigemptyset(&sigs); 555 sigaddset(&sigs, sig); 556 sigprocmask(SIG_UNBLOCK, &sigs, NULL); 557 kill(getpid(), sig); 558 /* If the default action is to ignore, fall back to _exit(). */ 559 } 560 _exit(exiting_exitstatus); 561 } 562