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