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. All advertising materials mentioning features or use of this software 17 * must display the following acknowledgement: 18 * This product includes software developed by the University of 19 * California, Berkeley and its contributors. 20 * 4. Neither the name of the University nor the names of its contributors 21 * may be used to endorse or promote products derived from this software 22 * without specific prior written permission. 23 * 24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34 * SUCH DAMAGE. 35 * 36 * @(#)trap.c 8.5 (Berkeley) 6/5/95 37 * $FreeBSD: src/bin/sh/trap.c,v 1.48 2012/01/16 11:07:46 dumbbell Exp $ 38 */ 39 40 #include <signal.h> 41 #include <unistd.h> 42 #include <stdlib.h> 43 44 #include "shell.h" 45 #include "main.h" 46 #include "nodes.h" /* for other headers */ 47 #include "eval.h" 48 #include "jobs.h" 49 #include "show.h" 50 #include "options.h" 51 #include "syntax.h" 52 #include "output.h" 53 #include "memalloc.h" 54 #include "error.h" 55 #include "trap.h" 56 #include "mystring.h" 57 #include "builtins.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 74 MKINIT char sigmode[NSIG]; /* current value of signal */ 75 int pendingsigs; /* indicates some signal received */ 76 int in_dotrap; /* do we execute in a trap handler? */ 77 static char *volatile trap[NSIG]; /* trap handler commands */ 78 static volatile sig_atomic_t gotsig[NSIG]; 79 /* indicates specified signal received */ 80 static int ignore_sigchld; /* Used while handling SIGCHLD traps. */ 81 volatile sig_atomic_t gotwinch; 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 && sigstring_to_signum(*argv) == -1) { 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 #ifndef NO_HISTORY 295 case SIGWINCH: 296 if (rootshell && iflag) 297 action = S_CATCH; 298 break; 299 #endif 300 } 301 } 302 303 t = &sigmode[signo]; 304 if (*t == 0) { 305 /* 306 * current setting unknown 307 */ 308 if (!getsigaction(signo, &sigact)) { 309 /* 310 * Pretend it worked; maybe we should give a warning 311 * here, but other shells don't. We don't alter 312 * sigmode, so that we retry every time. 313 */ 314 return; 315 } 316 if (sigact == SIG_IGN) { 317 if (mflag && (signo == SIGTSTP || 318 signo == SIGTTIN || signo == SIGTTOU)) { 319 *t = S_IGN; /* don't hard ignore these */ 320 } else 321 *t = S_HARD_IGN; 322 } else { 323 *t = S_RESET; /* force to be set */ 324 } 325 } 326 if (*t == S_HARD_IGN || *t == action) 327 return; 328 switch (action) { 329 case S_DFL: sigact = SIG_DFL; break; 330 case S_CATCH: sigact = onsig; break; 331 case S_IGN: sigact = SIG_IGN; break; 332 } 333 *t = action; 334 sa.sa_handler = sigact; 335 sa.sa_flags = 0; 336 sigemptyset(&sa.sa_mask); 337 sigaction(signo, &sa, NULL); 338 } 339 340 341 /* 342 * Return the current setting for sig w/o changing it. 343 */ 344 static int 345 getsigaction(int signo, sig_t *sigact) 346 { 347 struct sigaction sa; 348 349 if (sigaction(signo, NULL, &sa) == -1) 350 return 0; 351 *sigact = (sig_t) sa.sa_handler; 352 return 1; 353 } 354 355 356 /* 357 * Ignore a signal. 358 */ 359 void 360 ignoresig(int signo) 361 { 362 363 if (sigmode[signo] != S_IGN && sigmode[signo] != S_HARD_IGN) { 364 signal(signo, SIG_IGN); 365 } 366 sigmode[signo] = S_HARD_IGN; 367 } 368 369 370 /* 371 * Signal handler. 372 */ 373 void 374 onsig(int signo) 375 { 376 377 if (signo == SIGINT && trap[SIGINT] == NULL) { 378 onint(); 379 return; 380 } 381 382 if (signo != SIGCHLD || !ignore_sigchld) 383 gotsig[signo] = 1; 384 pendingsigs++; 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 /* 390 * If a trap is set, not ignored and not the null command, we need 391 * to make sure traps are executed even when a child blocks signals. 392 */ 393 if (Tflag && 394 trap[signo] != NULL && 395 ! (trap[signo][0] == '\0') && 396 ! (trap[signo][0] == ':' && trap[signo][1] == '\0')) 397 breakwaitcmd = 1; 398 399 #ifndef NO_HISTORY 400 if (signo == SIGWINCH) 401 gotwinch = 1; 402 #endif 403 } 404 405 406 /* 407 * Called to execute a trap. Perhaps we should avoid entering new trap 408 * handlers while we are executing a trap handler. 409 */ 410 void 411 dotrap(void) 412 { 413 int i; 414 int savestatus, prev_evalskip, prev_skipcount; 415 416 in_dotrap++; 417 for (;;) { 418 for (i = 1; i < NSIG; i++) { 419 if (gotsig[i]) { 420 gotsig[i] = 0; 421 if (trap[i]) { 422 /* 423 * Ignore SIGCHLD to avoid infinite 424 * recursion if the trap action does 425 * a fork. 426 */ 427 if (i == SIGCHLD) 428 ignore_sigchld++; 429 430 /* 431 * Backup current evalskip 432 * state and reset it before 433 * executing a trap, so that the 434 * trap is not disturbed by an 435 * ongoing break/continue/return 436 * statement. 437 */ 438 prev_evalskip = evalskip; 439 prev_skipcount = skipcount; 440 evalskip = 0; 441 442 last_trapsig = i; 443 savestatus = exitstatus; 444 evalstring(trap[i], 0); 445 exitstatus = savestatus; 446 447 /* 448 * If such a command was not 449 * already in progress, allow a 450 * break/continue/return in the 451 * trap action to have an effect 452 * outside of it. 453 */ 454 if (prev_evalskip != 0) { 455 evalskip = prev_evalskip; 456 skipcount = prev_skipcount; 457 } 458 459 if (i == SIGCHLD) 460 ignore_sigchld--; 461 } 462 break; 463 } 464 } 465 if (i >= NSIG) 466 break; 467 } 468 in_dotrap--; 469 pendingsigs = 0; 470 } 471 472 473 /* 474 * Controls whether the shell is interactive or not. 475 */ 476 void 477 setinteractive(int on) 478 { 479 static int is_interactive = -1; 480 481 if (on == is_interactive) 482 return; 483 setsignal(SIGINT); 484 setsignal(SIGQUIT); 485 setsignal(SIGTERM); 486 #ifndef NO_HISTORY 487 setsignal(SIGWINCH); 488 #endif 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 volatile 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 goto l1; 523 } 524 if (setjmp(loc2.loc)) { 525 goto l2; 526 } 527 handler = &loc1; 528 if ((p = trap[0]) != NULL && *p != '\0') { 529 /* 530 * Reset evalskip, or the trap on EXIT could be 531 * interrupted if the last command was a "return". 532 */ 533 evalskip = 0; 534 trap[0] = NULL; 535 evalstring(p, 0); 536 } 537 l1: handler = &loc2; /* probably unnecessary */ 538 flushall(); 539 #if JOBS 540 setjobctl(0); 541 #endif 542 l2: 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