trap.c revision 217425
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 35static char sccsid[] = "@(#)trap.c 8.5 (Berkeley) 6/5/95"; 36#endif 37#endif /* not lint */ 38#include <sys/cdefs.h> 39__FBSDID("$FreeBSD: head/bin/sh/trap.c 217425 2011-01-14 21:30:27Z jilles $"); 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 "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 74MKINIT char sigmode[NSIG]; /* current value of signal */ 75int pendingsigs; /* indicates some signal received */ 76int in_dotrap; /* do we execute in a trap handler? */ 77static char *volatile trap[NSIG]; /* trap handler commands */ 78static volatile sig_atomic_t gotsig[NSIG]; 79 /* indicates specified signal received */ 80static int ignore_sigchld; /* Used while handling SIGCHLD traps. */ 81volatile sig_atomic_t gotwinch; 82 83static int exiting; /* exitshell() has been called */ 84static int exiting_exitstatus; /* value passed to exitshell() */ 85 86static int getsigaction(int, sig_t *); 87 88 89/* 90 * Map a string to a signal number. 91 * 92 * Note: the signal number may exceed NSIG. 93 */ 94static int 95sigstring_to_signum(char *sig) 96{ 97 98 if (is_number(sig)) { 99 int signo; 100 101 signo = atoi(sig); 102 return ((signo >= 0 && signo < NSIG) ? signo : (-1)); 103 } else if (strcasecmp(sig, "exit") == 0) { 104 return (0); 105 } else { 106 int n; 107 108 if (strncasecmp(sig, "sig", 3) == 0) 109 sig += 3; 110 for (n = 1; n < sys_nsig; n++) 111 if (sys_signame[n] && 112 strcasecmp(sys_signame[n], sig) == 0) 113 return (n); 114 } 115 return (-1); 116} 117 118 119/* 120 * Print a list of valid signal names. 121 */ 122static void 123printsignals(void) 124{ 125 int n, outlen; 126 127 outlen = 0; 128 for (n = 1; n < sys_nsig; n++) { 129 if (sys_signame[n]) { 130 out1fmt("%s", sys_signame[n]); 131 outlen += strlen(sys_signame[n]); 132 } else { 133 out1fmt("%d", n); 134 outlen += 3; /* good enough */ 135 } 136 ++outlen; 137 if (outlen > 71 || n == sys_nsig - 1) { 138 out1str("\n"); 139 outlen = 0; 140 } else { 141 out1c(' '); 142 } 143 } 144} 145 146 147/* 148 * The trap builtin. 149 */ 150int 151trapcmd(int argc, char **argv) 152{ 153 char *action; 154 int signo; 155 int errors = 0; 156 157 if (argc <= 1) { 158 for (signo = 0 ; signo < sys_nsig ; signo++) { 159 if (signo < NSIG && trap[signo] != NULL) { 160 out1str("trap -- "); 161 out1qstr(trap[signo]); 162 if (signo == 0) { 163 out1str(" exit\n"); 164 } else if (sys_signame[signo]) { 165 out1fmt(" %s\n", sys_signame[signo]); 166 } else { 167 out1fmt(" %d\n", signo); 168 } 169 } 170 } 171 return 0; 172 } 173 action = NULL; 174 if (*++argv && strcmp(*argv, "--") == 0) 175 argv++; 176 if (*argv && sigstring_to_signum(*argv) == -1) { 177 if ((*argv)[0] != '-') { 178 action = *argv; 179 argv++; 180 } else if ((*argv)[1] == '\0') { 181 argv++; 182 } else if ((*argv)[1] == 'l' && (*argv)[2] == '\0') { 183 printsignals(); 184 return 0; 185 } else { 186 error("bad option %s", *argv); 187 } 188 } 189 while (*argv) { 190 if ((signo = sigstring_to_signum(*argv)) == -1) { 191 warning("bad signal %s", *argv); 192 errors = 1; 193 } 194 INTOFF; 195 if (action) 196 action = savestr(action); 197 if (trap[signo]) 198 ckfree(trap[signo]); 199 trap[signo] = action; 200 if (signo != 0) 201 setsignal(signo); 202 INTON; 203 argv++; 204 } 205 return errors; 206} 207 208 209/* 210 * Clear traps on a fork. 211 */ 212void 213clear_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 */ 233int 234have_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 */ 249void 250setsignal(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 */ 340static int 341getsigaction(int signo, sig_t *sigact) 342{ 343 struct sigaction sa; 344 345 if (sigaction(signo, (struct sigaction *)0, &sa) == -1) 346 return 0; 347 *sigact = (sig_t) sa.sa_handler; 348 return 1; 349} 350 351 352/* 353 * Ignore a signal. 354 */ 355void 356ignoresig(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#ifdef mkinit 367INCLUDE <signal.h> 368INCLUDE "trap.h" 369 370SHELLPROC { 371 char *sm; 372 373 clear_traps(); 374 for (sm = sigmode ; sm < sigmode + NSIG ; sm++) { 375 if (*sm == S_IGN) 376 *sm = S_HARD_IGN; 377 } 378} 379#endif 380 381 382/* 383 * Signal handler. 384 */ 385void 386onsig(int signo) 387{ 388 389 if (signo == SIGINT && trap[SIGINT] == NULL) { 390 onint(); 391 return; 392 } 393 394 if (signo != SIGCHLD || !ignore_sigchld) 395 gotsig[signo] = 1; 396 pendingsigs++; 397 398 /* If we are currently in a wait builtin, prepare to break it */ 399 if ((signo == SIGINT || signo == SIGQUIT) && in_waitcmd != 0) 400 breakwaitcmd = 1; 401 /* 402 * If a trap is set, not ignored and not the null command, we need 403 * to make sure traps are executed even when a child blocks signals. 404 */ 405 if (Tflag && 406 trap[signo] != NULL && 407 ! (trap[signo][0] == '\0') && 408 ! (trap[signo][0] == ':' && trap[signo][1] == '\0')) 409 breakwaitcmd = 1; 410 411#ifndef NO_HISTORY 412 if (signo == SIGWINCH) 413 gotwinch = 1; 414#endif 415} 416 417 418/* 419 * Called to execute a trap. Perhaps we should avoid entering new trap 420 * handlers while we are executing a trap handler. 421 */ 422void 423dotrap(void) 424{ 425 int i; 426 int savestatus; 427 428 in_dotrap++; 429 for (;;) { 430 for (i = 1; i < NSIG; i++) { 431 if (gotsig[i]) { 432 gotsig[i] = 0; 433 if (trap[i]) { 434 /* 435 * Ignore SIGCHLD to avoid infinite 436 * recursion if the trap action does 437 * a fork. 438 */ 439 if (i == SIGCHLD) 440 ignore_sigchld++; 441 savestatus = exitstatus; 442 evalstring(trap[i], 0); 443 exitstatus = savestatus; 444 if (i == SIGCHLD) 445 ignore_sigchld--; 446 } 447 break; 448 } 449 } 450 if (i >= NSIG) 451 break; 452 } 453 in_dotrap--; 454 pendingsigs = 0; 455} 456 457 458/* 459 * Controls whether the shell is interactive or not. 460 */ 461void 462setinteractive(int on) 463{ 464 static int is_interactive = -1; 465 466 if (on == is_interactive) 467 return; 468 setsignal(SIGINT); 469 setsignal(SIGQUIT); 470 setsignal(SIGTERM); 471#ifndef NO_HISTORY 472 setsignal(SIGWINCH); 473#endif 474 is_interactive = on; 475} 476 477 478/* 479 * Called to exit the shell. 480 */ 481void 482exitshell(int status) 483{ 484 TRACE(("exitshell(%d) pid=%d\n", status, getpid())); 485 exiting = 1; 486 exiting_exitstatus = status; 487 exitshell_savedstatus(); 488} 489 490void 491exitshell_savedstatus(void) 492{ 493 struct jmploc loc1, loc2; 494 char *p; 495 496 if (!exiting) 497 exiting_exitstatus = oexitstatus; 498 exitstatus = oexitstatus = exiting_exitstatus; 499 if (setjmp(loc1.loc)) { 500 goto l1; 501 } 502 if (setjmp(loc2.loc)) { 503 goto l2; 504 } 505 handler = &loc1; 506 if ((p = trap[0]) != NULL && *p != '\0') { 507 trap[0] = NULL; 508 evalstring(p, 0); 509 } 510l1: handler = &loc2; /* probably unnecessary */ 511 flushall(); 512#if JOBS 513 setjobctl(0); 514#endif 515l2: _exit(exiting_exitstatus); 516} 517