trap.c revision 125727
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 37#ifndef lint 38#if 0 39static char sccsid[] = "@(#)trap.c 8.5 (Berkeley) 6/5/95"; 40#endif 41#endif /* not lint */ 42#include <sys/cdefs.h> 43__FBSDID("$FreeBSD: head/bin/sh/trap.c 125727 2004-02-12 05:03:37Z njl $"); 44 45#include <signal.h> 46#include <unistd.h> 47#include <stdlib.h> 48 49#include "shell.h" 50#include "main.h" 51#include "nodes.h" /* for other headers */ 52#include "eval.h" 53#include "jobs.h" 54#include "show.h" 55#include "options.h" 56#include "syntax.h" 57#include "output.h" 58#include "memalloc.h" 59#include "error.h" 60#include "trap.h" 61#include "mystring.h" 62#include "myhistedit.h" 63 64 65/* 66 * Sigmode records the current value of the signal handlers for the various 67 * modes. A value of zero means that the current handler is not known. 68 * S_HARD_IGN indicates that the signal was ignored on entry to the shell, 69 */ 70 71#define S_DFL 1 /* default signal handling (SIG_DFL) */ 72#define S_CATCH 2 /* signal is caught */ 73#define S_IGN 3 /* signal is ignored (SIG_IGN) */ 74#define S_HARD_IGN 4 /* signal is ignored permanently */ 75#define S_RESET 5 /* temporary - to reset a hard ignored sig */ 76 77 78MKINIT char sigmode[NSIG]; /* current value of signal */ 79int pendingsigs; /* indicates some signal received */ 80int in_dotrap; /* do we execute in a trap handler? */ 81static char *volatile trap[NSIG]; /* trap handler commands */ 82static volatile sig_atomic_t gotsig[NSIG]; 83 /* indicates specified signal received */ 84static int ignore_sigchld; /* Used while handling SIGCHLD traps. */ 85volatile sig_atomic_t gotwinch; 86 87static 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 */ 95static int 96sigstring_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] && 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 > 70 || 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; 155 156 if (argc <= 1) { 157 for (signo = 0 ; signo < sys_nsig ; signo++) { 158 if (signo < NSIG && trap[signo] != NULL) { 159 if (signo == 0) { 160 out1fmt("trap -- '%s' %s\n", 161 trap[signo], "exit"); 162 } else if (sys_signame[signo]) { 163 out1fmt("trap -- '%s' %s\n", 164 trap[signo], sys_signame[signo]); 165 } else { 166 out1fmt("trap -- '%s' %d\n", 167 trap[signo], 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 error("bad signal %s", *argv); 192 INTOFF; 193 if (action) 194 action = savestr(action); 195 if (trap[signo]) 196 ckfree(trap[signo]); 197 trap[signo] = action; 198 if (signo != 0) 199 setsignal(signo); 200 INTON; 201 argv++; 202 } 203 return 0; 204} 205 206 207/* 208 * Clear traps on a fork. 209 */ 210void 211clear_traps(void) 212{ 213 char *volatile *tp; 214 215 for (tp = trap ; tp <= &trap[NSIG - 1] ; tp++) { 216 if (*tp && **tp) { /* trap not NULL or SIG_IGN */ 217 INTOFF; 218 ckfree(*tp); 219 *tp = NULL; 220 if (tp != &trap[0]) 221 setsignal(tp - trap); 222 INTON; 223 } 224 } 225} 226 227 228/* 229 * Set the signal handler for the specified signal. The routine figures 230 * out what it should be set to. 231 */ 232void 233setsignal(int signo) 234{ 235 int action; 236 sig_t sig, sigact = SIG_DFL; 237 char *t; 238 239 if ((t = trap[signo]) == NULL) 240 action = S_DFL; 241 else if (*t != '\0') 242 action = S_CATCH; 243 else 244 action = S_IGN; 245 if (action == S_DFL) { 246 switch (signo) { 247 case SIGINT: 248 action = S_CATCH; 249 break; 250 case SIGQUIT: 251#ifdef DEBUG 252 { 253 extern int debug; 254 255 if (debug) 256 break; 257 } 258#endif 259 action = S_CATCH; 260 break; 261 case SIGTERM: 262 if (rootshell && iflag) 263 action = S_IGN; 264 break; 265#if JOBS 266 case SIGTSTP: 267 case SIGTTOU: 268 if (rootshell && mflag) 269 action = S_IGN; 270 break; 271#endif 272#ifndef NO_HISTORY 273 case SIGWINCH: 274 if (rootshell && iflag) 275 action = S_CATCH; 276 break; 277#endif 278 } 279 } 280 281 t = &sigmode[signo]; 282 if (*t == 0) { 283 /* 284 * current setting unknown 285 */ 286 if (!getsigaction(signo, &sigact)) { 287 /* 288 * Pretend it worked; maybe we should give a warning 289 * here, but other shells don't. We don't alter 290 * sigmode, so that we retry every time. 291 */ 292 return; 293 } 294 if (sigact == SIG_IGN) { 295 if (mflag && (signo == SIGTSTP || 296 signo == SIGTTIN || signo == SIGTTOU)) { 297 *t = S_IGN; /* don't hard ignore these */ 298 } else 299 *t = S_HARD_IGN; 300 } else { 301 *t = S_RESET; /* force to be set */ 302 } 303 } 304 if (*t == S_HARD_IGN || *t == action) 305 return; 306 switch (action) { 307 case S_DFL: sigact = SIG_DFL; break; 308 case S_CATCH: sigact = onsig; break; 309 case S_IGN: sigact = SIG_IGN; break; 310 } 311 *t = action; 312 sig = signal(signo, sigact); 313 if (sig != SIG_ERR && action == S_CATCH) 314 siginterrupt(signo, 1); 315} 316 317 318/* 319 * Return the current setting for sig w/o changing it. 320 */ 321static int 322getsigaction(int signo, sig_t *sigact) 323{ 324 struct sigaction sa; 325 326 if (sigaction(signo, (struct sigaction *)0, &sa) == -1) 327 return 0; 328 *sigact = (sig_t) sa.sa_handler; 329 return 1; 330} 331 332 333/* 334 * Ignore a signal. 335 */ 336void 337ignoresig(int signo) 338{ 339 340 if (sigmode[signo] != S_IGN && sigmode[signo] != S_HARD_IGN) { 341 signal(signo, SIG_IGN); 342 } 343 sigmode[signo] = S_HARD_IGN; 344} 345 346 347#ifdef mkinit 348INCLUDE <signal.h> 349INCLUDE "trap.h" 350 351SHELLPROC { 352 char *sm; 353 354 clear_traps(); 355 for (sm = sigmode ; sm < sigmode + NSIG ; sm++) { 356 if (*sm == S_IGN) 357 *sm = S_HARD_IGN; 358 } 359} 360#endif 361 362 363/* 364 * Signal handler. 365 */ 366void 367onsig(int signo) 368{ 369 370 if (signo == SIGINT && trap[SIGINT] == NULL) { 371 onint(); 372 return; 373 } 374 375 if (signo != SIGCHLD || !ignore_sigchld) 376 gotsig[signo] = 1; 377 pendingsigs++; 378 379 /* If we are currently in a wait builtin, prepare to break it */ 380 if ((signo == SIGINT || signo == SIGQUIT) && in_waitcmd != 0) 381 breakwaitcmd = 1; 382 /* 383 * If a trap is set, not ignored and not the null command, we need 384 * to make sure traps are executed even when a child blocks signals. 385 */ 386 if (Tflag && 387 trap[signo] != NULL && 388 ! trap[signo][0] == '\0' && 389 ! (trap[signo][0] == ':' && trap[signo][1] == '\0')) 390 breakwaitcmd = 1; 391 392#ifndef NO_HISTORY 393 if (signo == SIGWINCH) 394 gotwinch = 1; 395#endif 396} 397 398 399/* 400 * Called to execute a trap. Perhaps we should avoid entering new trap 401 * handlers while we are executing a trap handler. 402 */ 403void 404dotrap(void) 405{ 406 int i; 407 int savestatus; 408 409 in_dotrap++; 410 for (;;) { 411 for (i = 1; i < NSIG; i++) { 412 if (gotsig[i]) { 413 gotsig[i] = 0; 414 if (trap[i]) { 415 /* 416 * Ignore SIGCHLD to avoid infinite recursion 417 * if the trap action does a fork. 418 */ 419 if (i == SIGCHLD) 420 ignore_sigchld++; 421 savestatus = exitstatus; 422 evalstring(trap[i]); 423 exitstatus = savestatus; 424 if (i == SIGCHLD) 425 ignore_sigchld--; 426 } 427 break; 428 } 429 } 430 if (i >= NSIG) 431 break; 432 } 433 in_dotrap--; 434 pendingsigs = 0; 435} 436 437 438/* 439 * Controls whether the shell is interactive or not. 440 */ 441void 442setinteractive(int on) 443{ 444 static int is_interactive = -1; 445 446 if (on == is_interactive) 447 return; 448 setsignal(SIGINT); 449 setsignal(SIGQUIT); 450 setsignal(SIGTERM); 451#ifndef NO_HISTORY 452 setsignal(SIGWINCH); 453#endif 454 is_interactive = on; 455} 456 457 458/* 459 * Called to exit the shell. 460 */ 461void 462exitshell(int status) 463{ 464 struct jmploc loc1, loc2; 465 char *p; 466 467 TRACE(("exitshell(%d) pid=%d\n", status, getpid())); 468 if (setjmp(loc1.loc)) { 469 goto l1; 470 } 471 if (setjmp(loc2.loc)) { 472 goto l2; 473 } 474 handler = &loc1; 475 if ((p = trap[0]) != NULL && *p != '\0') { 476 trap[0] = NULL; 477 evalstring(p); 478 } 479l1: handler = &loc2; /* probably unnecessary */ 480 flushall(); 481#if JOBS 482 setjobctl(0); 483#endif 484l2: _exit(status); 485} 486