trap.c revision 100351
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 100351 2002-07-19 08:09:04Z tjr $"); 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 63 64/* 65 * Sigmode records the current value of the signal handlers for the various 66 * modes. A value of zero means that the current handler is not known. 67 * S_HARD_IGN indicates that the signal was ignored on entry to the shell, 68 */ 69 70#define S_DFL 1 /* default signal handling (SIG_DFL) */ 71#define S_CATCH 2 /* signal is caught */ 72#define S_IGN 3 /* signal is ignored (SIG_IGN) */ 73#define S_HARD_IGN 4 /* signal is ignored permanently */ 74#define S_RESET 5 /* temporary - to reset a hard ignored sig */ 75 76 77MKINIT char sigmode[NSIG]; /* current value of signal */ 78int pendingsigs; /* indicates some signal received */ 79int in_dotrap; /* do we execute in a trap handler? */ 80static char *volatile trap[NSIG]; /* trap handler commands */ 81static volatile sig_atomic_t gotsig[NSIG]; 82 /* indicates specified signal received */ 83static int ignore_sigchld; /* Used while handling SIGCHLD traps. */ 84 85static int getsigaction(int, sig_t *); 86 87 88/* 89 * Map a string to a signal number. 90 */ 91static int 92sigstring_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 < NSIG; n++) 108 if (strcasecmp(sys_signame[n], sig) == 0) 109 return (n); 110 } 111 return (-1); 112} 113 114 115/* 116 * Print a list of valid signal names. 117 */ 118static void 119printsignals(void) 120{ 121 int n; 122 123 for (n = 1; n < NSIG; n++) { 124 out1fmt("%s", sys_signame[n]); 125 if (n == (NSIG / 2) || n == (NSIG - 1)) 126 out1str("\n"); 127 else 128 out1c(' '); 129 } 130} 131 132 133/* 134 * The trap builtin. 135 */ 136int 137trapcmd(int argc, char **argv) 138{ 139 char *action; 140 int signo; 141 142 if (argc <= 1) { 143 for (signo = 0 ; signo < NSIG ; signo++) { 144 if (trap[signo] != NULL) 145 out1fmt("trap -- '%s' %s\n", trap[signo], 146 (signo) ? sys_signame[signo] : "exit"); 147 } 148 return 0; 149 } 150 action = NULL; 151 if (*++argv && strcmp(*argv, "--") == 0) 152 argv++; 153 if (*argv && sigstring_to_signum(*argv) == -1) { 154 if ((*argv)[0] != '-') { 155 action = *argv; 156 argv++; 157 } else if ((*argv)[1] == '\0') { 158 argv++; 159 } else if ((*argv)[1] == 'l' && (*argv)[2] == '\0') { 160 printsignals(); 161 return 0; 162 } else { 163 error("bad option %s", *argv); 164 } 165 } 166 while (*argv) { 167 if ((signo = sigstring_to_signum(*argv)) == -1) 168 error("bad signal %s", *argv); 169 INTOFF; 170 if (action) 171 action = savestr(action); 172 if (trap[signo]) 173 ckfree(trap[signo]); 174 trap[signo] = action; 175 if (signo != 0) 176 setsignal(signo); 177 INTON; 178 argv++; 179 } 180 return 0; 181} 182 183 184/* 185 * Clear traps on a fork. 186 */ 187void 188clear_traps(void) 189{ 190 char *volatile *tp; 191 192 for (tp = trap ; tp <= &trap[NSIG - 1] ; tp++) { 193 if (*tp && **tp) { /* trap not NULL or SIG_IGN */ 194 INTOFF; 195 ckfree(*tp); 196 *tp = NULL; 197 if (tp != &trap[0]) 198 setsignal(tp - trap); 199 INTON; 200 } 201 } 202} 203 204 205/* 206 * Set the signal handler for the specified signal. The routine figures 207 * out what it should be set to. 208 */ 209void 210setsignal(int signo) 211{ 212 int action; 213 sig_t sig, sigact = SIG_DFL; 214 char *t; 215 216 if ((t = trap[signo]) == NULL) 217 action = S_DFL; 218 else if (*t != '\0') 219 action = S_CATCH; 220 else 221 action = S_IGN; 222 if (action == S_DFL) { 223 switch (signo) { 224 case SIGINT: 225 action = S_CATCH; 226 break; 227 case SIGQUIT: 228#ifdef DEBUG 229 { 230 extern int debug; 231 232 if (debug) 233 break; 234 } 235#endif 236 action = S_CATCH; 237 break; 238 case SIGTERM: 239 if (rootshell && iflag) 240 action = S_IGN; 241 break; 242#if JOBS 243 case SIGTSTP: 244 case SIGTTOU: 245 if (rootshell && mflag) 246 action = S_IGN; 247 break; 248#endif 249 } 250 } 251 252 t = &sigmode[signo]; 253 if (*t == 0) { 254 /* 255 * current setting unknown 256 */ 257 if (!getsigaction(signo, &sigact)) { 258 /* 259 * Pretend it worked; maybe we should give a warning 260 * here, but other shells don't. We don't alter 261 * sigmode, so that we retry every time. 262 */ 263 return; 264 } 265 if (sigact == SIG_IGN) { 266 if (mflag && (signo == SIGTSTP || 267 signo == SIGTTIN || signo == SIGTTOU)) { 268 *t = S_IGN; /* don't hard ignore these */ 269 } else 270 *t = S_HARD_IGN; 271 } else { 272 *t = S_RESET; /* force to be set */ 273 } 274 } 275 if (*t == S_HARD_IGN || *t == action) 276 return; 277 switch (action) { 278 case S_DFL: sigact = SIG_DFL; break; 279 case S_CATCH: sigact = onsig; break; 280 case S_IGN: sigact = SIG_IGN; break; 281 } 282 *t = action; 283 sig = signal(signo, sigact); 284 if (sig != SIG_ERR && action == S_CATCH) 285 siginterrupt(signo, 1); 286} 287 288 289/* 290 * Return the current setting for sig w/o changing it. 291 */ 292static int 293getsigaction(int signo, sig_t *sigact) 294{ 295 struct sigaction sa; 296 297 if (sigaction(signo, (struct sigaction *)0, &sa) == -1) 298 return 0; 299 *sigact = (sig_t) sa.sa_handler; 300 return 1; 301} 302 303 304/* 305 * Ignore a signal. 306 */ 307void 308ignoresig(int signo) 309{ 310 311 if (sigmode[signo] != S_IGN && sigmode[signo] != S_HARD_IGN) { 312 signal(signo, SIG_IGN); 313 } 314 sigmode[signo] = S_HARD_IGN; 315} 316 317 318#ifdef mkinit 319INCLUDE <signal.h> 320INCLUDE "trap.h" 321 322SHELLPROC { 323 char *sm; 324 325 clear_traps(); 326 for (sm = sigmode ; sm < sigmode + NSIG ; sm++) { 327 if (*sm == S_IGN) 328 *sm = S_HARD_IGN; 329 } 330} 331#endif 332 333 334/* 335 * Signal handler. 336 */ 337void 338onsig(int signo) 339{ 340 341 if (signo == SIGINT && trap[SIGINT] == NULL) { 342 onint(); 343 return; 344 } 345 346 if (signo != SIGCHLD || !ignore_sigchld) 347 gotsig[signo] = 1; 348 pendingsigs++; 349 350 /* If we are currently in a wait builtin, prepare to break it */ 351 if ((signo == SIGINT || signo == SIGQUIT) && in_waitcmd != 0) 352 breakwaitcmd = 1; 353 /* 354 * If a trap is set, not ignored and not the null command, we need 355 * to make sure traps are executed even when a child blocks signals. 356 */ 357 if (Tflag && 358 trap[signo] != NULL && 359 ! trap[signo][0] == '\0' && 360 ! (trap[signo][0] == ':' && trap[signo][1] == '\0')) 361 breakwaitcmd = 1; 362} 363 364 365/* 366 * Called to execute a trap. Perhaps we should avoid entering new trap 367 * handlers while we are executing a trap handler. 368 */ 369void 370dotrap(void) 371{ 372 int i; 373 int savestatus; 374 375 in_dotrap++; 376 for (;;) { 377 for (i = 1; i < NSIG; i++) { 378 if (gotsig[i]) { 379 gotsig[i] = 0; 380 if (trap[i]) { 381 /* 382 * Ignore SIGCHLD to avoid infinite recursion 383 * if the trap action does a fork. 384 */ 385 if (i == SIGCHLD) 386 ignore_sigchld++; 387 savestatus = exitstatus; 388 evalstring(trap[i]); 389 exitstatus = savestatus; 390 if (i == SIGCHLD) 391 ignore_sigchld--; 392 } 393 break; 394 } 395 } 396 if (i >= NSIG) 397 break; 398 } 399 in_dotrap--; 400 pendingsigs = 0; 401} 402 403 404/* 405 * Controls whether the shell is interactive or not. 406 */ 407void 408setinteractive(int on) 409{ 410 static int is_interactive = -1; 411 412 if (on == is_interactive) 413 return; 414 setsignal(SIGINT); 415 setsignal(SIGQUIT); 416 setsignal(SIGTERM); 417 is_interactive = on; 418} 419 420 421/* 422 * Called to exit the shell. 423 */ 424void 425exitshell(int status) 426{ 427 struct jmploc loc1, loc2; 428 char *p; 429 430 TRACE(("exitshell(%d) pid=%d\n", status, getpid())); 431 if (setjmp(loc1.loc)) { 432 goto l1; 433 } 434 if (setjmp(loc2.loc)) { 435 goto l2; 436 } 437 handler = &loc1; 438 if ((p = trap[0]) != NULL && *p != '\0') { 439 trap[0] = NULL; 440 evalstring(p); 441 } 442l1: handler = &loc2; /* probably unnecessary */ 443 flushall(); 444#if JOBS 445 setjobctl(0); 446#endif 447l2: _exit(status); 448} 449