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      1 /*	$NetBSD: trap.c,v 1.31 2005/01/11 19:38:57 christos Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 1991, 1993
      5  *	The Regents of the University of California.  All rights reserved.
      6  *
      7  * This code is derived from software contributed to Berkeley by
      8  * Kenneth Almquist.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  * 3. Neither the name of the University nor the names of its contributors
     19  *    may be used to endorse or promote products derived from this software
     20  *    without specific prior written permission.
     21  *
     22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     32  * SUCH DAMAGE.
     33  */
     34 
     35 #include <sys/cdefs.h>
     36 #ifndef lint
     37 #if 0
     38 static char sccsid[] = "@(#)trap.c	8.5 (Berkeley) 6/5/95";
     39 #else
     40 __RCSID("$NetBSD: trap.c,v 1.31 2005/01/11 19:38:57 christos Exp $");
     41 #endif
     42 #endif /* not lint */
     43 
     44 #include <signal.h>
     45 #include <unistd.h>
     46 #include <stdlib.h>
     47 
     48 #include "shell.h"
     49 #include "main.h"
     50 #include "nodes.h"	/* for other headers */
     51 #include "eval.h"
     52 #include "jobs.h"
     53 #include "show.h"
     54 #include "options.h"
     55 #include "syntax.h"
     56 #include "output.h"
     57 #include "memalloc.h"
     58 #include "error.h"
     59 #include "trap.h"
     60 #include "mystring.h"
     61 #include "var.h"
     62 
     63 static const char *sys_signame[NSIG] = {
     64 	"Unused",
     65 	"HUP",      "INT",    "QUIT",    "ILL",
     66 	"TRAP",     "ABRT",   "BUS",     "FPE",
     67 	"KILL",     "USR1",   "SEGV",    "USR2",
     68 	"PIPE",     "ALRM",   "TERM",
     69 	"Unknown",
     70 	"CHLD",
     71 	"CONT",     "STOP",   "TSTP",    "TTIN",
     72 	"TTOU",     "URG",    "XCPU",    "XFSZ",
     73 	"VTALRM",   "PROF",   "WINCH",   "IO",
     74 	"PWR",      "SYS"
     75 };
     76 
     77 /*
     78  * Sigmode records the current value of the signal handlers for the various
     79  * modes.  A value of zero means that the current handler is not known.
     80  * S_HARD_IGN indicates that the signal was ignored on entry to the shell,
     81  */
     82 
     83 #define S_DFL 1			/* default signal handling (SIG_DFL) */
     84 #define S_CATCH 2		/* signal is caught */
     85 #define S_IGN 3			/* signal is ignored (SIG_IGN) */
     86 #define S_HARD_IGN 4		/* signal is ignored permenantly */
     87 #define S_RESET 5		/* temporary - to reset a hard ignored sig */
     88 
     89 
     90 char *trap[NSIG+1];		/* trap handler commands */
     91 MKINIT char sigmode[NSIG];	/* current value of signal */
     92 char gotsig[NSIG];		/* indicates specified signal received */
     93 int pendingsigs;		/* indicates some signal received */
     94 
     95 static int getsigaction(int, sig_t *);
     96 
     97 /*
     98  * return the signal number described by `p' (as a number or a name)
     99  * or -1 if it isn't one
    100  */
    101 
    102 static int
    103 signame_to_signum(const char *p)
    104 {
    105 	int i;
    106 
    107 	if (is_number(p))
    108 		return number(p);
    109 
    110 	if (strcasecmp(p, "exit") == 0 )
    111 		return 0;
    112 
    113 	if (strncasecmp(p, "sig", 3) == 0)
    114 		p += 3;
    115 
    116 	for (i = 0; i < NSIG; ++i)
    117 		if (strcasecmp (p, sys_signame[i]) == 0)
    118 			return i;
    119 	return -1;
    120 }
    121 
    122 /*
    123  * Print a list of valid signal names
    124  */
    125 static void
    126 printsignals(void)
    127 {
    128 	int n;
    129 
    130 	out1str("EXIT ");
    131 
    132 	for (n = 1; n < NSIG; n++) {
    133 		out1fmt("%s", sys_signame[n]);
    134 		if ((n == NSIG/2) ||  n == (NSIG - 1))
    135 			out1str("\n");
    136 		else
    137 			out1c(' ');
    138 	}
    139 }
    140 
    141 /*
    142  * The trap builtin.
    143  */
    144 
    145 int
    146 trapcmd(int argc, char **argv)
    147 {
    148 	char *action;
    149 	char **ap;
    150 	int signo;
    151 
    152 	if (argc <= 1) {
    153 		for (signo = 0 ; signo <= NSIG ; signo++)
    154 			if (trap[signo] != NULL) {
    155 				out1fmt("trap -- ");
    156 				print_quoted(trap[signo]);
    157 				out1fmt(" %s\n",
    158 				    (signo) ? sys_signame[signo] : "EXIT");
    159 			}
    160 		return 0;
    161 	}
    162 	ap = argv + 1;
    163 
    164 	action = NULL;
    165 
    166 	if (strcmp(*ap, "--") == 0)
    167 		if (*++ap == NULL)
    168 			return 0;
    169 
    170 	if (signame_to_signum(*ap) == -1) {
    171 		if ((*ap)[0] == '-') {
    172 			if ((*ap)[1] == '\0')
    173 				ap++;
    174 			else if ((*ap)[1] == 'l' && (*ap)[2] == '\0') {
    175 				printsignals();
    176 				return 0;
    177 			}
    178 			else
    179 				error("bad option %s\n", *ap);
    180 		}
    181 		else
    182 			action = *ap++;
    183 	}
    184 
    185 	while (*ap) {
    186 		if (is_number(*ap))
    187 			signo = number(*ap);
    188 		else
    189 			signo = signame_to_signum(*ap);
    190 
    191 		if (signo < 0 || signo > NSIG)
    192 			error("%s: bad trap", *ap);
    193 
    194 		INTOFF;
    195 		if (action)
    196 			action = savestr(action);
    197 
    198 		if (trap[signo])
    199 			ckfree(trap[signo]);
    200 
    201 		trap[signo] = action;
    202 
    203 		if (signo != 0)
    204 			setsignal(signo, 0);
    205 		INTON;
    206 		ap++;
    207 	}
    208 	return 0;
    209 }
    210 
    211 
    212 
    213 /*
    214  * Clear traps on a fork or vfork.
    215  * Takes one arg vfork, to tell it to not be destructive of
    216  * the parents variables.
    217  */
    218 
    219 void
    220 clear_traps(int vforked)
    221 {
    222 	char **tp;
    223 
    224 	for (tp = trap ; tp <= &trap[NSIG] ; tp++) {
    225 		if (*tp && **tp) {	/* trap not NULL or SIG_IGN */
    226 			INTOFF;
    227 			if (!vforked) {
    228 				ckfree(*tp);
    229 				*tp = NULL;
    230 			}
    231 			if (tp != &trap[0])
    232 				setsignal(tp - trap, vforked);
    233 			INTON;
    234 		}
    235 	}
    236 }
    237 
    238 
    239 
    240 /*
    241  * Set the signal handler for the specified signal.  The routine figures
    242  * out what it should be set to.
    243  */
    244 
    245 long
    246 setsignal(int signo, int vforked)
    247 {
    248 	int action;
    249 	sig_t sigact = SIG_DFL;
    250 	struct sigaction act, oact;
    251 	char *t, tsig;
    252 
    253 	if ((t = trap[signo]) == NULL)
    254 		action = S_DFL;
    255 	else if (*t != '\0')
    256 		action = S_CATCH;
    257 	else
    258 		action = S_IGN;
    259 	if (rootshell && !vforked && action == S_DFL) {
    260 		switch (signo) {
    261 		case SIGINT:
    262 			if (iflag || minusc || sflag == 0)
    263 				action = S_CATCH;
    264 			break;
    265 		case SIGQUIT:
    266 #ifdef DEBUG
    267 			if (debug)
    268 				break;
    269 #endif
    270 			/* FALLTHROUGH */
    271 		case SIGTERM:
    272 			if (iflag)
    273 				action = S_IGN;
    274 			break;
    275 #if JOBS
    276 		case SIGTSTP:
    277 		case SIGTTOU:
    278 			if (mflag)
    279 				action = S_IGN;
    280 			break;
    281 #endif
    282 		}
    283 	}
    284 
    285 	t = &sigmode[signo - 1];
    286 	tsig = *t;
    287 	if (tsig == 0) {
    288 		/*
    289 		 * current setting unknown
    290 		 */
    291 		if (!getsigaction(signo, &sigact)) {
    292 			/*
    293 			 * Pretend it worked; maybe we should give a warning
    294 			 * here, but other shells don't. We don't alter
    295 			 * sigmode, so that we retry every time.
    296 			 */
    297 			return 0;
    298 		}
    299 		if (sigact == SIG_IGN) {
    300 			if (mflag && (signo == SIGTSTP ||
    301 			     signo == SIGTTIN || signo == SIGTTOU)) {
    302 				tsig = S_IGN;	/* don't hard ignore these */
    303 			} else
    304 				tsig = S_HARD_IGN;
    305 		} else {
    306 			tsig = S_RESET;	/* force to be set */
    307 		}
    308 	}
    309 	if (tsig == S_HARD_IGN || tsig == action)
    310 		return 0;
    311 	switch (action) {
    312 		case S_DFL:	sigact = SIG_DFL;	break;
    313 		case S_CATCH:  	sigact = onsig;		break;
    314 		case S_IGN:	sigact = SIG_IGN;	break;
    315 	}
    316 	if (!vforked)
    317 		*t = action;
    318     act.sa_handler = sigact;
    319     sigemptyset(&act.sa_mask);
    320     act.sa_flags = 0;
    321 #ifdef SA_INTERRUPT
    322     act.sa_flags |= SA_INTERRUPT;
    323 #endif
    324     if(sigaction(signo, &act, &oact) < 0)
    325         return (long) SIG_ERR;
    326     return (long) oact.sa_handler;
    327 }
    328 
    329 /*
    330  * Return the current setting for sig w/o changing it.
    331  */
    332 static int
    333 getsigaction(int signo, sig_t *sigact)
    334 {
    335 	struct sigaction sa;
    336 
    337 	if (sigaction(signo, (struct sigaction *)0, &sa) == -1)
    338 		return 0;
    339 	*sigact = (sig_t) sa.sa_handler;
    340 	return 1;
    341 }
    342 
    343 /*
    344  * Ignore a signal.
    345  */
    346 
    347 void
    348 ignoresig(int signo, int vforked)
    349 {
    350 	if (sigmode[signo - 1] != S_IGN && sigmode[signo - 1] != S_HARD_IGN)
    351 		bsd_signal(signo, SIG_IGN);
    352 	if (!vforked)
    353 		sigmode[signo - 1] = S_HARD_IGN;
    354 }
    355 
    356 
    357 #ifdef mkinit
    358 INCLUDE <signal.h>
    359 INCLUDE "trap.h"
    360 
    361 SHELLPROC {
    362 	char *sm;
    363 
    364 	clear_traps(0);
    365 	for (sm = sigmode ; sm < sigmode + NSIG ; sm++) {
    366 		if (*sm == S_IGN)
    367 			*sm = S_HARD_IGN;
    368 	}
    369 }
    370 #endif
    371 
    372 
    373 
    374 /*
    375  * Signal handler.
    376  */
    377 
    378 void
    379 onsig(int signo)
    380 {
    381 	bsd_signal(signo, onsig);
    382 	if (signo == SIGINT && trap[SIGINT] == NULL) {
    383 		onint();
    384 		return;
    385 	}
    386 	gotsig[signo - 1] = 1;
    387 	pendingsigs++;
    388 }
    389 
    390 
    391 
    392 /*
    393  * Called to execute a trap.  Perhaps we should avoid entering new trap
    394  * handlers while we are executing a trap handler.
    395  */
    396 
    397 void
    398 dotrap(void)
    399 {
    400 	int i;
    401 	int savestatus;
    402 
    403 	for (;;) {
    404 		for (i = 1 ; ; i++) {
    405 			if (gotsig[i - 1])
    406 				break;
    407 			if (i >= NSIG)
    408 				goto done;
    409 		}
    410 		gotsig[i - 1] = 0;
    411 		savestatus=exitstatus;
    412 		evalstring(trap[i], 0);
    413 		exitstatus=savestatus;
    414 	}
    415 done:
    416 	pendingsigs = 0;
    417 }
    418 
    419 
    420 
    421 /*
    422  * Controls whether the shell is interactive or not.
    423  */
    424 
    425 
    426 void
    427 setinteractive(int on)
    428 {
    429 	static int is_interactive;
    430 
    431 	if (on == is_interactive)
    432 		return;
    433 	setsignal(SIGINT, 0);
    434 	setsignal(SIGQUIT, 0);
    435 	setsignal(SIGTERM, 0);
    436 	is_interactive = on;
    437 }
    438 
    439 
    440 
    441 /*
    442  * Called to exit the shell.
    443  */
    444 
    445 void
    446 exitshell(int status)
    447 {
    448 	struct jmploc loc1, loc2;
    449 	char *p;
    450 
    451 	TRACE(("pid %d, exitshell(%d)\n", getpid(), status));
    452 	if (setjmp(loc1.loc)) {
    453 		goto l1;
    454 	}
    455 	if (setjmp(loc2.loc)) {
    456 		goto l2;
    457 	}
    458 	handler = &loc1;
    459 	if ((p = trap[0]) != NULL && *p != '\0') {
    460 		trap[0] = NULL;
    461 		evalstring(p, 0);
    462 	}
    463 l1:   handler = &loc2;			/* probably unnecessary */
    464 	flushall();
    465 #if JOBS
    466 	setjobctl(0);
    467 #endif
    468 l2:   _exit(status);
    469 	/* NOTREACHED */
    470 }
    471