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trap.c revision 1.13 
      1 /*	$NetBSD: trap.c,v 1.13 1995/05/11 21:30:28 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. All advertising materials mentioning features or use of this software
     19  *    must display the following acknowledgement:
     20  *	This product includes software developed by the University of
     21  *	California, Berkeley and its contributors.
     22  * 4. Neither the name of the University nor the names of its contributors
     23  *    may be used to endorse or promote products derived from this software
     24  *    without specific prior written permission.
     25  *
     26  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     27  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     28  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     29  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     30  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     31  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     32  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     33  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     34  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     35  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     36  * SUCH DAMAGE.
     37  */
     38 
     39 #ifndef lint
     40 #if 0
     41 static char sccsid[] = "@(#)trap.c	8.3 (Berkeley) 5/4/95";
     42 #else
     43 static char rcsid[] = "$NetBSD: trap.c,v 1.13 1995/05/11 21:30:28 christos Exp $";
     44 #endif
     45 #endif /* not lint */
     46 
     47 #include <signal.h>
     48 #include <unistd.h>
     49 #include <stdlib.h>
     50 
     51 #include "shell.h"
     52 #include "main.h"
     53 #include "nodes.h"	/* for other headers */
     54 #include "eval.h"
     55 #include "jobs.h"
     56 #include "show.h"
     57 #include "options.h"
     58 #include "syntax.h"
     59 #include "output.h"
     60 #include "memalloc.h"
     61 #include "error.h"
     62 #include "trap.h"
     63 #include "mystring.h"
     64 
     65 
     66 /*
     67  * Sigmode records the current value of the signal handlers for the various
     68  * modes.  A value of zero means that the current handler is not known.
     69  * S_HARD_IGN indicates that the signal was ignored on entry to the shell,
     70  */
     71 
     72 #define S_DFL 1			/* default signal handling (SIG_DFL) */
     73 #define S_CATCH 2		/* signal is caught */
     74 #define S_IGN 3			/* signal is ignored (SIG_IGN) */
     75 #define S_HARD_IGN 4		/* signal is ignored permenantly */
     76 #define S_RESET 5		/* temporary - to reset a hard ignored sig */
     77 
     78 
     79 extern char nullstr[1];		/* null string */
     80 
     81 char *trap[NSIG+1];		/* trap handler commands */
     82 MKINIT char sigmode[NSIG];	/* current value of signal */
     83 char gotsig[NSIG];		/* indicates specified signal received */
     84 int pendingsigs;			/* indicates some signal received */
     85 
     86 /*
     87  * The trap builtin.
     88  */
     89 
     90 int
     91 trapcmd(argc, argv)
     92 	int argc;
     93 	char **argv;
     94 {
     95 	char *action;
     96 	char **ap;
     97 	int signo;
     98 
     99 	if (argc <= 1) {
    100 		for (signo = 0 ; signo <= NSIG ; signo++) {
    101 			if (trap[signo] != NULL)
    102 				out1fmt("%d: %s\n", signo, trap[signo]);
    103 		}
    104 		return 0;
    105 	}
    106 	ap = argv + 1;
    107 	if (is_number(*ap))
    108 		action = NULL;
    109 	else
    110 		action = *ap++;
    111 	while (*ap) {
    112 		if ((signo = number(*ap)) < 0 || signo > NSIG)
    113 			error("%s: bad trap", *ap);
    114 		INTOFF;
    115 		if (action)
    116 			action = savestr(action);
    117 		if (trap[signo])
    118 			ckfree(trap[signo]);
    119 		trap[signo] = action;
    120 		if (signo != 0)
    121 			setsignal(signo);
    122 		INTON;
    123 		ap++;
    124 	}
    125 	return 0;
    126 }
    127 
    128 
    129 
    130 /*
    131  * Clear traps on a fork.
    132  */
    133 
    134 void
    135 clear_traps() {
    136 	char **tp;
    137 
    138 	for (tp = trap ; tp <= &trap[NSIG] ; tp++) {
    139 		if (*tp && **tp) {	/* trap not NULL or SIG_IGN */
    140 			INTOFF;
    141 			ckfree(*tp);
    142 			*tp = NULL;
    143 			if (tp != &trap[0])
    144 				setsignal(tp - trap);
    145 			INTON;
    146 		}
    147 	}
    148 }
    149 
    150 
    151 
    152 /*
    153  * Set the signal handler for the specified signal.  The routine figures
    154  * out what it should be set to.
    155  */
    156 
    157 long
    158 setsignal(signo)
    159 	int signo;
    160 {
    161 	int action;
    162 	sig_t sigact = SIG_DFL;
    163 	char *t;
    164 	extern void onsig();
    165 	extern sig_t getsigaction();
    166 
    167 	if ((t = trap[signo]) == NULL)
    168 		action = S_DFL;
    169 	else if (*t != '\0')
    170 		action = S_CATCH;
    171 	else
    172 		action = S_IGN;
    173 	if (rootshell && action == S_DFL) {
    174 		switch (signo) {
    175 		case SIGINT:
    176 			if (iflag)
    177 				action = S_CATCH;
    178 			break;
    179 		case SIGQUIT:
    180 #ifdef DEBUG
    181 			{
    182 			extern int debug;
    183 
    184 			if (debug)
    185 				break;
    186 			}
    187 #endif
    188 			/* FALLTHROUGH */
    189 		case SIGTERM:
    190 			if (iflag)
    191 				action = S_IGN;
    192 			break;
    193 #if JOBS
    194 		case SIGTSTP:
    195 		case SIGTTOU:
    196 			if (mflag)
    197 				action = S_IGN;
    198 			break;
    199 #endif
    200 		}
    201 	}
    202 	t = &sigmode[signo - 1];
    203 	if (*t == 0) {
    204 		/*
    205 		 * current setting unknown
    206 		 */
    207 		sigact = getsigaction(signo);
    208 		if (sigact == SIG_IGN) {
    209 			if (mflag && (signo == SIGTSTP ||
    210 			     signo == SIGTTIN || signo == SIGTTOU)) {
    211 				*t = S_IGN;	/* don't hard ignore these */
    212 			} else
    213 				*t = S_HARD_IGN;
    214 		} else {
    215 			*t = S_RESET;	/* force to be set */
    216 		}
    217 	}
    218 	if (*t == S_HARD_IGN || *t == action)
    219 		return 0;
    220 	switch (action) {
    221 		case S_DFL:	sigact = SIG_DFL;	break;
    222 		case S_CATCH:  	sigact = onsig;		break;
    223 		case S_IGN:	sigact = SIG_IGN;	break;
    224 	}
    225 	*t = action;
    226 	return (long)signal(signo, sigact);
    227 }
    228 
    229 /*
    230  * Return the current setting for sig w/o changing it.
    231  */
    232 sig_t
    233 getsigaction(signo)
    234 	int signo;
    235 {
    236 	struct sigaction sa;
    237 
    238 	if (sigaction(signo, (struct sigaction *)0, &sa) == -1)
    239 		error("Sigaction system call failed");
    240 
    241 	return (sig_t) sa.sa_handler;
    242 }
    243 
    244 /*
    245  * Ignore a signal.
    246  */
    247 
    248 void
    249 ignoresig(signo)
    250 	int signo;
    251 {
    252 	if (sigmode[signo - 1] != S_IGN && sigmode[signo - 1] != S_HARD_IGN) {
    253 		signal(signo, SIG_IGN);
    254 	}
    255 	sigmode[signo - 1] = S_HARD_IGN;
    256 }
    257 
    258 
    259 #ifdef mkinit
    260 INCLUDE <signal.h>
    261 INCLUDE "trap.h"
    262 
    263 SHELLPROC {
    264 	char *sm;
    265 
    266 	clear_traps();
    267 	for (sm = sigmode ; sm < sigmode + NSIG ; sm++) {
    268 		if (*sm == S_IGN)
    269 			*sm = S_HARD_IGN;
    270 	}
    271 }
    272 #endif
    273 
    274 
    275 
    276 /*
    277  * Signal handler.
    278  */
    279 
    280 void
    281 onsig(signo)
    282 	int signo;
    283 {
    284 	signal(signo, onsig);
    285 	if (signo == SIGINT && trap[SIGINT] == NULL) {
    286 		onint();
    287 		return;
    288 	}
    289 	gotsig[signo - 1] = 1;
    290 	pendingsigs++;
    291 }
    292 
    293 
    294 
    295 /*
    296  * Called to execute a trap.  Perhaps we should avoid entering new trap
    297  * handlers while we are executing a trap handler.
    298  */
    299 
    300 void
    301 dotrap() {
    302 	int i;
    303 	int savestatus;
    304 
    305 	for (;;) {
    306 		for (i = 1 ; ; i++) {
    307 			if (gotsig[i - 1])
    308 				break;
    309 			if (i >= NSIG)
    310 				goto done;
    311 		}
    312 		gotsig[i - 1] = 0;
    313 		savestatus=exitstatus;
    314 		evalstring(trap[i]);
    315 		exitstatus=savestatus;
    316 	}
    317 done:
    318 	pendingsigs = 0;
    319 }
    320 
    321 
    322 
    323 /*
    324  * Controls whether the shell is interactive or not.
    325  */
    326 
    327 
    328 void
    329 setinteractive(on)
    330 	int on;
    331 {
    332 	static int is_interactive;
    333 
    334 	if (on == is_interactive)
    335 		return;
    336 	setsignal(SIGINT);
    337 	setsignal(SIGQUIT);
    338 	setsignal(SIGTERM);
    339 	is_interactive = on;
    340 }
    341 
    342 
    343 
    344 /*
    345  * Called to exit the shell.
    346  */
    347 
    348 void
    349 exitshell(status)
    350 	int status;
    351 {
    352 	struct jmploc loc1, loc2;
    353 	char *p;
    354 
    355 	TRACE(("exitshell(%d) pid=%d\n", status, getpid()));
    356 	if (setjmp(loc1.loc)) {
    357 		goto l1;
    358 	}
    359 	if (setjmp(loc2.loc)) {
    360 		goto l2;
    361 	}
    362 	handler = &loc1;
    363 	if ((p = trap[0]) != NULL && *p != '\0') {
    364 		trap[0] = NULL;
    365 		evalstring(p);
    366 	}
    367 l1:   handler = &loc2;			/* probably unnecessary */
    368 	flushall();
    369 #if JOBS
    370 	setjobctl(0);
    371 #endif
    372 l2:   _exit(status);
    373 }
    374