1 /* sighandle.c -- Library routines for manipulating chains of signal handlers
2 Copyright (C) 1992 Free Software Foundation, Inc.
3
4 This program is free software; you can redistribute it and/or modify
5 it under the terms of the GNU General Public License as published by
6 the Free Software Foundation; either version 2, or (at your option)
7 any later version.
8
9 This program is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 GNU General Public License for more details. */
13
14 /* Written by Paul Sander, HaL Computer Systems, Inc. <paul@hal.com>
15 Brian Berliner <berliner@Sun.COM> added POSIX support */
16
17 /*************************************************************************
18 *
19 * signal.c -- This file contains code that manipulates chains of signal
20 * handlers.
21 *
22 * Facilities are provided to register a signal handler for
23 * any specific signal. When a signal is received, all of the
24 * registered signal handlers are invoked in the reverse order
25 * in which they are registered. Note that the signal handlers
26 * must not themselves make calls to the signal handling
27 * facilities.
28 *
29 *************************************************************************/
30
31 #ifdef HAVE_CONFIG_H
32 #include "config.h"
33 #endif
34 #include "system.h"
35
36 #include <sys/types.h>
37 #include <stdio.h>
38 #include <signal.h>
39
40 /* Add prototype support. */
41 #ifndef PROTO
42 #if defined (USE_PROTOTYPES) ? USE_PROTOTYPES : defined (__STDC__)
43 #define PROTO(ARGS) ARGS
44 #else
45 #define PROTO(ARGS) ()
46 #endif
47 #endif
48
49 #ifdef STDC_HEADERS
50 #include <stdlib.h>
51 #else
52 #if __STDC__
53 char *calloc(unsigned nelem, unsigned size);
54 char *malloc(unsigned size);
55 #else
56 char *calloc();
57 char *malloc();
58 #endif /* __STDC__ */
59 #endif /* STDC_HEADERS */
60
61 /* Define the highest signal number (usually) */
62 #ifndef SIGMAX
63 #define SIGMAX 64
64 #endif
65
66 /* Define linked list of signal handlers structure */
67 struct SIG_hlist {
68 RETSIGTYPE (*handler)();
69 struct SIG_hlist *next;
70 };
71
72 /*
73 * Define array of lists of signal handlers. Note that this depends on
74 * the implementation to initialize each element to a null pointer.
75 */
76
77 static struct SIG_hlist **SIG_handlers;
78
79 /* Define array of default signal vectors */
80
81 #ifdef POSIX_SIGNALS
82 static struct sigaction *SIG_defaults;
83 #else
84 #ifdef BSD_SIGNALS
85 static struct sigvec *SIG_defaults;
86 #else
87 static RETSIGTYPE (**SIG_defaults) PROTO ((int));
88 #endif
89 #endif
90
91 /* Critical section housekeeping */
92 static int SIG_crSectNest = 0; /* Nesting level */
93 #ifdef POSIX_SIGNALS
94 static sigset_t SIG_crSectMask; /* Signal mask */
95 #else
96 static int SIG_crSectMask; /* Signal mask */
97 #endif
98
99 /*
100 * Initialize the signal handler arrays
101 */
102
SIG_init()103 static int SIG_init()
104 {
105 int i;
106 #ifdef POSIX_SIGNALS
107 sigset_t sigset_test;
108 #endif
109
110 if (SIG_defaults && SIG_handlers) /* already allocated */
111 return (0);
112
113 #ifdef POSIX_SIGNALS
114 (void) sigfillset(&sigset_test);
115 for (i = 1; i < SIGMAX && sigismember(&sigset_test, i) == 1; i++)
116 ;
117 if (i < SIGMAX)
118 i = SIGMAX;
119 i++;
120 if (!SIG_defaults)
121 SIG_defaults = (struct sigaction *)
122 calloc(i, sizeof(struct sigaction));
123 (void) sigemptyset(&SIG_crSectMask);
124 #else
125 i = SIGMAX+1;
126 #ifdef BSD_SIGNALS
127 if (!SIG_defaults)
128 SIG_defaults = (struct sigvec *)
129 calloc(i, sizeof(struct sigvec));
130 #else
131 if (!SIG_defaults)
132 SIG_defaults = (RETSIGTYPE (**) PROTO ((int)) )
133 calloc(i, sizeof(RETSIGTYPE (**) PROTO ((int)) ));
134 #endif
135 SIG_crSectMask = 0;
136 #endif
137 if (!SIG_handlers)
138 SIG_handlers = (struct SIG_hlist **)
139 calloc(i, sizeof(struct SIG_hlist *));
140 return (!SIG_defaults || !SIG_handlers);
141 }
142
143 /*
144 * The following invokes each signal handler in the reverse order in which
145 * they were registered.
146 */
147 static RETSIGTYPE SIG_handle PROTO ((int));
148
SIG_handle(sig)149 static RETSIGTYPE SIG_handle(sig)
150 int sig;
151 {
152 struct SIG_hlist *this;
153
154 /* Dispatch signal handlers */
155 this = SIG_handlers[sig];
156 while (this != (struct SIG_hlist *) NULL)
157 {
158 (*this->handler)(sig);
159 this = this->next;
160 }
161
162 return;
163 }
164
165 /*
166 * The following registers a signal handler. If the handler is already
167 * registered, it is not registered twice, nor is the order in which signal
168 * handlers are invoked changed. If this is the first signal handler
169 * registered for a given signal, the old sigvec structure is saved for
170 * restoration later.
171 */
172
SIG_register(sig,fn)173 int SIG_register(sig,fn)
174 int sig;
175 RETSIGTYPE (*fn)();
176 {
177 int val;
178 struct SIG_hlist *this;
179 #ifdef POSIX_SIGNALS
180 struct sigaction act;
181 sigset_t sigset_mask, sigset_omask;
182 #else
183 #ifdef BSD_SIGNALS
184 struct sigvec vec;
185 int mask;
186 #endif
187 #endif
188
189 /* Initialize */
190 if (SIG_init() != 0)
191 return (-1);
192 val = 0;
193
194 /* Block this signal while we look at handler chain */
195 #ifdef POSIX_SIGNALS
196 (void) sigemptyset(&sigset_mask);
197 (void) sigaddset(&sigset_mask, sig);
198 (void) sigprocmask(SIG_BLOCK, &sigset_mask, &sigset_omask);
199 #else
200 #ifdef BSD_SIGNALS
201 mask = sigblock(sigmask(sig));
202 #endif
203 #endif
204
205 /* See if this handler was already registered */
206 this = SIG_handlers[sig];
207 while (this != (struct SIG_hlist *) NULL)
208 {
209 if (this->handler == fn) break;
210 this = this->next;
211 }
212
213 /* Register the new handler only if it is not already registered. */
214 if (this == (struct SIG_hlist *) NULL)
215 {
216
217 /*
218 * If this is the first handler registered for this signal,
219 * set up the signal handler dispatcher
220 */
221
222 if (SIG_handlers[sig] == (struct SIG_hlist *) NULL)
223 {
224 #ifdef POSIX_SIGNALS
225 act.sa_handler = SIG_handle;
226 (void) sigemptyset(&act.sa_mask);
227 act.sa_flags = 0;
228 val = sigaction(sig, &act, &SIG_defaults[sig]);
229 #else
230 #ifdef BSD_SIGNALS
231 memset (&vec, 0, sizeof (vec));
232 vec.sv_handler = SIG_handle;
233 val = sigvec(sig, &vec, &SIG_defaults[sig]);
234 #else
235 if ((SIG_defaults[sig] = signal(sig, SIG_handle)) == SIG_ERR)
236 val = -1;
237 #endif
238 #endif
239 }
240
241 /* If not, register it */
242 if ((val == 0) && (this == (struct SIG_hlist *) NULL))
243 {
244 this = (struct SIG_hlist *)
245 malloc(sizeof(struct SIG_hlist));
246 if (this == NULL)
247 {
248 val = -1;
249 }
250 else
251 {
252 this->handler = fn;
253 this->next = SIG_handlers[sig];
254 SIG_handlers[sig] = this;
255 }
256 }
257 }
258
259 /* Unblock the signal */
260 #ifdef POSIX_SIGNALS
261 (void) sigprocmask(SIG_SETMASK, &sigset_omask, NULL);
262 #else
263 #ifdef BSD_SIGNALS
264 (void) sigsetmask(mask);
265 #endif
266 #endif
267
268 return val;
269 }
270
271 /*
272 * The following deregisters a signal handler. If the last signal handler for
273 * a given signal is deregistered, the default sigvec information is restored.
274 */
275
SIG_deregister(sig,fn)276 int SIG_deregister(sig,fn)
277 int sig;
278 RETSIGTYPE (*fn)();
279 {
280 int val;
281 struct SIG_hlist *this;
282 struct SIG_hlist *last;
283 #ifdef POSIX_SIGNALS
284 sigset_t sigset_mask, sigset_omask;
285 #else
286 #ifdef BSD_SIGNALS
287 int mask;
288 #endif
289 #endif
290
291 /* Initialize */
292 if (SIG_init() != 0)
293 return (-1);
294 val = 0;
295 last = (struct SIG_hlist *) NULL;
296
297 /* Block this signal while we look at handler chain */
298 #ifdef POSIX_SIGNALS
299 (void) sigemptyset(&sigset_mask);
300 (void) sigaddset(&sigset_mask, sig);
301 (void) sigprocmask(SIG_BLOCK, &sigset_mask, &sigset_omask);
302 #else
303 #ifdef BSD_SIGNALS
304 mask = sigblock(sigmask(sig));
305 #endif
306 #endif
307
308 /* Search for the signal handler */
309 this = SIG_handlers[sig];
310 while ((this != (struct SIG_hlist *) NULL) && (this->handler != fn))
311 {
312 last = this;
313 this = this->next;
314 }
315
316 /* If it was registered, remove it */
317 if (this != (struct SIG_hlist *) NULL)
318 {
319 if (last == (struct SIG_hlist *) NULL)
320 {
321 SIG_handlers[sig] = this->next;
322 }
323 else
324 {
325 last->next = this->next;
326 }
327 free((char *) this);
328 }
329
330 /* Restore default behavior if there are no registered handlers */
331 if (SIG_handlers[sig] == (struct SIG_hlist *) NULL)
332 {
333 #ifdef POSIX_SIGNALS
334 val = sigaction(sig, &SIG_defaults[sig],
335 (struct sigaction *) NULL);
336 #else
337 #ifdef BSD_SIGNALS
338 val = sigvec(sig, &SIG_defaults[sig], (struct sigvec *) NULL);
339 #else
340 if (signal(sig, SIG_defaults[sig]) == SIG_ERR)
341 val = -1;
342 #endif
343 #endif
344 }
345
346 /* Unblock the signal */
347 #ifdef POSIX_SIGNALS
348 (void) sigprocmask(SIG_SETMASK, &sigset_omask, NULL);
349 #else
350 #ifdef BSD_SIGNALS
351 (void) sigsetmask(mask);
352 #endif
353 #endif
354
355 return val;
356 }
357
358 /*
359 * The following begins a critical section.
360 */
361
SIG_beginCrSect()362 void SIG_beginCrSect()
363 {
364 if (SIG_init() == 0)
365 {
366 if (SIG_crSectNest == 0)
367 {
368 #ifdef POSIX_SIGNALS
369 sigset_t sigset_mask;
370
371 (void) sigfillset(&sigset_mask);
372 (void) sigprocmask(SIG_SETMASK,
373 &sigset_mask, &SIG_crSectMask);
374 #else
375 #ifdef BSD_SIGNALS
376 SIG_crSectMask = sigblock(~0);
377 #else
378 /* TBD */
379 #endif
380 #endif
381 }
382 SIG_crSectNest++;
383 }
384 }
385
386 /*
387 * Return nonzero if currently in a critical section.
388 * Otherwise return zero.
389 */
390
SIG_inCrSect()391 int SIG_inCrSect()
392 {
393 return SIG_crSectNest > 0;
394 }
395
396 /*
397 * The following ends a critical section.
398 */
399
SIG_endCrSect()400 void SIG_endCrSect()
401 {
402 if (SIG_init() == 0)
403 {
404 SIG_crSectNest--;
405 if (SIG_crSectNest == 0)
406 {
407 #ifdef POSIX_SIGNALS
408 (void) sigprocmask(SIG_SETMASK, &SIG_crSectMask, NULL);
409 #else
410 #ifdef BSD_SIGNALS
411 (void) sigsetmask(SIG_crSectMask);
412 #else
413 /* TBD */
414 #endif
415 #endif
416 }
417 }
418 }
419