9f8886c7 |
1 | /* -*-c-*- |
2 | * |
8656dc50 |
3 | * $Id: sig.c,v 1.3 2004/04/08 01:36:13 mdw Exp $ |
9f8886c7 |
4 | * |
5 | * Signal handling |
6 | * |
7 | * (c) 1999 Straylight/Edgeware |
8 | */ |
9 | |
d4efbcd9 |
10 | /*----- Licensing notice --------------------------------------------------* |
9f8886c7 |
11 | * |
12 | * This file is part of the mLib utilities library. |
13 | * |
14 | * mLib is free software; you can redistribute it and/or modify |
15 | * it under the terms of the GNU Library General Public License as |
16 | * published by the Free Software Foundation; either version 2 of the |
17 | * License, or (at your option) any later version. |
d4efbcd9 |
18 | * |
9f8886c7 |
19 | * mLib is distributed in the hope that it will be useful, |
20 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
21 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
22 | * GNU Library General Public License for more details. |
d4efbcd9 |
23 | * |
9f8886c7 |
24 | * You should have received a copy of the GNU Library General Public |
25 | * License along with mLib; if not, write to the Free |
26 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
27 | * MA 02111-1307, USA. |
28 | */ |
29 | |
9f8886c7 |
30 | /*----- Header files ------------------------------------------------------*/ |
31 | |
32 | #include <errno.h> |
33 | #include <signal.h> |
34 | #include <stdio.h> |
35 | #include <stdlib.h> |
36 | #include <string.h> |
37 | |
38 | #include <fcntl.h> |
39 | |
40 | #include "alloc.h" |
41 | #include "fdflags.h" |
42 | #include "report.h" |
43 | #include "sel.h" |
44 | #include "sig.h" |
45 | |
46 | /*----- Data structures ---------------------------------------------------*/ |
47 | |
48 | typedef struct sigstate { |
49 | struct sigaction sa; |
50 | sig *list; |
51 | } sigstate; |
52 | |
53 | /*----- Static variables --------------------------------------------------*/ |
54 | |
55 | static sel_file sigsel; |
56 | static int sigfd; |
57 | static sigstate *sigs; |
f9adeb47 |
58 | static sigset_t ss_all, ss_caught; |
59 | static unsigned nsig; |
9f8886c7 |
60 | |
61 | /*----- Main code ---------------------------------------------------------*/ |
62 | |
63 | /* --- @sig_handler@ --- * |
64 | * |
65 | * Arguments: @int n@ = signal number |
66 | * |
67 | * Returns: --- |
68 | * |
f9adeb47 |
69 | * Use: Generic signal handler. Writes a single byte to the |
70 | * signal pipe. The byte contains the signal number. Also |
71 | * sets the appropriate bit in @ss_caught@ to indicate which |
72 | * signals are pending. |
9f8886c7 |
73 | */ |
74 | |
75 | static void sig_handler(int n) |
76 | { |
f9adeb47 |
77 | int e = errno; |
9f8886c7 |
78 | unsigned char sch = (unsigned char)n; |
f9adeb47 |
79 | sigprocmask(SIG_BLOCK, &ss_all, 0); |
80 | sigaddset(&ss_caught, n); |
9f8886c7 |
81 | write(sigfd, &sch, 1); |
f9adeb47 |
82 | /* The system should reset the signal mask here. */ |
83 | errno = e; |
9f8886c7 |
84 | } |
85 | |
86 | /* --- @sig_read@ --- * |
87 | * |
88 | * Arguments: @int fd@ = file descriptor to read |
89 | * @unsigned mode@ = thing to do with descriptor |
90 | * @void *p@ = uninteresting argument |
91 | * |
92 | * Returns: --- |
93 | * |
94 | * Use: Dispatches signals to their handlers safely. |
95 | */ |
96 | |
97 | static void sig_read(int fd, unsigned mode, void *p) |
98 | { |
99 | sigset_t ss; |
9f8886c7 |
100 | |
f9adeb47 |
101 | /* --- Read the currently caught signals --- * |
102 | * |
103 | * Block signals while the mask is being copied. |
104 | */ |
105 | |
106 | { |
107 | sigset_t oss; |
108 | unsigned char buf[256]; |
109 | |
110 | sigprocmask(SIG_BLOCK, &ss_all, &oss); |
111 | ss = ss_caught; |
112 | sigemptyset(&ss_caught); |
113 | while (read(fd, buf, sizeof(buf)) > 0) |
114 | /* Do nothing */; |
115 | sigprocmask(SIG_SETMASK, &oss, 0); |
116 | } |
117 | |
118 | /* --- Process the caught signals --- */ |
119 | |
120 | { |
121 | int i; |
122 | for (i = 0; i < nsig; i++) { |
9f8886c7 |
123 | sig *s; |
f9adeb47 |
124 | if (!sigismember(&ss, i)) |
9f8886c7 |
125 | continue; |
f9adeb47 |
126 | s = sigs[i].list; |
9f8886c7 |
127 | while (s) { |
128 | sig *ss = s; |
129 | s = s->next; |
f9adeb47 |
130 | ss->proc(i, ss->p); |
9f8886c7 |
131 | } |
132 | } |
133 | } |
d4efbcd9 |
134 | } |
9f8886c7 |
135 | |
136 | /* --- @sig_add@ --- * |
137 | * |
138 | * Arguments: @sig *s@ = pointer to signal handler block |
139 | * @int n@ = number of the signal |
140 | * @void (*proc)(int n, void *p)@ = signal handler function |
141 | * @void *p@ = argument to pass to handler |
142 | * |
143 | * Returns: --- |
144 | * |
145 | * Use: Adds a signal handler. |
146 | */ |
147 | |
148 | void sig_add(sig *s, int n, void (*proc)(int /*n*/, void */*p*/), void *p) |
149 | { |
150 | sigstate *ss = &sigs[n]; |
151 | |
152 | /* --- Initialize the block --- */ |
153 | |
154 | s->proc = proc; |
155 | s->p = p; |
156 | s->sig = n; |
157 | s->next = ss->list; |
158 | s->prev = 0; |
159 | |
160 | /* --- Engage a signal handler, maybe --- */ |
161 | |
162 | if (!ss->list) { |
163 | struct sigaction sa; |
164 | sa.sa_handler = sig_handler; |
165 | sa.sa_flags = SA_NOCLDSTOP; |
166 | #ifdef SA_RESTART |
167 | sa.sa_flags |= SA_RESTART; |
168 | #endif |
169 | sigemptyset(&sa.sa_mask); |
f9adeb47 |
170 | sigaddset(&ss_all, n); |
9f8886c7 |
171 | sigaction(n, &sa, &ss->sa); |
172 | } |
173 | |
174 | /* --- Link the block into the list --- */ |
175 | |
176 | if (ss->list) |
177 | ss->list->prev = s; |
178 | ss->list = s; |
179 | } |
180 | |
181 | /* --- @sig_remove@ --- * |
182 | * |
183 | * Arguments: @sig *s@ = pointer to signal handler block |
184 | * |
185 | * Returns: --- |
186 | * |
187 | * Use: Removes the signal handler from the list. |
188 | */ |
189 | |
190 | void sig_remove(sig *s) |
191 | { |
192 | sigstate *ss = &sigs[s->sig]; |
193 | |
194 | /* --- Unlink the handler block --- */ |
195 | |
196 | if (s->next) |
197 | s->next->prev = s->prev; |
198 | if (s->prev) |
199 | s->prev->next = s->next; |
200 | else |
201 | ss->list = s->next; |
202 | |
203 | /* --- Maybe remove the handler --- */ |
204 | |
f9adeb47 |
205 | if (!ss->list) { |
9f8886c7 |
206 | sigaction(s->sig, &ss->sa, 0); |
f9adeb47 |
207 | sigdelset(&ss_all, s->sig); |
208 | } |
9f8886c7 |
209 | } |
210 | |
211 | /* --- @sig_init@ --- * |
212 | * |
213 | * Arguments: @sel_state *s@ = pointer to select state |
214 | * |
215 | * Returns: --- |
216 | * |
217 | * Use: Initializes the signal handling system ready for use. |
218 | */ |
219 | |
220 | void sig_init(sel_state *s) |
221 | { |
222 | int fd[2]; |
9f8886c7 |
223 | |
224 | /* --- Work out how many signals there are --- */ |
225 | |
226 | { |
227 | sigset_t ss; |
228 | unsigned min = 0, max = 0; |
229 | |
230 | sigemptyset(&ss); |
231 | |
232 | /* --- Get a good upper bound --- * |
233 | * |
234 | * Cap the search at 256. I'll be sending signal numbers as bytes. |
235 | */ |
236 | |
237 | nsig = 1; |
238 | while (sigaddset(&ss, nsig) == 0) { |
239 | if (nsig == 256) |
240 | goto counted; |
241 | nsig <<= 1; |
242 | } |
243 | |
244 | /* --- Now binary search until I find the actual limit --- */ |
245 | |
246 | min = nsig >> 1; |
247 | max = nsig; |
248 | for (;;) { |
249 | nsig = (min + max) >> 1; |
250 | if (nsig == min) |
251 | break; |
252 | if (sigaddset(&ss, nsig)) |
253 | max = nsig; |
254 | else |
255 | min = nsig; |
256 | } |
257 | counted:; |
258 | } |
259 | |
260 | /* --- Initialize the signal state table --- */ |
261 | |
262 | { |
263 | unsigned i; |
264 | |
265 | sigs = xmalloc(nsig * sizeof(*sigs)); |
266 | for (i = 0; i < nsig; i++) |
267 | sigs[i].list = 0; |
268 | } |
269 | |
270 | /* --- Create the signal pipe --- */ |
271 | |
272 | if (pipe(fd)) |
273 | die(1, "couldn't create pipe for signal handling"); |
274 | |
275 | /* --- Set both ends to nonblocking and close-on-exec --- */ |
276 | |
277 | fdflags(fd[0], O_NONBLOCK, O_NONBLOCK, FD_CLOEXEC, FD_CLOEXEC); |
278 | fdflags(fd[1], O_NONBLOCK, O_NONBLOCK, FD_CLOEXEC, FD_CLOEXEC); |
279 | |
280 | /* --- Set everything up for the future --- */ |
d4efbcd9 |
281 | |
9f8886c7 |
282 | sigfd = fd[1]; |
283 | sel_initfile(s, &sigsel, fd[0], SEL_READ, sig_read, 0); |
284 | sel_addfile(&sigsel); |
f9adeb47 |
285 | sigemptyset(&ss_all); |
286 | sigemptyset(&ss_caught); |
9f8886c7 |
287 | } |
288 | |
289 | /*----- That's all, folks -------------------------------------------------*/ |