9f8886c7 |
1 | /* -*-c-*- |
2 | * |
9f8886c7 |
3 | * Signal handling |
4 | * |
5 | * (c) 1999 Straylight/Edgeware |
6 | */ |
7 | |
d4efbcd9 |
8 | /*----- Licensing notice --------------------------------------------------* |
9f8886c7 |
9 | * |
10 | * This file is part of the mLib utilities library. |
11 | * |
12 | * mLib is free software; you can redistribute it and/or modify |
13 | * it under the terms of the GNU Library General Public License as |
14 | * published by the Free Software Foundation; either version 2 of the |
15 | * License, or (at your option) any later version. |
d4efbcd9 |
16 | * |
9f8886c7 |
17 | * mLib is distributed in the hope that it will be useful, |
18 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
20 | * GNU Library General Public License for more details. |
d4efbcd9 |
21 | * |
9f8886c7 |
22 | * You should have received a copy of the GNU Library General Public |
23 | * License along with mLib; if not, write to the Free |
24 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
25 | * MA 02111-1307, USA. |
26 | */ |
27 | |
9f8886c7 |
28 | /*----- Header files ------------------------------------------------------*/ |
29 | |
30 | #include <errno.h> |
31 | #include <signal.h> |
32 | #include <stdio.h> |
33 | #include <stdlib.h> |
34 | #include <string.h> |
35 | |
36 | #include <fcntl.h> |
37 | |
38 | #include "alloc.h" |
39 | #include "fdflags.h" |
b05d9857 |
40 | #include "macros.h" |
9f8886c7 |
41 | #include "report.h" |
42 | #include "sel.h" |
43 | #include "sig.h" |
44 | |
45 | /*----- Data structures ---------------------------------------------------*/ |
46 | |
47 | typedef struct sigstate { |
48 | struct sigaction sa; |
49 | sig *list; |
50 | } sigstate; |
51 | |
52 | /*----- Static variables --------------------------------------------------*/ |
53 | |
54 | static sel_file sigsel; |
55 | static int sigfd; |
56 | static sigstate *sigs; |
f9adeb47 |
57 | static sigset_t ss_all, ss_caught; |
58 | static unsigned nsig; |
9f8886c7 |
59 | |
60 | /*----- Main code ---------------------------------------------------------*/ |
61 | |
62 | /* --- @sig_handler@ --- * |
63 | * |
64 | * Arguments: @int n@ = signal number |
65 | * |
66 | * Returns: --- |
67 | * |
f9adeb47 |
68 | * Use: Generic signal handler. Writes a single byte to the |
69 | * signal pipe. The byte contains the signal number. Also |
70 | * sets the appropriate bit in @ss_caught@ to indicate which |
71 | * signals are pending. |
9f8886c7 |
72 | */ |
73 | |
74 | static void sig_handler(int n) |
75 | { |
f9adeb47 |
76 | int e = errno; |
9f8886c7 |
77 | unsigned char sch = (unsigned char)n; |
f9adeb47 |
78 | sigprocmask(SIG_BLOCK, &ss_all, 0); |
79 | sigaddset(&ss_caught, n); |
b05d9857 |
80 | DISCARD(write(sigfd, &sch, 1)); |
f9adeb47 |
81 | /* The system should reset the signal mask here. */ |
82 | errno = e; |
9f8886c7 |
83 | } |
84 | |
85 | /* --- @sig_read@ --- * |
86 | * |
87 | * Arguments: @int fd@ = file descriptor to read |
88 | * @unsigned mode@ = thing to do with descriptor |
89 | * @void *p@ = uninteresting argument |
90 | * |
91 | * Returns: --- |
92 | * |
93 | * Use: Dispatches signals to their handlers safely. |
94 | */ |
95 | |
96 | static void sig_read(int fd, unsigned mode, void *p) |
97 | { |
98 | sigset_t ss; |
9f8886c7 |
99 | |
f9adeb47 |
100 | /* --- Read the currently caught signals --- * |
101 | * |
102 | * Block signals while the mask is being copied. |
103 | */ |
104 | |
105 | { |
106 | sigset_t oss; |
107 | unsigned char buf[256]; |
108 | |
109 | sigprocmask(SIG_BLOCK, &ss_all, &oss); |
110 | ss = ss_caught; |
111 | sigemptyset(&ss_caught); |
112 | while (read(fd, buf, sizeof(buf)) > 0) |
113 | /* Do nothing */; |
114 | sigprocmask(SIG_SETMASK, &oss, 0); |
115 | } |
116 | |
117 | /* --- Process the caught signals --- */ |
118 | |
119 | { |
120 | int i; |
121 | for (i = 0; i < nsig; i++) { |
9f8886c7 |
122 | sig *s; |
f9adeb47 |
123 | if (!sigismember(&ss, i)) |
9f8886c7 |
124 | continue; |
f9adeb47 |
125 | s = sigs[i].list; |
9f8886c7 |
126 | while (s) { |
127 | sig *ss = s; |
128 | s = s->next; |
f9adeb47 |
129 | ss->proc(i, ss->p); |
9f8886c7 |
130 | } |
131 | } |
132 | } |
d4efbcd9 |
133 | } |
9f8886c7 |
134 | |
135 | /* --- @sig_add@ --- * |
136 | * |
137 | * Arguments: @sig *s@ = pointer to signal handler block |
138 | * @int n@ = number of the signal |
139 | * @void (*proc)(int n, void *p)@ = signal handler function |
140 | * @void *p@ = argument to pass to handler |
141 | * |
142 | * Returns: --- |
143 | * |
144 | * Use: Adds a signal handler. |
145 | */ |
146 | |
147 | void sig_add(sig *s, int n, void (*proc)(int /*n*/, void */*p*/), void *p) |
148 | { |
149 | sigstate *ss = &sigs[n]; |
150 | |
151 | /* --- Initialize the block --- */ |
152 | |
153 | s->proc = proc; |
154 | s->p = p; |
155 | s->sig = n; |
156 | s->next = ss->list; |
157 | s->prev = 0; |
158 | |
159 | /* --- Engage a signal handler, maybe --- */ |
160 | |
161 | if (!ss->list) { |
162 | struct sigaction sa; |
163 | sa.sa_handler = sig_handler; |
164 | sa.sa_flags = SA_NOCLDSTOP; |
165 | #ifdef SA_RESTART |
166 | sa.sa_flags |= SA_RESTART; |
167 | #endif |
168 | sigemptyset(&sa.sa_mask); |
f9adeb47 |
169 | sigaddset(&ss_all, n); |
9f8886c7 |
170 | sigaction(n, &sa, &ss->sa); |
171 | } |
172 | |
173 | /* --- Link the block into the list --- */ |
174 | |
175 | if (ss->list) |
176 | ss->list->prev = s; |
177 | ss->list = s; |
178 | } |
179 | |
180 | /* --- @sig_remove@ --- * |
181 | * |
182 | * Arguments: @sig *s@ = pointer to signal handler block |
183 | * |
184 | * Returns: --- |
185 | * |
186 | * Use: Removes the signal handler from the list. |
187 | */ |
188 | |
189 | void sig_remove(sig *s) |
190 | { |
191 | sigstate *ss = &sigs[s->sig]; |
192 | |
193 | /* --- Unlink the handler block --- */ |
194 | |
195 | if (s->next) |
196 | s->next->prev = s->prev; |
197 | if (s->prev) |
198 | s->prev->next = s->next; |
199 | else |
200 | ss->list = s->next; |
201 | |
202 | /* --- Maybe remove the handler --- */ |
203 | |
f9adeb47 |
204 | if (!ss->list) { |
9f8886c7 |
205 | sigaction(s->sig, &ss->sa, 0); |
f9adeb47 |
206 | sigdelset(&ss_all, s->sig); |
207 | } |
9f8886c7 |
208 | } |
209 | |
210 | /* --- @sig_init@ --- * |
211 | * |
212 | * Arguments: @sel_state *s@ = pointer to select state |
213 | * |
214 | * Returns: --- |
215 | * |
216 | * Use: Initializes the signal handling system ready for use. |
217 | */ |
218 | |
219 | void sig_init(sel_state *s) |
220 | { |
221 | int fd[2]; |
9f8886c7 |
222 | |
223 | /* --- Work out how many signals there are --- */ |
224 | |
225 | { |
226 | sigset_t ss; |
227 | unsigned min = 0, max = 0; |
228 | |
229 | sigemptyset(&ss); |
230 | |
231 | /* --- Get a good upper bound --- * |
232 | * |
233 | * Cap the search at 256. I'll be sending signal numbers as bytes. |
234 | */ |
235 | |
236 | nsig = 1; |
237 | while (sigaddset(&ss, nsig) == 0) { |
238 | if (nsig == 256) |
239 | goto counted; |
240 | nsig <<= 1; |
241 | } |
242 | |
243 | /* --- Now binary search until I find the actual limit --- */ |
244 | |
245 | min = nsig >> 1; |
246 | max = nsig; |
247 | for (;;) { |
248 | nsig = (min + max) >> 1; |
249 | if (nsig == min) |
250 | break; |
251 | if (sigaddset(&ss, nsig)) |
252 | max = nsig; |
253 | else |
254 | min = nsig; |
255 | } |
256 | counted:; |
257 | } |
258 | |
259 | /* --- Initialize the signal state table --- */ |
260 | |
261 | { |
262 | unsigned i; |
263 | |
264 | sigs = xmalloc(nsig * sizeof(*sigs)); |
265 | for (i = 0; i < nsig; i++) |
266 | sigs[i].list = 0; |
267 | } |
268 | |
269 | /* --- Create the signal pipe --- */ |
270 | |
271 | if (pipe(fd)) |
272 | die(1, "couldn't create pipe for signal handling"); |
273 | |
274 | /* --- Set both ends to nonblocking and close-on-exec --- */ |
275 | |
276 | fdflags(fd[0], O_NONBLOCK, O_NONBLOCK, FD_CLOEXEC, FD_CLOEXEC); |
277 | fdflags(fd[1], O_NONBLOCK, O_NONBLOCK, FD_CLOEXEC, FD_CLOEXEC); |
278 | |
279 | /* --- Set everything up for the future --- */ |
d4efbcd9 |
280 | |
9f8886c7 |
281 | sigfd = fd[1]; |
282 | sel_initfile(s, &sigsel, fd[0], SEL_READ, sig_read, 0); |
283 | sel_addfile(&sigsel); |
f9adeb47 |
284 | sigemptyset(&ss_all); |
285 | sigemptyset(&ss_caught); |
9f8886c7 |
286 | } |
287 | |
288 | /*----- That's all, folks -------------------------------------------------*/ |