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1 | /* -*-c-*- |
2 | * |
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3 | * Signal handling |
4 | * |
5 | * (c) 1999 Straylight/Edgeware |
6 | */ |
7 | |
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8 | /*----- Licensing notice --------------------------------------------------* |
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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. |
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16 | * |
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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. |
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21 | * |
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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 | |
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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" |
40 | #include "report.h" |
41 | #include "sel.h" |
42 | #include "sig.h" |
43 | |
44 | /*----- Data structures ---------------------------------------------------*/ |
45 | |
46 | typedef struct sigstate { |
47 | struct sigaction sa; |
48 | sig *list; |
49 | } sigstate; |
50 | |
51 | /*----- Static variables --------------------------------------------------*/ |
52 | |
53 | static sel_file sigsel; |
54 | static int sigfd; |
55 | static sigstate *sigs; |
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56 | static sigset_t ss_all, ss_caught; |
57 | static unsigned nsig; |
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58 | |
59 | /*----- Main code ---------------------------------------------------------*/ |
60 | |
61 | /* --- @sig_handler@ --- * |
62 | * |
63 | * Arguments: @int n@ = signal number |
64 | * |
65 | * Returns: --- |
66 | * |
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67 | * Use: Generic signal handler. Writes a single byte to the |
68 | * signal pipe. The byte contains the signal number. Also |
69 | * sets the appropriate bit in @ss_caught@ to indicate which |
70 | * signals are pending. |
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71 | */ |
72 | |
73 | static void sig_handler(int n) |
74 | { |
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75 | int e = errno; |
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76 | unsigned char sch = (unsigned char)n; |
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77 | sigprocmask(SIG_BLOCK, &ss_all, 0); |
78 | sigaddset(&ss_caught, n); |
82c76535 |
79 | if (write(sigfd, &sch, 1)) /*hunoz*/; |
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80 | /* The system should reset the signal mask here. */ |
81 | errno = e; |
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82 | } |
83 | |
84 | /* --- @sig_read@ --- * |
85 | * |
86 | * Arguments: @int fd@ = file descriptor to read |
87 | * @unsigned mode@ = thing to do with descriptor |
88 | * @void *p@ = uninteresting argument |
89 | * |
90 | * Returns: --- |
91 | * |
92 | * Use: Dispatches signals to their handlers safely. |
93 | */ |
94 | |
95 | static void sig_read(int fd, unsigned mode, void *p) |
96 | { |
97 | sigset_t ss; |
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98 | |
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99 | /* --- Read the currently caught signals --- * |
100 | * |
101 | * Block signals while the mask is being copied. |
102 | */ |
103 | |
104 | { |
105 | sigset_t oss; |
106 | unsigned char buf[256]; |
107 | |
108 | sigprocmask(SIG_BLOCK, &ss_all, &oss); |
109 | ss = ss_caught; |
110 | sigemptyset(&ss_caught); |
111 | while (read(fd, buf, sizeof(buf)) > 0) |
112 | /* Do nothing */; |
113 | sigprocmask(SIG_SETMASK, &oss, 0); |
114 | } |
115 | |
116 | /* --- Process the caught signals --- */ |
117 | |
118 | { |
119 | int i; |
120 | for (i = 0; i < nsig; i++) { |
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121 | sig *s; |
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122 | if (!sigismember(&ss, i)) |
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123 | continue; |
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124 | s = sigs[i].list; |
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125 | while (s) { |
126 | sig *ss = s; |
127 | s = s->next; |
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128 | ss->proc(i, ss->p); |
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129 | } |
130 | } |
131 | } |
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132 | } |
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133 | |
134 | /* --- @sig_add@ --- * |
135 | * |
136 | * Arguments: @sig *s@ = pointer to signal handler block |
137 | * @int n@ = number of the signal |
138 | * @void (*proc)(int n, void *p)@ = signal handler function |
139 | * @void *p@ = argument to pass to handler |
140 | * |
141 | * Returns: --- |
142 | * |
143 | * Use: Adds a signal handler. |
144 | */ |
145 | |
146 | void sig_add(sig *s, int n, void (*proc)(int /*n*/, void */*p*/), void *p) |
147 | { |
148 | sigstate *ss = &sigs[n]; |
149 | |
150 | /* --- Initialize the block --- */ |
151 | |
152 | s->proc = proc; |
153 | s->p = p; |
154 | s->sig = n; |
155 | s->next = ss->list; |
156 | s->prev = 0; |
157 | |
158 | /* --- Engage a signal handler, maybe --- */ |
159 | |
160 | if (!ss->list) { |
161 | struct sigaction sa; |
162 | sa.sa_handler = sig_handler; |
163 | sa.sa_flags = SA_NOCLDSTOP; |
164 | #ifdef SA_RESTART |
165 | sa.sa_flags |= SA_RESTART; |
166 | #endif |
167 | sigemptyset(&sa.sa_mask); |
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168 | sigaddset(&ss_all, n); |
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169 | sigaction(n, &sa, &ss->sa); |
170 | } |
171 | |
172 | /* --- Link the block into the list --- */ |
173 | |
174 | if (ss->list) |
175 | ss->list->prev = s; |
176 | ss->list = s; |
177 | } |
178 | |
179 | /* --- @sig_remove@ --- * |
180 | * |
181 | * Arguments: @sig *s@ = pointer to signal handler block |
182 | * |
183 | * Returns: --- |
184 | * |
185 | * Use: Removes the signal handler from the list. |
186 | */ |
187 | |
188 | void sig_remove(sig *s) |
189 | { |
190 | sigstate *ss = &sigs[s->sig]; |
191 | |
192 | /* --- Unlink the handler block --- */ |
193 | |
194 | if (s->next) |
195 | s->next->prev = s->prev; |
196 | if (s->prev) |
197 | s->prev->next = s->next; |
198 | else |
199 | ss->list = s->next; |
200 | |
201 | /* --- Maybe remove the handler --- */ |
202 | |
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203 | if (!ss->list) { |
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204 | sigaction(s->sig, &ss->sa, 0); |
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205 | sigdelset(&ss_all, s->sig); |
206 | } |
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207 | } |
208 | |
209 | /* --- @sig_init@ --- * |
210 | * |
211 | * Arguments: @sel_state *s@ = pointer to select state |
212 | * |
213 | * Returns: --- |
214 | * |
215 | * Use: Initializes the signal handling system ready for use. |
216 | */ |
217 | |
218 | void sig_init(sel_state *s) |
219 | { |
220 | int fd[2]; |
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221 | |
222 | /* --- Work out how many signals there are --- */ |
223 | |
224 | { |
225 | sigset_t ss; |
226 | unsigned min = 0, max = 0; |
227 | |
228 | sigemptyset(&ss); |
229 | |
230 | /* --- Get a good upper bound --- * |
231 | * |
232 | * Cap the search at 256. I'll be sending signal numbers as bytes. |
233 | */ |
234 | |
235 | nsig = 1; |
236 | while (sigaddset(&ss, nsig) == 0) { |
237 | if (nsig == 256) |
238 | goto counted; |
239 | nsig <<= 1; |
240 | } |
241 | |
242 | /* --- Now binary search until I find the actual limit --- */ |
243 | |
244 | min = nsig >> 1; |
245 | max = nsig; |
246 | for (;;) { |
247 | nsig = (min + max) >> 1; |
248 | if (nsig == min) |
249 | break; |
250 | if (sigaddset(&ss, nsig)) |
251 | max = nsig; |
252 | else |
253 | min = nsig; |
254 | } |
255 | counted:; |
256 | } |
257 | |
258 | /* --- Initialize the signal state table --- */ |
259 | |
260 | { |
261 | unsigned i; |
262 | |
263 | sigs = xmalloc(nsig * sizeof(*sigs)); |
264 | for (i = 0; i < nsig; i++) |
265 | sigs[i].list = 0; |
266 | } |
267 | |
268 | /* --- Create the signal pipe --- */ |
269 | |
270 | if (pipe(fd)) |
271 | die(1, "couldn't create pipe for signal handling"); |
272 | |
273 | /* --- Set both ends to nonblocking and close-on-exec --- */ |
274 | |
275 | fdflags(fd[0], O_NONBLOCK, O_NONBLOCK, FD_CLOEXEC, FD_CLOEXEC); |
276 | fdflags(fd[1], O_NONBLOCK, O_NONBLOCK, FD_CLOEXEC, FD_CLOEXEC); |
277 | |
278 | /* --- Set everything up for the future --- */ |
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279 | |
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280 | sigfd = fd[1]; |
281 | sel_initfile(s, &sigsel, fd[0], SEL_READ, sig_read, 0); |
282 | sel_addfile(&sigsel); |
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283 | sigemptyset(&ss_all); |
284 | sigemptyset(&ss_caught); |
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285 | } |
286 | |
287 | /*----- That's all, folks -------------------------------------------------*/ |