| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * Signal handling |
| 4 | * |
| 5 | * (c) 1999 Straylight/Edgeware |
| 6 | */ |
| 7 | |
| 8 | /*----- Licensing notice --------------------------------------------------* |
| 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. |
| 16 | * |
| 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. |
| 21 | * |
| 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 | |
| 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 "macros.h" |
| 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; |
| 57 | static sigset_t ss_all, ss_caught; |
| 58 | static unsigned nsig; |
| 59 | |
| 60 | /*----- Main code ---------------------------------------------------------*/ |
| 61 | |
| 62 | /* --- @sig_handler@ --- * |
| 63 | * |
| 64 | * Arguments: @int n@ = signal number |
| 65 | * |
| 66 | * Returns: --- |
| 67 | * |
| 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. |
| 72 | */ |
| 73 | |
| 74 | static void sig_handler(int n) |
| 75 | { |
| 76 | int e = errno; |
| 77 | unsigned char sch = (unsigned char)n; |
| 78 | sigprocmask(SIG_BLOCK, &ss_all, 0); |
| 79 | sigaddset(&ss_caught, n); |
| 80 | DISCARD(write(sigfd, &sch, 1)); |
| 81 | /* The system should reset the signal mask here. */ |
| 82 | errno = e; |
| 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; |
| 99 | |
| 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++) { |
| 122 | sig *s; |
| 123 | if (!sigismember(&ss, i)) |
| 124 | continue; |
| 125 | s = sigs[i].list; |
| 126 | while (s) { |
| 127 | sig *ss = s; |
| 128 | s = s->next; |
| 129 | ss->proc(i, ss->p); |
| 130 | } |
| 131 | } |
| 132 | } |
| 133 | } |
| 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); |
| 169 | sigaddset(&ss_all, n); |
| 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 | |
| 204 | if (!ss->list) { |
| 205 | sigaction(s->sig, &ss->sa, 0); |
| 206 | sigdelset(&ss_all, s->sig); |
| 207 | } |
| 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]; |
| 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 --- */ |
| 280 | |
| 281 | sigfd = fd[1]; |
| 282 | sel_initfile(s, &sigsel, fd[0], SEL_READ, sig_read, 0); |
| 283 | sel_addfile(&sigsel); |
| 284 | sigemptyset(&ss_all); |
| 285 | sigemptyset(&ss_caught); |
| 286 | } |
| 287 | |
| 288 | /*----- That's all, folks -------------------------------------------------*/ |