obt/signal.c

   1 /* -*- indent-tabs-mode: nil; tab-width: 4; c-basic-offset: 4; -*-
   2
   3    obt/signal.c for the Openbox window manager
   4    Copyright (c) 2010        Dana Jansens
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 2 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    See the COPYING file for a copy of the GNU General Public License.
  17 */
  18
  19 #include "signal.h"
  20
  21 #ifdef HAVE_STDIO_H
  22 #include <stdio.h>
  23 #endif
  24 #ifdef HAVE_STDLIB_H
  25 #include <stdlib.h>
  26 #endif
  27 #ifdef HAVE_SIGNAL_H
  28 #  include <signal.h>
  29 #endif
  30 #ifdef HAVE_UNISTD_H
  31 #  include <unistd.h>
  32 #endif
  33
  34 typedef struct _ObtSignalCallback ObtSignalCallback;
  35
  36 struct _ObtSignalCallback
  37 {
  38     ObtSignalHandler func;
  39     gpointer data;
  40 };
  41
  42 static gboolean signal_prepare(GSource *source, gint *timeout);
  43 static gboolean signal_check(GSource *source);
  44 static gboolean signal_occurred(GSource *source, GSourceFunc callback,
  45                                gpointer data);
  46 static void sighandler(gint sig);
  47
  48 /* this should be more than the number of possible signals on any
  49    architecture... */
  50 #define NUM_SIGNALS 99
  51
  52 /* a set of all possible signals */
  53 static sigset_t all_signals_set;
  54
  55 /* keep track of what signals have a signal handler installed, and remember
  56    the action we replaced when installing it for when we clean up */
  57 static struct {
  58     guint installed; /* a ref count */
  59     struct sigaction oldact;
  60 } all_signals[NUM_SIGNALS];
  61
  62 /* signals which cause a core dump, these can't be used for callbacks */
  63 static const gint core_signals[] =
  64 {
  65     SIGABRT,
  66     SIGSEGV,
  67     SIGFPE,
  68     SIGILL,
  69     SIGQUIT,
  70     SIGTRAP,
  71     SIGSYS,
  72     SIGBUS,
  73     SIGXCPU,
  74     SIGXFSZ
  75 };
  76 #define NUM_CORE_SIGNALS (gint)(sizeof(core_signals) / sizeof(core_signals[0]))
  77
  78 static GSourceFuncs source_funcs = {
  79     signal_prepare,
  80     signal_check,
  81     signal_occurred,
  82     NULL
  83 };
  84 static GSource *gsource = NULL;
  85 static guint listeners = 0; /* a ref count for the signal listener */
  86 static gboolean signal_fired;
  87 guint signals_fired[NUM_SIGNALS];
  88 GSList *callbacks[NUM_SIGNALS];
  89
  90 void obt_signal_listen(void)
  91 {
  92     if (!listeners) {
  93         guint i;
  94         struct sigaction action;
  95         sigset_t sigset;
  96
  97         /* initialize the all_signals_set */
  98         sigfillset(&all_signals_set);
  99
 100         sigemptyset(&sigset);
 101         action.sa_handler = sighandler;
 102         action.sa_mask = sigset;
 103         action.sa_flags = SA_NOCLDSTOP;
 104
 105         /* always grab all the signals that cause core dumps */
 106         for (i = 0; i < NUM_CORE_SIGNALS; ++i) {
 107             /* SIGABRT is curiously not grabbed here!! that's because when we
 108                get one of the core_signals, we use abort() to dump the core.
 109                And having the abort() only go back to our signal handler again
 110                is less than optimal */
 111             if (core_signals[i] != SIGABRT) {
 112                 sigaction(core_signals[i], &action,
 113                           &all_signals[core_signals[i]].oldact);
 114                 all_signals[core_signals[i]].installed++;
 115             }
 116         }
 117
 118         gsource = g_source_new(&source_funcs, sizeof(GSource));
 119         g_source_set_priority(gsource, G_PRIORITY_HIGH);
 120
 121         g_source_attach(gsource, NULL);
 122     }
 123
 124     ++listeners;
 125 }
 126
 127 void obt_signal_stop(void)
 128 {
 129     --listeners;
 130
 131     if (!listeners) {
 132         gint i;
 133         GSList *it, *next;
 134
 135         g_source_unref(gsource);
 136         gsource = NULL;
 137
 138         /* remove user defined signal handlers */
 139         for (i = 0; i < NUM_SIGNALS; ++i)
 140             for (it = callbacks[i]; it; it = next) {
 141                 ObtSignalCallback *cb = it->data;
 142                 next = g_slist_next(it);
 143                 obt_signal_remove_callback(i, cb->func);
 144             }
 145
 146         /* release all the signals that cause core dumps */
 147         for (i = 0; i < NUM_CORE_SIGNALS; ++i) {
 148             if (all_signals[core_signals[i]].installed) {
 149                 sigaction(core_signals[i],
 150                           &all_signals[core_signals[i]].oldact, NULL);
 151                 all_signals[core_signals[i]].installed--;
 152             }
 153         }
 154
 155 #ifdef DEBUG
 156         for (i = 0; i < NUM_SIGNALS; ++i)
 157             g_assert(all_signals[i].installed == 0);
 158 #endif
 159     }
 160 }
 161
 162 void obt_signal_add_callback(gint sig, ObtSignalHandler func, gpointer data)
 163 {
 164     ObtSignalCallback *cb;
 165     gint i;
 166
 167     g_return_if_fail(func != NULL);
 168     g_return_if_fail(sig >= 0 && sig <= NUM_SIGNALS);
 169     for (i = 0; i < NUM_CORE_SIGNALS; ++i)
 170         g_return_if_fail(sig != core_signals[i]);
 171
 172     cb = g_slice_new(ObtSignalCallback);
 173     cb->func = func;
 174     cb->data = data;
 175     callbacks[sig] = g_slist_prepend(callbacks[sig], cb);
 176
 177     /* install the signal handler */
 178     if (!all_signals[sig].installed) {
 179         struct sigaction action;
 180         sigset_t sigset;
 181
 182         sigemptyset(&sigset);
 183         action.sa_handler = sighandler;
 184         action.sa_mask = sigset;
 185         action.sa_flags = SA_NOCLDSTOP;
 186
 187         sigaction(sig, &action, &all_signals[sig].oldact);
 188     }
 189
 190     all_signals[sig].installed++;
 191 }
 192
 193 void obt_signal_remove_callback(gint sig, ObtSignalHandler func)
 194 {
 195     GSList *it;
 196     gint i;
 197
 198     g_return_if_fail(func != NULL);
 199     g_return_if_fail(sig >= 0 && sig <= NUM_SIGNALS);
 200     for (i = 0; i < NUM_CORE_SIGNALS; ++i)
 201         g_return_if_fail(sig != core_signals[i]);
 202
 203     for (it = callbacks[sig]; it; it = g_slist_next(it)) {
 204         ObtSignalCallback *cb = it->data;
 205         if (cb->func == func) {
 206             g_assert(all_signals[sig].installed > 0);
 207
 208             callbacks[sig] = g_slist_delete_link(callbacks[sig], it);
 209             g_slice_free(ObtSignalCallback, cb);
 210
 211             /* uninstall the signal handler */
 212             all_signals[sig].installed--;
 213             if (!all_signals[sig].installed)
 214                 sigaction(sig, &all_signals[sig].oldact, NULL);
 215             break;
 216         }
 217     }
 218 }
 219
 220 static gboolean signal_prepare(GSource *source, gint *timeout)
 221 {
 222     *timeout = -1;
 223     return signal_fired;
 224 }
 225
 226 static gboolean signal_check(GSource *source)
 227 {
 228     return signal_fired;
 229 }
 230
 231 static gboolean signal_occurred(GSource *source, GSourceFunc callback,
 232                                 gpointer data)
 233 {
 234     guint i;
 235     sigset_t oldset;
 236     guint fired[NUM_SIGNALS];
 237
 238     /* block signals so that we can do this without the data changing
 239        on us */
 240     sigprocmask(SIG_SETMASK, &all_signals_set, &oldset);
 241
 242     /* make a copy of the signals that fired */
 243     for (i = 0; i < NUM_SIGNALS; ++i) {
 244         fired[i] = signals_fired[i];
 245         signals_fired[i] = 0;
 246     }
 247     signal_fired = FALSE;
 248
 249     sigprocmask(SIG_SETMASK, &oldset, NULL);
 250
 251     /* call the signal callbacks for the signals */
 252     for (i = 0; i < NUM_SIGNALS; ++i) {
 253         while (fired[i]) {
 254             GSList *it;
 255             for (it = callbacks[i]; it; it = g_slist_next(it)) {
 256                 const ObtSignalCallback *cb = it->data;
 257                 cb->func(i, cb->data);
 258             }
 259             --fired[i];
 260         }
 261     }
 262
 263     return TRUE; /* repeat */
 264 }
 265
 266 static void sighandler(gint sig)
 267 {
 268     guint i;
 269
 270     g_return_if_fail(sig < NUM_SIGNALS);
 271
 272     for (i = 0; i < NUM_CORE_SIGNALS; ++i)
 273         if (sig == core_signals[i]) {
 274             /* XXX special case for signals that default to core dump.
 275                but throw some helpful output here... */
 276
 277             fprintf(stderr, "How are you gentlemen? All your base are"
 278                     " belong to us. (Openbox received signal %d)\n", sig);
 279
 280             /* die with a core dump */
 281             abort();
 282         }
 283
 284     signal_fired = TRUE;
 285     ++signals_fired[sig];
 286
 287     /* i don't think we want to modify the GMainContext inside a signal
 288        handler, so use a GSource instead of an idle func to call back
 289        to the application */
 290 }