lib/sigevent.c

   1 /* Quagga signal handling functions.
   2  * Copyright (C) 2004 Paul Jakma,
   3  *
   4  * This file is part of Quagga.
   5  *
   6  * Quagga is free software; you can redistribute it and/or modify it
   7  * under the terms of the GNU General Public License as published by the
   8  * Free Software Foundation; either version 2, or (at your option) any
   9  * later version.
  10  *
  11  * Quagga is distributed in the hope that it will be useful, but
  12  * WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License along
  17  * with this program; see the file COPYING; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
  19  */
  20
  21 #include <zebra.h>
  22 #include <sigevent.h>
  23 #include <log.h>
  24 #include <memory.h>
  25
  26 #ifdef SA_SIGINFO
  27 #ifdef HAVE_UCONTEXT_H
  28 #ifdef GNU_LINUX
  29 /* get REG_EIP from ucontext.h */
  30 #ifndef __USE_GNU
  31 #define __USE_GNU
  32 #endif /* __USE_GNU */
  33 #endif /* GNU_LINUX */
  34 #include <ucontext.h>
  35 #endif /* HAVE_UCONTEXT_H */
  36 #endif /* SA_SIGINFO */
  37
  38
  39 /* master signals descriptor struct */
  40 struct quagga_sigevent_master_t
  41 {
  42   struct thread *t;
  43
  44   struct quagga_signal_t *signals;
  45   int sigc;
  46
  47   volatile sig_atomic_t caught;
  48 } sigmaster;
  49
  50 /* Generic signal handler
  51  * Schedules signal event thread
  52  */
  53 static void
  54 quagga_signal_handler (int signo)
  55 {
  56   int i;
  57   struct quagga_signal_t *sig;
  58
  59   for (i = 0; i < sigmaster.sigc; i++)
  60     {
  61       sig = &(sigmaster.signals[i]);
  62
  63       if (sig->signal == signo)
  64         sig->caught = 1;
  65     }
  66
  67   sigmaster.caught = 1;
  68 }
  69
  70 /* check if signals have been caught and run appropriate handlers */
  71 int
  72 quagga_sigevent_process (void)
  73 {
  74   struct quagga_signal_t *sig;
  75   int i;
  76 #ifdef SIGEVENT_BLOCK_SIGNALS
  77   /* shouldnt need to block signals, but potentially may be needed */
  78   sigset_t newmask, oldmask;
  79
  80   /*
  81    * Block most signals, but be careful not to defer SIGTRAP because
  82    * doing so breaks gdb, at least on NetBSD 2.0.  Avoid asking to
  83    * block SIGKILL, just because we shouldn't be able to do so.
  84    */
  85   sigfillset (&newmask);
  86   sigdelset (&newmask, SIGTRAP);
  87   sigdelset (&newmask, SIGKILL);
  88
  89   if ( (sigprocmask (SIG_BLOCK, &newmask, &oldmask)) < 0)
  90     {
  91       zlog_err ("quagga_signal_timer: couldnt block signals!");
  92       return -1;
  93     }
  94 #endif /* SIGEVENT_BLOCK_SIGNALS */
  95
  96   if (sigmaster.caught > 0)
  97     {
  98       sigmaster.caught = 0;
  99       /* must not read or set sigmaster.caught after here,
 100        * race condition with per-sig caught flags if one does
 101        */
 102
 103       for (i = 0; i < sigmaster.sigc; i++)
 104         {
 105           sig = &(sigmaster.signals[i]);
 106
 107           if (sig->caught > 0)
 108             {
 109               sig->caught = 0;
 110               if (sig->handler)
 111                 sig->handler ();
 112             }
 113         }
 114     }
 115
 116 #ifdef SIGEVENT_BLOCK_SIGNALS
 117   if ( sigprocmask (SIG_UNBLOCK, &oldmask, NULL) < 0 );
 118     return -1;
 119 #endif /* SIGEVENT_BLOCK_SIGNALS */
 120
 121   return 0;
 122 }
 123
 124 #ifdef SIGEVENT_SCHEDULE_THREAD
 125 /* timer thread to check signals. Shouldnt be needed */
 126 int
 127 quagga_signal_timer (struct thread *t)
 128 {
 129   struct quagga_sigevent_master_t *sigm;
 130   struct quagga_signal_t *sig;
 131   int i;
 132
 133   sigm = THREAD_ARG (t);
 134   sigm->t = NULL;
 135   thread_add_timer(sigm->t->master, quagga_signal_timer, &sigmaster, QUAGGA_SIGNAL_TIMER_INTERVAL,
 136                    &sigm->t);
 137   return quagga_sigevent_process ();
 138 }
 139 #endif /* SIGEVENT_SCHEDULE_THREAD */
 140
 141 /* Initialization of signal handles. */
 142 /* Signal wrapper. */
 143 static int
 144 signal_set (int signo)
 145 {
 146   int ret;
 147   struct sigaction sig;
 148   struct sigaction osig;
 149
 150   sig.sa_handler = &quagga_signal_handler;
 151   sigfillset (&sig.sa_mask);
 152   sig.sa_flags = 0;
 153   if (signo == SIGALRM) {
 154 #ifdef SA_INTERRUPT
 155       sig.sa_flags |= SA_INTERRUPT; /* SunOS */
 156 #endif
 157   } else {
 158 #ifdef SA_RESTART
 159       sig.sa_flags |= SA_RESTART;
 160 #endif /* SA_RESTART */
 161   }
 162
 163   ret = sigaction (signo, &sig, &osig);
 164   if (ret < 0)
 165     return ret;
 166   else
 167     return 0;
 168 }
 169
 170 #ifdef SA_SIGINFO
 171
 172 /* XXX This function should be enhanced to support more platforms
 173        (it currently works only on Linux/x86). */
 174 static void *
 175 program_counter(void *context)
 176 {
 177 #ifdef HAVE_UCONTEXT_H
 178 #ifdef GNU_LINUX
 179   /* these are from GNU libc, rather than Linux, strictly speaking */
 180 # if defined(REG_EIP)
 181 #  define REG_INDEX REG_EIP
 182 # elif defined(REG_RIP)
 183 #  define REG_INDEX REG_RIP
 184 # elif defined(__powerpc__)
 185 #  define REG_INDEX 32
 186 # endif
 187 #elif defined(SUNOS_5) /* !GNU_LINUX */
 188 # define REG_INDEX REG_PC
 189 #endif /* GNU_LINUX */
 190
 191 #ifdef REG_INDEX
 192 # ifdef HAVE_UCONTEXT_T_UC_MCONTEXT_GREGS
 193 #  define REGS gregs[REG_INDEX]
 194 # elif defined(HAVE_UCONTEXT_T_UC_MCONTEXT_UC_REGS)
 195 #  define REGS uc_regs->gregs[REG_INDEX]
 196 # endif /* HAVE_UCONTEXT_T_UC_MCONTEXT_GREGS */
 197 #endif /* REG_INDEX */
 198
 199 #ifdef REGS
 200   if (context)
 201     return (void *)(((ucontext_t *)context)->uc_mcontext.REGS);
 202 #elif defined(HAVE_UCONTEXT_T_UC_MCONTEXT_REGS__NIP)
 203   /* older Linux / struct pt_regs ? */
 204   if (context)
 205     return (void *)(((ucontext_t *)context)->uc_mcontext.regs->nip);
 206 #endif /* REGS */
 207
 208 #endif /* HAVE_UCONTEXT_H */
 209   return NULL;
 210 }
 211
 212 #endif /* SA_SIGINFO */
 213
 214 static void __attribute__ ((noreturn))
 215 exit_handler(int signo
 216 #ifdef SA_SIGINFO
 217              , siginfo_t *siginfo, void *context
 218 #endif
 219             )
 220 {
 221   zlog_signal(signo, "exiting..."
 222 #ifdef SA_SIGINFO
 223               , siginfo, program_counter(context)
 224 #endif
 225              );
 226   _exit(128+signo);
 227 }
 228
 229 static void __attribute__ ((noreturn))
 230 core_handler(int signo
 231 #ifdef SA_SIGINFO
 232              , siginfo_t *siginfo, void *context
 233 #endif
 234             )
 235 {
 236   /* make sure we don't hang in here.  default for SIGALRM is terminate.
 237    * - if we're in backtrace for more than a second, abort. */
 238   struct sigaction sa_default = { .sa_handler = SIG_DFL };
 239   sigaction (SIGALRM, &sa_default, NULL);
 240
 241   sigset_t sigset;
 242   sigemptyset (&sigset);
 243   sigaddset (&sigset, SIGALRM);
 244   sigprocmask (SIG_UNBLOCK, &sigset, NULL);
 245
 246   alarm (1);
 247
 248   zlog_signal(signo, "aborting..."
 249 #ifdef SA_SIGINFO
 250               , siginfo, program_counter(context)
 251 #endif
 252              );
 253   /* dump memory stats on core */
 254   log_memstats_stderr ("core_handler");
 255   abort();
 256 }
 257
 258 static void
 259 trap_default_signals(void)
 260 {
 261   static const int core_signals[] = {
 262     SIGQUIT,
 263     SIGILL,
 264 #ifdef SIGEMT
 265     SIGEMT,
 266 #endif
 267     SIGFPE,
 268     SIGBUS,
 269     SIGSEGV,
 270 #ifdef SIGSYS
 271     SIGSYS,
 272 #endif
 273 #ifdef SIGXCPU
 274     SIGXCPU,
 275 #endif
 276 #ifdef SIGXFSZ
 277     SIGXFSZ,
 278 #endif
 279   };
 280   static const int exit_signals[] = {
 281     SIGHUP,
 282     SIGINT,
 283     SIGALRM,
 284     SIGTERM,
 285     SIGUSR1,
 286     SIGUSR2,
 287 #ifdef SIGPOLL
 288     SIGPOLL,
 289 #endif
 290 #ifdef SIGVTALRM
 291     SIGVTALRM,
 292 #endif
 293 #ifdef SIGSTKFLT
 294     SIGSTKFLT,
 295 #endif
 296   };
 297   static const int ignore_signals[] = {
 298     SIGPIPE,
 299   };
 300   static const struct {
 301     const int *sigs;
 302     u_int nsigs;
 303     void (*handler)(int signo
 304 #ifdef SA_SIGINFO
 305                     , siginfo_t *info, void *context
 306 #endif
 307                    );
 308   } sigmap[] = {
 309     { core_signals, array_size(core_signals), core_handler},
 310     { exit_signals, array_size(exit_signals), exit_handler},
 311     { ignore_signals, array_size(ignore_signals), NULL},
 312   };
 313   u_int i;
 314
 315   for (i = 0; i < array_size(sigmap); i++)
 316     {
 317       u_int j;
 318
 319       for (j = 0; j < sigmap[i].nsigs; j++)
 320         {
 321           struct sigaction oact;
 322           if ((sigaction(sigmap[i].sigs[j],NULL,&oact) == 0) &&
 323               (oact.sa_handler == SIG_DFL))
 324             {
 325               struct sigaction act;
 326               sigfillset (&act.sa_mask);
 327               if (sigmap[i].handler == NULL)
 328                 {
 329                   act.sa_handler = SIG_IGN;
 330                   act.sa_flags = 0;
 331                 }
 332               else
 333                 {
 334 #ifdef SA_SIGINFO
 335                   /* Request extra arguments to signal handler. */
 336                   act.sa_sigaction = sigmap[i].handler;
 337                   act.sa_flags = SA_SIGINFO;
 338 #else
 339                   act.sa_handler = sigmap[i].handler;
 340                   act.sa_flags = 0;
 341 #endif
 342 #ifdef SA_RESETHAND
 343                   /* don't try to print backtraces recursively */
 344                   if (sigmap[i].handler == core_handler)
 345                     act.sa_flags |= SA_RESETHAND;
 346 #endif
 347                 }
 348               if (sigaction(sigmap[i].sigs[j],&act,NULL) < 0)
 349                 zlog_warn("Unable to set signal handler for signal %d: %s",
 350                           sigmap[i].sigs[j],safe_strerror(errno));
 351
 352             }
 353         }
 354     }
 355 }
 356
 357 void
 358 signal_init (struct thread_master *m, int sigc,
 359              struct quagga_signal_t signals[])
 360 {
 361
 362   int i = 0;
 363   struct quagga_signal_t *sig;
 364
 365   /* First establish some default handlers that can be overridden by
 366      the application. */
 367   trap_default_signals();
 368
 369   while (i < sigc)
 370     {
 371       sig = &signals[i];
 372       if ( signal_set (sig->signal) < 0 )
 373         exit (-1);
 374       i++;
 375     }
 376
 377   sigmaster.sigc = sigc;
 378   sigmaster.signals = signals;
 379
 380 #ifdef SIGEVENT_SCHEDULE_THREAD
 381   sigmaster.t = NULL;
 382   thread_add_timer(m, quagga_signal_timer, &sigmaster, QUAGGA_SIGNAL_TIMER_INTERVAL,
 383                    &sigmaster.t);
 384 #endif /* SIGEVENT_SCHEDULE_THREAD */
 385 }