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
  17  * along with Quagga; see the file COPYING.  If not, write to the Free
  18  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
  19  * 02111-1307, USA.
  20  */
  21
  22 #include <zebra.h>
  23 #include <sigevent.h>
  24 #include <log.h>
  25 #include <memory.h>
  26
  27 #ifdef SA_SIGINFO
  28 #ifdef HAVE_UCONTEXT_H
  29 #ifdef GNU_LINUX
  30 /* get REG_EIP from ucontext.h */
  31 #ifndef __USE_GNU
  32 #define __USE_GNU
  33 #endif /* __USE_GNU */
  34 #endif /* GNU_LINUX */
  35 #include <ucontext.h>
  36 #endif /* HAVE_UCONTEXT_H */
  37 #endif /* SA_SIGINFO */
  38
  39
  40 /* master signals descriptor struct */
  41 struct quagga_sigevent_master_t
  42 {
  43   struct thread *t;
  44
  45   struct quagga_signal_t *signals;
  46   int sigc;
  47
  48   volatile sig_atomic_t caught;
  49 } sigmaster;
  50
  51 /* Generic signal handler
  52  * Schedules signal event thread
  53  */
  54 static void
  55 quagga_signal_handler (int signo)
  56 {
  57   int i;
  58   struct quagga_signal_t *sig;
  59
  60   for (i = 0; i < sigmaster.sigc; i++)
  61     {
  62       sig = &(sigmaster.signals[i]);
  63
  64       if (sig->signal == signo)
  65         sig->caught = 1;
  66     }
  67
  68   sigmaster.caught = 1;
  69 }
  70
  71 /* check if signals have been caught and run appropriate handlers */
  72 int
  73 quagga_sigevent_process (void)
  74 {
  75   struct quagga_signal_t *sig;
  76   int i;
  77 #ifdef SIGEVENT_BLOCK_SIGNALS
  78   /* shouldnt need to block signals, but potentially may be needed */
  79   sigset_t newmask, oldmask;
  80
  81   /*
  82    * Block most signals, but be careful not to defer SIGTRAP because
  83    * doing so breaks gdb, at least on NetBSD 2.0.  Avoid asking to
  84    * block SIGKILL, just because we shouldn't be able to do so.
  85    */
  86   sigfillset (&newmask);
  87   sigdelset (&newmask, SIGTRAP);
  88   sigdelset (&newmask, SIGKILL);
  89
  90   if ( (sigprocmask (SIG_BLOCK, &newmask, &oldmask)) < 0)
  91     {
  92       zlog_err ("quagga_signal_timer: couldnt block signals!");
  93       return -1;
  94     }
  95 #endif /* SIGEVENT_BLOCK_SIGNALS */
  96
  97   if (sigmaster.caught > 0)
  98     {
  99       sigmaster.caught = 0;
 100       /* must not read or set sigmaster.caught after here,
 101        * race condition with per-sig caught flags if one does
 102        */
 103
 104       for (i = 0; i < sigmaster.sigc; i++)
 105         {
 106           sig = &(sigmaster.signals[i]);
 107
 108           if (sig->caught > 0)
 109             {
 110               sig->caught = 0;
 111               if (sig->handler)
 112                 sig->handler ();
 113             }
 114         }
 115     }
 116
 117 #ifdef SIGEVENT_BLOCK_SIGNALS
 118   if ( sigprocmask (SIG_UNBLOCK, &oldmask, NULL) < 0 );
 119     return -1;
 120 #endif /* SIGEVENT_BLOCK_SIGNALS */
 121
 122   return 0;
 123 }
 124
 125 #ifdef SIGEVENT_SCHEDULE_THREAD
 126 /* timer thread to check signals. Shouldnt be needed */
 127 int
 128 quagga_signal_timer (struct thread *t)
 129 {
 130   struct quagga_sigevent_master_t *sigm;
 131   struct quagga_signal_t *sig;
 132   int i;
 133
 134   sigm = THREAD_ARG (t);
 135   sigm->t = NULL;
 136   thread_add_timer(sigm->t->master, quagga_signal_timer, &sigmaster, QUAGGA_SIGNAL_TIMER_INTERVAL,
 137                    &sigm->t);
 138   return quagga_sigevent_process ();
 139 }
 140 #endif /* SIGEVENT_SCHEDULE_THREAD */
 141
 142 /* Initialization of signal handles. */
 143 /* Signal wrapper. */
 144 static int
 145 signal_set (int signo)
 146 {
 147   int ret;
 148   struct sigaction sig;
 149   struct sigaction osig;
 150
 151   sig.sa_handler = &quagga_signal_handler;
 152   sigfillset (&sig.sa_mask);
 153   sig.sa_flags = 0;
 154   if (signo == SIGALRM) {
 155 #ifdef SA_INTERRUPT
 156       sig.sa_flags |= SA_INTERRUPT; /* SunOS */
 157 #endif
 158   } else {
 159 #ifdef SA_RESTART
 160       sig.sa_flags |= SA_RESTART;
 161 #endif /* SA_RESTART */
 162   }
 163
 164   ret = sigaction (signo, &sig, &osig);
 165   if (ret < 0)
 166     return ret;
 167   else
 168     return 0;
 169 }
 170
 171 #ifdef SA_SIGINFO
 172
 173 /* XXX This function should be enhanced to support more platforms
 174        (it currently works only on Linux/x86). */
 175 static void *
 176 program_counter(void *context)
 177 {
 178 #ifdef HAVE_UCONTEXT_H
 179 #ifdef GNU_LINUX
 180   /* these are from GNU libc, rather than Linux, strictly speaking */
 181 # if defined(REG_EIP)
 182 #  define REG_INDEX REG_EIP
 183 # elif defined(REG_RIP)
 184 #  define REG_INDEX REG_RIP
 185 # elif defined(__powerpc__)
 186 #  define REG_INDEX 32
 187 # endif
 188 #elif defined(SUNOS_5) /* !GNU_LINUX */
 189 # define REG_INDEX REG_PC
 190 #endif /* GNU_LINUX */
 191
 192 #ifdef REG_INDEX
 193 # ifdef HAVE_UCONTEXT_T_UC_MCONTEXT_GREGS
 194 #  define REGS gregs[REG_INDEX]
 195 # elif defined(HAVE_UCONTEXT_T_UC_MCONTEXT_UC_REGS)
 196 #  define REGS uc_regs->gregs[REG_INDEX]
 197 # endif /* HAVE_UCONTEXT_T_UC_MCONTEXT_GREGS */
 198 #endif /* REG_INDEX */
 199
 200 #ifdef REGS
 201   if (context)
 202     return (void *)(((ucontext_t *)context)->uc_mcontext.REGS);
 203 #elif defined(HAVE_UCONTEXT_T_UC_MCONTEXT_REGS__NIP)
 204   /* older Linux / struct pt_regs ? */
 205   if (context)
 206     return (void *)(((ucontext_t *)context)->uc_mcontext.regs->nip);
 207 #endif /* REGS */
 208
 209 #endif /* HAVE_UCONTEXT_H */
 210   return NULL;
 211 }
 212
 213 #endif /* SA_SIGINFO */
 214
 215 static void __attribute__ ((noreturn))
 216 exit_handler(int signo
 217 #ifdef SA_SIGINFO
 218              , siginfo_t *siginfo, void *context
 219 #endif
 220             )
 221 {
 222   zlog_signal(signo, "exiting..."
 223 #ifdef SA_SIGINFO
 224               , siginfo, program_counter(context)
 225 #endif
 226              );
 227   _exit(128+signo);
 228 }
 229
 230 static void __attribute__ ((noreturn))
 231 core_handler(int signo
 232 #ifdef SA_SIGINFO
 233              , siginfo_t *siginfo, void *context
 234 #endif
 235             )
 236 {
 237   /* make sure we don't hang in here.  default for SIGALRM is terminate.
 238    * - if we're in backtrace for more than a second, abort. */
 239   struct sigaction sa_default = { .sa_handler = SIG_DFL };
 240   sigaction (SIGALRM, &sa_default, NULL);
 241
 242   sigset_t sigset;
 243   sigemptyset (&sigset);
 244   sigaddset (&sigset, SIGALRM);
 245   sigprocmask (SIG_UNBLOCK, &sigset, NULL);
 246
 247   alarm (1);
 248
 249   zlog_signal(signo, "aborting..."
 250 #ifdef SA_SIGINFO
 251               , siginfo, program_counter(context)
 252 #endif
 253              );
 254   /* dump memory stats on core */
 255   log_memstats_stderr ("core_handler");
 256   abort();
 257 }
 258
 259 static void
 260 trap_default_signals(void)
 261 {
 262   static const int core_signals[] = {
 263     SIGQUIT,
 264     SIGILL,
 265 #ifdef SIGEMT
 266     SIGEMT,
 267 #endif
 268     SIGFPE,
 269     SIGBUS,
 270     SIGSEGV,
 271 #ifdef SIGSYS
 272     SIGSYS,
 273 #endif
 274 #ifdef SIGXCPU
 275     SIGXCPU,
 276 #endif
 277 #ifdef SIGXFSZ
 278     SIGXFSZ,
 279 #endif
 280   };
 281   static const int exit_signals[] = {
 282     SIGHUP,
 283     SIGINT,
 284     SIGALRM,
 285     SIGTERM,
 286     SIGUSR1,
 287     SIGUSR2,
 288 #ifdef SIGPOLL
 289     SIGPOLL,
 290 #endif
 291 #ifdef SIGVTALRM
 292     SIGVTALRM,
 293 #endif
 294 #ifdef SIGSTKFLT
 295     SIGSTKFLT,
 296 #endif
 297   };
 298   static const int ignore_signals[] = {
 299     SIGPIPE,
 300   };
 301   static const struct {
 302     const int *sigs;
 303     u_int nsigs;
 304     void (*handler)(int signo
 305 #ifdef SA_SIGINFO
 306                     , siginfo_t *info, void *context
 307 #endif
 308                    );
 309   } sigmap[] = {
 310     { core_signals, array_size(core_signals), core_handler},
 311     { exit_signals, array_size(exit_signals), exit_handler},
 312     { ignore_signals, array_size(ignore_signals), NULL},
 313   };
 314   u_int i;
 315
 316   for (i = 0; i < array_size(sigmap); i++)
 317     {
 318       u_int j;
 319
 320       for (j = 0; j < sigmap[i].nsigs; j++)
 321         {
 322           struct sigaction oact;
 323           if ((sigaction(sigmap[i].sigs[j],NULL,&oact) == 0) &&
 324               (oact.sa_handler == SIG_DFL))
 325             {
 326               struct sigaction act;
 327               sigfillset (&act.sa_mask);
 328               if (sigmap[i].handler == NULL)
 329                 {
 330                   act.sa_handler = SIG_IGN;
 331                   act.sa_flags = 0;
 332                 }
 333               else
 334                 {
 335 #ifdef SA_SIGINFO
 336                   /* Request extra arguments to signal handler. */
 337                   act.sa_sigaction = sigmap[i].handler;
 338                   act.sa_flags = SA_SIGINFO;
 339 #else
 340                   act.sa_handler = sigmap[i].handler;
 341                   act.sa_flags = 0;
 342 #endif
 343 #ifdef SA_RESETHAND
 344                   /* don't try to print backtraces recursively */
 345                   if (sigmap[i].handler == core_handler)
 346                     act.sa_flags |= SA_RESETHAND;
 347 #endif
 348                 }
 349               if (sigaction(sigmap[i].sigs[j],&act,NULL) < 0)
 350                 zlog_warn("Unable to set signal handler for signal %d: %s",
 351                           sigmap[i].sigs[j],safe_strerror(errno));
 352
 353             }
 354         }
 355     }
 356 }
 357
 358 void
 359 signal_init (struct thread_master *m, int sigc,
 360              struct quagga_signal_t signals[])
 361 {
 362
 363   int i = 0;
 364   struct quagga_signal_t *sig;
 365
 366   /* First establish some default handlers that can be overridden by
 367      the application. */
 368   trap_default_signals();
 369
 370   while (i < sigc)
 371     {
 372       sig = &signals[i];
 373       if ( signal_set (sig->signal) < 0 )
 374         exit (-1);
 375       i++;
 376     }
 377
 378   sigmaster.sigc = sigc;
 379   sigmaster.signals = signals;
 380
 381 #ifdef SIGEVENT_SCHEDULE_THREAD
 382   sigmaster.t = NULL;
 383   thread_add_timer(m, quagga_signal_timer, &sigmaster, QUAGGA_SIGNAL_TIMER_INTERVAL,
 384                    &sigmaster.t);
 385 #endif /* SIGEVENT_SCHEDULE_THREAD */
 386 }