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