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glibc  2.9
Defines | Functions | Variables
segfault.c File Reference
#include <alloca.h>
#include <ctype.h>
#include <errno.h>
#include <execinfo.h>
#include <fcntl.h>
#include <signal.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <stdio-common/_itoa.h>
#include <ldsodefs.h>
#include <bp-checks.h>
#include <sigcontextinfo.h>
#include <register-dump.h>
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Defines

#define WRITE_STRING(s)   write (fd, s, strlen (s))
#define INSTALL_FOR_SIG(sig, name)

Functions

static void write_strsignal (int fd, int signal)
static void catch_segfault (int signal, SIGCONTEXT ctx)
static void __attribute__ ((constructor))

Variables

static const char * fname

Define Documentation

#define INSTALL_FOR_SIG (   sig,
  name 
)
Value:
where = __strcasestr (sigs, name);                            \
      if (all || (where != NULL                                             \
                && (where == sigs || !isalnum (where[-1]))                  \
                && !isalnum (where[sizeof (name) - 1])))                    \
	sigaction (sig, &sa, NULL);
#define WRITE_STRING (   s)    write (fd, s, strlen (s))

Definition at line 46 of file segfault.c.


Function Documentation

static void __attribute__ ( (constructor)  ) [static]

Definition at line 148 of file segfault.c.

{
  struct sigaction sa;
  const char *sigs = getenv ("SEGFAULT_SIGNALS");
  const char *name;

  sa.sa_handler = (void *) catch_segfault;
  sigemptyset (&sa.sa_mask);
  sa.sa_flags = SA_RESTART;

  /* Maybe we are expected to use an alternative stack.  */
  if (getenv ("SEGFAULT_USE_ALTSTACK") != 0)
    {
      void *stack_mem = malloc (2 * SIGSTKSZ);
      struct sigaltstack ss;

      if (stack_mem != NULL)
       {
         ss.ss_sp = stack_mem;
         ss.ss_flags = 0;
         ss.ss_size = 2 * SIGSTKSZ;

         if (sigaltstack (&ss, NULL) == 0)
           sa.sa_flags |= SA_ONSTACK;
       }
    }

  if (sigs == NULL)
    sigaction (SIGSEGV, &sa, NULL);
  else if (sigs[0] == '\0')
    /* Do not do anything.  */
    return;
  else
    {
      const char *where;
      int all = __strcasecmp (sigs, "all") == 0;

#define INSTALL_FOR_SIG(sig, name) \
      where = __strcasestr (sigs, name);                             \
      if (all || (where != NULL                                             \
                && (where == sigs || !isalnum (where[-1]))                  \
                && !isalnum (where[sizeof (name) - 1])))                    \
       sigaction (sig, &sa, NULL);

      INSTALL_FOR_SIG (SIGSEGV, "segv");
      INSTALL_FOR_SIG (SIGILL, "ill");
#ifdef SIGBUS
      INSTALL_FOR_SIG (SIGBUS, "bus");
#endif
#ifdef SIGSTKFLT
      INSTALL_FOR_SIG (SIGSTKFLT, "stkflt");
#endif
      INSTALL_FOR_SIG (SIGABRT, "abrt");
      INSTALL_FOR_SIG (SIGFPE, "fpe");
    }

  /* Preserve the output file name if there is any given.  */
  name = getenv ("SEGFAULT_OUTPUT_NAME");
  if (name != NULL && name[0] != '\0')
    {
      int ret = access (name, R_OK | W_OK);

      if (ret == 0 || (ret == -1 && errno == ENOENT))
       fname = __strdup (name);
    }
}

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static void catch_segfault ( int  signal,
SIGCONTEXT  ctx 
) [static]

Definition at line 73 of file segfault.c.

{
  int fd, cnt, i;
  void **arr;
  struct sigaction sa;
  uintptr_t pc;

  /* This is the name of the file we are writing to.  If none is given
     or we cannot write to this file write to stderr.  */
  fd = 2;
  if (fname != NULL)
    {
      fd = open (fname, O_TRUNC | O_WRONLY | O_CREAT, 0666);
      if (fd == -1)
       fd = 2;
    }

  WRITE_STRING ("*** ");
  write_strsignal (fd, signal);
  WRITE_STRING ("\n");

#ifdef REGISTER_DUMP
  REGISTER_DUMP;
#endif

  WRITE_STRING ("\nBacktrace:\n");

  /* Get the backtrace.  */
  arr = alloca (256 * sizeof (void *));
  cnt = backtrace (arr, 256);

  /* Now try to locate the PC from signal context in the backtrace.
     Normally it will be found at arr[2], but it might appear later
     if there were some signal handler wrappers.  Allow a few bytes
     difference to cope with as many arches as possible.  */
  pc = (uintptr_t) GET_PC (ctx);
  for (i = 0; i < cnt; ++i)
    if ((uintptr_t) arr[i] >= pc - 16 && (uintptr_t) arr[i] <= pc + 16)
      break;

  /* If we haven't found it, better dump full backtrace even including
     the signal handler frames instead of not dumping anything.  */
  if (i == cnt)
    i = 0;

  /* Now generate nicely formatted output.  */
  __backtrace_symbols_fd (arr + i, cnt - i, fd);

#ifdef HAVE_PROC_SELF
  /* Now the link map.  */
  int mapfd = open ("/proc/self/maps", O_RDONLY);
  if (mapfd != -1)
    {
      write (fd, "\nMemory map:\n\n", 14);

      char buf[256];
      ssize_t n;

      while ((n = TEMP_FAILURE_RETRY (read (mapfd, buf, sizeof (buf)))) > 0)
       TEMP_FAILURE_RETRY (write (fd, buf, n));

      close (mapfd);
    }
#endif

  /* Pass on the signal (so that a core file is produced).  */
  sa.sa_handler = SIG_DFL;
  sigemptyset (&sa.sa_mask);
  sa.sa_flags = 0;
  sigaction (signal, &sa, NULL);
  raise (signal);
}

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static void write_strsignal ( int  fd,
int  signal 
) [static]

Definition at line 55 of file segfault.c.

{
  if (signal < 0 || signal >= _NSIG || _sys_siglist[signal] == NULL)
    {
      char buf[30];
      char *ptr = _itoa_word (signal, &buf[sizeof (buf)], 10, 0);
      WRITE_STRING ("signal ");
      write (fd, buf, &buf[sizeof (buf)] - ptr);
    }
  else
    WRITE_STRING (_sys_siglist[signal]);
}

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Variable Documentation

const char* fname [static]

Definition at line 49 of file segfault.c.