2.5-18.1

debug/segfault.c

@@ -0,0 +1,214 @@
+/* Catch segmentation faults and print backtrace.
+   Copyright (C) 1998, 1999, 2000, 2001, 2002, 2004
+   Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Ulrich Drepper <drepper@cygnus.com>, 1998.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, write to the Free
+   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+   02111-1307 USA.  */
+
+#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>
+
+/* This file defines macros to access the content of the sigcontext element
+   passed up by the signal handler.  */
+#include <sigcontextinfo.h>
+
+/* Get code to possibly dump the content of all registers.  */
+#include <register-dump.h>
+
+/* We'll use tis a lot.  */
+#define WRITE_STRING(s) write (fd, s, strlen (s))
+
+/* Name of the output file.  */
+static const char *fname;
+
+
+/* We better should not use `strerror' since it can call far too many
+   other functions which might fail.  Do it here ourselves.  */
+static void
+write_strsignal (int fd, int signal)
+{
+  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]);
+}
+
+
+/* This function is called when a segmentation fault is caught.  The system
+   is in an instable state now.  This means especially that malloc() might
+   not work anymore.  */
+static void
+catch_segfault (int signal, SIGCONTEXT ctx)
+{
+  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);
+}
+
+
+static void
+__attribute__ ((constructor))
+install_handler (void)
+{
+  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);
+    }
+}