Imported Upstream version 1.13.4upstream/1.13.4

1 files changed, 286 insertions, 0 deletions

diff --git a/lib/fatal-signal.c b/lib/fatal-signal.c
new file mode 100644
index 0000000..aca9027
--- /dev/null
+++ b/lib/fatal-signal.c
@@ -0,0 +1,286 @@
+/* Emergency actions in case of a fatal signal.
+   Copyright (C) 2003-2004, 2006-2011 Free Software Foundation, Inc.
+   Written by Bruno Haible <bruno@clisp.org>, 2003.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program 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 General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+
+#include <config.h>
+
+/* Specification.  */
+#include "fatal-signal.h"
+
+#include <stdbool.h>
+#include <stdlib.h>
+#include <signal.h>
+#include <unistd.h>
+
+#include "sig-handler.h"
+#include "xalloc.h"
+
+#define SIZEOF(a) (sizeof(a) / sizeof(a[0]))
+
+/* ========================================================================= */
+
+
+/* The list of fatal signals.
+   These are those signals whose default action is to terminate the process
+   without a core dump, except
+     SIGKILL - because it cannot be caught,
+     SIGALRM SIGUSR1 SIGUSR2 SIGPOLL SIGIO SIGLOST - because applications
+       often use them for their own purpose,
+     SIGPROF SIGVTALRM - because they are used for profiling,
+     SIGSTKFLT - because it is more similar to SIGFPE, SIGSEGV, SIGBUS,
+     SIGSYS - because it is more similar to SIGABRT, SIGSEGV,
+     SIGPWR - because it of too special use,
+     SIGRTMIN...SIGRTMAX - because they are reserved for application use.
+   plus
+     SIGXCPU, SIGXFSZ - because they are quite similar to SIGTERM.  */
+
+static int fatal_signals[] =
+  {
+    /* ISO C 99 signals.  */
+#ifdef SIGINT
+    SIGINT,
+#endif
+#ifdef SIGTERM
+    SIGTERM,
+#endif
+    /* POSIX:2001 signals.  */
+#ifdef SIGHUP
+    SIGHUP,
+#endif
+#ifdef SIGPIPE
+    SIGPIPE,
+#endif
+    /* BSD signals.  */
+#ifdef SIGXCPU
+    SIGXCPU,
+#endif
+#ifdef SIGXFSZ
+    SIGXFSZ,
+#endif
+    /* Woe32 signals.  */
+#ifdef SIGBREAK
+    SIGBREAK,
+#endif
+    0
+  };
+
+#define num_fatal_signals (SIZEOF (fatal_signals) - 1)
+
+/* Eliminate signals whose signal handler is SIG_IGN.  */
+
+static void
+init_fatal_signals (void)
+{
+  static bool fatal_signals_initialized = false;
+  if (!fatal_signals_initialized)
+    {
+      size_t i;
+
+      for (i = 0; i < num_fatal_signals; i++)
+        {
+          struct sigaction action;
+
+          if (sigaction (fatal_signals[i], NULL, &action) >= 0
+              && get_handler (&action) == SIG_IGN)
+            fatal_signals[i] = -1;
+        }
+
+      fatal_signals_initialized = true;
+    }
+}
+
+
+/* ========================================================================= */
+
+
+typedef void (*action_t) (void);
+
+/* Type of an entry in the actions array.
+   The 'action' field is accessed from within the fatal_signal_handler(),
+   therefore we mark it as 'volatile'.  */
+typedef struct
+{
+  volatile action_t action;
+}
+actions_entry_t;
+
+/* The registered cleanup actions.  */
+static actions_entry_t static_actions[32];
+static actions_entry_t * volatile actions = static_actions;
+static sig_atomic_t volatile actions_count = 0;
+static size_t actions_allocated = SIZEOF (static_actions);
+
+
+/* The saved signal handlers.
+   Size 32 would not be sufficient: On HP-UX, SIGXCPU = 33, SIGXFSZ = 34.  */
+static struct sigaction saved_sigactions[64];
+
+
+/* Uninstall the handlers.  */
+static inline void
+uninstall_handlers ()
+{
+  size_t i;
+
+  for (i = 0; i < num_fatal_signals; i++)
+    if (fatal_signals[i] >= 0)
+      {
+        int sig = fatal_signals[i];
+        if (saved_sigactions[sig].sa_handler == SIG_IGN)
+          saved_sigactions[sig].sa_handler = SIG_DFL;
+        sigaction (sig, &saved_sigactions[sig], NULL);
+      }
+}
+
+
+/* The signal handler.  It gets called asynchronously.  */
+static void
+fatal_signal_handler (int sig)
+{
+  for (;;)
+    {
+      /* Get the last registered cleanup action, in a reentrant way.  */
+      action_t action;
+      size_t n = actions_count;
+      if (n == 0)
+        break;
+      n--;
+      actions_count = n;
+      action = actions[n].action;
+      /* Execute the action.  */
+      action ();
+    }
+
+  /* Now execute the signal's default action.
+     If the signal being delivered was blocked, the re-raised signal would be
+     delivered when this handler returns.  But the way we install this handler,
+     no signal is blocked, and the re-raised signal is delivered already
+     during raise().  */
+  uninstall_handlers ();
+  raise (sig);
+}
+
+
+/* Install the handlers.  */
+static inline void
+install_handlers ()
+{
+  size_t i;
+  struct sigaction action;
+
+  action.sa_handler = &fatal_signal_handler;
+  /* If we get a fatal signal while executing fatal_signal_handler, enter
+     fatal_signal_handler recursively, since it is reentrant.  Hence no
+     SA_RESETHAND.  */
+  action.sa_flags = SA_NODEFER;
+  sigemptyset (&action.sa_mask);
+  for (i = 0; i < num_fatal_signals; i++)
+    if (fatal_signals[i] >= 0)
+      {
+        int sig = fatal_signals[i];
+
+        if (!(sig < sizeof (saved_sigactions) / sizeof (saved_sigactions[0])))
+          abort ();
+        sigaction (sig, &action, &saved_sigactions[sig]);
+      }
+}
+
+
+/* Register a cleanup function to be executed when a catchable fatal signal
+   occurs.  */
+void
+at_fatal_signal (action_t action)
+{
+  static bool cleanup_initialized = false;
+  if (!cleanup_initialized)
+    {
+      init_fatal_signals ();
+      install_handlers ();
+      cleanup_initialized = true;
+    }
+
+  if (actions_count == actions_allocated)
+    {
+      /* Extend the actions array.  Note that we cannot use xrealloc(),
+         because then the cleanup() function could access an already
+         deallocated array.  */
+      actions_entry_t *old_actions = actions;
+      size_t old_actions_allocated = actions_allocated;
+      size_t new_actions_allocated = 2 * actions_allocated;
+      actions_entry_t *new_actions =
+        XNMALLOC (new_actions_allocated, actions_entry_t);
+      size_t k;
+
+      /* Don't use memcpy() here, because memcpy takes non-volatile arguments
+         and is therefore not guaranteed to complete all memory stores before
+         the next statement.  */
+      for (k = 0; k < old_actions_allocated; k++)
+        new_actions[k] = old_actions[k];
+      actions = new_actions;
+      actions_allocated = new_actions_allocated;
+      /* Now we can free the old actions array.  */
+      if (old_actions != static_actions)
+        free (old_actions);
+    }
+  /* The two uses of 'volatile' in the types above (and ISO C 99 section
+     5.1.2.3.(5)) ensure that we increment the actions_count only after
+     the new action has been written to the memory location
+     actions[actions_count].  */
+  actions[actions_count].action = action;
+  actions_count++;
+}
+
+
+/* ========================================================================= */
+
+
+static sigset_t fatal_signal_set;
+
+static void
+init_fatal_signal_set ()
+{
+  static bool fatal_signal_set_initialized = false;
+  if (!fatal_signal_set_initialized)
+    {
+      size_t i;
+
+      init_fatal_signals ();
+
+      sigemptyset (&fatal_signal_set);
+      for (i = 0; i < num_fatal_signals; i++)
+        if (fatal_signals[i] >= 0)
+          sigaddset (&fatal_signal_set, fatal_signals[i]);
+
+      fatal_signal_set_initialized = true;
+    }
+}
+
+/* Temporarily delay the catchable fatal signals.  */
+void
+block_fatal_signals ()
+{
+  init_fatal_signal_set ();
+  sigprocmask (SIG_BLOCK, &fatal_signal_set, NULL);
+}
+
+/* Stop delaying the catchable fatal signals.  */
+void
+unblock_fatal_signals ()
+{
+  init_fatal_signal_set ();
+  sigprocmask (SIG_UNBLOCK, &fatal_signal_set, NULL);
+}