/* Interfaces to system-dependent kernel and library entries.
- Copyright (C) 1985-1988, 1993-1995, 1999-2014 Free Software
+ Copyright (C) 1985-1988, 1993-1995, 1999-2015 Free Software
Foundation, Inc.
This file is part of GNU Emacs.
#include "msdos.h"
#endif
-#ifdef HAVE_SYS_RESOURCE_H
-#include <sys/resource.h>
-#endif
#include <sys/param.h>
#include <sys/file.h>
#include <fcntl.h>
interrupts_deferred = 1;
#endif
}
-
-void
-ignore_sigio (void)
-{
-#ifdef USABLE_SIGIO
- signal (SIGIO, SIG_IGN);
-#endif
-}
\f
#ifndef MSDOS
/* Block SIGCHLD. */
#ifdef HAVE_STACK_OVERFLOW_HANDLING
-/* -1 if stack grows down as expected on most OS/ABI variants, 1 otherwise. */
-
-static int stack_direction;
-
/* Alternate stack used by SIGSEGV handler below. */
static unsigned char sigsegv_stack[SIGSTKSZ];
+
+/* Return true if SIGINFO indicates a stack overflow. */
+
+static bool
+stack_overflow (siginfo_t *siginfo)
+{
+ /* In theory, a more-accurate heuristic can be obtained by using
+ GNU/Linux pthread_getattr_np along with POSIX pthread_attr_getstack
+ and pthread_attr_getguardsize to find the location and size of the
+ guard area. In practice, though, these functions are so hard to
+ use reliably that they're not worth bothering with. E.g., see:
+ https://sourceware.org/bugzilla/show_bug.cgi?id=16291
+ Other operating systems also have problems, e.g., Solaris's
+ stack_violation function is tailor-made for this problem, but it
+ doesn't work on Solaris 11.2 x86-64 with a 32-bit executable.
+
+ GNU libsigsegv is overkill for Emacs; otherwise it might be a
+ candidate here. */
+
+ if (!siginfo)
+ return false;
+
+ /* The faulting address. */
+ char *addr = siginfo->si_addr;
+ if (!addr)
+ return false;
+
+ /* The known top and bottom of the stack. The actual stack may
+ extend a bit beyond these boundaries. */
+ char *bot = stack_bottom;
+ char *top = near_C_stack_top ();
+
+ /* Log base 2 of the stack heuristic ratio. This ratio is the size
+ of the known stack divided by the size of the guard area past the
+ end of the stack top. The heuristic is that a bad address is
+ considered to be a stack overflow if it occurs within
+ stacksize>>LG_STACK_HEURISTIC bytes above the top of the known
+ stack. This heuristic is not exactly correct but it's good
+ enough in practice. */
+ enum { LG_STACK_HEURISTIC = 8 };
+
+ if (bot < top)
+ return 0 <= addr - top && addr - top < (top - bot) >> LG_STACK_HEURISTIC;
+ else
+ return 0 <= top - addr && top - addr < (bot - top) >> LG_STACK_HEURISTIC;
+}
+
+
/* Attempt to recover from SIGSEGV caused by C stack overflow. */
static void
{
/* Hard GC error may lead to stack overflow caused by
too nested calls to mark_object. No way to survive. */
- if (!gc_in_progress)
- {
- struct rlimit rlim;
+ bool fatal = gc_in_progress;
- if (!getrlimit (RLIMIT_STACK, &rlim))
- {
- enum { STACK_DANGER_ZONE = 16 * 1024 };
- char *beg, *end, *addr;
-
- beg = stack_bottom;
- end = stack_bottom + stack_direction * rlim.rlim_cur;
- if (beg > end)
- addr = beg, beg = end, end = addr;
- addr = (char *) siginfo->si_addr;
- /* If we're somewhere on stack and too close to
- one of its boundaries, most likely this is it. */
- if (beg < addr && addr < end
- && (addr - beg < STACK_DANGER_ZONE
- || end - addr < STACK_DANGER_ZONE))
- siglongjmp (return_to_command_loop, 1);
- }
- }
+#ifdef FORWARD_SIGNAL_TO_MAIN_THREAD
+ if (!fatal && !pthread_equal (pthread_self (), main_thread))
+ fatal = true;
+#endif
+
+ if (!fatal && stack_overflow (siginfo))
+ siglongjmp (return_to_command_loop, 1);
/* Otherwise we can't do anything with this. */
deliver_fatal_thread_signal (sig);
struct sigaction sa;
stack_t ss;
- stack_direction = ((char *) &ss < stack_bottom) ? -1 : 1;
-
ss.ss_sp = sigsegv_stack;
ss.ss_size = sizeof (sigsegv_stack);
ss.ss_flags = 0;
/* If a backtrace is available, output the top lines of it to stderr.
Do not output more than BACKTRACE_LIMIT or BACKTRACE_LIMIT_MAX lines.
This function may be called from a signal handler, so it should
- not invoke async-unsafe functions like malloc. */
+ not invoke async-unsafe functions like malloc.
+
+ If BACKTRACE_LIMIT is -1, initialize tables that 'backtrace' uses
+ but do not output anything. This avoids some problems that can
+ otherwise occur if the malloc arena is corrupted before 'backtrace'
+ is called, since 'backtrace' may call malloc if the tables are not
+ initialized.
+
+ If the static variable THREAD_BACKTRACE_NPOINTERS is nonzero, a
+ fatal error has occurred in some other thread; generate a thread
+ backtrace instead, ignoring BACKTRACE_LIMIT. */
void
emacs_backtrace (int backtrace_limit)
{
else
{
buffer = main_backtrace_buffer;
+
+ /* Work around 'backtrace' bug; see Bug#19959 and glibc bug#18084. */
+ if (bounded_limit < 0)
+ {
+ backtrace (buffer, 1);
+ return;
+ }
+
npointers = backtrace (buffer, bounded_limit + 1);
}