+2014-08-26 Dmitry Antipov <dmantipov@yandex.ru>
+
+ Detect features needed to handle C stack overflows.
+ * configure.ac: Check for sigaltstack and related sigaction
+ support. Unconditionally check for sigsetjmp and siglongjmp.
+ (HAVE_STACK_OVERFLOW_HANDLING): Define if we can support it.
+
2014-08-25 Ken Brown <kbrown@cornell.edu>
* configure.ac (G_SLICE_ALWAYS_MALLOC): Remove obsolete macro.
[Define to 1 if timerfd functions are supported as in GNU/Linux.])
fi
+# Alternate stack for signal handlers.
+AC_CACHE_CHECK([whether signals can be handled on alternate stack],
+ [emacs_cv_alternate_stack],
+ [AC_COMPILE_IFELSE(
+ [AC_LANG_PROGRAM([[#include <signal.h>
+ ]],
+ [[stack_t ss;
+ struct sigaction sa;
+ ss.ss_sp = malloc (SIGSTKSZ);
+ ss.ss_size = SIGSTKSZ;
+ sa.sa_flags = SA_SIGINFO | SA_ONSTACK;
+ sigaltstack (&ss, 0);
+ sigaction (SIGSEGV, &sa, 0);]])],
+ [emacs_cv_alternate_stack=yes],
+ [emacs_cv_alternate_stack=no])])
+
# Do we have res_init, for detecting changes in /etc/resolv.conf?
# On Darwin, res_init appears not to be useful: see bug#562 and
# http://lists.gnu.org/archive/html/emacs-devel/2007-11/msg01467.html
[emacs_cv_func__setjmp=no])])
if test $emacs_cv_func__setjmp = yes; then
AC_DEFINE([HAVE__SETJMP], 1, [Define to 1 if _setjmp and _longjmp work.])
-else
- AC_CACHE_CHECK([for sigsetjmp], [emacs_cv_func_sigsetjmp],
- [AC_LINK_IFELSE(
- [AC_LANG_PROGRAM(
- [[#include <setjmp.h>
- ]],
- [[sigjmp_buf j;
- if (! sigsetjmp (j, 1))
- siglongjmp (j, 1);]])],
- [emacs_cv_func_sigsetjmp=yes],
- [emacs_cv_func_sigsetjmp=no])])
- if test $emacs_cv_func_sigsetjmp = yes; then
- AC_DEFINE([HAVE_SIGSETJMP], 1,
- [Define to 1 if sigsetjmp and siglongjmp work.
- The value of this symbol is irrelevant if HAVE__SETJMP is defined.])
- fi
+fi
+
+# We need to preserve signal mask to handle C stack overflows.
+AC_CACHE_CHECK([for sigsetjmp], [emacs_cv_func_sigsetjmp],
+ [AC_LINK_IFELSE(
+ [AC_LANG_PROGRAM(
+ [[#include <setjmp.h>
+ ]],
+ [[sigjmp_buf j;
+ if (! sigsetjmp (j, 1))
+ siglongjmp (j, 1);]])],
+ [emacs_cv_func_sigsetjmp=yes],
+ [emacs_cv_func_sigsetjmp=no])])
+if test $emacs_cv_func_sigsetjmp = yes; then
+ AC_DEFINE([HAVE_SIGSETJMP], 1,
+ [Define to 1 if sigsetjmp and siglongjmp work.])
+fi
+
+# We need all of these features to handle C stack overflows.
+if test "$ac_cv_header_sys_resource_h" = "yes" -a \
+ "$ac_cv_func_getrlimit" = "yes" -a \
+ "$emacs_cv_func_sigsetjmp" = "yes" -a \
+ "$emacs_cv_alternate_stack" = yes; then
+ AC_DEFINE([HAVE_STACK_OVERFLOW_HANDLING], 1,
+ [Define to 1 if C stack overflow can be handled in some cases.])
fi
case $opsys in
+2014-08-26 Dmitry Antipov <dmantipov@yandex.ru>
+
+ * startup.el (normal-top-level): Use top-level-message.
+
2014-08-25 Lars Magne Ingebrigtsen <larsi@gnus.org>
* net/shr.el (shr-copy-url): Encode copied URL to avoid getting
reads the initialization files, etc.
It is the default value of the variable `top-level'."
(if command-line-processed
- (message "Back to top level.")
+ (message top-level-message)
(setq command-line-processed t)
;; Look in each dir in load-path for a subdirs.el file. If we
+2014-08-26 Dmitry Antipov <dmantipov@yandex.ru>
+
+ Handle C stack overflow caused by too nested Lisp evaluation.
+ * lisp.h (toplevel) [HAVE_STACK_OVERFLOW_HANDLING]: Declare
+ siglongjmp point to transfer control from SIGSEGV handler.
+ * keyboard.c (return_to_command_loop, recover_top_level_message)
+ [HAVE_STACK_OVERFLOW_HANDLING]: New variables.
+ (regular_top_level_message): New variable.
+ (command_loop) [HAVE_STACK_OVERFLOW_HANDLING]: Handle non-local
+ exit from SIGSEGV handler and adjust message displayed by Vtop_level
+ if appropriate.
+ (syms_of_keyboard): DEFVAR Vtop_level_message and initialize
+ new variables described above.
+ * sysdep.c [HAVE_SYS_RESOURCE_H]: Include sys/resource.h as such.
+ (stack_grows_down, sigsegv_stack, handle_sigsegv)
+ [HAVE_STACK_OVERFLOW_HANDLING]: New variables and function.
+ (init_sigsegv): New function.
+ (init_signals): Use it.
+
2014-08-25 Ken Brown <kbrown@cornell.edu>
* emacs.c (main): Remove use of obsolete macro
static ptrdiff_t before_command_key_count;
static ptrdiff_t before_command_echo_length;
+#ifdef HAVE_STACK_OVERFLOW_HANDLING
+
+/* For longjmp to recover from C stack overflow. */
+sigjmp_buf return_to_command_loop;
+
+/* Message displayed by Vtop_level when recovering from C stack overflow. */
+static Lisp_Object recover_top_level_message;
+
+#endif /* HAVE_STACK_OVERFLOW_HANDLING */
+
+/* Message normally displayed by Vtop_level. */
+static Lisp_Object regular_top_level_message;
+
/* For longjmp to where kbd input is being done. */
static sys_jmp_buf getcjmp;
Lisp_Object
command_loop (void)
{
+#ifdef HAVE_STACK_OVERFLOW_HANDLING
+ /* At least on GNU/Linux, saving signal mask is important here. */
+ if (sigsetjmp (return_to_command_loop, 1) != 0)
+ {
+ /* Comes here from handle_sigsegv, see sysdep.c. */
+ init_eval ();
+ Vtop_level_message = recover_top_level_message;
+ }
+ else
+ Vtop_level_message = regular_top_level_message;
+#endif /* HAVE_STACK_OVERFLOW_HANDLING */
if (command_loop_level > 0 || minibuf_level > 0)
{
Lisp_Object val;
Vlispy_mouse_stem = build_pure_c_string ("mouse");
staticpro (&Vlispy_mouse_stem);
+ regular_top_level_message = build_pure_c_string ("Back to top level");
+#ifdef HAVE_STACK_OVERFLOW_HANDLING
+ recover_top_level_message
+ = build_pure_c_string ("Re-entering top level after C stack overflow");
+#endif
+ DEFVAR_LISP ("top-level-message", Vtop_level_message,
+ doc: /* Message displayed by `normal-top-level'. */);
+ Vtop_level_message = regular_top_level_message;
+
/* Tool-bars. */
DEFSYM (QCimage, ":image");
DEFSYM (Qhelp_echo, "help-echo");
extern Lisp_Object Qup, Qdown;
extern Lisp_Object last_undo_boundary;
extern bool input_pending;
+#ifdef HAVE_STACK_OVERFLOW_HANDLING
+extern sigjmp_buf return_to_command_loop;
+#endif
extern Lisp_Object menu_bar_items (Lisp_Object);
extern Lisp_Object tool_bar_items (Lisp_Object, int *);
extern void discard_mouse_events (void);
# include <sys/user.h>
# undef frame
-# include <sys/resource.h>
# include <math.h>
#endif
#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>
xsignal0 (Qarith_error);
}
+#ifdef HAVE_STACK_OVERFLOW_HANDLING
+
+/* True if stack grows down as expected on most OS/ABI variants. */
+
+static bool stack_grows_down;
+
+/* Alternate stack used by SIGSEGV handler below. */
+
+static unsigned char sigsegv_stack[SIGSTKSZ];
+
+/* Attempt to recover from SIGSEGV caused by C stack overflow. */
+
+static void
+handle_sigsegv (int sig, siginfo_t *siginfo, void *arg)
+{
+ /* 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;
+
+ if (!getrlimit (RLIMIT_STACK, &rlim))
+ {
+ enum { STACK_EXTRA = 16 * 1024 };
+ char *fault_addr = (char *) siginfo->si_addr;
+ unsigned long used = (stack_grows_down
+ ? stack_bottom - fault_addr
+ : fault_addr - stack_bottom);
+
+ if (used + STACK_EXTRA > rlim.rlim_cur)
+ /* Most likely this is it. */
+ siglongjmp (return_to_command_loop, 1);
+ }
+ }
+}
+
+static bool
+init_sigsegv (void)
+{
+ struct sigaction sa;
+ stack_t ss;
+
+ stack_grows_down = ((char *) &ss < stack_bottom);
+
+ ss.ss_sp = sigsegv_stack;
+ ss.ss_size = sizeof (sigsegv_stack);
+ ss.ss_flags = 0;
+ if (sigaltstack (&ss, NULL) < 0)
+ return 0;
+
+ sigfillset (&sa.sa_mask);
+ sa.sa_sigaction = handle_sigsegv;
+ sa.sa_flags = SA_SIGINFO | SA_ONSTACK | emacs_sigaction_flags ();
+ return sigaction (SIGSEGV, &sa, NULL) < 0 ? 0 : 1;
+}
+
+#else /* not HAVE_STACK_OVERFLOW_HANDLING */
+
+static bool
+init_sigsegv (void)
+{
+ return 0;
+}
+
+#endif /* HAVE_STACK_OVERFLOW_HANDLING */
+
static void
deliver_arith_signal (int sig)
{
#ifdef SIGBUS
sigaction (SIGBUS, &thread_fatal_action, 0);
#endif
- sigaction (SIGSEGV, &thread_fatal_action, 0);
+ if (!init_sigsegv ())
+ sigaction (SIGSEGV, &thread_fatal_action, 0);
#ifdef SIGSYS
sigaction (SIGSYS, &thread_fatal_action, 0);
#endif
projects / emacs.git / commitdiff