Handle C stack overflow caused by too nested Lisp evaluation.
* 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. * src/lisp.h (toplevel) [HAVE_STACK_OVERFLOW_HANDLING]: Declare siglongjmp point to transfer control from SIGSEGV handler. * src/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. * src/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. * lisp/startup.el (normal-top-level): Use top-level-message.
This commit is contained in:
Dmitry Antipov
parent
940ac42ae3
commit
ebd31792b2
8 changed files with 179 additions and 19 deletions
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@ -1,3 +1,10 @@
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2014-08-26 Dmitry Antipov <dmantipov@yandex.ru>
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Detect features needed to handle C stack overflows.
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* configure.ac: Check for sigaltstack and related sigaction
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support. Unconditionally check for sigsetjmp and siglongjmp.
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(HAVE_STACK_OVERFLOW_HANDLING): Define if we can support it.
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2014-08-25 Ken Brown <kbrown@cornell.edu>
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* configure.ac (G_SLICE_ALWAYS_MALLOC): Remove obsolete macro.
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57
configure.ac
57
configure.ac
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@ -3728,6 +3728,22 @@ if test "$emacs_cv_have_timerfd" = yes; then
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[Define to 1 if timerfd functions are supported as in GNU/Linux.])
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fi
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# Alternate stack for signal handlers.
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AC_CACHE_CHECK([whether signals can be handled on alternate stack],
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[emacs_cv_alternate_stack],
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[AC_COMPILE_IFELSE(
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[AC_LANG_PROGRAM([[#include <signal.h>
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]],
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[[stack_t ss;
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struct sigaction sa;
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ss.ss_sp = malloc (SIGSTKSZ);
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ss.ss_size = SIGSTKSZ;
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sa.sa_flags = SA_SIGINFO | SA_ONSTACK;
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sigaltstack (&ss, 0);
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sigaction (SIGSEGV, &sa, 0);]])],
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[emacs_cv_alternate_stack=yes],
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[emacs_cv_alternate_stack=no])])
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# Do we have res_init, for detecting changes in /etc/resolv.conf?
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# On Darwin, res_init appears not to be useful: see bug#562 and
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# http://lists.gnu.org/archive/html/emacs-devel/2007-11/msg01467.html
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@ -4447,22 +4463,31 @@ AC_CACHE_CHECK([for _setjmp], [emacs_cv_func__setjmp],
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[emacs_cv_func__setjmp=no])])
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if test $emacs_cv_func__setjmp = yes; then
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AC_DEFINE([HAVE__SETJMP], 1, [Define to 1 if _setjmp and _longjmp work.])
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else
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AC_CACHE_CHECK([for sigsetjmp], [emacs_cv_func_sigsetjmp],
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[AC_LINK_IFELSE(
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[AC_LANG_PROGRAM(
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[[#include <setjmp.h>
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]],
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[[sigjmp_buf j;
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if (! sigsetjmp (j, 1))
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siglongjmp (j, 1);]])],
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[emacs_cv_func_sigsetjmp=yes],
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[emacs_cv_func_sigsetjmp=no])])
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if test $emacs_cv_func_sigsetjmp = yes; then
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AC_DEFINE([HAVE_SIGSETJMP], 1,
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[Define to 1 if sigsetjmp and siglongjmp work.
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The value of this symbol is irrelevant if HAVE__SETJMP is defined.])
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fi
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fi
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# We need to preserve signal mask to handle C stack overflows.
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AC_CACHE_CHECK([for sigsetjmp], [emacs_cv_func_sigsetjmp],
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[AC_LINK_IFELSE(
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[AC_LANG_PROGRAM(
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[[#include <setjmp.h>
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]],
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[[sigjmp_buf j;
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if (! sigsetjmp (j, 1))
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siglongjmp (j, 1);]])],
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[emacs_cv_func_sigsetjmp=yes],
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[emacs_cv_func_sigsetjmp=no])])
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if test $emacs_cv_func_sigsetjmp = yes; then
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AC_DEFINE([HAVE_SIGSETJMP], 1,
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[Define to 1 if sigsetjmp and siglongjmp work.])
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fi
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# We need all of these features to handle C stack overflows.
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if test "$ac_cv_header_sys_resource_h" = "yes" -a \
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"$ac_cv_func_getrlimit" = "yes" -a \
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"$emacs_cv_func_sigsetjmp" = "yes" -a \
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"$emacs_cv_alternate_stack" = yes; then
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AC_DEFINE([HAVE_STACK_OVERFLOW_HANDLING], 1,
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[Define to 1 if C stack overflow can be handled in some cases.])
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fi
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case $opsys in
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@ -1,3 +1,7 @@
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2014-08-26 Dmitry Antipov <dmantipov@yandex.ru>
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* startup.el (normal-top-level): Use top-level-message.
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2014-08-25 Lars Magne Ingebrigtsen <larsi@gnus.org>
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* net/shr.el (shr-copy-url): Encode copied URL to avoid getting
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@ -497,7 +497,7 @@ It sets `command-line-processed', processes the command-line,
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reads the initialization files, etc.
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It is the default value of the variable `top-level'."
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(if command-line-processed
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(message "Back to top level.")
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(message top-level-message)
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(setq command-line-processed t)
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;; Look in each dir in load-path for a subdirs.el file. If we
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@ -1,3 +1,22 @@
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2014-08-26 Dmitry Antipov <dmantipov@yandex.ru>
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Handle C stack overflow caused by too nested Lisp evaluation.
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* lisp.h (toplevel) [HAVE_STACK_OVERFLOW_HANDLING]: Declare
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siglongjmp point to transfer control from SIGSEGV handler.
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* keyboard.c (return_to_command_loop, recover_top_level_message)
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[HAVE_STACK_OVERFLOW_HANDLING]: New variables.
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(regular_top_level_message): New variable.
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(command_loop) [HAVE_STACK_OVERFLOW_HANDLING]: Handle non-local
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exit from SIGSEGV handler and adjust message displayed by Vtop_level
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if appropriate.
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(syms_of_keyboard): DEFVAR Vtop_level_message and initialize
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new variables described above.
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* sysdep.c [HAVE_SYS_RESOURCE_H]: Include sys/resource.h as such.
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(stack_grows_down, sigsegv_stack, handle_sigsegv)
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[HAVE_STACK_OVERFLOW_HANDLING]: New variables and function.
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(init_sigsegv): New function.
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(init_signals): Use it.
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2014-08-25 Ken Brown <kbrown@cornell.edu>
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* emacs.c (main): Remove use of obsolete macro
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@ -133,6 +133,19 @@ static ptrdiff_t this_single_command_key_start;
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static ptrdiff_t before_command_key_count;
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static ptrdiff_t before_command_echo_length;
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#ifdef HAVE_STACK_OVERFLOW_HANDLING
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/* For longjmp to recover from C stack overflow. */
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sigjmp_buf return_to_command_loop;
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/* Message displayed by Vtop_level when recovering from C stack overflow. */
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static Lisp_Object recover_top_level_message;
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#endif /* HAVE_STACK_OVERFLOW_HANDLING */
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/* Message normally displayed by Vtop_level. */
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static Lisp_Object regular_top_level_message;
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/* For longjmp to where kbd input is being done. */
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static sys_jmp_buf getcjmp;
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@ -1134,6 +1147,17 @@ static Lisp_Object top_level_1 (Lisp_Object);
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Lisp_Object
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command_loop (void)
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{
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#ifdef HAVE_STACK_OVERFLOW_HANDLING
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/* At least on GNU/Linux, saving signal mask is important here. */
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if (sigsetjmp (return_to_command_loop, 1) != 0)
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{
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/* Comes here from handle_sigsegv, see sysdep.c. */
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init_eval ();
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Vtop_level_message = recover_top_level_message;
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}
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else
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Vtop_level_message = regular_top_level_message;
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#endif /* HAVE_STACK_OVERFLOW_HANDLING */
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if (command_loop_level > 0 || minibuf_level > 0)
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{
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Lisp_Object val;
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@ -11000,6 +11024,15 @@ syms_of_keyboard (void)
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Vlispy_mouse_stem = build_pure_c_string ("mouse");
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staticpro (&Vlispy_mouse_stem);
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regular_top_level_message = build_pure_c_string ("Back to top level");
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#ifdef HAVE_STACK_OVERFLOW_HANDLING
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recover_top_level_message
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= build_pure_c_string ("Re-entering top level after C stack overflow");
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#endif
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DEFVAR_LISP ("top-level-message", Vtop_level_message,
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doc: /* Message displayed by `normal-top-level'. */);
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Vtop_level_message = regular_top_level_message;
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/* Tool-bars. */
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DEFSYM (QCimage, ":image");
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DEFSYM (Qhelp_echo, "help-echo");
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@ -4093,6 +4093,9 @@ extern Lisp_Object Qdisabled, QCfilter;
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extern Lisp_Object Qup, Qdown;
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extern Lisp_Object last_undo_boundary;
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extern bool input_pending;
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#ifdef HAVE_STACK_OVERFLOW_HANDLING
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extern sigjmp_buf return_to_command_loop;
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#endif
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extern Lisp_Object menu_bar_items (Lisp_Object);
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extern Lisp_Object tool_bar_items (Lisp_Object, int *);
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extern void discard_mouse_events (void);
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73
src/sysdep.c
73
src/sysdep.c
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@ -46,7 +46,6 @@ along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>. */
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# include <sys/user.h>
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# undef frame
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# include <sys/resource.h>
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# include <math.h>
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#endif
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@ -72,6 +71,9 @@ along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>. */
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#include "msdos.h"
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#endif
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#ifdef HAVE_SYS_RESOURCE_H
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#include <sys/resource.h>
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#endif
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#include <sys/param.h>
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#include <sys/file.h>
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#include <fcntl.h>
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xsignal0 (Qarith_error);
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}
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#ifdef HAVE_STACK_OVERFLOW_HANDLING
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/* True if stack grows down as expected on most OS/ABI variants. */
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static bool stack_grows_down;
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/* Alternate stack used by SIGSEGV handler below. */
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static unsigned char sigsegv_stack[SIGSTKSZ];
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/* Attempt to recover from SIGSEGV caused by C stack overflow. */
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static void
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handle_sigsegv (int sig, siginfo_t *siginfo, void *arg)
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{
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/* Hard GC error may lead to stack overflow caused by
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too nested calls to mark_object. No way to survive. */
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if (!gc_in_progress)
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{
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struct rlimit rlim;
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if (!getrlimit (RLIMIT_STACK, &rlim))
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{
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enum { STACK_EXTRA = 16 * 1024 };
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char *fault_addr = (char *) siginfo->si_addr;
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unsigned long used = (stack_grows_down
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? stack_bottom - fault_addr
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: fault_addr - stack_bottom);
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if (used + STACK_EXTRA > rlim.rlim_cur)
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/* Most likely this is it. */
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siglongjmp (return_to_command_loop, 1);
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}
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}
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}
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static bool
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init_sigsegv (void)
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{
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struct sigaction sa;
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stack_t ss;
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stack_grows_down = ((char *) &ss < stack_bottom);
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ss.ss_sp = sigsegv_stack;
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ss.ss_size = sizeof (sigsegv_stack);
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ss.ss_flags = 0;
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if (sigaltstack (&ss, NULL) < 0)
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return 0;
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sigfillset (&sa.sa_mask);
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sa.sa_sigaction = handle_sigsegv;
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sa.sa_flags = SA_SIGINFO | SA_ONSTACK | emacs_sigaction_flags ();
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return sigaction (SIGSEGV, &sa, NULL) < 0 ? 0 : 1;
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}
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#else /* not HAVE_STACK_OVERFLOW_HANDLING */
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static bool
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init_sigsegv (void)
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{
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return 0;
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}
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#endif /* HAVE_STACK_OVERFLOW_HANDLING */
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static void
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deliver_arith_signal (int sig)
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{
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@ -1982,7 +2050,8 @@ init_signals (bool dumping)
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#ifdef SIGBUS
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sigaction (SIGBUS, &thread_fatal_action, 0);
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#endif
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sigaction (SIGSEGV, &thread_fatal_action, 0);
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if (!init_sigsegv ())
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sigaction (SIGSEGV, &thread_fatal_action, 0);
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#ifdef SIGSYS
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sigaction (SIGSYS, &thread_fatal_action, 0);
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#endif
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