Commit ebd31792 authored by Dmitry Antipov's avatar Dmitry Antipov

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.
parent 940ac42a
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.
......
......@@ -3728,6 +3728,22 @@ if test "$emacs_cv_have_timerfd" = yes; then
[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
......@@ -4447,22 +4463,31 @@ AC_CACHE_CHECK([for _setjmp], [emacs_cv_func__setjmp],
[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
......
......@@ -497,7 +497,7 @@ It sets `command-line-processed', processes the command-line,
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
......
......@@ -133,6 +133,19 @@ static ptrdiff_t this_single_command_key_start;
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;
......@@ -1134,6 +1147,17 @@ static Lisp_Object top_level_1 (Lisp_Object);
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;
......@@ -11000,6 +11024,15 @@ syms_of_keyboard (void)
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");
......
......@@ -4093,6 +4093,9 @@ extern Lisp_Object Qdisabled, QCfilter;
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);
......
......@@ -46,7 +46,6 @@ along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>. */
# include <sys/user.h>
# undef frame
# include <sys/resource.h>
# include <math.h>
#endif
......@@ -72,6 +71,9 @@ along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>. */
#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>
......@@ -1716,6 +1718,72 @@ handle_arith_signal (int sig)
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)
{
......@@ -1982,7 +2050,8 @@ init_signals (bool dumping)
#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
......
Markdown is supported
0% or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment