diff options
| -rw-r--r-- | ChangeLog | 7 | ||||
| -rw-r--r-- | configure.ac | 57 | ||||
| -rw-r--r-- | lisp/ChangeLog | 4 | ||||
| -rw-r--r-- | lisp/startup.el | 2 | ||||
| -rw-r--r-- | src/ChangeLog | 19 | ||||
| -rw-r--r-- | src/keyboard.c | 33 | ||||
| -rw-r--r-- | src/lisp.h | 3 | ||||
| -rw-r--r-- | src/sysdep.c | 73 |
8 files changed, 179 insertions, 19 deletions
diff --git a/ChangeLog b/ChangeLog index de9f3a0bef4..67fc0b87bcb 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,10 @@ +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. diff --git a/configure.ac b/configure.ac index 967f0195d0f..d6476d2e1c7 100644 --- a/configure.ac +++ b/configure.ac @@ -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 diff --git a/lisp/ChangeLog b/lisp/ChangeLog index 65a59f4da6d..12d283e7120 100644 --- a/lisp/ChangeLog +++ b/lisp/ChangeLog @@ -1,3 +1,7 @@ +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 diff --git a/lisp/startup.el b/lisp/startup.el index 144d732272f..1d5ae250505 100644 --- a/lisp/startup.el +++ b/lisp/startup.el @@ -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 diff --git a/src/ChangeLog b/src/ChangeLog index 391d2e52100..f618ba02448 100644 --- a/src/ChangeLog +++ b/src/ChangeLog @@ -1,3 +1,22 @@ +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 diff --git a/src/keyboard.c b/src/keyboard.c index 9b0b19ada2f..ed00b38a7db 100644 --- a/src/keyboard.c +++ b/src/keyboard.c @@ -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"); diff --git a/src/lisp.h b/src/lisp.h index 1e2a8b6535f..012e5fad18d 100644 --- a/src/lisp.h +++ b/src/lisp.h @@ -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); diff --git a/src/sysdep.c b/src/sysdep.c index 25bec264f46..f32bd5d1bb6 100644 --- a/src/sysdep.c +++ b/src/sysdep.c @@ -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 |