binutils-gdb/gdb/event-top.h
Tom Tromey 3b3978bca2 Introduce thread-safe way to handle SIGSEGV
The gdb demangler installs a SIGSEGV handler in order to protect gdb
from demangler bugs.  However, this is not thread-safe, as signal
handlers are global to the process.

This patch changes gdb to always install a global SIGSEGV handler, and
then lets threads indicate their interest in handling the signal by
setting a thread-local variable.

This patch then arranges for the demangler code to use this; being
sure to arrange for calls to warning and the like to be done on the
main thread.

One thing I wondered while writing this patch is if there are any
systems that do not have "sigaction".  If gdb could assume this, it
would simplify this code.

gdb/ChangeLog
2019-11-26  Tom Tromey  <tom@tromey.com>

	* event-top.h (thread_local_segv_handler): Declare.
	* event-top.c (thread_local_segv_handler): New global.
	(install_handle_sigsegv, handle_sigsegv): New functions.
	(async_init_signals): Install SIGSEGV handler.
	* cp-support.c (gdb_demangle_jmp_buf): Change type.  Now
	thread-local.
	(report_failed_demangle): New function.
	(gdb_demangle): Make core_dump_allowed atomic.  Remove signal
	handler-setting code, instead use segv_handler.  Run warning code
	on main thread.

Change-Id: Ic832bbb033b64744e4b44f14b41db7e4168ce427
2019-11-26 14:02:57 -07:00

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2.8 KiB
C

/* Definitions used by event-top.c, for GDB, the GNU debugger.
Copyright (C) 1999-2019 Free Software Foundation, Inc.
Written by Elena Zannoni <ezannoni@cygnus.com> of Cygnus Solutions.
This file is part of GDB.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
#ifndef EVENT_TOP_H
#define EVENT_TOP_H
#include <signal.h>
struct cmd_list_element;
/* Exported functions from event-top.c.
FIXME: these should really go into top.h. */
extern void display_gdb_prompt (const char *new_prompt);
extern void gdb_setup_readline (int);
extern void gdb_disable_readline (void);
extern void async_init_signals (void);
extern void change_line_handler (int);
extern void command_line_handler (gdb::unique_xmalloc_ptr<char> &&rl);
extern void command_handler (const char *command);
#ifdef SIGTSTP
extern void handle_sigtstp (int sig);
#endif
extern void handle_sigint (int sig);
extern void handle_sigterm (int sig);
extern void async_request_quit (void *arg);
extern void stdin_event_handler (int error, void *client_data);
extern void async_disable_stdin (void);
extern void async_enable_stdin (void);
/* Exported variables from event-top.c.
FIXME: these should really go into top.h. */
extern bool set_editing_cmd_var;
extern bool exec_done_display_p;
extern struct prompts the_prompts;
extern void (*after_char_processing_hook) (void);
extern int call_stdin_event_handler_again_p;
extern void gdb_readline_no_editing_callback (void *client_data);
/* Wrappers for rl_callback_handler_remove and
rl_callback_handler_install that keep track of whether the callback
handler is installed in readline. Do not call the readline
versions directly. */
extern void gdb_rl_callback_handler_remove (void);
extern void gdb_rl_callback_handler_install (const char *prompt);
/* Reinstall the readline callback handler (with no prompt), if not
currently installed. */
extern void gdb_rl_callback_handler_reinstall (void);
/* The SIGSEGV handler for this thread, or NULL if there is none. GDB
always installs a global SIGSEGV handler, and then lets threads
indicate their interest in handling the signal by setting this
thread-local variable. */
extern thread_local void (*thread_local_segv_handler) (int);
#endif