FreeChainXenon/binutils-gdb
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

Introduce alternate_signal_stack RAII class

Browse source 
This introduces a new RAII class that temporarily installs an
alternate signal stack (on systems that have sigaltstack); then
changes the one gdb use of sigaltstack to use this class instead.

This will be used in a later patch, when creating new threads that may
want to handle SIGSEGV.

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

	* main.c (setup_alternate_signal_stack): Remove.
	(captured_main_1): Use gdb::alternate_signal_stack.
	* gdbsupport/alt-stack.h: New file.

Change-Id: I721c047ae9d51a35fd274a6dbc00a58c6440dae6
This commit is contained in:
Tom Tromey 2019-09-29 09:27:11 -06:00
parent 21987b9c06
commit c3efb96548
3 changed files with 78 additions and 24 deletions
Download patch file Download diff file Expand all files Collapse all files

6
gdb/ChangeLog
View file

@ -1,3 +1,9 @@
2019-11-26 Tom Tromey <tom@tromey.com>
* main.c (setup_alternate_signal_stack): Remove.
(captured_main_1): Use gdb::alternate_signal_stack.
* gdbsupport/alt-stack.h: New file.
2019-11-26 Tom Tromey <tom@tromey.com>
* gdbsupport/signals-state-save-restore.c (original_signal_mask):

70
gdb/gdbsupport/alt-stack.h Normal file
View file

@ -0,0 +1,70 @@
/* Temporarily install an alternate signal stack
Copyright (C) 2019 Free Software Foundation, Inc.
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 GDBSUPPORT_ALT_STACK_H
#define GDBSUPPORT_ALT_STACK_H
#include <signal.h>
namespace gdb
{
/* Try to set up an alternate signal stack for SIGSEGV handlers.
This allows us to handle SIGSEGV signals generated when the
normal process stack is exhausted. If this stack is not set
up (sigaltstack is unavailable or fails) and a SIGSEGV is
generated when the normal stack is exhausted then the program
will behave as though no SIGSEGV handler was installed. */
class alternate_signal_stack
{
public:
alternate_signal_stack ()
{
#ifdef HAVE_SIGALTSTACK
m_stack.reset ((char *) xmalloc (SIGSTKSZ));
stack_t stack;
stack.ss_sp = m_stack.get ();
stack.ss_size = SIGSTKSZ;
stack.ss_flags = 0;
sigaltstack (&stack, &m_old_stack);
#endif
}
~alternate_signal_stack ()
{
#ifdef HAVE_SIGALTSTACK
sigaltstack (&m_old_stack, nullptr);
#endif
}
DISABLE_COPY_AND_ASSIGN (alternate_signal_stack);
private:
#ifdef HAVE_SIGALTSTACK
gdb::unique_xmalloc_ptr<char> m_stack;
stack_t m_old_stack;
#endif
};
}
#endif /* GDBSUPPORT_ALT_STACK_H */

26
gdb/main.c
View file

@ -52,6 +52,7 @@
#ifdef GDBTK
#include "gdbtk/generic/gdbtk.h"
#endif
#include "gdbsupport/alt-stack.h"
/* The selected interpreter. This will be used as a set command
variable, so it should always be malloc'ed - since
@ -334,29 +335,6 @@ get_init_files (std::vector<std::string> *system_gdbinit,
*local_gdbinit = localinit;
}
/* Try to set up an alternate signal stack for SIGSEGV handlers.
This allows us to handle SIGSEGV signals generated when the
normal process stack is exhausted. If this stack is not set
up (sigaltstack is unavailable or fails) and a SIGSEGV is
generated when the normal stack is exhausted then the program
will behave as though no SIGSEGV handler was installed. */
static void
setup_alternate_signal_stack (void)
{
#ifdef HAVE_SIGALTSTACK
stack_t ss;
/* FreeBSD versions older than 11.0 use char * for ss_sp instead of
void *. This cast works with both types. */
ss.ss_sp = (char *) xmalloc (SIGSTKSZ);
ss.ss_size = SIGSTKSZ;
ss.ss_flags = 0;
sigaltstack(&ss, NULL);
#endif
}
/* Call command_loop. */
/* Prevent inlining this function for the benefit of GDB's selftests
@ -898,7 +876,7 @@ captured_main_1 (struct captured_main_args *context)
save_original_signals_state (quiet);
/* Try to set up an alternate signal stack for SIGSEGV handlers. */
setup_alternate_signal_stack ();
gdb::alternate_signal_stack signal_stack;
/* Initialize all files. */
gdb_init (gdb_program_name);