[pushed] Introduce alternate_signal_stack RAII class
Commit Message
Sourceware to Gerrit sync has submitted this change.
Change URL: https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/169
......................................................................
Introduce alternate_signal_stack RAII class
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
---
M gdb/ChangeLog
A gdb/gdbsupport/alt-stack.h
M gdb/main.c
3 files changed, 78 insertions(+), 24 deletions(-)
@@ -1,5 +1,11 @@
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):
Remove comment.
(save_original_signals_state, restore_original_signals_state): Use
new file mode 100644
@@ -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 */
@@ -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 @@
*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 @@
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);