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author | Tom Tromey <tom@tromey.com> | 2019-03-04 15:12:04 -0700 |
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committer | Tom Tromey <tom@tromey.com> | 2019-11-26 14:02:57 -0700 |
commit | 3b3978bca2a204a772563c8e121e4a02be72e802 (patch) | |
tree | 70076c2fc0433920de0b7a71ae12b34311a5fdfa /gdb/event-top.c | |
parent | 9411c49ecc09df989ecddb05e1756e0a9da0d1c8 (diff) | |
download | fsf-binutils-gdb-3b3978bca2a204a772563c8e121e4a02be72e802.zip fsf-binutils-gdb-3b3978bca2a204a772563c8e121e4a02be72e802.tar.gz fsf-binutils-gdb-3b3978bca2a204a772563c8e121e4a02be72e802.tar.bz2 |
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
Diffstat (limited to 'gdb/event-top.c')
-rw-r--r-- | gdb/event-top.c | 41 |
1 files changed, 41 insertions, 0 deletions
diff --git a/gdb/event-top.c b/gdb/event-top.c index 6c6e0ff..9ec599e 100644 --- a/gdb/event-top.c +++ b/gdb/event-top.c @@ -848,6 +848,45 @@ gdb_readline_no_editing_callback (gdb_client_data client_data) } +/* See event-top.h. */ + +thread_local void (*thread_local_segv_handler) (int); + +static void handle_sigsegv (int sig); + +/* Install the SIGSEGV handler. */ +static void +install_handle_sigsegv () +{ +#if defined (HAVE_SIGACTION) + struct sigaction sa; + sa.sa_handler = handle_sigsegv; + sigemptyset (&sa.sa_mask); +#ifdef HAVE_SIGALTSTACK + sa.sa_flags = SA_ONSTACK; +#else + sa.sa_flags = 0; +#endif + sigaction (SIGSEGV, &sa, nullptr); +#else + signal (SIGSEGV, handle_sigsegv); +#endif +} + +/* Handler for SIGSEGV. */ + +static void +handle_sigsegv (int sig) +{ + install_handle_sigsegv (); + + if (thread_local_segv_handler == nullptr) + abort (); + thread_local_segv_handler (sig); +} + + + /* The serial event associated with the QUIT flag. set_quit_flag sets this, and check_quit_flag clears it. Used by interruptible_select to be able to do interruptible I/O with no race with the SIGINT @@ -915,6 +954,8 @@ async_init_signals (void) sigtstp_token = create_async_signal_handler (async_sigtstp_handler, NULL); #endif + + install_handle_sigsegv (); } /* See defs.h. */ |