[pacman-dev] [PATCH 2/2] create coredump on segfault

[Andrew Gregory]

Overriding the segfault handler prevents the creation of core dumps by
the default handler, which makes debugging segfaults difficult.

Signed-off-by: Andrew Gregory 
---
 src/pacman/sighandler.c | 28 ++--
 1 file changed, 22 insertions(+), 6 deletions(-)

diff --git a/src/pacman/sighandler.c b/src/pacman/sighandler.c
index a4849a0c..082756b5 100644
--- a/src/pacman/sighandler.c
+++ b/src/pacman/sighandler.c
@@ -38,6 +38,15 @@ static ssize_t xwrite(int fd, const void *buf, size_t count)
return ret;
 }
 
+static void _reset_handler(int signum)
+{
+   struct sigaction new_action;
+   sigemptyset(&new_action.sa_mask);
+   new_action.sa_handler = SIG_DFL;
+   new_action.sa_flags = 0;
+   sigaction(signum, &new_action, NULL);
+}
+
 /** Catches thrown signals. Performs necessary cleanup to ensure database is
  * in a consistent state.
  * @param signum the thrown signal
@@ -76,19 +85,26 @@ void install_soft_interrupt_handler(void)
 
 void remove_soft_interrupt_handler(void)
 {
-   struct sigaction new_action;
-   sigemptyset(&new_action.sa_mask);
-   new_action.sa_handler = SIG_DFL;
-   new_action.sa_flags = 0;
-   sigaction(SIGINT, &new_action, NULL);
-   sigaction(SIGHUP, &new_action, NULL);
+   _reset_handler(SIGINT);
+   _reset_handler(SIGHUP);
 }
 
 static void segv_handler(int signum)
 {
+   sigset_t segvset;
const char msg[] = "\nerror: segmentation fault\n"
"Please submit a full bug report with --debug if 
appropriate.\n";
xwrite(STDERR_FILENO, msg, sizeof(msg) - 1);
+
+   /* restore the default handler */
+   _reset_handler(signum);
+   /* unblock SIGSEGV */
+   sigaddset(&segvset, signum);
+   sigprocmask(SIG_UNBLOCK, &segvset, NULL);
+   /* re-raise to trigger a core dump */
+   raise(signum);
+
+   /* raise should immediately abort, but just to make absolutely sure */
_Exit(signum);
 }
 
-- 
2.21.0

[pacman-dev] [PATCH 1/2] sighandler: block signals while handling SIGSEGV

[Andrew Gregory]

If we get SIGSEGV we need to bail out quickly, leaving other signals
unblocked could lead to other signal handlers getting triggered.

Signed-off-by: Andrew Gregory 
---

Signals are hard.  I'd appreciate if somebody could double check my
math on these patches.

 src/pacman/sighandler.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/pacman/sighandler.c b/src/pacman/sighandler.c
index ebcdebae..a4849a0c 100644
--- a/src/pacman/sighandler.c
+++ b/src/pacman/sighandler.c
@@ -96,7 +96,7 @@ void install_segv_handler(void)
 {
struct sigaction new_action;
new_action.sa_handler = segv_handler;
-   sigemptyset(&new_action.sa_mask);
+   sigfillset(&new_action.sa_mask);
new_action.sa_flags = SA_RESTART;
sigaction(SIGSEGV, &new_action, NULL);
 }
-- 
2.21.0