The patch catches the SIGSEGV signal and prints the backtrace
using libunwind, hopefully makes it easier to debug.
Signed-off-by: William Tu <u9012...@gmail.com>
---
.travis.yml | 1 +
configure.ac | 1 +
lib/fatal-signal.c | 40 +++++++++++++++++++++++++++++++++++++++-
m4/openvswitch.m4 | 10 ++++++++++
4 files changed, 51 insertions(+), 1 deletion(-)
diff --git a/.travis.yml b/.travis.yml
index 370b3d0a6c98..f5d62387c89b 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -25,6 +25,7 @@ addons:
- selinux-policy-dev
- libunbound-dev
- libunbound-dev:i386
+ - libunwind-dev
before_install: ./.travis/${TRAVIS_OS_NAME}-prepare.sh
diff --git a/configure.ac b/configure.ac
index 1d45c4fdd153..15922418062b 100644
--- a/configure.ac
+++ b/configure.ac
@@ -139,6 +139,7 @@ OVS_LIBTOOL_VERSIONS
OVS_CHECK_CXX
AX_FUNC_POSIX_MEMALIGN
OVS_CHECK_UNBOUND
+OVS_CHECK_UNWIND
OVS_CHECK_INCLUDE_NEXT([stdio.h string.h])
AC_CONFIG_FILES([
diff --git a/lib/fatal-signal.c b/lib/fatal-signal.c
index 3b905b6de766..a7325c1ba37e 100644
--- a/lib/fatal-signal.c
+++ b/lib/fatal-signal.c
@@ -34,6 +34,11 @@
#include "openvswitch/type-props.h"
+#ifdef HAVE_UNWIND
+#define UNW_LOCAL_ONLY
+#include <libunwind.h>
+#endif
+
#ifndef SIG_ATOMIC_MAX
#define SIG_ATOMIC_MAX TYPE_MAXIMUM(sig_atomic_t)
#endif
@@ -42,7 +47,8 @@ VLOG_DEFINE_THIS_MODULE(fatal_signal);
/* Signals to catch. */
#ifndef _WIN32
-static const int fatal_signals[] = { SIGTERM, SIGINT, SIGHUP, SIGALRM };
+static const int fatal_signals[] = { SIGTERM, SIGINT, SIGHUP, SIGALRM,
+ SIGSEGV };
#else
static const int fatal_signals[] = { SIGTERM };
#endif
@@ -151,6 +157,32 @@ fatal_signal_add_hook(void (*hook_cb)(void *aux), void
(*cancel_cb)(void *aux),
ovs_mutex_unlock(&mutex);
}
+#ifdef HAVE_UNWIND
+static void
+show_backtrace(void) {
+ char buf[4096];
+ unw_cursor_t cursor;
+ unw_context_t uc;
+ unw_word_t ip, sp;
+ unw_word_t offset;
+
+ unw_getcontext(&uc);
+ unw_init_local(&cursor, &uc);
+
+ while (unw_step(&cursor) > 0) {
+ unw_get_reg(&cursor, UNW_REG_IP, &ip);
+ unw_get_reg(&cursor, UNW_REG_SP, &sp);
+ unw_get_proc_name(&cursor, buf, 4095, &offset);
+ VLOG_WARN("0x%016lx <%s+0x%lx>\n", ip, buf, offset);
+ }
+}
+#else
+static void
+show_backtrace(void) {
+ /* Nothing. */
+}
+#endif
+
/* Handles fatal signal number 'sig_nr'.
*
* Ordinarily this is the actual signal handler. When other code needs to
@@ -164,6 +196,12 @@ void
fatal_signal_handler(int sig_nr)
{
#ifndef _WIN32
+ if (sig_nr == SIGSEGV) {
+ show_backtrace();
+ fflush(stderr);
+ signal(sig_nr, SIG_DFL);
+ raise(sig_nr);
+ }
ignore(write(signal_fds[1], "", 1));
#else
SetEvent(wevent);
diff --git a/m4/openvswitch.m4 b/m4/openvswitch.m4
index cd6b51d86c16..f8bb069e80c9 100644
--- a/m4/openvswitch.m4
+++ b/m4/openvswitch.m4
@@ -705,3 +705,13 @@ AC_DEFUN([OVS_CHECK_UNBOUND],
fi
AM_CONDITIONAL([HAVE_UNBOUND], [test "$HAVE_UNBOUND" = yes])
AC_SUBST([HAVE_UNBOUND])])
+
+dnl Checks for libunwind.
+AC_DEFUN([OVS_CHECK_UNWIND],
+ [AC_CHECK_LIB(unwind, unw_backtrace, [HAVE_UNWIND=yes], [HAVE_UNWIND=no])
+ if test "$HAVE_UNWIND" = yes; then
+ AC_DEFINE([HAVE_UNWIND], [1], [Define to 1 if unwind is detected.])
+ LIBS="$LIBS -lunwind"
+ fi
+ AM_CONDITIONAL([HAVE_UNWIND], [test "$HAVE_UNWIND" = yes])
+ AC_SUBST([HAVE_UNWIND])])
--
2.7.4
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