From 83714577a9c99c9971ce2d3968ab773b37f4ea5b Mon Sep 17 00:00:00 2001
From: Martin Willi <martin@revosec.ch>
Date: Fri, 5 Apr 2013 16:26:27 +0200
Subject: [PATCH] backtrace: add an alternative stack unwinding implementation
 using libunwind

---
 configure.in                        |  9 +++++++
 src/libstrongswan/Makefile.am       |  2 +-
 src/libstrongswan/utils/backtrace.c | 39 +++++++++++++++++++++++++----
 3 files changed, 44 insertions(+), 6 deletions(-)

diff --git a/configure.in b/configure.in
index f0a2ec961..311b15c6b 100644
--- a/configure.in
+++ b/configure.in
@@ -238,6 +238,7 @@ ARG_ENABL_SET([radattr],        [enable plugin to inject and process custom RADI
 ARG_ENABL_SET([vstr],           [enforce using the Vstr string library to replace glibc-like printf hooks.])
 ARG_ENABL_SET([monolithic],     [build monolithic version of libstrongswan that includes all enabled plugins. Similarly, the plugins of charon are assembled in libcharon.])
 ARG_ENABL_SET([bfd-backtraces], [use binutils libbfd to resolve backtraces for memory leaks and segfaults.])
+ARG_ENABL_SET([unwind-backtraces],[use libunwind to create backtraces for memory leaks and segfaults.])
 ARG_ENABL_SET([unit-tests],     [enable unit tests using the check test framework.])
 ARG_ENABL_SET([tkm],            [enable Trusted Key Manager support.])
 
@@ -886,6 +887,14 @@ if test x$bfd_backtraces = xtrue; then
 	AC_SUBST(BFDLIB)
 fi
 
+if test x$unwind_backtraces = xtrue; then
+	AC_CHECK_LIB([unwind],[main],[LIBS="$LIBS"],[AC_MSG_ERROR([libunwind not found!])],[])
+	AC_CHECK_HEADER([libunwind.h],[AC_DEFINE([HAVE_LIBUNWIND_H],,[have libunwind.h])],
+		[AC_MSG_ERROR([libunwind.h header not found!])])
+	UNWINDLIB="-lunwind"
+	AC_SUBST(UNWINDLIB)
+fi
+
 AM_CONDITIONAL(USE_DEV_HEADERS, [test "x$dev_headers" != xno])
 if test x$dev_headers = xyes; then
 	dev_headers="$includedir/strongswan"
diff --git a/src/libstrongswan/Makefile.am b/src/libstrongswan/Makefile.am
index 81e271a8a..ce6df2855 100644
--- a/src/libstrongswan/Makefile.am
+++ b/src/libstrongswan/Makefile.am
@@ -79,7 +79,7 @@ endif
 
 library.lo :	$(top_builddir)/config.status
 
-libstrongswan_la_LIBADD = $(PTHREADLIB) $(DLLIB) $(BTLIB) $(SOCKLIB) $(RTLIB) $(BFDLIB)
+libstrongswan_la_LIBADD = $(PTHREADLIB) $(DLLIB) $(BTLIB) $(SOCKLIB) $(RTLIB) $(BFDLIB) $(UNWINDLIB)
 
 INCLUDES = -I$(top_srcdir)/src/libstrongswan
 AM_CFLAGS = \
diff --git a/src/libstrongswan/utils/backtrace.c b/src/libstrongswan/utils/backtrace.c
index 77137f9f1..dd2be7a0a 100644
--- a/src/libstrongswan/utils/backtrace.c
+++ b/src/libstrongswan/utils/backtrace.c
@@ -373,7 +373,7 @@ void backtrace_deinit() {}
 METHOD(backtrace_t, log_, void,
 	private_backtrace_t *this, FILE *file, bool detailed)
 {
-#ifdef HAVE_BACKTRACE
+#if defined(HAVE_BACKTRACE) || defined(HAVE_LIBUNWIND_H)
 	size_t i;
 	char **strings;
 
@@ -420,9 +420,9 @@ METHOD(backtrace_t, log_, void,
 		}
 	}
 	free (strings);
-#else /* !HAVE_BACKTRACE */
-	println(file, "C library does not support backtrace().");
-#endif /* HAVE_BACKTRACE */
+#else /* !HAVE_BACKTRACE && !HAVE_LIBUNWIND_H */
+	println(file, "no support for backtrace()/libunwind");
+#endif /* HAVE_BACKTRACE/HAVE_LIBUNWIND_H */
 }
 
 METHOD(backtrace_t, contains_function, bool,
@@ -518,6 +518,33 @@ METHOD(backtrace_t, destroy, void,
 	free(this);
 }
 
+#ifdef HAVE_LIBUNWIND_H
+#define UNW_LOCAL_ONLY
+#include <libunwind.h>
+
+/**
+ * libunwind variant for glibc backtrace()
+ */
+static inline int backtrace_unwind(void **frames, int count)
+{
+	unw_context_t context;
+	unw_cursor_t cursor;
+	unw_word_t ip;
+	int depth = 0;
+
+	unw_getcontext(&context);
+	unw_init_local(&cursor, &context);
+	do
+	{
+		unw_get_reg(&cursor, UNW_REG_IP, &ip);
+		frames[depth++] = (void*)ip;
+	}
+	while (depth < count && unw_step(&cursor) > 0);
+
+	return depth;
+}
+#endif /* HAVE_UNWIND */
+
 /**
  * See header
  */
@@ -527,7 +554,9 @@ backtrace_t *backtrace_create(int skip)
 	void *frames[50];
 	int frame_count = 0;
 
-#ifdef HAVE_BACKTRACE
+#ifdef HAVE_LIBUNWIND_H
+	frame_count = backtrace_unwind(frames, countof(frames));
+#elif defined(HAVE_BACKTRACE)
 	frame_count = backtrace(frames, countof(frames));
 #endif /* HAVE_BACKTRACE */
 	frame_count = max(frame_count - skip, 0);