Merge pull request #3189 from opensourcerouting/libunwind

lib: add libunwind support for backtraces

Makefile.am

@@ -4,6 +4,7 @@ AUTOMAKE_OPTIONS = subdir-objects 1.12
 ACLOCAL_AMFLAGS = -I m4
 
 AM_CFLAGS = \
+	$(UNWIND_CFLAGS) \
 	$(SAN_FLAGS) \
 	$(WERROR) \
 	# end

configure.ac

@@ -958,10 +958,6 @@ case "$host_os" in
     AC_CHECK_LIB(socket, main)
     AC_CHECK_LIB(nsl, main)
     AC_CHECK_LIB(umem, main)
-    AC_CHECK_FUNCS([printstack], [
-      AC_DEFINE([HAVE_PRINTSTACK],1,[Solaris printstack])
-      AC_DEFINE([HAVE_STACK_TRACE],1,[Stack symbols decode functionality])
-    ])
     CURSES=-lcurses
     SOLARIS="solaris"
     ;;
@@ -1811,17 +1807,31 @@ dnl check for glibc 'backtrace'
 dnl --------------------------- 
 if test x"${enable_backtrace}" != x"no" ; then
   backtrace_ok=no
+  PKG_CHECK_MODULES([UNWIND], [libunwind], [
+    AC_DEFINE(HAVE_LIBUNWIND, 1, [libunwind])
+    backtrace_ok=yes
+  ], [
+    case "$host_os" in
+    sunos* | solaris2*)
+      AC_CHECK_FUNCS([printstack], [
+        AC_DEFINE([HAVE_PRINTSTACK], 1, [Solaris printstack])
+        backtrace_ok=yes
+      ])
+      ;;
+    esac
+    if test "$backtrace_ok" = no; then
       AC_CHECK_HEADER([execinfo.h], [
         AC_SEARCH_LIBS([backtrace], [execinfo], [
-      AC_DEFINE(HAVE_GLIBC_BACKTRACE,,[Glibc backtrace])
-      AC_DEFINE(HAVE_STACK_TRACE,,[Stack symbol decoding])
+          AC_DEFINE(HAVE_GLIBC_BACKTRACE, 1, [Glibc backtrace])
           backtrace_ok=yes
         ],, [-lm])
       ])
+    fi
+  ])
 
   if test x"${enable_backtrace}" = x"yes" -a x"${backtrace_ok}" = x"no"; then
     dnl user explicitly requested backtrace but we failed to find support
-    AC_MSG_FAILURE([failed to find backtrace support])
+    AC_MSG_FAILURE([failed to find backtrace or libunwind support])
   fi
 fi
 

lib/log.c

@@ -38,6 +38,12 @@
 #include <ucontext.h>
 #endif
 
+#ifdef HAVE_LIBUNWIND
+#define UNW_LOCAL_ONLY
+#include <libunwind.h>
+#include <dlfcn.h>
+#endif
+
 DEFINE_MTYPE_STATIC(LIB, ZLOG, "Logging")
 
 static int logfile_fd = -1; /* Used in signal handler. */
@@ -313,7 +319,9 @@ static char *num_append(char *s, int len, unsigned long x)
 	return str_append(s, len, t);
 }
 
-#if defined(SA_SIGINFO) || defined(HAVE_STACK_TRACE)
+#if defined(SA_SIGINFO) \
+	|| defined(HAVE_PRINTSTACK) \
+	|| defined(HAVE_GLIBC_BACKTRACE)
 static char *hex_append(char *s, int len, unsigned long x)
 {
 	char buf[30];
@@ -533,7 +541,37 @@ void zlog_signal(int signo, const char *action
    Needs to be enhanced to support syslog logging. */
 void zlog_backtrace_sigsafe(int priority, void *program_counter)
 {
-#ifdef HAVE_STACK_TRACE
+#ifdef HAVE_LIBUNWIND
+	char buf[100];
+	unw_cursor_t cursor;
+	unw_context_t uc;
+	unw_word_t ip, off, sp;
+	Dl_info dlinfo;
+
+	unw_getcontext(&uc);
+	unw_init_local(&cursor, &uc);
+	while (unw_step(&cursor) > 0) {
+		char name[128] = "?";
+
+		unw_get_reg(&cursor, UNW_REG_IP, &ip);
+		unw_get_reg(&cursor, UNW_REG_SP, &sp);
+
+		if (unw_is_signal_frame(&cursor))
+			dprintf(2, "    ---- signal ----\n");
+
+		if (!unw_get_proc_name(&cursor, buf, sizeof(buf), &off)) {
+			snprintf(name, sizeof(name), "%s+%#lx",
+				buf, (long)off);
+		}
+		dprintf(2, "%-30s %16lx %16lx", name, (long)ip, (long)sp);
+		if (dladdr((void *)ip, &dlinfo)) {
+			dprintf(2, " %s (mapped at %p)",
+				dlinfo.dli_fname, dlinfo.dli_fbase);
+		}
+		dprintf(2, "\n");
+
+	}
+#elif defined(HAVE_GLIBC_BACKTRACE) || defined(HAVE_PRINTSTACK)
 	static const char pclabel[] = "Program counter: ";
 	void *array[64];
 	int size;
@@ -624,9 +662,38 @@ void zlog_backtrace_sigsafe(int priority, void *program_counter)
 
 void zlog_backtrace(int priority)
 {
-#ifndef HAVE_GLIBC_BACKTRACE
-	zlog(priority, "No backtrace available on this platform.");
-#else
+#ifdef HAVE_LIBUNWIND
+	char buf[100];
+	unw_cursor_t cursor;
+	unw_context_t uc;
+	unw_word_t ip, off, sp;
+	Dl_info dlinfo;
+
+	unw_getcontext(&uc);
+	unw_init_local(&cursor, &uc);
+	zlog(priority, "Backtrace:");
+	while (unw_step(&cursor) > 0) {
+		char name[128] = "?";
+
+		unw_get_reg(&cursor, UNW_REG_IP, &ip);
+		unw_get_reg(&cursor, UNW_REG_SP, &sp);
+
+		if (unw_is_signal_frame(&cursor))
+			zlog(priority, "    ---- signal ----");
+
+		if (!unw_get_proc_name(&cursor, buf, sizeof(buf), &off))
+			snprintf(name, sizeof(name), "%s+%#lx",
+				buf, (long)off);
+
+		if (dladdr((void *)ip, &dlinfo))
+			zlog(priority, "%-30s %16lx %16lx %s (mapped at %p)",
+				name, (long)ip, (long)sp,
+				dlinfo.dli_fname, dlinfo.dli_fbase);
+		else
+			zlog(priority, "%-30s %16lx %16lx",
+				name, (long)ip, (long)sp);
+	}
+#elif defined(HAVE_GLIBC_BACKTRACE)
 	void *array[20];
 	int size, i;
 	char **strings;
@@ -651,7 +718,9 @@ void zlog_backtrace(int priority)
 			zlog(priority, "[bt %d] %s", i, strings[i]);
 		free(strings);
 	}
-#endif /* HAVE_GLIBC_BACKTRACE */
+#else /* !HAVE_GLIBC_BACKTRACE && !HAVE_LIBUNWIND */
+	zlog(priority, "No backtrace available on this platform.");
+#endif
 }
 
 void zlog(int priority, const char *format, ...)

lib/subdir.am

@@ -3,7 +3,7 @@
 #
 lib_LTLIBRARIES += lib/libfrr.la
 lib_libfrr_la_LDFLAGS = -version-info 0:0:0 -Xlinker -e_libfrr_version
-lib_libfrr_la_LIBADD = @LIBCAP@
+lib_libfrr_la_LIBADD = @LIBCAP@ $(UNWIND_LIBS)
 
 lib_libfrr_la_SOURCES = \
 	lib/agg_table.c \

tests/lib/test_segv.c

@@ -32,10 +32,39 @@ struct quagga_signal_t sigs[] = {};
 
 struct thread_master *master;
 
-static int threadfunc(struct thread *thread)
+void func1(int *arg);
+void func3(void);
+
+void func1(int *arg)
 {
 	int *null = NULL;
 	*null += 1;
+	*arg = 1;
+}
+
+static void func2(size_t depth, int *arg)
+{
+	/* variable stack frame size */
+	int buf[depth];
+	for (size_t i = 0; i < depth; i++)
+		buf[i] = arg[i] + 1;
+	if (depth > 0)
+		func2(depth - 1, buf);
+	else
+		func1(&buf[0]);
+	for (size_t i = 0; i < depth; i++)
+		buf[i] = arg[i] + 2;
+}
+
+void func3(void)
+{
+	int buf[6];
+	func2(6, buf);
+}
+
+static int threadfunc(struct thread *thread)
+{
+	func3();
 	return 0;
 }