Enable stack tracing with libdw for non-native personality traceesesyr/enable-libdw-mpers

libdw can handle compat processes, so it makes little sense to have
stack tracing disabled when it is used.

* syscall.c [!defined(USE_LIBUNWIND) && ENABLE_STACKTRACE]
(update_personality): Re-initialise unwinder on personality change.
* unwind.c [!defined(USE_LIBUNWIND) && (SUPPORTED_PERSONALITIES > 1)]
(unwind_tcb_print, unwind_tcb_capture): Do not return early.
* tests/Makefile.am (STACKTRACE_XFAIL_TESTS): New variable, initialise
it to $(STACKTRACE_TESTS) if ENABLE_STACKTRACE and USE_LIBUNWIND
are true, otherwise make it empty.
(XFAIL_TESTS_m32, XFAIL_TESTS_mx32): Initialise
it to $(STACKTRACE_XFAIL_TESTS) and not $(STACKTRACE_TESTS).
* NEWS: Mention the change.

Closes: https://github.com/strace/strace/issues/162

4 files changed, 19 insertions, 4 deletions

diff --git a/NEWS b/NEWS
index 70c3e0ae2..3462521b5 100644
--- a/NEWS
+++ b/NEWS
@@ -2,6 +2,8 @@ Noteworthy changes in release ?.? (????-??-??)
 ==============================================
 
 * Improvements
+  * libdw-based stack tracing is now enabled for non-native
+    personalities.
 
 * Bug fixes
 
diff --git a/syscall.c b/syscall.c
index d228ae4d5..9691de5b5 100644
--- a/syscall.c
+++ b/syscall.c
@@ -281,6 +281,13 @@ update_personality(struct tcb *tcp, unsigned int personality)
 			  "building strace with mpers support enabled.");
 		need_mpers_warning[personality] = false;
 	}
+
+#if defined(ENABLE_STACKTRACE) && !defined(USE_LIBUNWIND)
+	if (stack_trace_enabled) {
+		unwind_tcb_fin(tcp);
+		unwind_tcb_init(tcp);
+	}
+#endif
 }
 #endif
 
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 17f4b4245..b9a58f552 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -320,8 +320,14 @@ STACKTRACE_TESTS = strace-k.test strace-k-p.test
 if USE_DEMANGLE
 STACKTRACE_TESTS += strace-k-demangle.test
 endif
+if USE_LIBUNWIND
+STACKTRACE_XFAIL_TESTS = $(STACKTRACE_TESTS)
+else
+STACKTRACE_XFAIL_TESTS =
+endif
 else
 STACKTRACE_TESTS =
+STACKTRACE_XFAIL_TESTS =
 endif
 
 DECODER_TESTS = \
@@ -483,8 +489,8 @@ MISC_TESTS = \
 TESTS = $(GEN_TESTS) $(DECODER_TESTS) $(MISC_TESTS) $(STACKTRACE_TESTS)
 
 XFAIL_TESTS_ =
-XFAIL_TESTS_m32 = $(STACKTRACE_TESTS)
-XFAIL_TESTS_mx32 = $(STACKTRACE_TESTS)
+XFAIL_TESTS_m32 = $(STACKTRACE_XFAIL_TESTS)
+XFAIL_TESTS_mx32 = $(STACKTRACE_XFAIL_TESTS)
 XFAIL_TESTS = $(XFAIL_TESTS_$(MPERS_NAME)) $(XFAIL_TESTS_$(ARCH))
 
 TEST_LOG_COMPILER = env
diff --git a/unwind.c b/unwind.c
index 42e6a7fa4..7e7c12881 100644
--- a/unwind.c
+++ b/unwind.c
@@ -264,7 +264,7 @@ queue_print(struct unwind_queue_t *queue)
 void
 unwind_tcb_print(struct tcb *tcp)
 {
-#if SUPPORTED_PERSONALITIES > 1
+#if defined(USE_LIBUNWIND) && (SUPPORTED_PERSONALITIES > 1)
 	if (tcp->currpers != DEFAULT_PERSONALITY) {
 		/* disable stack trace */
 		return;
@@ -284,7 +284,7 @@ unwind_tcb_print(struct tcb *tcp)
 void
 unwind_tcb_capture(struct tcb *tcp)
 {
-#if SUPPORTED_PERSONALITIES > 1
+#if defined(USE_LIBUNWIND) && (SUPPORTED_PERSONALITIES > 1)
 	if (tcp->currpers != DEFAULT_PERSONALITY) {
 		/* disable stack trace */
 		return;