Fix problems in libbacktrace.

- Add a wait for stop to backtrace_test. There is a possible race
  condition that is exposed when using libunwind.
- Fix a few calls to unwind function calls.

Bug: 8410085
Change-Id: I7487d687f6d4b7b05b8a96ad1c5f7183681e5c95

3 files changed, 42 insertions, 6 deletions

diff --git a/libbacktrace/backtrace_test.c b/libbacktrace/backtrace_test.c
index 34d3519..6155c9b 100644
--- a/libbacktrace/backtrace_test.c
+++ b/libbacktrace/backtrace_test.c
@@ -22,6 +22,7 @@
 #include <signal.h>
 #include <sys/ptrace.h>
 #include <sys/wait.h>
+#include <errno.h>
 #include <unistd.h>
 #include <inttypes.h>
 
@@ -29,6 +30,8 @@
 
 #define FINISH(pid) dump_frames(&backtrace); if (pid < 0) exit(1); else return false;
 
+#define WAIT_INTERVAL_USECS   1000
+
 // Prototypes for functions in the test library.
 int test_level_one(int, int, int, int, bool (*)(pid_t));
 
@@ -52,6 +55,21 @@ void dump_frames(const backtrace_t* backtrace) {
   }
 }
 
+void wait_for_stop(pid_t pid, size_t max_usecs_to_wait) {
+  siginfo_t si;
+  size_t usecs_waited = 0;
+
+  while (ptrace(PTRACE_GETSIGINFO, pid, 0, &si) < 0 && (errno == EINTR || errno == ESRCH)) {
+    if (usecs_waited >= max_usecs_to_wait) {
+      printf("The process did not get to a stopping point in %zu usecs.\n",
+             usecs_waited);
+      break;
+    }
+    usleep(WAIT_INTERVAL_USECS);
+    usecs_waited += WAIT_INTERVAL_USECS;
+  }
+}
+
 bool check_frame(const backtrace_t* backtrace, size_t frame_num,
                  const char* expected_name) {
   if (backtrace->frames[frame_num].proc_name == NULL) {
@@ -153,6 +171,10 @@ void verify_proc_test(pid_t pid, bool (*verify_func)(pid_t)) {
     kill(pid, SIGKILL);
     exit(1);
   }
+
+  // Wait up to 1 second for the process to get to a point that we can trace it.
+  wait_for_stop(pid, 1000000);
+
   bool pass = verify_func(pid);
   if (ptrace(PTRACE_DETACH, pid, 0, 0) != 0) {
     printf("Failed to detach from pid %d\n", pid);
diff --git a/libbacktrace/unwind_local.c b/libbacktrace/unwind_local.c
index e0b72d8..d467d8a 100644
--- a/libbacktrace/unwind_local.c
+++ b/libbacktrace/unwind_local.c
@@ -48,6 +48,7 @@ static bool local_get_frames(backtrace_t* backtrace) {
   bool returnValue = true;
   backtrace->num_frames = 0;
   uintptr_t map_start;
+  unw_word_t value;
   do {
     frame = &backtrace->frames[backtrace->num_frames];
     frame->stack_size = 0;
@@ -56,18 +57,21 @@ static bool local_get_frames(backtrace_t* backtrace) {
     frame->proc_name = NULL;
     frame->proc_offset = 0;
 
-    ret = unw_get_reg(&cursor, UNW_REG_IP, &frame->pc);
+    ret = unw_get_reg(&cursor, UNW_REG_IP, &value);
     if (ret < 0) {
       ALOGW("get_frames: Failed to read IP %d\n", ret);
       returnValue = false;
       break;
     }
-    ret = unw_get_reg(&cursor, UNW_REG_SP, &frame->sp);
+    frame->pc = (uintptr_t)value;
+    ret = unw_get_reg(&cursor, UNW_REG_SP, &value);
     if (ret < 0) {
       ALOGW("get_frames: Failed to read IP %d\n", ret);
       returnValue = false;
       break;
     }
+    frame->sp = (uintptr_t)value;
+
     if (backtrace->num_frames) {
       backtrace_frame_data_t* prev = &backtrace->frames[backtrace->num_frames-1];
       prev->stack_size = frame->sp - prev->sp;
@@ -111,8 +115,11 @@ char* local_get_proc_name(const backtrace_t* backtrace, uintptr_t pc,
   unw_context_t* context = (unw_context_t*)backtrace->private_data;
   char buf[512];
 
+  *offset = 0;
+  unw_word_t value;
   if (unw_get_proc_name_by_ip(unw_local_addr_space, pc, buf, sizeof(buf),
-                              offset, context) >= 0 && buf[0] != '\0') {
+                              &value, context) >= 0 && buf[0] != '\0') {
+    *offset = (uintptr_t)value;
     char* symbol = demangle_symbol_name(buf);
     if (!symbol) {
       symbol = strdup(buf);
diff --git a/libbacktrace/unwind_remote.c b/libbacktrace/unwind_remote.c
index ebbde2e..1c624d7 100644
--- a/libbacktrace/unwind_remote.c
+++ b/libbacktrace/unwind_remote.c
@@ -46,6 +46,7 @@ static bool remote_get_frames(backtrace_t* backtrace) {
   bool returnValue = true;
   backtrace->num_frames = 0;
   uintptr_t map_start;
+  unw_word_t value;
   do {
     frame = &backtrace->frames[backtrace->num_frames];
     frame->stack_size = 0;
@@ -54,18 +55,21 @@ static bool remote_get_frames(backtrace_t* backtrace) {
     frame->proc_name = NULL;
     frame->proc_offset = 0;
 
-    ret = unw_get_reg(&cursor, UNW_REG_IP, &frame->pc);
+    ret = unw_get_reg(&cursor, UNW_REG_IP, &value);
     if (ret < 0) {
       ALOGW("remote_get_frames: Failed to read IP %d\n", ret);
       returnValue = false;
       break;
     }
-    ret = unw_get_reg(&cursor, UNW_REG_SP, &frame->sp);
+    frame->pc = (uintptr_t)value;
+    ret = unw_get_reg(&cursor, UNW_REG_SP, &value);
     if (ret < 0) {
       ALOGW("remote_get_frames: Failed to read SP %d\n", ret);
       returnValue = false;
       break;
     }
+    frame->sp = (uintptr_t)value;
+
     if (backtrace->num_frames) {
       backtrace_frame_data_t* prev = &backtrace->frames[backtrace->num_frames-1];
       prev->stack_size = frame->sp - prev->sp;
@@ -139,8 +143,11 @@ char* remote_get_proc_name(const backtrace_t* backtrace, uintptr_t pc,
   backtrace_private_t* data = (backtrace_private_t*)backtrace->private_data;
   char buf[512];
 
-  if (unw_get_proc_name_by_ip(data->addr_space, pc, buf, sizeof(buf), offset,
+  *offset = 0;
+  unw_word_t value;
+  if (unw_get_proc_name_by_ip(data->addr_space, pc, buf, sizeof(buf), &value,
                               data->upt_info) >= 0 && buf[0] != '\0') {
+    *offset = (uintptr_t)value;
     char* symbol = demangle_symbol_name(buf);
     if (!symbol) {
       symbol = strdup(buf);