Merge "Allow calling GetFunctionName before unwinding."

libbacktrace/BacktraceCurrent.h

@@ -36,7 +36,7 @@
 class BacktraceMap;
 
 class BacktraceCurrent : public Backtrace {
-public:
+ public:
   BacktraceCurrent(pid_t pid, pid_t tid, BacktraceMap* map) : Backtrace(pid, tid, map) {}
   virtual ~BacktraceCurrent() {}
 
@@ -46,10 +46,10 @@ public:
 
   bool Unwind(size_t num_ignore_frames, ucontext_t* ucontext) override;
 
-protected:
+ protected:
   bool DiscardFrame(const backtrace_frame_data_t& frame);
 
-private:
+ private:
   bool UnwindThread(size_t num_ignore_frames);
 
   virtual bool UnwindFromContext(size_t num_ignore_frames, ucontext_t* ucontext) = 0;

libbacktrace/BacktracePtrace.h

@@ -25,7 +25,7 @@
 class BacktraceMap;
 
 class BacktracePtrace : public Backtrace {
-public:
+ public:
   BacktracePtrace(pid_t pid, pid_t tid, BacktraceMap* map) : Backtrace(pid, tid, map) {}
   virtual ~BacktracePtrace() {}
 

libbacktrace/ThreadEntry.h

@@ -22,7 +22,7 @@
 #include <ucontext.h>
 
 class ThreadEntry {
-public:
+ public:
   static ThreadEntry* Get(pid_t pid, pid_t tid, bool create = true);
 
   static void Remove(ThreadEntry* entry);
@@ -47,7 +47,7 @@ public:
 
   inline ucontext_t* GetUcontext() { return &ucontext_; }
 
-private:
+ private:
   ThreadEntry(pid_t pid, pid_t tid);
   ~ThreadEntry();
 

libbacktrace/UnwindCurrent.cpp

@@ -23,12 +23,23 @@
 #define UNW_LOCAL_ONLY
 #include <libunwind.h>
 
+#include <android-base/logging.h>
 #include <backtrace/Backtrace.h>
 
 #include "BacktraceLog.h"
 #include "UnwindCurrent.h"
 
 std::string UnwindCurrent::GetFunctionNameRaw(uintptr_t pc, uintptr_t* offset) {
+  if (!initialized_) {
+    // If init local is not called, then trying to get a function name will
+    // fail, so try to initialize first.
+    std::unique_ptr<unw_cursor_t> cursor(new unw_cursor_t);
+    if (unw_init_local(cursor.get(), &context_) < 0) {
+      return "";
+    }
+    initialized_ = true;
+  }
+
   *offset = 0;
   char buf[512];
   unw_word_t value;
@@ -85,6 +96,7 @@ bool UnwindCurrent::UnwindFromContext(size_t num_ignore_frames, ucontext_t* ucon
     error_ = BACKTRACE_UNWIND_ERROR_SETUP_FAILED;
     return false;
   }
+  initialized_ = true;
 
   size_t num_frames = 0;
   do {
@@ -124,6 +136,11 @@ bool UnwindCurrent::UnwindFromContext(size_t num_ignore_frames, ucontext_t* ucon
         num_frames++;
       } else {
         num_ignore_frames--;
+        // Set the number of frames to zero to remove the frame added
+        // above. By definition, if we still have frames to ignore
+        // there should only be one frame in the vector.
+        CHECK(num_frames == 0);
+        frames_.resize(0);
       }
     }
     ret = unw_step (cursor.get());

libbacktrace/UnwindCurrent.h

@@ -32,18 +32,20 @@
 #include <libunwind.h>
 
 class UnwindCurrent : public BacktraceCurrent {
-public:
+ public:
   UnwindCurrent(pid_t pid, pid_t tid, BacktraceMap* map) : BacktraceCurrent(pid, tid, map) {}
   virtual ~UnwindCurrent() {}
 
   std::string GetFunctionNameRaw(uintptr_t pc, uintptr_t* offset) override;
 
-private:
+ private:
   void GetUnwContextFromUcontext(const ucontext_t* ucontext);
 
   bool UnwindFromContext(size_t num_ignore_frames, ucontext_t* ucontext) override;
 
   unw_context_t context_;
+
+  bool initialized_ = false;
 };
 
 #endif // _LIBBACKTRACE_UNWIND_CURRENT_H

libbacktrace/UnwindMap.h

@@ -28,28 +28,28 @@
 // libunwind.h first then this header.
 
 class UnwindMap : public BacktraceMap {
-public:
+ public:
   explicit UnwindMap(pid_t pid);
 
   unw_map_cursor_t* GetMapCursor() { return &map_cursor_; }
 
-protected:
+ protected:
   unw_map_cursor_t map_cursor_;
 };
 
 class UnwindMapRemote : public UnwindMap {
-public:
+ public:
   explicit UnwindMapRemote(pid_t pid);
   virtual ~UnwindMapRemote();
 
   bool Build() override;
 
-private:
+ private:
   bool GenerateMap();
 };
 
 class UnwindMapLocal : public UnwindMap {
-public:
+ public:
   UnwindMapLocal();
   virtual ~UnwindMapLocal();
 
@@ -60,7 +60,7 @@ public:
   void LockIterator() override { pthread_rwlock_rdlock(&map_lock_); }
   void UnlockIterator() override { pthread_rwlock_unlock(&map_lock_); }
 
-private:
+ private:
   bool GenerateMap();
 
   bool map_created_;

libbacktrace/UnwindPtrace.cpp

@@ -37,6 +37,7 @@ UnwindPtrace::~UnwindPtrace() {
     _UPT_destroy(upt_info_);
     upt_info_ = nullptr;
   }
+
   if (addr_space_) {
     // Remove the map from the address space before destroying it.
     // It will be freed in the UnwindMap destructor.
@@ -47,18 +48,14 @@ UnwindPtrace::~UnwindPtrace() {
   }
 }
 
-bool UnwindPtrace::Unwind(size_t num_ignore_frames, ucontext_t* ucontext) {
+bool UnwindPtrace::Init() {
-  if (GetMap() == nullptr) {
+  if (upt_info_) {
-    // Without a map object, we can't do anything.
+    return true;
-    error_ = BACKTRACE_UNWIND_ERROR_MAP_MISSING;
-    return false;
   }
 
-  error_ = BACKTRACE_UNWIND_NO_ERROR;
+  if (addr_space_) {
-
+    // If somehow the addr_space_ gets initialized but upt_info_ doesn't,
-  if (ucontext) {
+    // then that indicates there is some kind of failure.
-    BACK_LOGW("Unwinding from a specified context not supported yet.");
-    error_ = BACKTRACE_UNWIND_ERROR_UNSUPPORTED_OPERATION;
     return false;
   }
 
@@ -79,6 +76,28 @@ bool UnwindPtrace::Unwind(size_t num_ignore_frames, ucontext_t* ucontext) {
     return false;
   }
 
+  return true;
+}
+
+bool UnwindPtrace::Unwind(size_t num_ignore_frames, ucontext_t* ucontext) {
+  if (GetMap() == nullptr) {
+    // Without a map object, we can't do anything.
+    error_ = BACKTRACE_UNWIND_ERROR_MAP_MISSING;
+    return false;
+  }
+
+  error_ = BACKTRACE_UNWIND_NO_ERROR;
+
+  if (ucontext) {
+    BACK_LOGW("Unwinding from a specified context not supported yet.");
+    error_ = BACKTRACE_UNWIND_ERROR_UNSUPPORTED_OPERATION;
+    return false;
+  }
+
+  if (!Init()) {
+    return false;
+  }
+
   unw_cursor_t cursor;
   int ret = unw_init_remote(&cursor, addr_space_, upt_info_);
   if (ret < 0) {
@@ -115,10 +134,10 @@ bool UnwindPtrace::Unwind(size_t num_ignore_frames, ucontext_t* ucontext) {
         prev->stack_size = frame->sp - prev->sp;
       }
 
-      frame->func_name = GetFunctionName(frame->pc, &frame->func_offset);
-
       FillInMap(frame->pc, &frame->map);
 
+      frame->func_name = GetFunctionName(frame->pc, &frame->func_offset);
+
       num_frames++;
     } else {
       num_ignore_frames--;
@@ -130,6 +149,10 @@ bool UnwindPtrace::Unwind(size_t num_ignore_frames, ucontext_t* ucontext) {
 }
 
 std::string UnwindPtrace::GetFunctionNameRaw(uintptr_t pc, uintptr_t* offset) {
+  if (!Init()) {
+    return "";
+  }
+
   *offset = 0;
   char buf[512];
   unw_word_t value;

libbacktrace/UnwindPtrace.h

@@ -30,7 +30,7 @@
 #include "BacktracePtrace.h"
 
 class UnwindPtrace : public BacktracePtrace {
-public:
+ public:
   UnwindPtrace(pid_t pid, pid_t tid, BacktraceMap* map);
   virtual ~UnwindPtrace();
 
@@ -38,7 +38,9 @@ public:
 
   std::string GetFunctionNameRaw(uintptr_t pc, uintptr_t* offset) override;
 
-private:
+ private:
+  bool Init();
+
   unw_addr_space_t addr_space_;
   struct UPT_info* upt_info_;
 };

libbacktrace/backtrace_test.cpp

@@ -43,6 +43,7 @@
 #include <backtrace/BacktraceMap.h>
 
 #include <android-base/stringprintf.h>
+#include <android-base/unique_fd.h>
 #include <cutils/atomic.h>
 #include <cutils/threads.h>
 
@@ -85,13 +86,13 @@ int test_level_one(int, int, int, int, void (*)(void*), void*);
 int test_recursive_call(int, void (*)(void*), void*);
 }
 
-uint64_t NanoTime() {
+static uint64_t NanoTime() {
   struct timespec t = { 0, 0 };
   clock_gettime(CLOCK_MONOTONIC, &t);
   return static_cast<uint64_t>(t.tv_sec * NS_PER_SEC + t.tv_nsec);
 }
 
-std::string DumpFrames(Backtrace* backtrace) {
+static std::string DumpFrames(Backtrace* backtrace) {
   if (backtrace->NumFrames() == 0) {
     return "   No frames to dump.\n";
   }
@@ -103,7 +104,7 @@ std::string DumpFrames(Backtrace* backtrace) {
   return frame;
 }
 
-void WaitForStop(pid_t pid) {
+static void WaitForStop(pid_t pid) {
   uint64_t start = NanoTime();
 
   siginfo_t si;
@@ -116,7 +117,28 @@ void WaitForStop(pid_t pid) {
   }
 }
 
-bool ReadyLevelBacktrace(Backtrace* backtrace) {
+static void CreateRemoteProcess(pid_t* pid) {
+  if ((*pid = fork()) == 0) {
+    while (true)
+      ;
+    _exit(0);
+  }
+  ASSERT_NE(-1, *pid);
+
+  ASSERT_TRUE(ptrace(PTRACE_ATTACH, *pid, 0, 0) == 0);
+
+  // Wait for the process to get to a stopping point.
+  WaitForStop(*pid);
+}
+
+static void FinishRemoteProcess(pid_t pid) {
+  ASSERT_TRUE(ptrace(PTRACE_DETACH, pid, 0, 0) == 0);
+
+  kill(pid, SIGKILL);
+  ASSERT_EQ(waitpid(pid, nullptr, 0), pid);
+}
+
+static bool ReadyLevelBacktrace(Backtrace* backtrace) {
   // See if test_level_four is in the backtrace.
   bool found = false;
   for (Backtrace::const_iterator it = backtrace->begin(); it != backtrace->end(); ++it) {
@@ -129,7 +151,7 @@ bool ReadyLevelBacktrace(Backtrace* backtrace) {
   return found;
 }
 
-void VerifyLevelDump(Backtrace* backtrace) {
+static void VerifyLevelDump(Backtrace* backtrace) {
   ASSERT_GT(backtrace->NumFrames(), static_cast<size_t>(0))
     << DumpFrames(backtrace);
   ASSERT_LT(backtrace->NumFrames(), static_cast<size_t>(MAX_BACKTRACE_FRAMES))
@@ -157,7 +179,7 @@ void VerifyLevelDump(Backtrace* backtrace) {
     << DumpFrames(backtrace);
 }
 
-void VerifyLevelBacktrace(void*) {
+static void VerifyLevelBacktrace(void*) {
   std::unique_ptr<Backtrace> backtrace(
       Backtrace::Create(BACKTRACE_CURRENT_PROCESS, BACKTRACE_CURRENT_THREAD));
   ASSERT_TRUE(backtrace.get() != nullptr);
@@ -167,11 +189,11 @@ void VerifyLevelBacktrace(void*) {
   VerifyLevelDump(backtrace.get());
 }
 
-bool ReadyMaxBacktrace(Backtrace* backtrace) {
+static bool ReadyMaxBacktrace(Backtrace* backtrace) {
   return (backtrace->NumFrames() == MAX_BACKTRACE_FRAMES);
 }
 
-void VerifyMaxDump(Backtrace* backtrace) {
+static void VerifyMaxDump(Backtrace* backtrace) {
   ASSERT_EQ(backtrace->NumFrames(), static_cast<size_t>(MAX_BACKTRACE_FRAMES))
     << DumpFrames(backtrace);
   // Verify that the last frame is our recursive call.
@@ -179,7 +201,7 @@ void VerifyMaxDump(Backtrace* backtrace) {
     << DumpFrames(backtrace);
 }
 
-void VerifyMaxBacktrace(void*) {
+static void VerifyMaxBacktrace(void*) {
   std::unique_ptr<Backtrace> backtrace(
       Backtrace::Create(BACKTRACE_CURRENT_PROCESS, BACKTRACE_CURRENT_THREAD));
   ASSERT_TRUE(backtrace.get() != nullptr);
@@ -189,7 +211,7 @@ void VerifyMaxBacktrace(void*) {
   VerifyMaxDump(backtrace.get());
 }
 
-void ThreadSetState(void* data) {
+static void ThreadSetState(void* data) {
   thread_t* thread = reinterpret_cast<thread_t*>(data);
   android_atomic_acquire_store(1, &thread->state);
   volatile int i = 0;
@@ -198,16 +220,7 @@ void ThreadSetState(void* data) {
   }
 }
 
-void VerifyThreadTest(pid_t tid, void (*VerifyFunc)(Backtrace*)) {
+static bool WaitForNonZero(int32_t* value, uint64_t seconds) {
-  std::unique_ptr<Backtrace> backtrace(Backtrace::Create(getpid(), tid));
-  ASSERT_TRUE(backtrace.get() != nullptr);
-  ASSERT_TRUE(backtrace->Unwind(0));
-  ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, backtrace->GetError());
-
-  VerifyFunc(backtrace.get());
-}
-
-bool WaitForNonZero(int32_t* value, uint64_t seconds) {
   uint64_t start = NanoTime();
   do {
     if (android_atomic_acquire_load(value)) {
@@ -240,9 +253,8 @@ TEST(libbacktrace, local_trace) {
   ASSERT_NE(test_level_one(1, 2, 3, 4, VerifyLevelBacktrace, nullptr), 0);
 }
 
-void VerifyIgnoreFrames(
+static void VerifyIgnoreFrames(Backtrace* bt_all, Backtrace* bt_ign1, Backtrace* bt_ign2,
-    Backtrace* bt_all, Backtrace* bt_ign1,
+                               const char* cur_proc) {
-    Backtrace* bt_ign2, const char* cur_proc) {
   EXPECT_EQ(bt_all->NumFrames(), bt_ign1->NumFrames() + 1)
     << "All backtrace:\n" << DumpFrames(bt_all) << "Ignore 1 backtrace:\n" << DumpFrames(bt_ign1);
   EXPECT_EQ(bt_all->NumFrames(), bt_ign2->NumFrames() + 2)
@@ -266,7 +278,7 @@ void VerifyIgnoreFrames(
   }
 }
 
-void VerifyLevelIgnoreFrames(void*) {
+static void VerifyLevelIgnoreFrames(void*) {
   std::unique_ptr<Backtrace> all(
       Backtrace::Create(BACKTRACE_CURRENT_PROCESS, BACKTRACE_CURRENT_THREAD));
   ASSERT_TRUE(all.get() != nullptr);
@@ -296,9 +308,8 @@ TEST(libbacktrace, local_max_trace) {
   ASSERT_NE(test_recursive_call(MAX_BACKTRACE_FRAMES+10, VerifyMaxBacktrace, nullptr), 0);
 }
 
-void VerifyProcTest(pid_t pid, pid_t tid, bool share_map,
+static void VerifyProcTest(pid_t pid, pid_t tid, bool share_map, bool (*ReadyFunc)(Backtrace*),
-                    bool (*ReadyFunc)(Backtrace*),
+                           void (*VerifyFunc)(Backtrace*)) {
-                    void (*VerifyFunc)(Backtrace*)) {
   pid_t ptrace_tid;
   if (tid < 0) {
     ptrace_tid = pid;
@@ -376,7 +387,7 @@ TEST(libbacktrace, ptrace_max_trace) {
   ASSERT_EQ(waitpid(pid, &status, 0), pid);
 }
 
-void VerifyProcessIgnoreFrames(Backtrace* bt_all) {
+static void VerifyProcessIgnoreFrames(Backtrace* bt_all) {
   std::unique_ptr<Backtrace> ign1(Backtrace::Create(bt_all->Pid(), BACKTRACE_CURRENT_THREAD));
   ASSERT_TRUE(ign1.get() != nullptr);
   ASSERT_TRUE(ign1->Unwind(1));
@@ -404,12 +415,12 @@ TEST(libbacktrace, ptrace_ignore_frames) {
 }
 
 // Create a process with multiple threads and dump all of the threads.
-void* PtraceThreadLevelRun(void*) {
+static void* PtraceThreadLevelRun(void*) {
   EXPECT_NE(test_level_one(1, 2, 3, 4, nullptr, nullptr), 0);
   return nullptr;
 }
 
-void GetThreads(pid_t pid, std::vector<pid_t>* threads) {
+static void GetThreads(pid_t pid, std::vector<pid_t>* threads) {
   // Get the list of tasks.
   char task_path[128];
   snprintf(task_path, sizeof(task_path), "/proc/%d/task", pid);
@@ -461,11 +472,8 @@ TEST(libbacktrace, ptrace_threads) {
     }
     VerifyProcTest(pid, *it, false, ReadyLevelBacktrace, VerifyLevelDump);
   }
-  ASSERT_TRUE(ptrace(PTRACE_DETACH, pid, 0, 0) == 0);
 
-  kill(pid, SIGKILL);
+  FinishRemoteProcess(pid);
-  int status;
-  ASSERT_EQ(waitpid(pid, &status, 0), pid);
 }
 
 void VerifyLevelThread(void*) {
@@ -481,7 +489,7 @@ TEST(libbacktrace, thread_current_level) {
   ASSERT_NE(test_level_one(1, 2, 3, 4, VerifyLevelThread, nullptr), 0);
 }
 
-void VerifyMaxThread(void*) {
+static void VerifyMaxThread(void*) {
   std::unique_ptr<Backtrace> backtrace(Backtrace::Create(getpid(), gettid()));
   ASSERT_TRUE(backtrace.get() != nullptr);
   ASSERT_TRUE(backtrace->Unwind(0));
@@ -494,7 +502,7 @@ TEST(libbacktrace, thread_current_max) {
   ASSERT_NE(test_recursive_call(MAX_BACKTRACE_FRAMES+10, VerifyMaxThread, nullptr), 0);
 }
 
-void* ThreadLevelRun(void* data) {
+static void* ThreadLevelRun(void* data) {
   thread_t* thread = reinterpret_cast<thread_t*>(data);
 
   thread->tid = gettid();
@@ -585,7 +593,7 @@ TEST(libbacktrace, thread_ignore_frames) {
   android_atomic_acquire_store(0, &thread_data.state);
 }
 
-void* ThreadMaxRun(void* data) {
+static void* ThreadMaxRun(void* data) {
   thread_t* thread = reinterpret_cast<thread_t*>(data);
 
   thread->tid = gettid();
@@ -616,7 +624,7 @@ TEST(libbacktrace, thread_max_trace) {
   android_atomic_acquire_store(0, &thread_data.state);
 }
 
-void* ThreadDump(void* data) {
+static void* ThreadDump(void* data) {
   dump_thread_t* dump = reinterpret_cast<dump_thread_t*>(data);
   while (true) {
     if (android_atomic_acquire_load(dump->now)) {
@@ -873,11 +881,9 @@ struct map_test_t {
   uintptr_t end;
 };
 
-bool map_sort(map_test_t i, map_test_t j) {
+static bool map_sort(map_test_t i, map_test_t j) { return i.start < j.start; }
-  return i.start < j.start;
-}
 
-void VerifyMap(pid_t pid) {
+static void VerifyMap(pid_t pid) {
   char buffer[4096];
   snprintf(buffer, sizeof(buffer), "/proc/%d/maps", pid);
 
@@ -908,29 +914,15 @@ void VerifyMap(pid_t pid) {
 
 TEST(libbacktrace, verify_map_remote) {
   pid_t pid;
-
+  CreateRemoteProcess(&pid);
-  if ((pid = fork()) == 0) {
-    while (true) {
-    }
-    _exit(0);
-  }
-  ASSERT_LT(0, pid);
-
-  ASSERT_TRUE(ptrace(PTRACE_ATTACH, pid, 0, 0) == 0);
-
-  // Wait for the process to get to a stopping point.
-  WaitForStop(pid);
 
   // The maps should match exactly since the forked process has been paused.
   VerifyMap(pid);
 
-  ASSERT_TRUE(ptrace(PTRACE_DETACH, pid, 0, 0) == 0);
+  FinishRemoteProcess(pid);
-
-  kill(pid, SIGKILL);
-  ASSERT_EQ(waitpid(pid, nullptr, 0), pid);
 }
 
-void InitMemory(uint8_t* memory, size_t bytes) {
+static void InitMemory(uint8_t* memory, size_t bytes) {
   for (size_t i = 0; i < bytes; i++) {
     memory[i] = i;
     if (memory[i] == '\0') {
@@ -941,7 +933,7 @@ void InitMemory(uint8_t* memory, size_t bytes) {
   }
 }
 
-void* ThreadReadTest(void* data) {
+static void* ThreadReadTest(void* data) {
   thread_t* thread_data = reinterpret_cast<thread_t*>(data);
 
   thread_data->tid = gettid();
@@ -982,7 +974,7 @@ void* ThreadReadTest(void* data) {
   return nullptr;
 }
 
-void RunReadTest(Backtrace* backtrace, uintptr_t read_addr) {
+static void RunReadTest(Backtrace* backtrace, uintptr_t read_addr) {
   size_t pagesize = static_cast<size_t>(sysconf(_SC_PAGE_SIZE));
 
   // Create a page of data to use to do quick compares.
@@ -1043,7 +1035,7 @@ TEST(libbacktrace, thread_read) {
 volatile uintptr_t g_ready = 0;
 volatile uintptr_t g_addr = 0;
 
-void ForkedReadTest() {
+static void ForkedReadTest() {
   // Create two map pages.
   size_t pagesize = static_cast<size_t>(sysconf(_SC_PAGE_SIZE));
   uint8_t* memory;
@@ -1117,7 +1109,7 @@ TEST(libbacktrace, process_read) {
   ASSERT_TRUE(test_executed);
 }
 
-void VerifyFunctionsFound(const std::vector<std::string>& found_functions) {
+static void VerifyFunctionsFound(const std::vector<std::string>& found_functions) {
   // We expect to find these functions in libbacktrace_test. If we don't
   // find them, that's a bug in the memory read handling code in libunwind.
   std::list<std::string> expected_functions;
@@ -1137,7 +1129,7 @@ void VerifyFunctionsFound(const std::vector<std::string>& found_functions) {
   ASSERT_TRUE(expected_functions.empty()) << "Not all functions found in shared library.";
 }
 
-const char* CopySharedLibrary() {
+static const char* CopySharedLibrary() {
 #if defined(__LP64__)
   const char* lib_name = "lib64";
 #else
@@ -1293,7 +1285,7 @@ TEST(libbacktrace, check_unreadable_elf_remote) {
   VerifyFunctionsFound(found_functions);
 }
 
-bool FindFuncFrameInBacktrace(Backtrace* backtrace, uintptr_t test_func, size_t* frame_num) {
+static bool FindFuncFrameInBacktrace(Backtrace* backtrace, uintptr_t test_func, size_t* frame_num) {
   backtrace_map_t map;
   backtrace->FillInMap(test_func, &map);
   if (!BacktraceMap::IsValid(map)) {
@@ -1312,7 +1304,7 @@ bool FindFuncFrameInBacktrace(Backtrace* backtrace, uintptr_t test_func, size_t*
   return false;
 }
 
-void VerifyUnreadableElfFrame(Backtrace* backtrace, uintptr_t test_func, size_t frame_num) {
+static void VerifyUnreadableElfFrame(Backtrace* backtrace, uintptr_t test_func, size_t frame_num) {
   ASSERT_LT(backtrace->NumFrames(), static_cast<size_t>(MAX_BACKTRACE_FRAMES))
     << DumpFrames(backtrace);
 
@@ -1324,7 +1316,7 @@ void VerifyUnreadableElfFrame(Backtrace* backtrace, uintptr_t test_func, size_t
   ASSERT_LT(diff, 200U) << DumpFrames(backtrace);
 }
 
-void VerifyUnreadableElfBacktrace(uintptr_t test_func) {
+static void VerifyUnreadableElfBacktrace(uintptr_t test_func) {
   std::unique_ptr<Backtrace> backtrace(Backtrace::Create(BACKTRACE_CURRENT_PROCESS,
                                                          BACKTRACE_CURRENT_THREAD));
   ASSERT_TRUE(backtrace.get() != nullptr);
@@ -1418,12 +1410,38 @@ TEST(libbacktrace, unwind_thread_doesnt_exist) {
   ASSERT_EQ(BACKTRACE_UNWIND_ERROR_THREAD_DOESNT_EXIST, backtrace->GetError());
 }
 
+TEST(libbacktrace, local_get_function_name_before_unwind) {
+  std::unique_ptr<Backtrace> backtrace(
+      Backtrace::Create(BACKTRACE_CURRENT_PROCESS, BACKTRACE_CURRENT_THREAD));
+  ASSERT_TRUE(backtrace.get() != nullptr);
+
+  // Verify that trying to get a function name before doing an unwind works.
+  uintptr_t cur_func_offset = reinterpret_cast<uintptr_t>(&test_level_one) + 1;
+  size_t offset;
+  ASSERT_NE(std::string(""), backtrace->GetFunctionName(cur_func_offset, &offset));
+}
+
+TEST(libbacktrace, remote_get_function_name_before_unwind) {
+  pid_t pid;
+  CreateRemoteProcess(&pid);
+
+  // Now create an unwind object.
+  std::unique_ptr<Backtrace> backtrace(Backtrace::Create(pid, pid));
+
+  // Verify that trying to get a function name before doing an unwind works.
+  uintptr_t cur_func_offset = reinterpret_cast<uintptr_t>(&test_level_one) + 1;
+  size_t offset;
+  ASSERT_NE(std::string(""), backtrace->GetFunctionName(cur_func_offset, &offset));
+
+  FinishRemoteProcess(pid);
+}
+
 #if defined(ENABLE_PSS_TESTS)
 #include "GetPss.h"
 
 #define MAX_LEAK_BYTES (32*1024UL)
 
-void CheckForLeak(pid_t pid, pid_t tid) {
+static void CheckForLeak(pid_t pid, pid_t tid) {
   // Do a few runs to get the PSS stable.
   for (size_t i = 0; i < 100; i++) {
     Backtrace* backtrace = Backtrace::Create(pid, tid);
@@ -1472,24 +1490,10 @@ TEST(libbacktrace, check_for_leak_local_thread) {
 
 TEST(libbacktrace, check_for_leak_remote) {
   pid_t pid;
-
+  CreateRemoteProcess(&pid);
-  if ((pid = fork()) == 0) {
-    while (true) {
-    }
-    _exit(0);
-  }
-  ASSERT_LT(0, pid);
-
-  ASSERT_TRUE(ptrace(PTRACE_ATTACH, pid, 0, 0) == 0);
-
-  // Wait for the process to get to a stopping point.
-  WaitForStop(pid);
 
   CheckForLeak(pid, BACKTRACE_CURRENT_THREAD);
 
-  ASSERT_TRUE(ptrace(PTRACE_DETACH, pid, 0, 0) == 0);
+  FinishRemoteProcess(pid);
-
-  kill(pid, SIGKILL);
-  ASSERT_EQ(waitpid(pid, nullptr, 0), pid);
 }
 #endif