Add error reporting mechanism for failing Unwind.
Remove the logging of an error if a thread disappears before the unwind
can begin. This can happen, so allow the caller to determine if this
is really a problem worth logging.
Bug: 27449879
Change-Id: Ie81718d53fb0e519fa0a7db9fd5f314b72bfa431
diff --git a/debuggerd/backtrace.cpp b/debuggerd/backtrace.cpp
index b6916e5..32843d8 100644
--- a/debuggerd/backtrace.cpp
+++ b/debuggerd/backtrace.cpp
@@ -91,7 +91,8 @@
if (backtrace->Unwind(0)) {
dump_backtrace_to_log(backtrace.get(), log, " ");
} else {
- ALOGE("Unwind failed: tid = %d", tid);
+ ALOGE("Unwind failed: tid = %d: %s", tid,
+ backtrace->GetErrorString(backtrace->GetError()).c_str());
}
}
diff --git a/include/backtrace/Backtrace.h b/include/backtrace/Backtrace.h
index f440bd2..c896ab8 100644
--- a/include/backtrace/Backtrace.h
+++ b/include/backtrace/Backtrace.h
@@ -34,6 +34,24 @@
typedef uint32_t word_t;
#endif
+enum BacktraceUnwindError : uint32_t {
+ BACKTRACE_UNWIND_NO_ERROR,
+ // Something failed while trying to perform the setup to begin the unwind.
+ BACKTRACE_UNWIND_ERROR_SETUP_FAILED,
+ // There is no map information to use with the unwind.
+ BACKTRACE_UNWIND_ERROR_MAP_MISSING,
+ // An error occurred that indicates a programming error.
+ BACKTRACE_UNWIND_ERROR_INTERNAL,
+ // The thread to unwind has disappeared before the unwind can begin.
+ BACKTRACE_UNWIND_ERROR_THREAD_DOESNT_EXIST,
+ // The thread to unwind has not responded to a signal in a timely manner.
+ BACKTRACE_UNWIND_ERROR_THREAD_TIMEOUT,
+ // Attempt to do an unsupported operation.
+ BACKTRACE_UNWIND_ERROR_UNSUPPORTED_OPERATION,
+ // Attempt to do an offline unwind without a context.
+ BACKTRACE_UNWIND_ERROR_NO_CONTEXT,
+};
+
struct backtrace_frame_data_t {
size_t num; // The current fame number.
uintptr_t pc; // The absolute pc.
@@ -127,6 +145,10 @@
BacktraceMap* GetMap() { return map_; }
+ BacktraceUnwindError GetError() { return error_; }
+
+ std::string GetErrorString(BacktraceUnwindError error);
+
protected:
Backtrace(pid_t pid, pid_t tid, BacktraceMap* map);
@@ -145,6 +167,8 @@
bool map_shared_;
std::vector<backtrace_frame_data_t> frames_;
+
+ BacktraceUnwindError error_;
};
#endif // _BACKTRACE_BACKTRACE_H
diff --git a/libbacktrace/Backtrace.cpp b/libbacktrace/Backtrace.cpp
index baa3d0f..995abc0 100644
--- a/libbacktrace/Backtrace.cpp
+++ b/libbacktrace/Backtrace.cpp
@@ -148,3 +148,24 @@
return new UnwindPtrace(pid, tid, map);
}
}
+
+std::string Backtrace::GetErrorString(BacktraceUnwindError error) {
+ switch (error) {
+ case BACKTRACE_UNWIND_NO_ERROR:
+ return "No error";
+ case BACKTRACE_UNWIND_ERROR_SETUP_FAILED:
+ return "Setup failed";
+ case BACKTRACE_UNWIND_ERROR_MAP_MISSING:
+ return "No map found";
+ case BACKTRACE_UNWIND_ERROR_INTERNAL:
+ return "Internal libbacktrace error, please submit a bugreport";
+ case BACKTRACE_UNWIND_ERROR_THREAD_DOESNT_EXIST:
+ return "Thread doesn't exist";
+ case BACKTRACE_UNWIND_ERROR_THREAD_TIMEOUT:
+ return "Thread has not repsonded to signal in time";
+ case BACKTRACE_UNWIND_ERROR_UNSUPPORTED_OPERATION:
+ return "Attempt to use an unsupported feature";
+ case BACKTRACE_UNWIND_ERROR_NO_CONTEXT:
+ return "Attempt to do an offline unwind without a context";
+ }
+}
diff --git a/libbacktrace/BacktraceCurrent.cpp b/libbacktrace/BacktraceCurrent.cpp
index 8e22366..5173e2c 100644
--- a/libbacktrace/BacktraceCurrent.cpp
+++ b/libbacktrace/BacktraceCurrent.cpp
@@ -24,6 +24,8 @@
#include <ucontext.h>
#include <unistd.h>
+#include <stdlib.h>
+
#include <string>
#include <backtrace/Backtrace.h>
@@ -65,9 +67,11 @@
bool BacktraceCurrent::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) {
return UnwindFromContext(num_ignore_frames, ucontext);
}
@@ -138,11 +142,19 @@
BACK_LOGE("sigaction failed: %s", strerror(errno));
ThreadEntry::Remove(entry);
pthread_mutex_unlock(&g_sigaction_mutex);
+ error_ = BACKTRACE_UNWIND_ERROR_INTERNAL;
return false;
}
if (tgkill(Pid(), Tid(), THREAD_SIGNAL) != 0) {
- BACK_LOGE("tgkill %d failed: %s", Tid(), strerror(errno));
+ // Do not emit an error message, this might be expected. Set the
+ // error and let the caller decide.
+ if (errno == ESRCH) {
+ error_ = BACKTRACE_UNWIND_ERROR_THREAD_DOESNT_EXIST;
+ } else {
+ error_ = BACKTRACE_UNWIND_ERROR_INTERNAL;
+ }
+
sigaction(THREAD_SIGNAL, &oldact, nullptr);
ThreadEntry::Remove(entry);
pthread_mutex_unlock(&g_sigaction_mutex);
@@ -183,7 +195,13 @@
BACK_LOGW("Timed out waiting for signal handler to indicate it finished.");
}
} else {
- BACK_LOGE("Timed out waiting for signal handler to get ucontext data.");
+ // Check to see if the thread has disappeared.
+ if (tgkill(Pid(), Tid(), 0) == -1 && errno == ESRCH) {
+ error_ = BACKTRACE_UNWIND_ERROR_THREAD_DOESNT_EXIST;
+ } else {
+ error_ = BACKTRACE_UNWIND_ERROR_THREAD_TIMEOUT;
+ BACK_LOGE("Timed out waiting for signal handler to get ucontext data.");
+ }
}
ThreadEntry::Remove(entry);
diff --git a/libbacktrace/BacktraceOffline.cpp b/libbacktrace/BacktraceOffline.cpp
index e84ae74..ac14046 100644
--- a/libbacktrace/BacktraceOffline.cpp
+++ b/libbacktrace/BacktraceOffline.cpp
@@ -129,9 +129,11 @@
bool BacktraceOffline::Unwind(size_t num_ignore_frames, ucontext_t* context) {
if (context == nullptr) {
BACK_LOGW("The context is needed for offline backtracing.");
+ error_ = BACKTRACE_UNWIND_ERROR_NO_CONTEXT;
return false;
}
context_ = context;
+ error_ = BACKTRACE_UNWIND_NO_ERROR;
unw_addr_space_t addr_space = unw_create_addr_space(&accessors, 0);
unw_cursor_t cursor;
@@ -139,6 +141,7 @@
if (ret != 0) {
BACK_LOGW("unw_init_remote failed %d", ret);
unw_destroy_addr_space(addr_space);
+ error_ = BACKTRACE_UNWIND_ERROR_SETUP_FAILED;
return false;
}
size_t num_frames = 0;
diff --git a/libbacktrace/UnwindCurrent.cpp b/libbacktrace/UnwindCurrent.cpp
index 67e583f..666c481 100644
--- a/libbacktrace/UnwindCurrent.cpp
+++ b/libbacktrace/UnwindCurrent.cpp
@@ -70,6 +70,7 @@
int ret = unw_getcontext(&context_);
if (ret < 0) {
BACK_LOGW("unw_getcontext failed %d", ret);
+ error_ = BACKTRACE_UNWIND_ERROR_SETUP_FAILED;
return false;
}
} else {
@@ -81,6 +82,7 @@
int ret = unw_init_local(cursor.get(), &context_);
if (ret < 0) {
BACK_LOGW("unw_init_local failed %d", ret);
+ error_ = BACKTRACE_UNWIND_ERROR_SETUP_FAILED;
return false;
}
diff --git a/libbacktrace/UnwindPtrace.cpp b/libbacktrace/UnwindPtrace.cpp
index 07c2430..306d2ac 100644
--- a/libbacktrace/UnwindPtrace.cpp
+++ b/libbacktrace/UnwindPtrace.cpp
@@ -50,17 +50,22 @@
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;
}
addr_space_ = unw_create_addr_space(&_UPT_accessors, 0);
if (!addr_space_) {
BACK_LOGW("unw_create_addr_space failed.");
+ error_ = BACKTRACE_UNWIND_ERROR_SETUP_FAILED;
return false;
}
@@ -70,6 +75,7 @@
upt_info_ = reinterpret_cast<struct UPT_info*>(_UPT_create(Tid()));
if (!upt_info_) {
BACK_LOGW("Failed to create upt info.");
+ error_ = BACKTRACE_UNWIND_ERROR_SETUP_FAILED;
return false;
}
@@ -77,6 +83,7 @@
int ret = unw_init_remote(&cursor, addr_space_, upt_info_);
if (ret < 0) {
BACK_LOGW("unw_init_remote failed %d", ret);
+ error_ = BACKTRACE_UNWIND_ERROR_SETUP_FAILED;
return false;
}
diff --git a/libbacktrace/backtrace_test.cpp b/libbacktrace/backtrace_test.cpp
index ab09564..df6c6c1 100644
--- a/libbacktrace/backtrace_test.cpp
+++ b/libbacktrace/backtrace_test.cpp
@@ -162,6 +162,7 @@
Backtrace::Create(BACKTRACE_CURRENT_PROCESS, BACKTRACE_CURRENT_THREAD));
ASSERT_TRUE(backtrace.get() != nullptr);
ASSERT_TRUE(backtrace->Unwind(0));
+ ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, backtrace->GetError());
VerifyLevelDump(backtrace.get());
}
@@ -183,6 +184,7 @@
Backtrace::Create(BACKTRACE_CURRENT_PROCESS, BACKTRACE_CURRENT_THREAD));
ASSERT_TRUE(backtrace.get() != nullptr);
ASSERT_TRUE(backtrace->Unwind(0));
+ ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, backtrace->GetError());
VerifyMaxDump(backtrace.get());
}
@@ -200,6 +202,7 @@
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());
}
@@ -220,6 +223,7 @@
std::unique_ptr<Backtrace> backtrace(Backtrace::Create(getpid(), getpid()));
ASSERT_TRUE(backtrace.get() != nullptr);
ASSERT_TRUE(backtrace->Unwind(0));
+ ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, backtrace->GetError());
ASSERT_TRUE(backtrace->NumFrames() != 0);
for (const auto& frame : *backtrace ) {
@@ -267,16 +271,19 @@
Backtrace::Create(BACKTRACE_CURRENT_PROCESS, BACKTRACE_CURRENT_THREAD));
ASSERT_TRUE(all.get() != nullptr);
ASSERT_TRUE(all->Unwind(0));
+ ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, all->GetError());
std::unique_ptr<Backtrace> ign1(
Backtrace::Create(BACKTRACE_CURRENT_PROCESS, BACKTRACE_CURRENT_THREAD));
ASSERT_TRUE(ign1.get() != nullptr);
ASSERT_TRUE(ign1->Unwind(1));
+ ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, ign1->GetError());
std::unique_ptr<Backtrace> ign2(
Backtrace::Create(BACKTRACE_CURRENT_PROCESS, BACKTRACE_CURRENT_THREAD));
ASSERT_TRUE(ign2.get() != nullptr);
ASSERT_TRUE(ign2->Unwind(2));
+ ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, ign2->GetError());
VerifyIgnoreFrames(all.get(), ign1.get(), ign2.get(), "VerifyLevelIgnoreFrames");
}
@@ -314,6 +321,7 @@
std::unique_ptr<Backtrace> backtrace(Backtrace::Create(pid, tid, map.get()));
ASSERT_TRUE(backtrace.get() != nullptr);
ASSERT_TRUE(backtrace->Unwind(0));
+ ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, backtrace->GetError());
if (ReadyFunc(backtrace.get())) {
VerifyFunc(backtrace.get());
verified = true;
@@ -372,10 +380,12 @@
std::unique_ptr<Backtrace> ign1(Backtrace::Create(bt_all->Pid(), BACKTRACE_CURRENT_THREAD));
ASSERT_TRUE(ign1.get() != nullptr);
ASSERT_TRUE(ign1->Unwind(1));
+ ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, ign1->GetError());
std::unique_ptr<Backtrace> ign2(Backtrace::Create(bt_all->Pid(), BACKTRACE_CURRENT_THREAD));
ASSERT_TRUE(ign2.get() != nullptr);
ASSERT_TRUE(ign2->Unwind(2));
+ ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, ign2->GetError());
VerifyIgnoreFrames(bt_all, ign1.get(), ign2.get(), nullptr);
}
@@ -462,6 +472,7 @@
std::unique_ptr<Backtrace> backtrace(Backtrace::Create(getpid(), gettid()));
ASSERT_TRUE(backtrace.get() != nullptr);
ASSERT_TRUE(backtrace->Unwind(0));
+ ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, backtrace->GetError());
VerifyLevelDump(backtrace.get());
}
@@ -474,6 +485,7 @@
std::unique_ptr<Backtrace> backtrace(Backtrace::Create(getpid(), gettid()));
ASSERT_TRUE(backtrace.get() != nullptr);
ASSERT_TRUE(backtrace->Unwind(0));
+ ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, backtrace->GetError());
VerifyMaxDump(backtrace.get());
}
@@ -515,6 +527,7 @@
std::unique_ptr<Backtrace> backtrace(Backtrace::Create(getpid(), thread_data.tid));
ASSERT_TRUE(backtrace.get() != nullptr);
ASSERT_TRUE(backtrace->Unwind(0));
+ ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, backtrace->GetError());
VerifyLevelDump(backtrace.get());
@@ -554,14 +567,17 @@
std::unique_ptr<Backtrace> all(Backtrace::Create(getpid(), thread_data.tid));
ASSERT_TRUE(all.get() != nullptr);
ASSERT_TRUE(all->Unwind(0));
+ ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, all->GetError());
std::unique_ptr<Backtrace> ign1(Backtrace::Create(getpid(), thread_data.tid));
ASSERT_TRUE(ign1.get() != nullptr);
ASSERT_TRUE(ign1->Unwind(1));
+ ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, ign1->GetError());
std::unique_ptr<Backtrace> ign2(Backtrace::Create(getpid(), thread_data.tid));
ASSERT_TRUE(ign2.get() != nullptr);
ASSERT_TRUE(ign2->Unwind(2));
+ ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, ign2->GetError());
VerifyIgnoreFrames(all.get(), ign1.get(), ign2.get(), nullptr);
@@ -592,6 +608,7 @@
std::unique_ptr<Backtrace> backtrace(Backtrace::Create(getpid(), thread_data.tid));
ASSERT_TRUE(backtrace.get() != nullptr);
ASSERT_TRUE(backtrace->Unwind(0));
+ ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, backtrace->GetError());
VerifyMaxDump(backtrace.get());
@@ -718,18 +735,21 @@
Backtrace* back1 = Backtrace::Create(getpid(), BACKTRACE_CURRENT_THREAD, map1);
ASSERT_TRUE(back1 != nullptr);
EXPECT_TRUE(back1->Unwind(0));
+ ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, back1->GetError());
delete back1;
delete map1;
Backtrace* back2 = Backtrace::Create(getpid(), BACKTRACE_CURRENT_THREAD, map2);
ASSERT_TRUE(back2 != nullptr);
EXPECT_TRUE(back2->Unwind(0));
+ ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, back2->GetError());
delete back2;
delete map2;
Backtrace* back3 = Backtrace::Create(getpid(), BACKTRACE_CURRENT_THREAD, map3);
ASSERT_TRUE(back3 != nullptr);
EXPECT_TRUE(back3->Unwind(0));
+ ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, back3->GetError());
delete back3;
delete map3;
}
@@ -1308,6 +1328,7 @@
BACKTRACE_CURRENT_THREAD));
ASSERT_TRUE(backtrace.get() != nullptr);
ASSERT_TRUE(backtrace->Unwind(0));
+ ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, backtrace->GetError());
size_t frame_num;
ASSERT_TRUE(FindFuncFrameInBacktrace(backtrace.get(), test_func, &frame_num));
@@ -1364,6 +1385,7 @@
std::unique_ptr<Backtrace> backtrace(Backtrace::Create(pid, BACKTRACE_CURRENT_THREAD));
ASSERT_TRUE(backtrace.get() != nullptr);
ASSERT_TRUE(backtrace->Unwind(0));
+ ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, backtrace->GetError());
size_t frame_num;
if (FindFuncFrameInBacktrace(backtrace.get(),
@@ -1387,6 +1409,14 @@
ASSERT_TRUE(done) << "Test function never found in unwind.";
}
+TEST(libbacktrace, unwind_thread_doesnt_exist) {
+ std::unique_ptr<Backtrace> backtrace(
+ Backtrace::Create(BACKTRACE_CURRENT_PROCESS, 99999999));
+ ASSERT_TRUE(backtrace.get() != nullptr);
+ ASSERT_FALSE(backtrace->Unwind(0));
+ ASSERT_EQ(BACKTRACE_UNWIND_ERROR_THREAD_DOESNT_EXIST, backtrace->GetError());
+}
+
#if defined(ENABLE_PSS_TESTS)
#include "GetPss.h"
@@ -1398,6 +1428,7 @@
Backtrace* backtrace = Backtrace::Create(pid, tid);
ASSERT_TRUE(backtrace != nullptr);
ASSERT_TRUE(backtrace->Unwind(0));
+ ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, backtrace->GetError());
delete backtrace;
}
size_t stable_pss = GetPssBytes();
@@ -1408,6 +1439,7 @@
Backtrace* backtrace = Backtrace::Create(pid, tid);
ASSERT_TRUE(backtrace != nullptr);
ASSERT_TRUE(backtrace->Unwind(0));
+ ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, backtrace->GetError());
delete backtrace;
}
size_t new_pss = GetPssBytes();