Add error reporting mechanism for failing Unwind. (7c970c8a) · Commits · e / os / android_system_core

debuggerd/backtrace.cpp

+2 −1

Original line number	Diff line number	Diff line
		@@ -91,7 +91,8 @@ static void dump_thread(log_t* log, BacktraceMap* map, pid_t pid, pid_t tid) {
		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());
		}
		}

include/backtrace/Backtrace.h

+24 −0

Original line number	Diff line number	Diff line
		@@ -34,6 +34,24 @@ typedef uint64_t word_t;
		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 @@ public:

		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 @@ protected:
		bool map_shared_;

		std::vector<backtrace_frame_data_t> frames_;

		BacktraceUnwindError error_;
		};

		#endif // _BACKTRACE_BACKTRACE_H

libbacktrace/Backtrace.cpp

+21 −0

Original line number	Diff line number	Diff line
		@@ -148,3 +148,24 @@ Backtrace* Backtrace::Create(pid_t pid, pid_t tid, BacktraceMap* map) {
		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";
		}
		}

libbacktrace/BacktraceCurrent.cpp

+20 −2

Original line number	Diff line number	Diff line
		@@ -24,6 +24,8 @@
		#include <ucontext.h>
		#include <unistd.h>

		#include <stdlib.h>

		#include <string>

		#include <backtrace/Backtrace.h>
		@@ -65,9 +67,11 @@ size_t BacktraceCurrent::Read(uintptr_t addr, uint8_t* buffer, size_t bytes) {
		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 @@ bool BacktraceCurrent::UnwindThread(size_t num_ignore_frames) {
		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);
		@@ -183,8 +195,14 @@ bool BacktraceCurrent::UnwindThread(size_t num_ignore_frames) {
		BACK_LOGW("Timed out waiting for signal handler to indicate it finished.");
		}
		} else {
		// 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);

libbacktrace/BacktraceOffline.cpp

+3 −0

Original line number	Diff line number	Diff line
		@@ -129,9 +129,11 @@ static unw_accessors_t accessors = {
		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 @@ bool BacktraceOffline::Unwind(size_t num_ignore_frames, ucontext_t* context) {
		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;