Merge "libBacktraceOffline: improve unwinding callchains." am: e1d9e7c343 am: ac7b9ea890 (efb52b83) · Commits · e / os / android_system_core

libbacktrace/BacktraceOffline.cpp

+258 −23

Original line number	Diff line number	Diff line
		@@ -195,16 +195,29 @@ bool BacktraceOffline::Unwind(size_t num_ignore_frames, ucontext_t* context) {
		ret = unw_get_reg(&cursor, UNW_REG_IP, &pc);
		if (ret < 0) {
		BACK_LOGW("Failed to read IP %d", ret);
		error_.error_code = BACKTRACE_UNWIND_ERROR_ACCESS_REG_FAILED;
		error_.error_info.regno = UNW_REG_IP;
		break;
		}
		unw_word_t sp;
		ret = unw_get_reg(&cursor, UNW_REG_SP, &sp);
		if (ret < 0) {
		BACK_LOGW("Failed to read SP %d", ret);
		error_.error_code = BACKTRACE_UNWIND_ERROR_ACCESS_REG_FAILED;
		error_.error_info.regno = UNW_REG_SP;
		break;
		}

		if (num_ignore_frames == 0) {
		backtrace_map_t map;
		FillInMap(pc, &map);
		if (map.start == 0 \|\| (map.flags & PROT_EXEC) == 0) {
		// .eh_frame and .ARM.exidx doesn't know how to unwind from instructions setting up or
		// destroying stack frames. It can lead to wrong callchains, which may contain pcs outside
		// executable mapping areas. Stop unwinding once this is detected.
		error_.error_code = BACKTRACE_UNWIND_ERROR_MAP_MISSING;
		break;
		}
		frames_.resize(num_frames + 1);
		backtrace_frame_data_t* frame = &frames_[num_frames];
		frame->num = num_frames;
		@@ -217,7 +230,7 @@ bool BacktraceOffline::Unwind(size_t num_ignore_frames, ucontext_t* context) {
		prev->stack_size = frame->sp - prev->sp;
		}
		frame->func_name = GetFunctionName(frame->pc, &frame->func_offset);
		FillInMap(frame->pc, &frame->map);
		frame->map = map;
		num_frames++;
		} else {
		num_ignore_frames--;
		@@ -235,7 +248,6 @@ bool BacktraceOffline::Unwind(size_t num_ignore_frames, ucontext_t* context) {
		break;
		}
		}

		unw_destroy_addr_space(addr_space);
		context_ = nullptr;
		return true;
		@@ -272,9 +284,14 @@ size_t BacktraceOffline::Read(uintptr_t addr, uint8_t* buffer, size_t bytes) {
		if (read_size != 0) {
		return read_size;
		}
		// In some libraries (like /system/lib64/libskia.so), some CIE entries in .eh_frame use
		// augmentation "P", which makes libunwind/libunwindstack try to read personality routine in
		// memory. However, that is not available in offline unwinding. Work around this by returning
		// all zero data.
		error_.error_code = BACKTRACE_UNWIND_ERROR_ACCESS_MEM_FAILED;
		error_.error_info.addr = addr;
		return 0;
		memset(buffer, 0, bytes);
		return bytes;
		}

		bool BacktraceOffline::FindProcInfo(unw_addr_space_t addr_space, uint64_t ip,
		@@ -309,6 +326,23 @@ bool BacktraceOffline::FindProcInfo(unw_addr_space_t addr_space, uint64_t ip,
		// entry, it thinks that an ip address hits an entry when (entry.addr <= ip < next_entry.addr).
		// To prevent ip addresses hit in .eh_frame/.debug_frame being regarded as addresses hit in
		// .ARM.exidx, we need to check .eh_frame/.debug_frame first.

		// Check .debug_frame/.gnu_debugdata before .eh_frame, because .debug_frame can unwind from
		// instructions setting up or destroying stack frames, while .eh_frame can't.
		if (!is_debug_frame_used_ && (debug_frame->has_debug_frame \|\| debug_frame->has_gnu_debugdata)) {
		is_debug_frame_used_ = true;
		unw_dyn_info_t di;
		unw_word_t segbase = map.start - debug_frame->min_vaddr;
		// TODO: http://b/32916571
		// TODO: Do it ourselves is more efficient than calling libunwind functions.
		int found = dwarf_find_debug_frame(0, &di, ip, segbase, filename.c_str(), map.start, map.end);
		if (found == 1) {
		int ret = dwarf_search_unwind_table(addr_space, ip, &di, proc_info, need_unwind_info, this);
		if (ret == 0) {
		return true;
		}
		}
		}
		if (debug_frame->has_eh_frame) {
		if (ip_vaddr >= debug_frame->eh_frame.min_func_vaddr &&
		ip_vaddr < debug_frame->text_end_vaddr) {
		@@ -338,20 +372,6 @@ bool BacktraceOffline::FindProcInfo(unw_addr_space_t addr_space, uint64_t ip,
		}
		}
		}
		if (!is_debug_frame_used_ && (debug_frame->has_debug_frame \|\| debug_frame->has_gnu_debugdata)) {
		is_debug_frame_used_ = true;
		unw_dyn_info_t di;
		unw_word_t segbase = map.start - debug_frame->min_vaddr;
		// TODO: http://b/32916571
		// TODO: Do it ourselves is more efficient than calling libunwind functions.
		int found = dwarf_find_debug_frame(0, &di, ip, segbase, filename.c_str(), map.start, map.end);
		if (found == 1) {
		int ret = dwarf_search_unwind_table(addr_space, ip, &di, proc_info, need_unwind_info, this);
		if (ret == 0) {
		return true;
		}
		}
		}

		if (debug_frame->has_arm_exidx) {
		auto& func_vaddrs = debug_frame->arm_exidx.func_vaddr_array;
		@@ -610,14 +630,14 @@ DebugFrameInfo* BacktraceOffline::GetDebugFrameInFile(const std::string& filenam
		return debug_frame;
		}

		static bool OmitEncodedValue(uint8_t encode, const uint8_t*& p) {
		static bool OmitEncodedValue(uint8_t encode, const uint8_t*& p, bool is_elf64) {
		if (encode == DW_EH_PE_omit) {
		return 0;
		}
		uint8_t format = encode & 0x0f;
		switch (format) {
		case DW_EH_PE_ptr:
		p += sizeof(unw_word_t);
		p += is_elf64 ? 8 : 4;
		break;
		case DW_EH_PE_uleb128:
		case DW_EH_PE_sleb128:
		@@ -645,7 +665,7 @@ static bool OmitEncodedValue(uint8_t encode, const uint8_t*& p) {
		}

		static bool GetFdeTableOffsetInEhFrameHdr(const std::vector<uint8_t>& data,
		uint64_t* table_offset_in_eh_frame_hdr) {
		uint64_t* table_offset_in_eh_frame_hdr, bool is_elf64) {
		const uint8_t* p = data.data();
		const uint8_t* end = p + data.size();
		if (p + 4 > end) {
		@@ -663,7 +683,8 @@ static bool GetFdeTableOffsetInEhFrameHdr(const std::vector<uint8_t>& data,
		return false;
		}

		if (!OmitEncodedValue(eh_frame_ptr_encode, p) \|\| !OmitEncodedValue(fde_count_encode, p)) {
		if (!OmitEncodedValue(eh_frame_ptr_encode, p, is_elf64) \|\|
		!OmitEncodedValue(fde_count_encode, p, is_elf64)) {
		return false;
		}
		if (p >= end) {
		@@ -673,11 +694,214 @@ static bool GetFdeTableOffsetInEhFrameHdr(const std::vector<uint8_t>& data,
		return true;
		}

		static uint64_t ReadFromBuffer(const uint8_t*& p, size_t size) {
		uint64_t result = 0;
		int shift = 0;
		while (size-- > 0) {
		uint64_t tmp = *p++;
		result \|= tmp << shift;
		shift += 8;
		}
		return result;
		}

		static uint64_t ReadSignValueFromBuffer(const uint8_t*& p, size_t size) {
		uint64_t result = 0;
		int shift = 0;
		for (size_t i = 0; i < size; ++i) {
		uint64_t tmp = *p++;
		result \|= tmp << shift;
		shift += 8;
		}
		if (*(p - 1) & 0x80) {
		result \|= (-1ULL) << (size * 8);
		}
		return result;
		}

		static const char* ReadStrFromBuffer(const uint8_t*& p) {
		const char* result = reinterpret_cast<const char*>(p);
		p += strlen(result) + 1;
		return result;
		}

		static int64_t ReadLEB128FromBuffer(const uint8_t*& p) {
		int64_t result = 0;
		int64_t tmp;
		int shift = 0;
		while (*p & 0x80) {
		tmp = *p & 0x7f;
		result \|= tmp << shift;
		shift += 7;
		p++;
		}
		tmp = *p;
		result \|= tmp << shift;
		if (*p & 0x40) {
		result \|= -((tmp & 0x40) << shift);
		}
		p++;
		return result;
		}

		static uint64_t ReadULEB128FromBuffer(const uint8_t*& p) {
		uint64_t result = 0;
		uint64_t tmp;
		int shift = 0;
		while (*p & 0x80) {
		tmp = *p & 0x7f;
		result \|= tmp << shift;
		shift += 7;
		p++;
		}
		tmp = *p;
		result \|= tmp << shift;
		p++;
		return result;
		}

		static uint64_t ReadEhEncoding(const uint8_t*& p, uint8_t encoding, bool is_elf64,
		uint64_t section_vaddr, const uint8_t* section_begin) {
		const uint8_t* init_addr = p;
		uint64_t result = 0;
		switch (encoding & 0x0f) {
		case DW_EH_PE_absptr:
		result = ReadFromBuffer(p, is_elf64 ? 8 : 4);
		break;
		case DW_EH_PE_omit:
		result = 0;
		break;
		case DW_EH_PE_uleb128:
		result = ReadULEB128FromBuffer(p);
		break;
		case DW_EH_PE_udata2:
		result = ReadFromBuffer(p, 2);
		break;
		case DW_EH_PE_udata4:
		result = ReadFromBuffer(p, 4);
		break;
		case DW_EH_PE_udata8:
		result = ReadFromBuffer(p, 8);
		break;
		case DW_EH_PE_sleb128:
		result = ReadLEB128FromBuffer(p);
		break;
		case DW_EH_PE_sdata2:
		result = ReadSignValueFromBuffer(p, 2);
		break;
		case DW_EH_PE_sdata4:
		result = ReadSignValueFromBuffer(p, 4);
		break;
		case DW_EH_PE_sdata8:
		result = ReadSignValueFromBuffer(p, 8);
		break;
		}
		switch (encoding & 0xf0) {
		case DW_EH_PE_pcrel:
		result += init_addr - section_begin + section_vaddr;
		break;
		case DW_EH_PE_datarel:
		result += section_vaddr;
		break;
		}
		return result;
		}

		static bool BuildEhFrameHdr(DebugFrameInfo* info, bool is_elf64) {
		// For each fde entry, collect its (func_vaddr, fde_vaddr) pair.
		std::vector<std::pair<uint64_t, uint64_t>> index_table;
		// Map form cie_offset to fde encoding.
		std::unordered_map<size_t, uint8_t> cie_map;
		const uint8_t* eh_frame_begin = info->eh_frame.data.data();
		const uint8_t* eh_frame_end = eh_frame_begin + info->eh_frame.data.size();
		const uint8_t* p = eh_frame_begin;
		uint64_t eh_frame_vaddr = info->eh_frame.vaddr;
		while (p < eh_frame_end) {
		const uint8_t* unit_begin = p;
		uint64_t unit_len = ReadFromBuffer(p, 4);
		size_t secbytes = 4;
		if (unit_len == 0xffffffff) {
		unit_len = ReadFromBuffer(p, 8);
		secbytes = 8;
		}
		const uint8_t* unit_end = p + unit_len;
		uint64_t cie_id = ReadFromBuffer(p, secbytes);
		if (cie_id == 0) {
		// This is a CIE.
		// Read version
		uint8_t version = *p++;
		// Read augmentation
		const char* augmentation = ReadStrFromBuffer(p);
		if (version >= 4) {
		// Read address size and segment size
		p += 2;
		}
		// Read code alignment factor
		ReadULEB128FromBuffer(p);
		// Read data alignment factor
		ReadLEB128FromBuffer(p);
		// Read return address register
		if (version == 1) {
		p++;
		} else {
		ReadULEB128FromBuffer(p);
		}
		uint8_t fde_pointer_encoding = 0;
		if (augmentation[0] == 'z') {
		// Read augmentation length.
		ReadULEB128FromBuffer(p);
		for (int i = 1; augmentation[i] != '\0'; ++i) {
		char c = augmentation[i];
		if (c == 'R') {
		fde_pointer_encoding = *p++;
		} else if (c == 'P') {
		// Read personality handler
		uint8_t encoding = *p++;
		OmitEncodedValue(encoding, p, is_elf64);
		} else if (c == 'L') {
		// Read lsda encoding
		p++;
		}
		}
		}
		cie_map[unit_begin - eh_frame_begin] = fde_pointer_encoding;
		} else {
		// This is an FDE.
		size_t cie_offset = p - secbytes - eh_frame_begin - cie_id;
		auto it = cie_map.find(cie_offset);
		if (it != cie_map.end()) {
		uint8_t fde_pointer_encoding = it->second;
		uint64_t initial_location =
		ReadEhEncoding(p, fde_pointer_encoding, is_elf64, eh_frame_vaddr, eh_frame_begin);
		uint64_t fde_vaddr = unit_begin - eh_frame_begin + eh_frame_vaddr;
		index_table.push_back(std::make_pair(initial_location, fde_vaddr));
		}
		}
		p = unit_end;
		}
		if (index_table.empty()) {
		return false;
		}
		std::sort(index_table.begin(), index_table.end());
		info->eh_frame.hdr_vaddr = 0;
		info->eh_frame.hdr_data.resize(index_table.size() * 8);
		uint32_t* ptr = reinterpret_cast<uint32_t*>(info->eh_frame.hdr_data.data());
		for (auto& pair : index_table) {
		*ptr++ = static_cast<uint32_t>(pair.first - info->eh_frame.hdr_vaddr);
		*ptr++ = static_cast<uint32_t>(pair.second - info->eh_frame.hdr_vaddr);
		}
		info->eh_frame.fde_table_offset = 0;
		info->eh_frame.min_func_vaddr = index_table[0].first;
		return true;
		}

		template <class ELFT>
		DebugFrameInfo* ReadDebugFrameFromELFFile(const llvm::object::ELFFile<ELFT>* elf) {
		DebugFrameInfo* result = new DebugFrameInfo;
		result->eh_frame.hdr_vaddr = 0;
		result->text_end_vaddr = std::numeric_limits<uint64_t>::max();

		bool is_elf64 = (elf->getHeader()->getFileClass() == llvm::ELF::ELFCLASS64);
		bool has_eh_frame_hdr = false;
		bool has_eh_frame = false;

		@@ -697,8 +921,7 @@ DebugFrameInfo* ReadDebugFrameFromELFFile(const llvm::object::ELFFile<ELFT>* elf
		data->data(), data->data() + data->size());

		uint64_t fde_table_offset;
		if (GetFdeTableOffsetInEhFrameHdr(result->eh_frame.hdr_data,
		&fde_table_offset)) {
		if (GetFdeTableOffsetInEhFrameHdr(result->eh_frame.hdr_data, &fde_table_offset, is_elf64)) {
		result->eh_frame.fde_table_offset = fde_table_offset;
		// Make sure we have at least one entry in fde_table.
		if (fde_table_offset + 2 * sizeof(int32_t) <= data->size()) {
		@@ -755,6 +978,18 @@ DebugFrameInfo* ReadDebugFrameFromELFFile(const llvm::object::ELFFile<ELFT>* elf
		}
		}

		if (has_eh_frame) {
		if (!has_eh_frame_hdr) {
		// Some libraries (like /vendor/lib64/egl/eglSubDriverAndroid.so) contain empty
		// .eh_frame_hdr.
		if (BuildEhFrameHdr(result, is_elf64)) {
		has_eh_frame_hdr = true;
		}
		}
		if (has_eh_frame_hdr) {
		result->has_eh_frame = true;
		}
		}
		if (has_eh_frame_hdr && has_eh_frame) {
		result->has_eh_frame = true;
		}

libbacktrace/backtrace_offline_test.cpp

+54 −8

Original line number	Diff line number	Diff line
		@@ -252,13 +252,41 @@ bool ReadOfflineTestData(const std::string offline_testdata_path, OfflineTestDat
		return false;
		}
		HexStringToRawData(&line[pos], &testdata->unw_context, size);
		#if defined(__arm__)
		} else if (android::base::StartsWith(line, "regs:")) {
		uint64_t pc;
		uint64_t sp;
		sscanf(line.c_str(), "regs: pc: %" SCNx64 " sp: %" SCNx64, &pc, &sp);
		testdata->unw_context.regs[13] = sp;
		testdata->unw_context.regs[15] = pc;
		std::vector<std::string> strs = android::base::Split(line.substr(6), " ");
		if (strs.size() % 2 != 0) {
		return false;
		}
		std::vector<std::pair<std::string, uint64_t>> items;
		for (size_t i = 0; i + 1 < strs.size(); i += 2) {
		if (!android::base::EndsWith(strs[i], ":")) {
		return false;
		}
		uint64_t value = std::stoul(strs[i + 1], nullptr, 16);
		items.push_back(std::make_pair(strs[i].substr(0, strs[i].size() - 1), value));
		}
		#if defined(__arm__)
		for (auto& item : items) {
		if (item.first == "sp") {
		testdata->unw_context.regs[13] = item.second;
		} else if (item.first == "pc") {
		testdata->unw_context.regs[15] = item.second;
		} else {
		return false;
		}
		}
		#elif defined(__aarch64__)
		for (auto& item : items) {
		if (item.first == "pc") {
		testdata->unw_context.uc_mcontext.pc = item.second;
		} else if (item.first == "sp") {
		testdata->unw_context.uc_mcontext.sp = item.second;
		} else if (item.first == "x29") {
		testdata->unw_context.uc_mcontext.regs[UNW_AARCH64_X29] = item.second;
		} else {
		return false;
		}
		}
		#endif
		} else if (android::base::StartsWith(line, "stack:")) {
		size_t size;
		@@ -397,8 +425,8 @@ static void LibUnwindingTest(const std::string& arch, const std::string& testdat
		std::string name = FunctionNameForAddress(vaddr_in_file, testdata.symbols);
		ASSERT_EQ(name, testdata.symbols[i].name);
		}
		ASSERT_EQ(BACKTRACE_UNWIND_ERROR_ACCESS_MEM_FAILED, backtrace->GetError().error_code);
		ASSERT_NE(0u, backtrace->GetError().error_info.addr);
		ASSERT_TRUE(backtrace->GetError().error_code == BACKTRACE_UNWIND_ERROR_ACCESS_MEM_FAILED \|\|
		backtrace->GetError().error_code == BACKTRACE_UNWIND_ERROR_MAP_MISSING);
		}

		// This test tests the situation that ranges of functions covered by .eh_frame and .ARM.exidx
		@@ -414,3 +442,21 @@ TEST(libbacktrace, offline_debug_frame_with_load_bias) {
		TEST(libbacktrace, offline_try_armexidx_after_debug_frame) {
		LibUnwindingTest("arm", "offline_testdata_for_libGLESv2_adreno", "libGLESv2_adreno.so");
		}

		TEST(libbacktrace, offline_cie_with_P_augmentation) {
		// Make sure we can unwind through functions with CIE entry containing P augmentation, which
		// makes unwinding library reading personality handler from memory. One example is
		// /system/lib64/libskia.so.
		LibUnwindingTest("arm64", "offline_testdata_for_libskia", "libskia.so");
		}

		TEST(libbacktrace, offline_empty_eh_frame_hdr) {
		// Make sure we can unwind through libraries with empty .eh_frame_hdr section. One example is
		// /vendor/lib64/egl/eglSubDriverAndroid.so.
		LibUnwindingTest("arm64", "offline_testdata_for_eglSubDriverAndroid", "eglSubDriverAndroid.so");
		}

		TEST(libbacktrace, offline_max_frames_limit) {
		// The length of callchain can reach 256 when recording an application.
		ASSERT_GE(MAX_BACKTRACE_FRAMES, 256);
		}

libbacktrace/include/backtrace/backtrace_constants.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -25,6 +25,6 @@
		// current thread of the specified pid.
		#define BACKTRACE_CURRENT_THREAD (-1)

		#define MAX_BACKTRACE_FRAMES 64
		#define MAX_BACKTRACE_FRAMES 256

		#endif // _BACKTRACE_BACKTRACE_CONSTANTS_H

libbacktrace/testdata/arm64/eglSubDriverAndroid.so

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libbacktrace/testdata/arm64/libskia.so

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+7.94 MiB

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