bool UnwindCurrent::UnwindFromContext(size_t num_ignore_frames, ucontext_t* ucontext) {
if (ucontext == nullptr) {
int ret = unw_getcontext(&context_);
if (ret < 0) {
BACK_LOGW("unw_getcontext failed %d", ret);
return false;
}
} else {
GetUnwContextFromUcontext(ucontext);
}
// The cursor structure is pretty large, do not put it on the stack.
std::unique_ptr<unw_cursor_t> cursor(new unw_cursor_t);
int ret = unw_init_local(cursor.get(), &context_);
if (ret < 0) {
BACK_LOGW("unw_init_local failed %d", ret);
return false;
}
size_t num_frames = 0;
do {
unw_word_t pc;
ret = unw_get_reg(cursor.get(), UNW_REG_IP, &pc);
if (ret < 0) {
BACK_LOGW("Failed to read IP %d", ret);
break;
}
unw_word_t sp;
ret = unw_get_reg(cursor.get(), UNW_REG_SP, &sp);
if (ret < 0) {
BACK_LOGW("Failed to read SP %d", ret);
break;
}
frames_.resize(num_frames+1);
backtrace_frame_data_t* frame = &frames_.at(num_frames);
frame->num = num_frames;
frame->pc = static_cast<uintptr_t>(pc);
frame->sp = static_cast<uintptr_t>(sp);
frame->stack_size = 0;
FillInMap(frame->pc, &frame->map);
// Check to see if we should skip this frame because it's coming
// from within the library, and we are doing a local unwind.
if (ucontext != nullptr || num_frames != 0 || !DiscardFrame(*frame)) {
if (num_ignore_frames == 0) {
// GetFunctionName is an expensive call, only do it if we are
// keeping the frame.
frame->func_name = GetFunctionName(frame->pc, &frame->func_offset);
if (num_frames > 0) {
// Set the stack size for the previous frame.
backtrace_frame_data_t* prev = &frames_.at(num_frames-1);
prev->stack_size = frame->sp - prev->sp;
}
num_frames++;
} else {
num_ignore_frames--;
}
}
ret = unw_step (cursor.get());
} while (ret > 0 && num_frames < MAX_BACKTRACE_FRAMES);
return true;
}
bool UnwindCurrent::UnwindFromContext(size_t num_ignore_frames, ucontext_t* ucontext) {
if (ucontext == nullptr) {
int ret = unw_getcontext(&context_);
if (ret < 0) {
BACK_LOGW("unw_getcontext failed %d", ret);
error_ = BACKTRACE_UNWIND_ERROR_SETUP_FAILED;
return false;
}
} else {
GetUnwContextFromUcontext(ucontext);
}
// The cursor structure is pretty large, do not put it on the stack.
std::unique_ptr<unw_cursor_t> cursor(new unw_cursor_t);
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;
}
initialized_ = true;
size_t num_frames = 0;
do {
unw_word_t pc;
ret = unw_get_reg(cursor.get(), UNW_REG_IP, &pc);
if (ret < 0) {
BACK_LOGW("Failed to read IP %d", ret);
break;
}
unw_word_t sp;
ret = unw_get_reg(cursor.get(), UNW_REG_SP, &sp);
if (ret < 0) {
BACK_LOGW("Failed to read SP %d", ret);
break;
}
frames_.resize(num_frames+1);
backtrace_frame_data_t* frame = &frames_.at(num_frames);
frame->num = num_frames;
frame->pc = static_cast<uintptr_t>(pc);
frame->sp = static_cast<uintptr_t>(sp);
frame->stack_size = 0;
FillInMap(frame->pc, &frame->map);
// Check to see if we should skip this frame because it's coming
// from within the library, and we are doing a local unwind.
if (ucontext != nullptr || num_frames != 0 || !DiscardFrame(*frame)) {
if (num_ignore_frames == 0) {
// GetFunctionName is an expensive call, only do it if we are
// keeping the frame.
frame->func_name = GetFunctionName(frame->pc, &frame->func_offset, &frame->map);
if (num_frames > 0) {
// Set the stack size for the previous frame.
backtrace_frame_data_t* prev = &frames_.at(num_frames-1);
prev->stack_size = frame->sp - prev->sp;
}
if (BacktraceMap::IsValid(frame->map)) {
frame->rel_pc = frame->pc - frame->map.start + frame->map.load_bias;
} else {
frame->rel_pc = frame->pc;
}
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);
}
}
// If the pc is in a device map, then don't try to step.
if (frame->map.flags & PROT_DEVICE_MAP) {
break;
}
// Verify the sp is not in a device map too.
backtrace_map_t map;
FillInMap(frame->sp, &map);
if (map.flags & PROT_DEVICE_MAP) {
break;
}
ret = unw_step (cursor.get());
} while (ret > 0 && num_frames < MAX_BACKTRACE_FRAMES);
return true;
}
