Add a new unwind method on error.
If a function crashes by jumping into unexecutable code, the old method
could not unwind through that. Add a fallback method to set the pc from
the default return address location.
In addition, add a new finished check for steps. This will provide a method
to indicate that this step is the last step. This prevents cases where
the fallback method might be triggered incorrectly.
Update the libbacktrace code to unwind using the new methodology.
Update the unwind tool to use the new unwind methodology.
Add a new option to crasher that calls through a null function.
Create a new object, Unwinder, that encapsulates the a basic unwind. For now,
libbacktrace will still use the custom code.
Added new unit tests to cover the new cases. Also add a test that
crashes calling a nullptr as a function, and then has call frames in
the signal stack.
Bug: 65842173
Test: Pass all unit tests, verify crasher dumps properly.
Change-Id: Ia18430ab107e9f7bdf0e14a9b74710b1280bd7f4
diff --git a/libunwindstack/Unwinder.cpp b/libunwindstack/Unwinder.cpp
new file mode 100644
index 0000000..1a86e16
--- /dev/null
+++ b/libunwindstack/Unwinder.cpp
@@ -0,0 +1,145 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <elf.h>
+#include <inttypes.h>
+#include <stdint.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <android-base/stringprintf.h>
+
+#include <unwindstack/Elf.h>
+#include <unwindstack/MapInfo.h>
+#include <unwindstack/Unwinder.h>
+
+namespace unwindstack {
+
+void Unwinder::FillInFrame(MapInfo* map_info, uint64_t* rel_pc) {
+ size_t frame_num = frames_.size();
+ frames_.resize(frame_num + 1);
+ FrameData* frame = &frames_.at(frame_num);
+ frame->num = frame_num;
+ frame->pc = regs_->pc();
+ frame->sp = regs_->sp();
+ frame->rel_pc = frame->pc;
+
+ if (map_info == nullptr) {
+ return;
+ }
+
+ Elf* elf = map_info->GetElf(process_memory_, true);
+ *rel_pc = elf->GetRelPc(regs_->pc(), map_info);
+ if (frame_num != 0) {
+ // Don't adjust the first frame pc.
+ frame->rel_pc = regs_->GetAdjustedPc(*rel_pc, elf);
+
+ // Adjust the original pc.
+ frame->pc -= *rel_pc - frame->rel_pc;
+ } else {
+ frame->rel_pc = *rel_pc;
+ }
+
+ frame->map_name = map_info->name;
+ frame->map_offset = map_info->elf_offset;
+ frame->map_start = map_info->start;
+ frame->map_end = map_info->end;
+
+ if (!elf->GetFunctionName(frame->rel_pc, &frame->function_name, &frame->function_offset)) {
+ frame->function_name = "";
+ frame->function_offset = 0;
+ }
+}
+
+void Unwinder::Unwind() {
+ frames_.clear();
+
+ bool return_address_attempt = false;
+ for (; frames_.size() < max_frames_;) {
+ MapInfo* map_info = maps_->Find(regs_->pc());
+
+ uint64_t rel_pc;
+ FillInFrame(map_info, &rel_pc);
+
+ bool stepped;
+ if (map_info == nullptr) {
+ stepped = false;
+ } else {
+ bool finished;
+ stepped = map_info->elf->Step(rel_pc + map_info->elf_offset, regs_, process_memory_.get(),
+ &finished);
+ if (stepped && finished) {
+ break;
+ }
+ }
+ if (!stepped) {
+ if (return_address_attempt) {
+ // Remove the speculative frame.
+ frames_.pop_back();
+ break;
+ } else {
+ // Steping didn't work, try this secondary method.
+ if (!regs_->SetPcFromReturnAddress(process_memory_.get())) {
+ break;
+ }
+ return_address_attempt = true;
+ }
+ } else {
+ return_address_attempt = false;
+ }
+ }
+}
+
+std::string Unwinder::FormatFrame(size_t frame_num) {
+ if (frame_num >= frames_.size()) {
+ return "";
+ }
+ return FormatFrame(frames_[frame_num],
+ regs_->MachineType() == EM_ARM || regs_->MachineType() == EM_386);
+}
+
+std::string Unwinder::FormatFrame(const FrameData& frame, bool bits32) {
+ std::string data;
+
+ if (bits32) {
+ data += android::base::StringPrintf(" #%02zu pc %08" PRIx64, frame.num, frame.rel_pc);
+ } else {
+ data += android::base::StringPrintf(" #%02zu pc %016" PRIx64, frame.num, frame.rel_pc);
+ }
+
+ if (frame.map_offset != 0) {
+ data += android::base::StringPrintf(" (offset 0x%" PRIx64 ")", frame.map_offset);
+ }
+
+ if (frame.map_start == frame.map_end) {
+ // No valid map associated with this frame.
+ data += " <unknown>";
+ } else if (!frame.map_name.empty()) {
+ data += " " + frame.map_name;
+ } else {
+ data += android::base::StringPrintf(" <anonymous:%" PRIx64 ">", frame.map_start);
+ }
+ if (!frame.function_name.empty()) {
+ data += " (" + frame.function_name;
+ if (frame.function_offset != 0) {
+ data += android::base::StringPrintf("+%" PRId64, frame.function_offset);
+ }
+ data += ')';
+ }
+ return data;
+}
+
+} // namespace unwindstack