Small behavioral changes to the unwinder.
- Be a little more lenient when reading the cies/fdes. If next entry data
winds up incorrect, don't fail, simply stop processing the entries. This
only applies when reading all of the cies/fdes at once.
- Fail to init an eh_frame with no entries and fallback to assuming the
eh_frame has no header instead.
- Change the step to always try debug_frame first which has the most
accurate information.
- Add small unit tests and a couple of offline unit tests to verify
this behavior.
These changes are needed to support offline unwinding since it depends
on this new behavior.
Bug: 65682279
Test: Ran new unit tests.
Change-Id: I3529f1b0c8e14cd7409494e5de2f3c9e78d0855e
diff --git a/libunwindstack/ElfInterface.cpp b/libunwindstack/ElfInterface.cpp
index 0e3ab2c..17cc16a 100644
--- a/libunwindstack/ElfInterface.cpp
+++ b/libunwindstack/ElfInterface.cpp
@@ -126,22 +126,26 @@
if (eh_frame_hdr_offset_ != 0) {
eh_frame_.reset(new DwarfEhFrameWithHdr<AddressType>(memory_));
if (!eh_frame_->Init(eh_frame_hdr_offset_, eh_frame_hdr_size_)) {
- // Even if the eh_frame_offset_ is non-zero, do not bother
- // trying to read that since something has gone wrong.
eh_frame_.reset(nullptr);
- eh_frame_hdr_offset_ = 0;
- eh_frame_hdr_size_ = static_cast<uint64_t>(-1);
}
- } else if (eh_frame_offset_ != 0) {
- // If there is a eh_frame section without a eh_frame_hdr section.
+ }
+
+ if (eh_frame_.get() == nullptr && eh_frame_offset_ != 0) {
+ // If there is an eh_frame section without an eh_frame_hdr section,
+ // or using the frame hdr object failed to init.
eh_frame_.reset(new DwarfEhFrame<AddressType>(memory_));
if (!eh_frame_->Init(eh_frame_offset_, eh_frame_size_)) {
eh_frame_.reset(nullptr);
- eh_frame_offset_ = 0;
- eh_frame_size_ = static_cast<uint64_t>(-1);
}
}
+ if (eh_frame_.get() == nullptr) {
+ eh_frame_hdr_offset_ = 0;
+ eh_frame_hdr_size_ = static_cast<uint64_t>(-1);
+ eh_frame_offset_ = 0;
+ eh_frame_size_ = static_cast<uint64_t>(-1);
+ }
+
if (debug_frame_offset_ != 0) {
debug_frame_.reset(new DwarfDebugFrame<AddressType>(memory_));
if (!debug_frame_->Init(debug_frame_offset_, debug_frame_size_)) {
@@ -436,15 +440,16 @@
}
uint64_t adjusted_pc = pc - load_bias;
- // Try the eh_frame first.
- DwarfSection* eh_frame = eh_frame_.get();
- if (eh_frame != nullptr && eh_frame->Step(adjusted_pc, regs, process_memory, finished)) {
+ // Try the debug_frame first since it contains the most specific unwind
+ // information.
+ DwarfSection* debug_frame = debug_frame_.get();
+ if (debug_frame != nullptr && debug_frame->Step(adjusted_pc, regs, process_memory, finished)) {
return true;
}
- // Try the debug_frame next.
- DwarfSection* debug_frame = debug_frame_.get();
- if (debug_frame != nullptr && debug_frame->Step(adjusted_pc, regs, process_memory, finished)) {
+ // Try the eh_frame next.
+ DwarfSection* eh_frame = eh_frame_.get();
+ if (eh_frame != nullptr && eh_frame->Step(adjusted_pc, regs, process_memory, finished)) {
return true;
}