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/DwarfSection.cpp b/libunwindstack/DwarfSection.cpp
index 1234eb1..8b30b76 100644
--- a/libunwindstack/DwarfSection.cpp
+++ b/libunwindstack/DwarfSection.cpp
@@ -47,7 +47,7 @@
return nullptr;
}
-bool DwarfSection::Step(uint64_t pc, Regs* regs, Memory* process_memory) {
+bool DwarfSection::Step(uint64_t pc, Regs* regs, Memory* process_memory, bool* finished) {
last_error_ = DWARF_ERROR_NONE;
const DwarfFde* fde = GetFdeFromPc(pc);
if (fde == nullptr || fde->cie == nullptr) {
@@ -62,7 +62,7 @@
}
// Now eval the actual registers.
- return Eval(fde->cie, process_memory, loc_regs, regs);
+ return Eval(fde->cie, process_memory, loc_regs, regs, finished);
}
template <typename AddressType>
@@ -92,7 +92,8 @@
template <typename AddressType>
bool DwarfSectionImpl<AddressType>::Eval(const DwarfCie* cie, Memory* regular_memory,
- const dwarf_loc_regs_t& loc_regs, Regs* regs) {
+ const dwarf_loc_regs_t& loc_regs, Regs* regs,
+ bool* finished) {
RegsImpl<AddressType>* cur_regs = reinterpret_cast<RegsImpl<AddressType>*>(regs);
if (cie->return_address_register >= cur_regs->total_regs()) {
last_error_ = DWARF_ERROR_ILLEGAL_VALUE;
@@ -224,12 +225,14 @@
// Find the return address location.
if (return_address_undefined) {
cur_regs->set_pc(0);
+ *finished = true;
} else {
cur_regs->set_pc((*cur_regs)[cie->return_address_register]);
+ *finished = false;
}
cur_regs->set_sp(cfa);
- // Stop if the cfa and pc are the same.
- return prev_cfa != cfa || prev_pc != cur_regs->pc();
+ // Return false if the unwind is not finished or the cfa and pc didn't change.
+ return *finished || prev_cfa != cfa || prev_pc != cur_regs->pc();
}
template <typename AddressType>