================
@@ -150,3 +158,161 @@ addr_t ArchitectureArm::GetOpcodeLoadAddress(addr_t
opcode_addr,
}
return opcode_addr & ~(1ull);
}
+
+// The ARM M-Profile Armv7-M Architecture Reference Manual
+// "Exception return behavior" describes how the processor
+// saves registers to the stack, decrements the stack pointer,
+// puts a special value in $lr, and then calls a registered
+// exception handler routine.
+//
+// Detect that special value in $lr, and if present, add
+// unwind rules for the registers that were saved above this
+// stack frame's CFA. Overwrite any register locations that
+// the current_unwindplan has for these registers; they are
+// not correct when we're invoked this way.
+UnwindPlanSP ArchitectureArm::GetArchitectureUnwindPlan(
+ Thread &thread, RegisterContextUnwind *regctx,
+ std::shared_ptr<const UnwindPlan> current_unwindplan) {
+
+ ProcessSP process_sp = thread.GetProcess();
+ if (!process_sp)
+ return {};
+
+ const ArchSpec arch = process_sp->GetTarget().GetArchitecture();
+ if (!arch.GetTriple().isArmMClass() || arch.GetAddressByteSize() != 4)
+ return {};
+
+ // Get the caller's LR value from regctx (the LR value
+ // at function entry to this function).
+ RegisterNumber ra_regnum(thread, eRegisterKindGeneric,
+ LLDB_REGNUM_GENERIC_RA);
+ uint32_t ra_regnum_lldb = ra_regnum.GetAsKind(eRegisterKindLLDB);
+
+ if (ra_regnum_lldb == LLDB_INVALID_REGNUM)
+ return {};
+
+ UnwindLLDB::ConcreteRegisterLocation regloc = {};
+ bool got_concrete_location = false;
+ if (regctx->SavedLocationForRegister(ra_regnum_lldb, regloc) ==
+ UnwindLLDB::RegisterSearchResult::eRegisterFound) {
+ got_concrete_location = true;
+ } else {
+ RegisterNumber pc_regnum(thread, eRegisterKindGeneric,
+ LLDB_REGNUM_GENERIC_PC);
+ uint32_t pc_regnum_lldb = pc_regnum.GetAsKind(eRegisterKindLLDB);
+ if (regctx->SavedLocationForRegister(pc_regnum_lldb, regloc) ==
+ UnwindLLDB::RegisterSearchResult::eRegisterFound)
+ got_concrete_location = true;
+ }
+
+ addr_t callers_return_address = LLDB_INVALID_ADDRESS;
+ if (got_concrete_location) {
+ const RegisterInfo *reg_info =
+ regctx->GetRegisterInfoAtIndex(ra_regnum_lldb);
+ if (reg_info) {
+ RegisterValue reg_value;
+ if (regctx->ReadRegisterValueFromRegisterLocation(regloc, reg_info,
+ reg_value)) {
+ callers_return_address = reg_value.GetAsUInt32();
+ }
+ }
+ }
+
+ if (callers_return_address == LLDB_INVALID_ADDRESS)
+ return {};
+
+ if (callers_return_address != 0xFFFFFFF1 &&
+ callers_return_address != 0xFFFFFFF9 &&
+ callers_return_address != 0xFFFFFFFD &&
+ callers_return_address != 0xFFFFFFE1 &&
+ callers_return_address != 0xFFFFFFE9 &&
+ callers_return_address != 0xFFFFFFED)
+ return {};
+
+ const RegisterKind plan_regkind = current_unwindplan->GetRegisterKind();
+ UnwindPlanSP new_plan = std::make_shared<UnwindPlan>(plan_regkind);
+ new_plan->SetSourceName("Arm Cortex-M exception return UnwindPlan");
+ new_plan->SetSourcedFromCompiler(eLazyBoolNo);
+ new_plan->SetUnwindPlanValidAtAllInstructions(eLazyBoolYes);
+ new_plan->SetUnwindPlanForSignalTrap(eLazyBoolYes);
+
+ // bit 4 will be 1 if only the general purpose registers were saved.
+ // bit 4 will be 0 if the GPRs + floating point registers were saved.
+ const bool fp_regs_saved = (callers_return_address & 0x10) == 0;
+
+ int stored_regs_size = 0x20;
----------------
DavidSpickett wrote:
int stored_regs_size = fp_regs_saved ? 0x68 : 0x20;
I don't mind the if style if it's like:
```
int a = 1;
if b:
a += 99;
```
But when it's two different constants the ternary is neater.
https://github.com/llvm/llvm-project/pull/153922
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