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Stack unwinding emulation: handle adjustment of FP 

This change is improving the instruction emulation based unwinding to
handle when the frame pointer is adjusted (increment/decrement) after
it has been initialized. The situation can occur in the prologue of
some function where FP is adjusted before it is copied back to SP.

Example code (thumb, generated by gcc 4.8):
< +0>: push  {r4, r7, lr}
< +2>: sub   sp, #0x14
< +4>: add   r7, sp, #0x0
...
<+50>: adds  r7, #0x14 ; The CL fixes the handling of this instruction
<+52>: mov   sp, r7    ; Previously unwinding from here was broken
<+54>: pop   {r4, r7, pc}

Differential revision: http://reviews.llvm.org/D17295

llvm-svn: 261318
This commit is contained in:
Tamas Berghammer 2016-02-19 10:59:25 +00:00
parent f23b23200d
commit 73bcca5b3d
1 changed files with 16 additions and 1 deletions
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17
lldb/source/Plugins/UnwindAssembly/InstEmulation/UnwindAssemblyInstEmulation.cpp
View File

@ -554,7 +554,6 @@ UnwindAssemblyInstEmulation::WriteRegister (EmulateInstruction *instruction,
case EmulateInstruction::eContextTableBranchReadMemory:
case EmulateInstruction::eContextWriteRegisterRandomBits:
case EmulateInstruction::eContextWriteMemoryRandomBits:
case EmulateInstruction::eContextArithmetic:
case EmulateInstruction::eContextAdvancePC:
case EmulateInstruction::eContextReturnFromException:
case EmulateInstruction::eContextPushRegisterOnStack:
@ -573,6 +572,22 @@ UnwindAssemblyInstEmulation::WriteRegister (EmulateInstruction *instruction,
// }
break;
case EmulateInstruction::eContextArithmetic:
{
// If we adjusted the current frame pointer by a constant then adjust the CFA offset
// with the same amount.
lldb::RegisterKind kind = m_unwind_plan_ptr->GetRegisterKind();
if (m_fp_is_cfa && reg_info->kinds[kind] == m_cfa_reg_info.kinds[kind] &&
context.info_type == EmulateInstruction::eInfoTypeRegisterPlusOffset &&
context.info.RegisterPlusOffset.reg.kinds[kind] == m_cfa_reg_info.kinds[kind])
{
const int64_t offset = context.info.RegisterPlusOffset.signed_offset;
m_curr_row->GetCFAValue().IncOffset(-1 * offset);
m_curr_row_modified = true;
}
}
break;
case EmulateInstruction::eContextAbsoluteBranchRegister:
case EmulateInstruction::eContextRelativeBranchImmediate:
{