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[lldb] Improve mid-function epilogue scanning for x86 #110965

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Merged
merged 1 commit into from
Oct 3, 2024
Merged

[lldb] Improve mid-function epilogue scanning for x86 #110965

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26 changes: 22 additions & 4 deletions lldb/source/Plugins/UnwindAssembly/x86/x86AssemblyInspectionEngine.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -809,7 +809,7 @@ bool x86AssemblyInspectionEngine::local_branch_p (
// Branch target is before the start of this function
return false;
}
if (offset + next_pc_value > func_range.GetByteSize()) {
if (offset + next_pc_value >= func_range.GetByteSize()) {
// Branch targets outside this function's bounds
return false;
}
Expand Down Expand Up @@ -967,6 +967,8 @@ bool x86AssemblyInspectionEngine::GetNonCallSiteUnwindPlanFromAssembly(

bool in_epilogue = false; // we're in the middle of an epilogue sequence
bool row_updated = false; // The UnwindPlan::Row 'row' has been updated
bool current_sp_offset_updated =
false; // current_sp_bytes_offset_from_fa has been updated this insn

m_cur_insn = data + current_func_text_offset;
if (!instruction_length(m_cur_insn, insn_len, size - current_func_text_offset)
Expand Down Expand Up @@ -1013,8 +1015,10 @@ bool x86AssemblyInspectionEngine::GetNonCallSiteUnwindPlanFromAssembly(
afa_value.SetUnspecified();
row_updated = true;
}
if (fa_value_ptr->GetRegisterNumber() == m_lldb_fp_regnum)
if (fa_value_ptr->GetRegisterNumber() == m_lldb_fp_regnum) {
current_sp_bytes_offset_from_fa = fa_value_ptr->GetOffset();
current_sp_offset_updated = true;
}
}

else if (mov_rbx_rsp_pattern_p()) {
Expand All @@ -1025,8 +1029,10 @@ bool x86AssemblyInspectionEngine::GetNonCallSiteUnwindPlanFromAssembly(
afa_value.SetUnspecified();
row_updated = true;
}
if (fa_value_ptr->GetRegisterNumber() == m_lldb_alt_fp_regnum)
if (fa_value_ptr->GetRegisterNumber() == m_lldb_alt_fp_regnum) {
current_sp_bytes_offset_from_fa = fa_value_ptr->GetOffset();
current_sp_offset_updated = true;
}
}

// This is the start() function (or a pthread equivalent), it starts with a
Expand All @@ -1039,6 +1045,7 @@ bool x86AssemblyInspectionEngine::GetNonCallSiteUnwindPlanFromAssembly(

else if (push_reg_p(machine_regno)) {
current_sp_bytes_offset_from_fa += m_wordsize;
current_sp_offset_updated = true;
// the PUSH instruction has moved the stack pointer - if the FA is set
// in terms of the stack pointer, we need to add a new row of
// instructions.
Expand All @@ -1064,6 +1071,7 @@ bool x86AssemblyInspectionEngine::GetNonCallSiteUnwindPlanFromAssembly(

else if (pop_reg_p(machine_regno)) {
current_sp_bytes_offset_from_fa -= m_wordsize;
current_sp_offset_updated = true;

if (nonvolatile_reg_p(machine_regno) &&
machine_regno_to_lldb_regno(machine_regno, lldb_regno) &&
Expand Down Expand Up @@ -1091,6 +1099,7 @@ bool x86AssemblyInspectionEngine::GetNonCallSiteUnwindPlanFromAssembly(

else if (pop_misc_reg_p()) {
current_sp_bytes_offset_from_fa -= m_wordsize;
current_sp_offset_updated = true;
if (fa_value_ptr->GetRegisterNumber() == m_lldb_sp_regnum) {
fa_value_ptr->SetIsRegisterPlusOffset(
m_lldb_sp_regnum, current_sp_bytes_offset_from_fa);
Expand Down Expand Up @@ -1126,6 +1135,7 @@ bool x86AssemblyInspectionEngine::GetNonCallSiteUnwindPlanFromAssembly(
}

current_sp_bytes_offset_from_fa -= m_wordsize;
current_sp_offset_updated = true;

if (fa_value_ptr->GetRegisterNumber() == m_lldb_sp_regnum) {
fa_value_ptr->SetIsRegisterPlusOffset(
Expand Down Expand Up @@ -1161,6 +1171,7 @@ bool x86AssemblyInspectionEngine::GetNonCallSiteUnwindPlanFromAssembly(

else if (sub_rsp_pattern_p(stack_offset)) {
current_sp_bytes_offset_from_fa += stack_offset;
current_sp_offset_updated = true;
if (fa_value_ptr->GetRegisterNumber() == m_lldb_sp_regnum) {
fa_value_ptr->SetOffset(current_sp_bytes_offset_from_fa);
row_updated = true;
Expand All @@ -1169,6 +1180,7 @@ bool x86AssemblyInspectionEngine::GetNonCallSiteUnwindPlanFromAssembly(

else if (add_rsp_pattern_p(stack_offset)) {
current_sp_bytes_offset_from_fa -= stack_offset;
current_sp_offset_updated = true;
if (fa_value_ptr->GetRegisterNumber() == m_lldb_sp_regnum) {
fa_value_ptr->SetOffset(current_sp_bytes_offset_from_fa);
row_updated = true;
Expand All @@ -1179,6 +1191,7 @@ bool x86AssemblyInspectionEngine::GetNonCallSiteUnwindPlanFromAssembly(
else if (push_extended_pattern_p() || push_imm_pattern_p() ||
push_misc_reg_p()) {
current_sp_bytes_offset_from_fa += m_wordsize;
current_sp_offset_updated = true;
if (fa_value_ptr->GetRegisterNumber() == m_lldb_sp_regnum) {
fa_value_ptr->SetOffset(current_sp_bytes_offset_from_fa);
row_updated = true;
Expand All @@ -1187,6 +1200,7 @@ bool x86AssemblyInspectionEngine::GetNonCallSiteUnwindPlanFromAssembly(

else if (lea_rsp_pattern_p(stack_offset)) {
current_sp_bytes_offset_from_fa -= stack_offset;
current_sp_offset_updated = true;
if (fa_value_ptr->GetRegisterNumber() == m_lldb_sp_regnum) {
fa_value_ptr->SetOffset(current_sp_bytes_offset_from_fa);
row_updated = true;
Expand All @@ -1206,6 +1220,7 @@ bool x86AssemblyInspectionEngine::GetNonCallSiteUnwindPlanFromAssembly(
if (fa_value_ptr->GetRegisterNumber() == m_lldb_fp_regnum) {
current_sp_bytes_offset_from_fa =
fa_value_ptr->GetOffset() - stack_offset;
current_sp_offset_updated = true;
}
}

Expand All @@ -1219,6 +1234,7 @@ bool x86AssemblyInspectionEngine::GetNonCallSiteUnwindPlanFromAssembly(
}
if (fa_value_ptr->GetRegisterNumber() == m_lldb_alt_fp_regnum) {
current_sp_bytes_offset_from_fa = fa_value_ptr->GetOffset() - stack_offset;
current_sp_offset_updated = true;
}
}

Expand Down Expand Up @@ -1251,6 +1267,7 @@ bool x86AssemblyInspectionEngine::GetNonCallSiteUnwindPlanFromAssembly(
row.reset(newrow);
current_sp_bytes_offset_from_fa =
prologue_completed_sp_bytes_offset_from_cfa;
current_sp_offset_updated = true;
is_aligned = prologue_completed_is_aligned;

saved_registers.clear();
Expand All @@ -1272,6 +1289,7 @@ bool x86AssemblyInspectionEngine::GetNonCallSiteUnwindPlanFromAssembly(
// global data
else if (call_next_insn_pattern_p()) {
current_sp_bytes_offset_from_fa += m_wordsize;
current_sp_offset_updated = true;
if (fa_value_ptr->GetRegisterNumber() == m_lldb_sp_regnum) {
fa_value_ptr->SetOffset(current_sp_bytes_offset_from_fa);
row_updated = true;
Expand Down Expand Up @@ -1304,7 +1322,7 @@ bool x86AssemblyInspectionEngine::GetNonCallSiteUnwindPlanFromAssembly(

// We may change the sp value without adding a new Row necessarily -- keep
// track of it either way.
if (!in_epilogue) {
if (!in_epilogue && current_sp_offset_updated) {
prologue_completed_sp_bytes_offset_from_cfa =
current_sp_bytes_offset_from_fa;
prologue_completed_is_aligned = is_aligned;
Expand Down
29 changes: 15 additions & 14 deletions lldb/unittests/UnwindAssembly/x86/Testx86AssemblyInspectionEngine.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2859,16 +2859,17 @@ TEST_F(Testx86AssemblyInspectionEngine, TestDisassemblyMidFunctionEpilogues) {

0x90, // <+18>: nop // prologue setup back

0x74, 0x7, // <+19>: je 6 <+27>
0x74, 0x8, // <+19>: je 7 <+28>
0x48, 0x83, 0xc4, 0x70, // <+21>: addq $0x70, %rsp
0x5d, // <+25>: popq %rbp
0xc3, // <+26>: retq // epilogue completed
0x90, // <+26>: nop // mid-epilogue non-epilogue
0xc3, // <+27>: retq // epilogue completed

0x90, // <+27>: nop // prologue setup back
0x90, // <+28>: nop // prologue setup back

0x48, 0x83, 0xc4, 0x70, // <+28>: addq $0x70, %rsp
0x5d, // <+32>: popq %rbp
0xc3, // <+33>: retq // epilogue completed
0x48, 0x83, 0xc4, 0x70, // <+29>: addq $0x70, %rsp
0x5d, // <+33>: popq %rbp
0xc3, // <+34>: retq // epilogue completed

};

Expand Down Expand Up @@ -2898,17 +2899,17 @@ TEST_F(Testx86AssemblyInspectionEngine, TestDisassemblyMidFunctionEpilogues) {
// Check that we've reinstated the stack frame setup
// unwind instructions after a mid-function retq
// row: CFA=ebp +8 => esp=CFA+0 eip=[CFA-8]
row_sp = unwind_plan.GetRowForFunctionOffset(27);
EXPECT_EQ(27ull, row_sp->GetOffset());
row_sp = unwind_plan.GetRowForFunctionOffset(28);
EXPECT_EQ(28ull, row_sp->GetOffset());
EXPECT_TRUE(row_sp->GetCFAValue().GetRegisterNumber() == k_ebp);
EXPECT_TRUE(row_sp->GetCFAValue().IsRegisterPlusOffset() == true);
EXPECT_EQ(wordsize * 2, row_sp->GetCFAValue().GetOffset());

// After last instruction in the function, verify that
// the stack frame has been unwound
// row: CFA=esp +4 => esp=CFA+0 eip=[CFA-4]
row_sp = unwind_plan.GetRowForFunctionOffset(33);
EXPECT_EQ(33ull, row_sp->GetOffset());
row_sp = unwind_plan.GetRowForFunctionOffset(34);
EXPECT_EQ(34ull, row_sp->GetOffset());
EXPECT_TRUE(row_sp->GetCFAValue().GetRegisterNumber() == k_esp);
EXPECT_TRUE(row_sp->GetCFAValue().IsRegisterPlusOffset() == true);
EXPECT_EQ(wordsize, row_sp->GetCFAValue().GetOffset());
Expand Down Expand Up @@ -2940,17 +2941,17 @@ TEST_F(Testx86AssemblyInspectionEngine, TestDisassemblyMidFunctionEpilogues) {
// Check that we've reinstated the stack frame setup
// unwind instructions after a mid-function retq
// row: CFA=rbp+16 => rsp=CFA+0 rip=[CFA-16]
row_sp = unwind_plan.GetRowForFunctionOffset(27);
EXPECT_EQ(27ull, row_sp->GetOffset());
row_sp = unwind_plan.GetRowForFunctionOffset(28);
EXPECT_EQ(28ull, row_sp->GetOffset());
EXPECT_TRUE(row_sp->GetCFAValue().GetRegisterNumber() == k_rbp);
EXPECT_TRUE(row_sp->GetCFAValue().IsRegisterPlusOffset() == true);
EXPECT_EQ(wordsize * 2, row_sp->GetCFAValue().GetOffset());

// After last instruction in the function, verify that
// the stack frame has been unwound
// row: CFA=rsp +8 => esp=CFA+0 rip=[CFA-8]
row_sp = unwind_plan.GetRowForFunctionOffset(33);
EXPECT_EQ(33ull, row_sp->GetOffset());
row_sp = unwind_plan.GetRowForFunctionOffset(34);
EXPECT_EQ(34ull, row_sp->GetOffset());
EXPECT_TRUE(row_sp->GetCFAValue().GetRegisterNumber() == k_rsp);
EXPECT_TRUE(row_sp->GetCFAValue().IsRegisterPlusOffset() == true);
EXPECT_EQ(wordsize, row_sp->GetCFAValue().GetOffset());
Expand Down
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