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LibDebug: Stub out LocListX and remove stub expression evaluator

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The expression evaluator is dead code that does nothing but crash on
all paths, as no opcodes are implemented.

Stubbing out the LocListX form fixes a crash while reading DWARF 5
debug data that contains location lists. These are just a new way
to store location expressions, and since we never implemented
expressions, we can just ignore these too.

As far as I can tell this is enough for DWARF 5 to work for us (since
we mainly just use the line tables).
This commit is contained in:
MacDue 2023-05-06 19:33:53 +01:00 committed by Andreas Kling
parent ce634957c1
commit cf79df0edb
Notes: sideshowbarker 2024-07-16 22:16:50 +09:00 
Author: https://github.com/MacDue
Commit: https://github.com/SerenityOS/serenity/commit/cf79df0edb
Pull-request: https://github.com/SerenityOS/serenity/pull/18688
Reviewed-by: https://github.com/BertalanD ✅
5 changed files with 6 additions and 84 deletions
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1
Userland/Libraries/LibDebug/CMakeLists.txt
View file

@ -7,7 +7,6 @@ set(SOURCES
Dwarf/CompilationUnit.cpp
Dwarf/DIE.cpp
Dwarf/DwarfInfo.cpp
Dwarf/Expression.cpp
Dwarf/LineProgram.cpp
ProcessInspector.cpp
StackFrameUtils.cpp

18
Userland/Libraries/LibDebug/DebugInfo.cpp
View file

@ -10,7 +10,6 @@
#include <AK/QuickSort.h>
#include <LibDebug/Dwarf/CompilationUnit.h>
#include <LibDebug/Dwarf/DwarfInfo.h>
#include <LibDebug/Dwarf/Expression.h>
namespace Debug {
@ -207,7 +206,7 @@ static ErrorOr<Optional<Dwarf::DIE>> parse_variable_type_die(Dwarf::DIE const& v
return type_die;
}
static ErrorOr<void> parse_variable_location(Dwarf::DIE const& variable_die, DebugInfo::VariableInfo& variable_info, PtraceRegisters const& regs)
static ErrorOr<void> parse_variable_location(Dwarf::DIE const& variable_die, DebugInfo::VariableInfo& variable_info, PtraceRegisters const&)
{
auto location_info = TRY(variable_die.get_attribute(Dwarf::Attribute::Location));
if (!location_info.has_value()) {
@ -219,20 +218,13 @@ static ErrorOr<void> parse_variable_location(Dwarf::DIE const& variable_die, Deb
switch (location_info.value().type()) {
case Dwarf::AttributeValue::Type::UnsignedNumber:
variable_info.location_type = DebugInfo::VariableInfo::LocationType::Address;
variable_info.location_data.address = location_info.value().as_unsigned();
break;
case Dwarf::AttributeValue::Type::DwarfExpression: {
auto expression_bytes = location_info.value().as_raw_bytes();
auto value = TRY(Dwarf::Expression::evaluate(expression_bytes, regs));
if (value.type != Dwarf::Expression::Type::None) {
VERIFY(value.type == Dwarf::Expression::Type::UnsignedInteger);
if (location_info->form() != Dwarf::AttributeDataForm::LocListX) {
variable_info.location_type = DebugInfo::VariableInfo::LocationType::Address;
variable_info.location_data.address = value.data.as_addr;
variable_info.location_data.address = location_info.value().as_unsigned();
} else {
dbgln("Warning: unsupported Dwarf 5 loclist");
}
break;
}
default:
dbgln("Warning: unhandled Dwarf location type: {}", to_underlying(location_info.value().type()));
}

1
Userland/Libraries/LibDebug/Dwarf/DwarfInfo.cpp
View file

@ -272,6 +272,7 @@ ErrorOr<AttributeValue> DwarfInfo::get_attribute_value(AttributeDataForm form, s
value.m_data.as_unsigned = index;
break;
}
case AttributeDataForm::LocListX:
case AttributeDataForm::RngListX: {
size_t index = TRY(debug_info_stream.read_value<LEB128<size_t>>());
value.m_type = AttributeValue::Type::UnsignedNumber;

33
Userland/Libraries/LibDebug/Dwarf/Expression.cpp
View file

@ -1,33 +0,0 @@
/*
* Copyright (c) 2020, Itamar S. <itamar8910@gmail.com>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include "Expression.h"
#include <AK/Format.h>
#include <AK/MemoryStream.h>
#include <sys/arch/regs.h>
namespace Debug::Dwarf::Expression {
ErrorOr<Value> evaluate(ReadonlyBytes bytes, [[maybe_unused]] PtraceRegisters const& regs)
{
FixedMemoryStream stream { bytes };
while (!stream.is_eof()) {
auto opcode = TRY(stream.read_value<u8>());
switch (static_cast<Operations>(opcode)) {
default:
dbgln("DWARF expr addr: {:p}", bytes.data());
dbgln("unsupported opcode: {}", opcode);
VERIFY_NOT_REACHED();
}
}
VERIFY_NOT_REACHED();
}
}

37
Userland/Libraries/LibDebug/Dwarf/Expression.h
View file

@ -1,37 +0,0 @@
/*
* Copyright (c) 2020, Itamar S. <itamar8910@gmail.com>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <AK/ByteBuffer.h>
#include <AK/Types.h>
struct PtraceRegisters;
namespace Debug::Dwarf::Expression {
enum class Type {
None,
UnsignedInteger,
Register,
};
struct Value {
Type type;
union {
FlatPtr as_addr;
u32 as_u32;
} data { 0 };
};
enum class Operations : u8 {
RegEbp = 0x75,
FbReg = 0x91,
};
ErrorOr<Value> evaluate(ReadonlyBytes, PtraceRegisters const&);
}