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llvm-mirror/lib/DebugInfo/DWARF/DWARFExpression.cpp
Soham Dixit 2186304c09 [DebugInfo] Bug 41152 - Improve dumping of empty location expressions 
Fixes PR41152 (https://bugs.llvm.org/show_bug.cgi?id=41152).

Reviewed by: jhenderson, dblaikie, SouraVX

Differential Revision: https://reviews.llvm.org/D103502
2021-06-29 09:21:00 +01:00

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//===-- DWARFExpression.cpp -----------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "llvm/DebugInfo/DWARF/DWARFExpression.h"
#include "llvm/DebugInfo/DWARF/DWARFUnit.h"
#include "llvm/MC/MCRegisterInfo.h"
#include "llvm/Support/Format.h"
#include <cassert>
#include <cstdint>
#include <vector>
using namespace llvm;
using namespace dwarf;
namespace llvm {
typedef std::vector<DWARFExpression::Operation::Description> DescVector;
static DescVector getDescriptions() {
DescVector Descriptions;
typedef DWARFExpression::Operation Op;
typedef Op::Description Desc;
Descriptions.resize(0xff);
Descriptions[DW_OP_addr] = Desc(Op::Dwarf2, Op::SizeAddr);
Descriptions[DW_OP_deref] = Desc(Op::Dwarf2);
Descriptions[DW_OP_const1u] = Desc(Op::Dwarf2, Op::Size1);
Descriptions[DW_OP_const1s] = Desc(Op::Dwarf2, Op::SignedSize1);
Descriptions[DW_OP_const2u] = Desc(Op::Dwarf2, Op::Size2);
Descriptions[DW_OP_const2s] = Desc(Op::Dwarf2, Op::SignedSize2);
Descriptions[DW_OP_const4u] = Desc(Op::Dwarf2, Op::Size4);
Descriptions[DW_OP_const4s] = Desc(Op::Dwarf2, Op::SignedSize4);
Descriptions[DW_OP_const8u] = Desc(Op::Dwarf2, Op::Size8);
Descriptions[DW_OP_const8s] = Desc(Op::Dwarf2, Op::SignedSize8);
Descriptions[DW_OP_constu] = Desc(Op::Dwarf2, Op::SizeLEB);
Descriptions[DW_OP_consts] = Desc(Op::Dwarf2, Op::SignedSizeLEB);
Descriptions[DW_OP_dup] = Desc(Op::Dwarf2);
Descriptions[DW_OP_drop] = Desc(Op::Dwarf2);
Descriptions[DW_OP_over] = Desc(Op::Dwarf2);
Descriptions[DW_OP_pick] = Desc(Op::Dwarf2, Op::Size1);
Descriptions[DW_OP_swap] = Desc(Op::Dwarf2);
Descriptions[DW_OP_rot] = Desc(Op::Dwarf2);
Descriptions[DW_OP_xderef] = Desc(Op::Dwarf2);
Descriptions[DW_OP_abs] = Desc(Op::Dwarf2);
Descriptions[DW_OP_and] = Desc(Op::Dwarf2);
Descriptions[DW_OP_div] = Desc(Op::Dwarf2);
Descriptions[DW_OP_minus] = Desc(Op::Dwarf2);
Descriptions[DW_OP_mod] = Desc(Op::Dwarf2);
Descriptions[DW_OP_mul] = Desc(Op::Dwarf2);
Descriptions[DW_OP_neg] = Desc(Op::Dwarf2);
Descriptions[DW_OP_not] = Desc(Op::Dwarf2);
Descriptions[DW_OP_or] = Desc(Op::Dwarf2);
Descriptions[DW_OP_plus] = Desc(Op::Dwarf2);
Descriptions[DW_OP_plus_uconst] = Desc(Op::Dwarf2, Op::SizeLEB);
Descriptions[DW_OP_shl] = Desc(Op::Dwarf2);
Descriptions[DW_OP_shr] = Desc(Op::Dwarf2);
Descriptions[DW_OP_shra] = Desc(Op::Dwarf2);
Descriptions[DW_OP_xor] = Desc(Op::Dwarf2);
Descriptions[DW_OP_skip] = Desc(Op::Dwarf2, Op::SignedSize2);
Descriptions[DW_OP_bra] = Desc(Op::Dwarf2, Op::SignedSize2);
Descriptions[DW_OP_eq] = Desc(Op::Dwarf2);
Descriptions[DW_OP_ge] = Desc(Op::Dwarf2);
Descriptions[DW_OP_gt] = Desc(Op::Dwarf2);
Descriptions[DW_OP_le] = Desc(Op::Dwarf2);
Descriptions[DW_OP_lt] = Desc(Op::Dwarf2);
Descriptions[DW_OP_ne] = Desc(Op::Dwarf2);
for (uint16_t LA = DW_OP_lit0; LA <= DW_OP_lit31; ++LA)
Descriptions[LA] = Desc(Op::Dwarf2);
for (uint16_t LA = DW_OP_reg0; LA <= DW_OP_reg31; ++LA)
Descriptions[LA] = Desc(Op::Dwarf2);
for (uint16_t LA = DW_OP_breg0; LA <= DW_OP_breg31; ++LA)
Descriptions[LA] = Desc(Op::Dwarf2, Op::SignedSizeLEB);
Descriptions[DW_OP_regx] = Desc(Op::Dwarf2, Op::SizeLEB);
Descriptions[DW_OP_fbreg] = Desc(Op::Dwarf2, Op::SignedSizeLEB);
Descriptions[DW_OP_bregx] = Desc(Op::Dwarf2, Op::SizeLEB, Op::SignedSizeLEB);
Descriptions[DW_OP_piece] = Desc(Op::Dwarf2, Op::SizeLEB);
Descriptions[DW_OP_deref_size] = Desc(Op::Dwarf2, Op::Size1);
Descriptions[DW_OP_xderef_size] = Desc(Op::Dwarf2, Op::Size1);
Descriptions[DW_OP_nop] = Desc(Op::Dwarf2);
Descriptions[DW_OP_push_object_address] = Desc(Op::Dwarf3);
Descriptions[DW_OP_call2] = Desc(Op::Dwarf3, Op::Size2);
Descriptions[DW_OP_call4] = Desc(Op::Dwarf3, Op::Size4);
Descriptions[DW_OP_call_ref] = Desc(Op::Dwarf3, Op::SizeRefAddr);
Descriptions[DW_OP_form_tls_address] = Desc(Op::Dwarf3);
Descriptions[DW_OP_call_frame_cfa] = Desc(Op::Dwarf3);
Descriptions[DW_OP_bit_piece] = Desc(Op::Dwarf3, Op::SizeLEB, Op::SizeLEB);
Descriptions[DW_OP_implicit_value] =
Desc(Op::Dwarf3, Op::SizeLEB, Op::SizeBlock);
Descriptions[DW_OP_stack_value] = Desc(Op::Dwarf3);
Descriptions[DW_OP_WASM_location] =
Desc(Op::Dwarf4, Op::SizeLEB, Op::WasmLocationArg);
Descriptions[DW_OP_GNU_push_tls_address] = Desc(Op::Dwarf3);
Descriptions[DW_OP_addrx] = Desc(Op::Dwarf4, Op::SizeLEB);
Descriptions[DW_OP_GNU_addr_index] = Desc(Op::Dwarf4, Op::SizeLEB);
Descriptions[DW_OP_GNU_const_index] = Desc(Op::Dwarf4, Op::SizeLEB);
Descriptions[DW_OP_GNU_entry_value] = Desc(Op::Dwarf4, Op::SizeLEB);
Descriptions[DW_OP_convert] = Desc(Op::Dwarf5, Op::BaseTypeRef);
Descriptions[DW_OP_entry_value] = Desc(Op::Dwarf5, Op::SizeLEB);
Descriptions[DW_OP_regval_type] =
Desc(Op::Dwarf5, Op::SizeLEB, Op::BaseTypeRef);
return Descriptions;
}
static DWARFExpression::Operation::Description getOpDesc(unsigned OpCode) {
// FIXME: Make this constexpr once all compilers are smart enough to do it.
static DescVector Descriptions = getDescriptions();
// Handle possible corrupted or unsupported operation.
if (OpCode >= Descriptions.size())
return {};
return Descriptions[OpCode];
}
bool DWARFExpression::Operation::extract(DataExtractor Data,
uint8_t AddressSize, uint64_t Offset,
Optional<DwarfFormat> Format) {
EndOffset = Offset;
Opcode = Data.getU8(&Offset);
Desc = getOpDesc(Opcode);
if (Desc.Version == Operation::DwarfNA)
return false;
for (unsigned Operand = 0; Operand < 2; ++Operand) {
unsigned Size = Desc.Op[Operand];
unsigned Signed = Size & Operation::SignBit;
if (Size == Operation::SizeNA)
break;
switch (Size & ~Operation::SignBit) {
case Operation::Size1:
Operands[Operand] = Data.getU8(&Offset);
if (Signed)
Operands[Operand] = (int8_t)Operands[Operand];
break;
case Operation::Size2:
Operands[Operand] = Data.getU16(&Offset);
if (Signed)
Operands[Operand] = (int16_t)Operands[Operand];
break;
case Operation::Size4:
Operands[Operand] = Data.getU32(&Offset);
if (Signed)
Operands[Operand] = (int32_t)Operands[Operand];
break;
case Operation::Size8:
Operands[Operand] = Data.getU64(&Offset);
break;
case Operation::SizeAddr:
Operands[Operand] = Data.getUnsigned(&Offset, AddressSize);
break;
case Operation::SizeRefAddr:
if (!Format)
return false;
Operands[Operand] =
Data.getUnsigned(&Offset, dwarf::getDwarfOffsetByteSize(*Format));
break;
case Operation::SizeLEB:
if (Signed)
Operands[Operand] = Data.getSLEB128(&Offset);
else
Operands[Operand] = Data.getULEB128(&Offset);
break;
case Operation::BaseTypeRef:
Operands[Operand] = Data.getULEB128(&Offset);
break;
case Operation::WasmLocationArg:
assert(Operand == 1);
switch (Operands[0]) {
case 0:
case 1:
case 2:
case 4:
Operands[Operand] = Data.getULEB128(&Offset);
break;
case 3: // global as uint32
Operands[Operand] = Data.getU32(&Offset);
break;
default:
return false; // Unknown Wasm location
}
break;
case Operation::SizeBlock:
// We need a size, so this cannot be the first operand
if (Operand == 0)
return false;
// Store the offset of the block as the value.
Operands[Operand] = Offset;
Offset += Operands[Operand - 1];
break;
default:
llvm_unreachable("Unknown DWARFExpression Op size");
}
OperandEndOffsets[Operand] = Offset;
}
EndOffset = Offset;
return true;
}
static void prettyPrintBaseTypeRef(DWARFUnit *U, raw_ostream &OS,
DIDumpOptions DumpOpts, uint64_t Operands[2],
unsigned Operand) {
assert(Operand < 2 && "operand out of bounds");
auto Die = U->getDIEForOffset(U->getOffset() + Operands[Operand]);
if (Die && Die.getTag() == dwarf::DW_TAG_base_type) {
OS << " (";
if (DumpOpts.Verbose)
OS << format("0x%08" PRIx64 " -> ", Operands[Operand]);
OS << format("0x%08" PRIx64 ")", U->getOffset() + Operands[Operand]);
if (auto Name = Die.find(dwarf::DW_AT_name))
OS << " \"" << Name->getAsCString() << "\"";
} else {
OS << format(" <invalid base_type ref: 0x%" PRIx64 ">",
Operands[Operand]);
}
}
static bool prettyPrintRegisterOp(DWARFUnit *U, raw_ostream &OS,
DIDumpOptions DumpOpts, uint8_t Opcode,
uint64_t Operands[2],
const MCRegisterInfo *MRI, bool isEH) {
if (!MRI)
return false;
uint64_t DwarfRegNum;
unsigned OpNum = 0;
if (Opcode == DW_OP_bregx || Opcode == DW_OP_regx ||
Opcode == DW_OP_regval_type)
DwarfRegNum = Operands[OpNum++];
else if (Opcode >= DW_OP_breg0 && Opcode < DW_OP_bregx)
DwarfRegNum = Opcode - DW_OP_breg0;
else
DwarfRegNum = Opcode - DW_OP_reg0;
if (Optional<unsigned> LLVMRegNum = MRI->getLLVMRegNum(DwarfRegNum, isEH)) {
if (const char *RegName = MRI->getName(*LLVMRegNum)) {
if ((Opcode >= DW_OP_breg0 && Opcode <= DW_OP_breg31) ||
Opcode == DW_OP_bregx)
OS << format(" %s%+" PRId64, RegName, Operands[OpNum]);
else
OS << ' ' << RegName;
if (Opcode == DW_OP_regval_type)
prettyPrintBaseTypeRef(U, OS, DumpOpts, Operands, 1);
return true;
}
}
return false;
}
bool DWARFExpression::Operation::print(raw_ostream &OS, DIDumpOptions DumpOpts,
const DWARFExpression *Expr,
const MCRegisterInfo *RegInfo,
DWARFUnit *U, bool isEH) {
if (Error) {
OS << "<decoding error>";
return false;
}
StringRef Name = OperationEncodingString(Opcode);
assert(!Name.empty() && "DW_OP has no name!");
OS << Name;
if ((Opcode >= DW_OP_breg0 && Opcode <= DW_OP_breg31) ||
(Opcode >= DW_OP_reg0 && Opcode <= DW_OP_reg31) ||
Opcode == DW_OP_bregx || Opcode == DW_OP_regx ||
Opcode == DW_OP_regval_type)
if (prettyPrintRegisterOp(U, OS, DumpOpts, Opcode, Operands, RegInfo, isEH))
return true;
for (unsigned Operand = 0; Operand < 2; ++Operand) {
unsigned Size = Desc.Op[Operand];
unsigned Signed = Size & Operation::SignBit;
if (Size == Operation::SizeNA)
break;
if (Size == Operation::BaseTypeRef && U) {
// For DW_OP_convert the operand may be 0 to indicate that conversion to
// the generic type should be done. The same holds for DW_OP_reinterpret,
// which is currently not supported.
if (Opcode == DW_OP_convert && Operands[Operand] == 0)
OS << " 0x0";
else
prettyPrintBaseTypeRef(U, OS, DumpOpts, Operands, Operand);
} else if (Size == Operation::WasmLocationArg) {
assert(Operand == 1);
switch (Operands[0]) {
case 0:
case 1:
case 2:
case 3: // global as uint32
case 4:
OS << format(" 0x%" PRIx64, Operands[Operand]);
break;
default: assert(false);
}
} else if (Size == Operation::SizeBlock) {
uint64_t Offset = Operands[Operand];
for (unsigned i = 0; i < Operands[Operand - 1]; ++i)
OS << format(" 0x%02x", Expr->Data.getU8(&Offset));
} else {
if (Signed)
OS << format(" %+" PRId64, (int64_t)Operands[Operand]);
else if (Opcode != DW_OP_entry_value &&
Opcode != DW_OP_GNU_entry_value)
OS << format(" 0x%" PRIx64, Operands[Operand]);
}
}
return true;
}
void DWARFExpression::print(raw_ostream &OS, DIDumpOptions DumpOpts,
const MCRegisterInfo *RegInfo, DWARFUnit *U,
bool IsEH) const {
uint32_t EntryValExprSize = 0;
uint64_t EntryValStartOffset = 0;
if (Data.getData().empty())
OS << "<empty>";
for (auto &Op : *this) {
if (!Op.print(OS, DumpOpts, this, RegInfo, U, IsEH)) {
uint64_t FailOffset = Op.getEndOffset();
while (FailOffset < Data.getData().size())
OS << format(" %02x", Data.getU8(&FailOffset));
return;
}
if (Op.getCode() == DW_OP_entry_value ||
Op.getCode() == DW_OP_GNU_entry_value) {
OS << "(";
EntryValExprSize = Op.getRawOperand(0);
EntryValStartOffset = Op.getEndOffset();
continue;
}
if (EntryValExprSize) {
EntryValExprSize -= Op.getEndOffset() - EntryValStartOffset;
if (EntryValExprSize == 0)
OS << ")";
}
if (Op.getEndOffset() < Data.getData().size())
OS << ", ";
}
}
bool DWARFExpression::Operation::verify(DWARFUnit *U) {
for (unsigned Operand = 0; Operand < 2; ++Operand) {
unsigned Size = Desc.Op[Operand];
if (Size == Operation::SizeNA)
break;
if (Size == Operation::BaseTypeRef) {
// For DW_OP_convert the operand may be 0 to indicate that conversion to
// the generic type should be done, so don't look up a base type in that
// case. The same holds for DW_OP_reinterpret, which is currently not
// supported.
if (Opcode == DW_OP_convert && Operands[Operand] == 0)
continue;
auto Die = U->getDIEForOffset(U->getOffset() + Operands[Operand]);
if (!Die || Die.getTag() != dwarf::DW_TAG_base_type) {
Error = true;
return false;
}
}
}
return true;
}
bool DWARFExpression::verify(DWARFUnit *U) {
for (auto &Op : *this)
if (!Op.verify(U))
return false;
return true;
}
/// A user-facing string representation of a DWARF expression. This might be an
/// Address expression, in which case it will be implicitly dereferenced, or a
/// Value expression.
struct PrintedExpr {
enum ExprKind {
Address,
Value,
};
ExprKind Kind;
SmallString<16> String;
PrintedExpr(ExprKind K = Address) : Kind(K) {}
};
static bool printCompactDWARFExpr(raw_ostream &OS, DWARFExpression::iterator I,
const DWARFExpression::iterator E,
const MCRegisterInfo &MRI) {
SmallVector<PrintedExpr, 4> Stack;
while (I != E) {
DWARFExpression::Operation &Op = *I;
uint8_t Opcode = Op.getCode();
switch (Opcode) {
case dwarf::DW_OP_regx: {
// DW_OP_regx: A register, with the register num given as an operand.
// Printed as the plain register name.
uint64_t DwarfRegNum = Op.getRawOperand(0);
Optional<unsigned> LLVMRegNum = MRI.getLLVMRegNum(DwarfRegNum, false);
if (!LLVMRegNum) {
OS << "<unknown register " << DwarfRegNum << ">";
return false;
}
raw_svector_ostream S(Stack.emplace_back(PrintedExpr::Value).String);
S << MRI.getName(*LLVMRegNum);
break;
}
case dwarf::DW_OP_bregx: {
int DwarfRegNum = Op.getRawOperand(0);
int64_t Offset = Op.getRawOperand(1);
Optional<unsigned> LLVMRegNum = MRI.getLLVMRegNum(DwarfRegNum, false);
if (!LLVMRegNum) {
OS << "<unknown register " << DwarfRegNum << ">";
return false;
}
raw_svector_ostream S(Stack.emplace_back().String);
S << MRI.getName(*LLVMRegNum);
if (Offset)
S << format("%+" PRId64, Offset);
break;
}
case dwarf::DW_OP_entry_value:
case dwarf::DW_OP_GNU_entry_value: {
// DW_OP_entry_value contains a sub-expression which must be rendered
// separately.
uint64_t SubExprLength = Op.getRawOperand(0);
DWARFExpression::iterator SubExprEnd = I.skipBytes(SubExprLength);
++I;
raw_svector_ostream S(Stack.emplace_back().String);
S << "entry(";
printCompactDWARFExpr(S, I, SubExprEnd, MRI);
S << ")";
I = SubExprEnd;
continue;
}
case dwarf::DW_OP_stack_value: {
// The top stack entry should be treated as the actual value of tne
// variable, rather than the address of the variable in memory.
assert(!Stack.empty());
Stack.back().Kind = PrintedExpr::Value;
break;
}
default:
if (Opcode >= dwarf::DW_OP_reg0 && Opcode <= dwarf::DW_OP_reg31) {
// DW_OP_reg<N>: A register, with the register num implied by the
// opcode. Printed as the plain register name.
uint64_t DwarfRegNum = Opcode - dwarf::DW_OP_reg0;
Optional<unsigned> LLVMRegNum = MRI.getLLVMRegNum(DwarfRegNum, false);
if (!LLVMRegNum) {
OS << "<unknown register " << DwarfRegNum << ">";
return false;
}
raw_svector_ostream S(Stack.emplace_back(PrintedExpr::Value).String);
S << MRI.getName(*LLVMRegNum);
} else if (Opcode >= dwarf::DW_OP_breg0 &&
Opcode <= dwarf::DW_OP_breg31) {
int DwarfRegNum = Opcode - dwarf::DW_OP_breg0;
int64_t Offset = Op.getRawOperand(0);
Optional<unsigned> LLVMRegNum = MRI.getLLVMRegNum(DwarfRegNum, false);
if (!LLVMRegNum) {
OS << "<unknown register " << DwarfRegNum << ">";
return false;
}
raw_svector_ostream S(Stack.emplace_back().String);
S << MRI.getName(*LLVMRegNum);
if (Offset)
S << format("%+" PRId64, Offset);
} else {
// If we hit an unknown operand, we don't know its effect on the stack,
// so bail out on the whole expression.
OS << "<unknown op " << dwarf::OperationEncodingString(Opcode) << " ("
<< (int)Opcode << ")>";
return false;
}
break;
}
++I;
}
assert(Stack.size() == 1 && "expected one value on stack");
if (Stack.front().Kind == PrintedExpr::Address)
OS << "[" << Stack.front().String << "]";
else
OS << Stack.front().String;
return true;
}
bool DWARFExpression::printCompact(raw_ostream &OS, const MCRegisterInfo &MRI) {
return printCompactDWARFExpr(OS, begin(), end(), MRI);
}
bool DWARFExpression::operator==(const DWARFExpression &RHS) const {
if (AddressSize != RHS.AddressSize || Format != RHS.Format)
return false;
return Data.getData() == RHS.Data.getData();
}
} // namespace llvm
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