Author: Jonas Devlieghere Date: 2025-07-03T13:46:47-07:00 New Revision: 1995fd9ac6be4ff0822589f00d5fcaa12688eb87
URL: https://github.com/llvm/llvm-project/commit/1995fd9ac6be4ff0822589f00d5fcaa12688eb87 DIFF: https://github.com/llvm/llvm-project/commit/1995fd9ac6be4ff0822589f00d5fcaa12688eb87.diff LOG: [lldb] Extract DW_OP_deref evaluation code (NFC) (#146801) The DWARF expression evaluator is essentially a large state machine implemented as a switch statement. For anything but trivial operations, having the evaluation logic implemented inline is difficult to follow, especially when there are nested switches. This commit moves evaluation of `DW_OP_deref` out-of-line, similar to `Evaluate_DW_OP_entry_value`. Added: Modified: lldb/include/lldb/Expression/DWARFExpression.h lldb/source/Expression/DWARFExpression.cpp Removed: ################################################################################ diff --git a/lldb/include/lldb/Expression/DWARFExpression.h b/lldb/include/lldb/Expression/DWARFExpression.h index 0adbe3e8df2ee..37853c0b5a8fc 100644 --- a/lldb/include/lldb/Expression/DWARFExpression.h +++ b/lldb/include/lldb/Expression/DWARFExpression.h @@ -35,6 +35,8 @@ namespace lldb_private { /// location expression or a location list and interprets it. class DWARFExpression { public: + using Stack = std::vector<Value>; + class Delegate { public: Delegate() = default; @@ -53,7 +55,7 @@ class DWARFExpression { virtual bool ParseVendorDWARFOpcode(uint8_t op, const DataExtractor &opcodes, lldb::offset_t &offset, - std::vector<Value> &stack) const = 0; + Stack &stack) const = 0; Delegate(const Delegate &) = delete; Delegate &operator=(const Delegate &) = delete; diff --git a/lldb/source/Expression/DWARFExpression.cpp b/lldb/source/Expression/DWARFExpression.cpp index 2df27513a0b3f..52891fcefd68b 100644 --- a/lldb/source/Expression/DWARFExpression.cpp +++ b/lldb/source/Expression/DWARFExpression.cpp @@ -589,7 +589,7 @@ bool DWARFExpression::LinkThreadLocalStorage( return true; } -static llvm::Error Evaluate_DW_OP_entry_value(std::vector<Value> &stack, +static llvm::Error Evaluate_DW_OP_entry_value(DWARFExpression::Stack &stack, ExecutionContext *exe_ctx, RegisterContext *reg_ctx, const DataExtractor &opcodes, @@ -654,7 +654,7 @@ static llvm::Error Evaluate_DW_OP_entry_value(std::vector<Value> &stack, addr_t return_pc = LLDB_INVALID_ADDRESS; uint32_t current_frame_idx = current_frame->GetFrameIndex(); - for (uint32_t parent_frame_idx = current_frame_idx + 1;;parent_frame_idx++) { + for (uint32_t parent_frame_idx = current_frame_idx + 1;; parent_frame_idx++) { parent_frame = thread->GetStackFrameAtIndex(parent_frame_idx); // If this is null, we're at the end of the stack. if (!parent_frame) @@ -860,6 +860,66 @@ ResolveLoadAddress(ExecutionContext *exe_ctx, lldb::ModuleSP &module_sp, return load_addr; } +static llvm::Error Evaluate_DW_OP_deref(DWARFExpression::Stack &stack, + ExecutionContext *exe_ctx, + lldb::ModuleSP module_sp, + Process *process) { + if (stack.empty()) + return llvm::createStringError("expression stack empty for DW_OP_deref"); + + const Value::ValueType value_type = stack.back().GetValueType(); + switch (value_type) { + case Value::ValueType::HostAddress: { + void *src = (void *)stack.back().GetScalar().ULongLong(); + intptr_t ptr; + ::memcpy(&ptr, src, sizeof(void *)); + stack.back().GetScalar() = ptr; + stack.back().ClearContext(); + } break; + case Value::ValueType::FileAddress: { + auto file_addr = stack.back().GetScalar().ULongLong(LLDB_INVALID_ADDRESS); + Address so_addr; + auto maybe_load_addr = ResolveLoadAddress(exe_ctx, module_sp, "DW_OP_deref", + file_addr, so_addr); + if (!maybe_load_addr) + return maybe_load_addr.takeError(); + stack.back().GetScalar() = *maybe_load_addr; + // Fall through to load address promotion code below. + } + [[fallthrough]]; + case Value::ValueType::Scalar: + // Promote Scalar to LoadAddress and fall through. + stack.back().SetValueType(Value::ValueType::LoadAddress); + [[fallthrough]]; + case Value::ValueType::LoadAddress: { + if (!exe_ctx) + return llvm::createStringError("NULL execution context for DW_OP_deref"); + if (!process) + return llvm::createStringError("NULL process for DW_OP_deref"); + lldb::addr_t pointer_addr = + stack.back().GetScalar().ULongLong(LLDB_INVALID_ADDRESS); + Status error; + lldb::addr_t pointer_value = + process->ReadPointerFromMemory(pointer_addr, error); + if (pointer_value == LLDB_INVALID_ADDRESS) + return llvm::joinErrors( + llvm::createStringError( + "Failed to dereference pointer from 0x%" PRIx64 + " for DW_OP_deref", + pointer_addr), + error.takeError()); + if (ABISP abi_sp = process->GetABI()) + pointer_value = abi_sp->FixCodeAddress(pointer_value); + stack.back().GetScalar() = pointer_value; + stack.back().ClearContext(); + } break; + case Value::ValueType::Invalid: + return llvm::createStringError("invalid value type for DW_OP_deref"); + } + + return llvm::Error::success(); +} + /// Helper function to move common code used to load sized data from a uint8_t /// buffer. /// @@ -890,7 +950,8 @@ llvm::Expected<Value> DWARFExpression::Evaluate( if (opcodes.GetByteSize() == 0) return llvm::createStringError( "no location, value may have been optimized out"); - std::vector<Value> stack; + + Stack stack; Process *process = nullptr; StackFrame *frame = nullptr; @@ -1019,69 +1080,9 @@ llvm::Expected<Value> DWARFExpression::Evaluate( // retrieved from the dereferenced address is the size of an address on the // target machine. case DW_OP_deref: { - if (stack.empty()) - return llvm::createStringError( - "expression stack empty for DW_OP_deref"); - Value::ValueType value_type = stack.back().GetValueType(); - switch (value_type) { - case Value::ValueType::HostAddress: { - void *src = (void *)stack.back().GetScalar().ULongLong(); - intptr_t ptr; - ::memcpy(&ptr, src, sizeof(void *)); - stack.back().GetScalar() = ptr; - stack.back().ClearContext(); - } break; - case Value::ValueType::FileAddress: { - auto file_addr = stack.back().GetScalar().ULongLong( - LLDB_INVALID_ADDRESS); - - Address so_addr; - auto maybe_load_addr = ResolveLoadAddress( - exe_ctx, module_sp, "DW_OP_deref", file_addr, so_addr); - - if (!maybe_load_addr) - return maybe_load_addr.takeError(); - - stack.back().GetScalar() = *maybe_load_addr; - // Fall through to load address promotion code below. - } - [[fallthrough]]; - case Value::ValueType::Scalar: - // Promote Scalar to LoadAddress and fall through. - stack.back().SetValueType(Value::ValueType::LoadAddress); - [[fallthrough]]; - case Value::ValueType::LoadAddress: - if (exe_ctx) { - if (process) { - lldb::addr_t pointer_addr = - stack.back().GetScalar().ULongLong(LLDB_INVALID_ADDRESS); - Status error; - lldb::addr_t pointer_value = - process->ReadPointerFromMemory(pointer_addr, error); - if (pointer_value != LLDB_INVALID_ADDRESS) { - if (ABISP abi_sp = process->GetABI()) - pointer_value = abi_sp->FixCodeAddress(pointer_value); - stack.back().GetScalar() = pointer_value; - stack.back().ClearContext(); - } else { - return llvm::createStringError( - "Failed to dereference pointer from 0x%" PRIx64 - " for DW_OP_deref: %s\n", - pointer_addr, error.AsCString()); - } - } else { - return llvm::createStringError("NULL process for DW_OP_deref"); - } - } else { - return llvm::createStringError( - "NULL execution context for DW_OP_deref"); - } - break; - - case Value::ValueType::Invalid: - return llvm::createStringError("invalid value type for DW_OP_deref"); - } - + if (llvm::Error err = + Evaluate_DW_OP_deref(stack, exe_ctx, module_sp, process)) + return err; } break; // OPCODE: DW_OP_deref_size @@ -1966,8 +1967,7 @@ llvm::Expected<Value> DWARFExpression::Evaluate( case Value::ValueType::Scalar: { uint32_t bit_size = piece_byte_size * 8; uint32_t bit_offset = 0; - if (!scalar.ExtractBitfield( - bit_size, bit_offset)) { + if (!scalar.ExtractBitfield(bit_size, bit_offset)) { return llvm::createStringError( "unable to extract %" PRIu64 " bytes from a %" PRIu64 " byte scalar value.", @@ -2409,8 +2409,7 @@ bool DWARFExpression::MatchesOperand( return MatchUnaryOp( MatchOpType(Instruction::Operand::Type::Dereference), MatchBinaryOp(MatchOpType(Instruction::Operand::Type::Sum), - MatchRegOp(*reg), - MatchImmOp(offset)))(operand); + MatchRegOp(*reg), MatchImmOp(offset)))(operand); } else { return MatchRegOp(*reg)(operand); } _______________________________________________ lldb-commits mailing list lldb-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-commits
