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/*
* Copyright (C) 2015 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef ART_LIBELFFILE_DWARF_DEBUG_LINE_OPCODE_WRITER_H_
#define ART_LIBELFFILE_DWARF_DEBUG_LINE_OPCODE_WRITER_H_
#include <cstdint>
#include "dwarf/dwarf_constants.h"
#include "dwarf/writer.h"
namespace art {
namespace dwarf {
// Writer for the .debug_line opcodes (DWARF-3).
// The writer is very light-weight, however it will do the following for you:
// * Choose the most compact encoding of a given opcode.
// * Keep track of current state and convert absolute values to deltas.
// * Divide by header-defined factors as appropriate.
template<typename Vector = std::vector<uint8_t>>
class DebugLineOpCodeWriter final : private Writer<Vector> {
static_assert(std::is_same<typename Vector::value_type, uint8_t>::value, "Invalid value type");
public:
static constexpr int kOpcodeBase = 13;
static constexpr bool kDefaultIsStmt = false;
static constexpr int kLineBase = -5;
static constexpr int kLineRange = 14;
void AddRow() {
this->PushUint8(DW_LNS_copy);
}
void AdvancePC(uint64_t absolute_address) {
DCHECK_NE(current_address_, 0u); // Use SetAddress for the first advance.
DCHECK_GE(absolute_address, current_address_);
if (absolute_address != current_address_) {
uint64_t delta = FactorCodeOffset(absolute_address - current_address_);
if (delta <= INT32_MAX) {
this->PushUint8(DW_LNS_advance_pc);
this->PushUleb128(static_cast<int>(delta));
current_address_ = absolute_address;
} else {
SetAddress(absolute_address);
}
}
}
void AdvanceLine(int absolute_line) {
int delta = absolute_line - current_line_;
if (delta != 0) {
this->PushUint8(DW_LNS_advance_line);
this->PushSleb128(delta);
current_line_ = absolute_line;
}
}
void SetFile(int file) {
if (current_file_ != file) {
this->PushUint8(DW_LNS_set_file);
this->PushUleb128(file);
current_file_ = file;
}
}
void SetColumn(int column) {
this->PushUint8(DW_LNS_set_column);
this->PushUleb128(column);
}
void SetIsStmt(bool is_stmt) {
if (is_stmt_ != is_stmt) {
this->PushUint8(DW_LNS_negate_stmt);
is_stmt_ = is_stmt;
}
}
void SetBasicBlock() {
this->PushUint8(DW_LNS_set_basic_block);
}
void SetPrologueEnd() {
uses_dwarf3_features_ = true;
this->PushUint8(DW_LNS_set_prologue_end);
}
void SetEpilogueBegin() {
uses_dwarf3_features_ = true;
this->PushUint8(DW_LNS_set_epilogue_begin);
}
void SetISA(int isa) {
uses_dwarf3_features_ = true;
this->PushUint8(DW_LNS_set_isa);
this->PushUleb128(isa);
}
void EndSequence() {
this->PushUint8(0);
this->PushUleb128(1);
this->PushUint8(DW_LNE_end_sequence);
current_address_ = 0;
current_file_ = 1;
current_line_ = 1;
is_stmt_ = kDefaultIsStmt;
}
// Uncoditionally set address using the long encoding.
// This gives the linker opportunity to relocate the address.
void SetAddress(uint64_t absolute_address) {
DCHECK_GE(absolute_address, current_address_);
FactorCodeOffset(absolute_address); // Check if it is factorable.
this->PushUint8(0);
if (use_64bit_address_) {
this->PushUleb128(1 + 8);
this->PushUint8(DW_LNE_set_address);
patch_locations_.push_back(this->data()->size());
this->PushUint64(absolute_address);
} else {
this->PushUleb128(1 + 4);
this->PushUint8(DW_LNE_set_address);
patch_locations_.push_back(this->data()->size());
this->PushUint32(absolute_address);
}
current_address_ = absolute_address;
}
void DefineFile(const char* filename,
int directory_index,
int modification_time,
int file_size) {
int size = 1 +
strlen(filename) + 1 +
UnsignedLeb128Size(directory_index) +
UnsignedLeb128Size(modification_time) +
UnsignedLeb128Size(file_size);
this->PushUint8(0);
this->PushUleb128(size);
size_t start = data()->size();
this->PushUint8(DW_LNE_define_file);
this->PushString(filename);
this->PushUleb128(directory_index);
this->PushUleb128(modification_time);
this->PushUleb128(file_size);
DCHECK_EQ(start + size, data()->size());
}
// Compact address and line opcode.
void AddRow(uint64_t absolute_address, int absolute_line) {
DCHECK_GE(absolute_address, current_address_);
// If the address is definitely too far, use the long encoding.
uint64_t delta_address = FactorCodeOffset(absolute_address - current_address_);
if (delta_address > UINT8_MAX) {
AdvancePC(absolute_address);
delta_address = 0;
}
// If the line is definitely too far, use the long encoding.
int delta_line = absolute_line - current_line_;
if (!(kLineBase <= delta_line && delta_line < kLineBase + kLineRange)) {
AdvanceLine(absolute_line);
delta_line = 0;
}
// Both address and line should be reasonable now. Use the short encoding.
int opcode = kOpcodeBase + (delta_line - kLineBase) +
(static_cast<int>(delta_address) * kLineRange);
if (opcode > UINT8_MAX) {
// If the address is still too far, try to increment it by const amount.
int const_advance = (0xFF - kOpcodeBase) / kLineRange;
opcode -= (kLineRange * const_advance);
if (opcode <= UINT8_MAX) {
this->PushUint8(DW_LNS_const_add_pc);
} else {
// Give up and use long encoding for address.
AdvancePC(absolute_address);
// Still use the opcode to do line advance and copy.
opcode = kOpcodeBase + (delta_line - kLineBase);
}
}
DCHECK(kOpcodeBase <= opcode && opcode <= 0xFF);
this->PushUint8(opcode); // Special opcode.
current_line_ = absolute_line;
current_address_ = absolute_address;
}
int GetCodeFactorBits() const {
return code_factor_bits_;
}
uint64_t CurrentAddress() const {
return current_address_;
}
int CurrentFile() const {
return current_file_;
}
int CurrentLine() const {
return current_line_;
}
const std::vector<uintptr_t>& GetPatchLocations() const {
return patch_locations_;
}
using Writer<Vector>::data;
DebugLineOpCodeWriter(bool use64bitAddress,
int codeFactorBits,
const typename Vector::allocator_type& alloc =
typename Vector::allocator_type())
: Writer<Vector>(&opcodes_),
opcodes_(alloc),
uses_dwarf3_features_(false),
use_64bit_address_(use64bitAddress),
code_factor_bits_(codeFactorBits),
current_address_(0),
current_file_(1),
current_line_(1),
is_stmt_(kDefaultIsStmt) {
}
private:
uint64_t FactorCodeOffset(uint64_t offset) const {
DCHECK_GE(code_factor_bits_, 0);
DCHECK_EQ((offset >> code_factor_bits_) << code_factor_bits_, offset);
return offset >> code_factor_bits_;
}
Vector opcodes_;
bool uses_dwarf3_features_;
bool use_64bit_address_;
int code_factor_bits_;
uint64_t current_address_;
int current_file_;
int current_line_;
bool is_stmt_;
std::vector<uintptr_t> patch_locations_;
DISALLOW_COPY_AND_ASSIGN(DebugLineOpCodeWriter);
};
} // namespace dwarf
} // namespace art
#endif // ART_LIBELFFILE_DWARF_DEBUG_LINE_OPCODE_WRITER_H_