blob: af9f091529c6800f65ca5e8da06aa6afa8bc2d0b [file] [log] [blame]
/*
* Copyright (C) 2016 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_COMPILER_DEBUG_ELF_SYMTAB_WRITER_H_
#define ART_COMPILER_DEBUG_ELF_SYMTAB_WRITER_H_
#include <unordered_set>
#include "debug/method_debug_info.h"
#include "elf_builder.h"
#include "utils.h"
namespace art {
namespace debug {
// The ARM specification defines three special mapping symbols
// $a, $t and $d which mark ARM, Thumb and data ranges respectively.
// These symbols can be used by tools, for example, to pretty
// print instructions correctly. Objdump will use them if they
// exist, but it will still work well without them.
// However, these extra symbols take space, so let's just generate
// one symbol which marks the whole .text section as code.
constexpr bool kGenerateSingleArmMappingSymbol = true;
template <typename ElfTypes>
static void WriteDebugSymbols(ElfBuilder<ElfTypes>* builder,
const ArrayRef<const MethodDebugInfo>& method_infos,
bool with_signature) {
uint64_t mapping_symbol_address = std::numeric_limits<uint64_t>::max();
auto* strtab = builder->GetStrTab();
auto* symtab = builder->GetSymTab();
if (method_infos.empty()) {
return;
}
// Find all addresses which contain deduped methods.
// The first instance of method is not marked deduped_, but the rest is.
std::unordered_set<uint64_t> deduped_addresses;
for (const MethodDebugInfo& info : method_infos) {
if (info.deduped) {
deduped_addresses.insert(info.code_address);
}
}
strtab->Start();
strtab->Write(""); // strtab should start with empty string.
std::string last_name;
size_t last_name_offset = 0;
for (const MethodDebugInfo& info : method_infos) {
if (info.deduped) {
continue; // Add symbol only for the first instance.
}
size_t name_offset;
if (info.trampoline_name != nullptr) {
name_offset = strtab->Write(info.trampoline_name);
} else {
DCHECK(info.dex_file != nullptr);
std::string name = info.dex_file->PrettyMethod(info.dex_method_index, with_signature);
if (deduped_addresses.find(info.code_address) != deduped_addresses.end()) {
name += " [DEDUPED]";
}
// If we write method names without signature, we might see the same name multiple times.
name_offset = (name == last_name ? last_name_offset : strtab->Write(name));
last_name = std::move(name);
last_name_offset = name_offset;
}
const auto* text = info.is_code_address_text_relative ? builder->GetText() : nullptr;
uint64_t address = info.code_address + (text != nullptr ? text->GetAddress() : 0);
// Add in code delta, e.g., thumb bit 0 for Thumb2 code.
address += CompiledMethod::CodeDelta(info.isa);
symtab->Add(name_offset, text, address, info.code_size, STB_GLOBAL, STT_FUNC);
// Conforming to aaelf, add $t mapping symbol to indicate start of a sequence of thumb2
// instructions, so that disassembler tools can correctly disassemble.
// Note that even if we generate just a single mapping symbol, ARM's Streamline
// requires it to match function symbol. Just address 0 does not work.
if (info.isa == kThumb2) {
if (address < mapping_symbol_address || !kGenerateSingleArmMappingSymbol) {
symtab->Add(strtab->Write("$t"), text, address & ~1, 0, STB_LOCAL, STT_NOTYPE);
mapping_symbol_address = address;
}
}
}
strtab->End();
// Symbols are buffered and written after names (because they are smaller).
// We could also do two passes in this function to avoid the buffering.
symtab->Start();
symtab->Write();
symtab->End();
}
} // namespace debug
} // namespace art
#endif // ART_COMPILER_DEBUG_ELF_SYMTAB_WRITER_H_