/*
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* Copyright (C) 2016 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef ART_COMPILER_DEBUG_ELF_SYMTAB_WRITER_H_
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#define ART_COMPILER_DEBUG_ELF_SYMTAB_WRITER_H_
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#include <map>
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#include <unordered_set>
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#include "base/utils.h"
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#include "debug/debug_info.h"
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#include "debug/method_debug_info.h"
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#include "dex/dex_file-inl.h"
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#include "dex/code_item_accessors.h"
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#include "elf/elf_builder.h"
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namespace art {
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namespace debug {
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// The ARM specification defines three special mapping symbols
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// $a, $t and $d which mark ARM, Thumb and data ranges respectively.
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// These symbols can be used by tools, for example, to pretty
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// print instructions correctly. Objdump will use them if they
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// exist, but it will still work well without them.
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// However, these extra symbols take space, so let's just generate
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// one symbol which marks the whole .text section as code.
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// Note that ARM's Streamline requires it to match function symbol.
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constexpr bool kGenerateArmMappingSymbol = true;
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// Magic name for .symtab symbols which enumerate dex files used
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// by this ELF file (currently mmapped inside the .dex section).
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constexpr const char* kDexFileSymbolName = "$dexfile";
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template <typename ElfTypes>
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static void WriteDebugSymbols(ElfBuilder<ElfTypes>* builder,
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bool mini_debug_info,
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const DebugInfo& debug_info) {
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uint64_t mapping_symbol_address = std::numeric_limits<uint64_t>::max();
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const auto* text = builder->GetText();
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auto* strtab = builder->GetStrTab();
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auto* symtab = builder->GetSymTab();
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if (debug_info.Empty()) {
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return;
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}
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// Find all addresses which contain deduped methods.
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// The first instance of method is not marked deduped_, but the rest is.
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std::unordered_set<uint64_t> deduped_addresses;
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for (const MethodDebugInfo& info : debug_info.compiled_methods) {
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if (info.deduped) {
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deduped_addresses.insert(info.code_address);
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}
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if (kGenerateArmMappingSymbol && info.isa == InstructionSet::kThumb2) {
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uint64_t address = info.code_address;
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address += info.is_code_address_text_relative ? text->GetAddress() : 0;
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mapping_symbol_address = std::min(mapping_symbol_address, address);
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}
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}
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strtab->Start();
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strtab->Write(""); // strtab should start with empty string.
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// Generate ARM mapping symbols. ELF local symbols must be added first.
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if (mapping_symbol_address != std::numeric_limits<uint64_t>::max()) {
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symtab->Add(strtab->Write("$t"), text, mapping_symbol_address, 0, STB_LOCAL, STT_NOTYPE);
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}
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// Add symbols for compiled methods.
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for (const MethodDebugInfo& info : debug_info.compiled_methods) {
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if (info.deduped) {
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continue; // Add symbol only for the first instance.
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}
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size_t name_offset;
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if (!info.custom_name.empty()) {
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name_offset = strtab->Write(info.custom_name);
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} else {
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DCHECK(info.dex_file != nullptr);
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std::string name = info.dex_file->PrettyMethod(info.dex_method_index, !mini_debug_info);
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if (deduped_addresses.find(info.code_address) != deduped_addresses.end()) {
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name += " [DEDUPED]";
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}
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name_offset = strtab->Write(name);
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}
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uint64_t address = info.code_address;
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address += info.is_code_address_text_relative ? text->GetAddress() : 0;
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// Add in code delta, e.g., thumb bit 0 for Thumb2 code.
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address += CompiledMethod::CodeDelta(info.isa);
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symtab->Add(name_offset, text, address, info.code_size, STB_GLOBAL, STT_FUNC);
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}
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// Add symbols for dex files.
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if (!debug_info.dex_files.empty() && builder->GetDex()->Exists()) {
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auto dex = builder->GetDex();
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for (auto it : debug_info.dex_files) {
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uint64_t dex_address = dex->GetAddress() + it.first /* offset within the section */;
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const DexFile* dex_file = it.second;
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typename ElfTypes::Word dex_name = strtab->Write(kDexFileSymbolName);
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symtab->Add(dex_name, dex, dex_address, dex_file->Size(), STB_GLOBAL, STT_FUNC);
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}
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}
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strtab->End();
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// Symbols are buffered and written after names (because they are smaller).
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symtab->WriteCachedSection();
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}
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} // namespace debug
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} // namespace art
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#endif // ART_COMPILER_DEBUG_ELF_SYMTAB_WRITER_H_
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