112 lines
4.2 KiB
C++
112 lines
4.2 KiB
C++
/*
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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 <unordered_set>
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#include "debug/method_debug_info.h"
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#include "elf_builder.h"
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#include "utils.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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constexpr bool kGenerateSingleArmMappingSymbol = true;
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template <typename ElfTypes>
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static void WriteDebugSymbols(ElfBuilder<ElfTypes>* builder,
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const ArrayRef<const MethodDebugInfo>& method_infos,
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bool with_signature) {
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uint64_t mapping_symbol_address = std::numeric_limits<uint64_t>::max();
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auto* strtab = builder->GetStrTab();
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auto* symtab = builder->GetSymTab();
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if (method_infos.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 : method_infos) {
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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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}
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strtab->Start();
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strtab->Write(""); // strtab should start with empty string.
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std::string last_name;
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size_t last_name_offset = 0;
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for (const MethodDebugInfo& info : method_infos) {
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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.trampoline_name != nullptr) {
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name_offset = strtab->Write(info.trampoline_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, with_signature);
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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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// If we write method names without signature, we might see the same name multiple times.
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name_offset = (name == last_name ? last_name_offset : strtab->Write(name));
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last_name = std::move(name);
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last_name_offset = name_offset;
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}
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const auto* text = info.is_code_address_text_relative ? builder->GetText() : nullptr;
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uint64_t address = info.code_address + (text != nullptr ? 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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// Conforming to aaelf, add $t mapping symbol to indicate start of a sequence of thumb2
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// instructions, so that disassembler tools can correctly disassemble.
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// Note that even if we generate just a single mapping symbol, ARM's Streamline
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// requires it to match function symbol. Just address 0 does not work.
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if (info.isa == kThumb2) {
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if (address < mapping_symbol_address || !kGenerateSingleArmMappingSymbol) {
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symtab->Add(strtab->Write("$t"), text, address & ~1, 0, STB_LOCAL, STT_NOTYPE);
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mapping_symbol_address = address;
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}
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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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// We could also do two passes in this function to avoid the buffering.
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symtab->Start();
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symtab->Write();
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symtab->End();
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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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