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/*
* 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 <map>
#include <unordered_set>
#include <unordered_map>
#include "base/utils.h"
#include "debug/debug_info.h"
#include "debug/method_debug_info.h"
#include "dex/code_item_accessors.h"
#include "dex/descriptors_names.h"
#include "dex/dex_file-inl.h"
#include "elf/elf_builder.h"
namespace art {
namespace debug {
// The ARM specification defines three special mapping symbols
// $a, $t and $d which mark ARM, Thumb and data ranges respectively.
// These symbols can be used by tools, for example, to pretty
// print instructions correctly. Objdump will use them if they
// exist, but it will still work well without them.
// However, these extra symbols take space, so let's just generate
// one symbol which marks the whole .text section as code.
// Note that ARM's Streamline requires it to match function symbol.
constexpr bool kGenerateArmMappingSymbol = true;
// Create magic symbol to let libunwindstack know that symtab is sorted by address.
constexpr bool kGenerateSortedSymbol = true;
constexpr const char kSortedSymbolName[] = "$android.symtab.sorted";
constexpr size_t kSortedSymbolMinCount = 100; // Don't bother if the table is very small (JIT).
// Magic name for .symtab symbols which enumerate dex files used
// by this ELF file (currently mmapped inside the .dex section).
constexpr const char* kDexFileSymbolName = "$dexfile";
// Return common parts of method names; shared by all methods in the given set.
// (e.g. "[DEDUPED] ?.<init>" or "com.android.icu.charset.CharsetEncoderICU.?")
static void GetDedupedName(const std::vector<const MethodDebugInfo*>& methods, std::string* out) {
DCHECK(!methods.empty());
const MethodDebugInfo* first = methods.front();
auto is_same_class = [&first](const MethodDebugInfo* mi) {
DCHECK(mi->dex_file != nullptr);
return mi->dex_file == first->dex_file && mi->class_def_index == first->class_def_index;
};
auto is_same_method_name = [&first](const MethodDebugInfo* mi) {
return strcmp(mi->dex_file->GetMethodName(mi->dex_method_index),
first->dex_file->GetMethodName(first->dex_method_index)) == 0;
};
bool all_same_class = std::all_of(methods.begin(), methods.end(), is_same_class);
bool all_same_method_name = std::all_of(methods.begin(), methods.end(), is_same_method_name);
*out = "[DEDUPED]";
if (all_same_class || all_same_method_name) {
*out += ' ';
if (all_same_class) {
auto& dex_class_def = first->dex_file->GetClassDef(first->class_def_index);
AppendPrettyDescriptor(first->dex_file->GetClassDescriptor(dex_class_def), &*out);
} else {
*out += '?';
}
*out += '.';
if (all_same_method_name) {
*out += first->dex_file->GetMethodName(first->dex_method_index);
} else {
*out += '?';
}
}
}
template <typename ElfTypes>
static void WriteDebugSymbols(ElfBuilder<ElfTypes>* builder,
bool mini_debug_info,
const DebugInfo& debug_info) {
uint64_t mapping_symbol_address = std::numeric_limits<uint64_t>::max();
const auto* text = builder->GetText();
auto* strtab = builder->GetStrTab();
auto* symtab = builder->GetSymTab();
if (debug_info.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 : debug_info.compiled_methods) {
if (info.deduped) {
deduped_addresses.insert(info.code_address);
}
if (kGenerateArmMappingSymbol && info.isa == InstructionSet::kThumb2) {
uint64_t address = info.code_address;
address += info.is_code_address_text_relative ? text->GetAddress() : 0;
mapping_symbol_address = std::min(mapping_symbol_address, address);
}
}
// Create list of deduped methods per function address.
// We have to do it separately since the first method does not have the deduped flag.
std::unordered_map<uint64_t, std::vector<const MethodDebugInfo*>> deduped_methods;
for (const MethodDebugInfo& info : debug_info.compiled_methods) {
if (deduped_addresses.find(info.code_address) != deduped_addresses.end()) {
deduped_methods[info.code_address].push_back(&info);
}
}
strtab->Start();
// Generate marker to annotate the symbol table as sorted (guaranteed by the ElfBuilder).
// Note that LOCAL symbols are sorted before GLOBAL ones, so don't mix the two types.
if (kGenerateSortedSymbol && debug_info.compiled_methods.size() >= kSortedSymbolMinCount) {
symtab->Add(strtab->Write(kSortedSymbolName), nullptr, 0, 0, STB_GLOBAL, STT_NOTYPE);
}
// Generate ARM mapping symbols. ELF local symbols must be added first.
if (mapping_symbol_address != std::numeric_limits<uint64_t>::max()) {
symtab->Add(strtab->Write("$t"), text, mapping_symbol_address, 0, STB_GLOBAL, STT_NOTYPE);
}
// Add symbols for compiled methods.
for (const MethodDebugInfo& info : debug_info.compiled_methods) {
if (info.deduped) {
continue; // Add symbol only for the first instance.
}
size_t name_offset;
if (!info.custom_name.empty()) {
name_offset = strtab->Write(info.custom_name);
} else {
DCHECK(info.dex_file != nullptr);
std::string name = info.dex_file->PrettyMethod(info.dex_method_index, !mini_debug_info);
if (deduped_addresses.find(info.code_address) != deduped_addresses.end()) {
// Create method name common to all the deduped methods if possible.
// Around half of the time, there is either common class or method name.
// NB: We used to return one method at random with tag, but developers found it confusing.
GetDedupedName(deduped_methods[info.code_address], &name);
}
name_offset = strtab->Write(name);
}
uint64_t address = info.code_address;
address += info.is_code_address_text_relative ? 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);
}
// Add symbols for dex files.
if (!debug_info.dex_files.empty() && builder->GetDex()->Exists()) {
auto dex = builder->GetDex();
for (auto it : debug_info.dex_files) {
uint64_t dex_address = dex->GetAddress() + it.first /* offset within the section */;
const DexFile* dex_file = it.second;
typename ElfTypes::Word dex_name = strtab->Write(kDexFileSymbolName);
symtab->Add(dex_name, dex, dex_address, dex_file->Size(), STB_GLOBAL, STT_FUNC);
}
}
strtab->End();
// Symbols are buffered and written after names (because they are smaller).
symtab->WriteCachedSection();
}
} // namespace debug
} // namespace art
#endif // ART_COMPILER_DEBUG_ELF_SYMTAB_WRITER_H_
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