1/* 2 * Copyright (C) 2015 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17#include "read_elf.h" 18 19#include <stdio.h> 20#include <string.h> 21#include <algorithm> 22#include <base/file.h> 23#include <base/logging.h> 24 25#pragma clang diagnostic push 26#pragma clang diagnostic ignored "-Wunused-parameter" 27 28#include <llvm/ADT/StringRef.h> 29#include <llvm/Object/Binary.h> 30#include <llvm/Object/ELFObjectFile.h> 31#include <llvm/Object/ObjectFile.h> 32 33#pragma clang diagnostic pop 34 35#include <elf.h> 36 37#include "utils.h" 38 39static bool GetBuildIdFromNoteSection(const char* section, size_t section_size, BuildId* build_id) { 40 const char* p = section; 41 const char* end = p + section_size; 42 while (p < end) { 43 CHECK_LE(p + 12, end); 44 size_t namesz = *reinterpret_cast<const uint32_t*>(p); 45 p += 4; 46 size_t descsz = *reinterpret_cast<const uint32_t*>(p); 47 p += 4; 48 uint32_t type = *reinterpret_cast<const uint32_t*>(p); 49 p += 4; 50 namesz = ALIGN(namesz, 4); 51 descsz = ALIGN(descsz, 4); 52 CHECK_LE(p + namesz + descsz, end); 53 if ((type == NT_GNU_BUILD_ID) && (strcmp(p, ELF_NOTE_GNU) == 0)) { 54 std::fill(build_id->begin(), build_id->end(), 0); 55 memcpy(build_id->data(), p + namesz, std::min(build_id->size(), descsz)); 56 return true; 57 } 58 p += namesz + descsz; 59 } 60 return false; 61} 62 63bool GetBuildIdFromNoteFile(const std::string& filename, BuildId* build_id) { 64 std::string content; 65 if (!android::base::ReadFileToString(filename, &content)) { 66 LOG(DEBUG) << "can't read note file " << filename; 67 return false; 68 } 69 if (GetBuildIdFromNoteSection(content.c_str(), content.size(), build_id) == false) { 70 LOG(DEBUG) << "can't read build_id from note file " << filename; 71 return false; 72 } 73 return true; 74} 75 76template <class ELFT> 77bool GetBuildIdFromELFFile(const llvm::object::ELFFile<ELFT>* elf, BuildId* build_id) { 78 for (auto section_iterator = elf->begin_sections(); section_iterator != elf->end_sections(); 79 ++section_iterator) { 80 if (section_iterator->sh_type == SHT_NOTE) { 81 auto contents = elf->getSectionContents(&*section_iterator); 82 if (contents.getError()) { 83 LOG(DEBUG) << "read note section error"; 84 continue; 85 } 86 if (GetBuildIdFromNoteSection(reinterpret_cast<const char*>(contents->data()), 87 contents->size(), build_id)) { 88 return true; 89 } 90 } 91 } 92 return false; 93} 94 95bool GetBuildIdFromElfFile(const std::string& filename, BuildId* build_id) { 96 auto owning_binary = llvm::object::createBinary(llvm::StringRef(filename)); 97 if (owning_binary.getError()) { 98 PLOG(DEBUG) << "can't open file " << filename; 99 return false; 100 } 101 bool result = false; 102 llvm::object::Binary* binary = owning_binary.get().getBinary(); 103 if (auto obj = llvm::dyn_cast<llvm::object::ObjectFile>(binary)) { 104 if (auto elf = llvm::dyn_cast<llvm::object::ELF32LEObjectFile>(obj)) { 105 result = GetBuildIdFromELFFile(elf->getELFFile(), build_id); 106 } else if (auto elf = llvm::dyn_cast<llvm::object::ELF64LEObjectFile>(obj)) { 107 result = GetBuildIdFromELFFile(elf->getELFFile(), build_id); 108 } else { 109 PLOG(DEBUG) << "unknown elf format in file " << filename; 110 } 111 } 112 if (!result) { 113 PLOG(DEBUG) << "can't read build_id from file " << filename; 114 } 115 return result; 116} 117