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