Christopher Ferris | a21bd93 | 2015-02-27 13:39:47 -0800 | [diff] [blame] | 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 | #define LOG_TAG "DEBUG" |
| 18 | |
| 19 | #include <elf.h> |
| 20 | #include <stdint.h> |
| 21 | #include <stdlib.h> |
| 22 | #include <string.h> |
| 23 | |
| 24 | #include <string> |
| 25 | |
| 26 | #include <backtrace/Backtrace.h> |
Elliott Hughes | 4f71319 | 2015-12-04 22:00:26 -0800 | [diff] [blame] | 27 | #include <android-base/stringprintf.h> |
Christopher Ferris | a21bd93 | 2015-02-27 13:39:47 -0800 | [diff] [blame] | 28 | #include <log/log.h> |
| 29 | |
| 30 | #include "elf_utils.h" |
| 31 | |
Yabin Cui | 03dca28 | 2015-04-14 10:27:54 -0700 | [diff] [blame] | 32 | #define NOTE_ALIGN(size) ((size + 3) & ~3) |
| 33 | |
Christopher Ferris | a21bd93 | 2015-02-27 13:39:47 -0800 | [diff] [blame] | 34 | template <typename HdrType, typename PhdrType, typename NhdrType> |
| 35 | static bool get_build_id( |
| 36 | Backtrace* backtrace, uintptr_t base_addr, uint8_t* e_ident, std::string* build_id) { |
| 37 | HdrType hdr; |
| 38 | |
| 39 | memcpy(&hdr.e_ident[0], e_ident, EI_NIDENT); |
| 40 | |
| 41 | // First read the rest of the header. |
| 42 | if (backtrace->Read(base_addr + EI_NIDENT, reinterpret_cast<uint8_t*>(&hdr) + EI_NIDENT, |
| 43 | sizeof(HdrType) - EI_NIDENT) != sizeof(HdrType) - EI_NIDENT) { |
| 44 | return false; |
| 45 | } |
| 46 | |
| 47 | for (size_t i = 0; i < hdr.e_phnum; i++) { |
| 48 | PhdrType phdr; |
| 49 | if (backtrace->Read(base_addr + hdr.e_phoff + i * hdr.e_phentsize, |
| 50 | reinterpret_cast<uint8_t*>(&phdr), sizeof(phdr)) != sizeof(phdr)) { |
| 51 | return false; |
| 52 | } |
| 53 | // Looking for the .note.gnu.build-id note. |
| 54 | if (phdr.p_type == PT_NOTE) { |
| 55 | size_t hdr_size = phdr.p_filesz; |
| 56 | uintptr_t addr = base_addr + phdr.p_offset; |
| 57 | while (hdr_size >= sizeof(NhdrType)) { |
| 58 | NhdrType nhdr; |
| 59 | if (backtrace->Read(addr, reinterpret_cast<uint8_t*>(&nhdr), sizeof(nhdr)) != sizeof(nhdr)) { |
| 60 | return false; |
| 61 | } |
| 62 | addr += sizeof(nhdr); |
| 63 | if (nhdr.n_type == NT_GNU_BUILD_ID) { |
| 64 | // Skip the name (which is the owner and should be "GNU"). |
Yabin Cui | 03dca28 | 2015-04-14 10:27:54 -0700 | [diff] [blame] | 65 | addr += NOTE_ALIGN(nhdr.n_namesz); |
Christopher Ferris | d917514 | 2015-10-22 13:34:48 -0700 | [diff] [blame] | 66 | uint8_t build_id_data[160]; |
| 67 | if (nhdr.n_descsz > sizeof(build_id_data)) { |
| 68 | ALOGE("Possible corrupted note, desc size value is too large: %u", |
| 69 | nhdr.n_descsz); |
Christopher Ferris | a21bd93 | 2015-02-27 13:39:47 -0800 | [diff] [blame] | 70 | return false; |
| 71 | } |
| 72 | if (backtrace->Read(addr, build_id_data, nhdr.n_descsz) != nhdr.n_descsz) { |
| 73 | return false; |
| 74 | } |
| 75 | |
| 76 | build_id->clear(); |
| 77 | for (size_t bytes = 0; bytes < nhdr.n_descsz; bytes++) { |
| 78 | *build_id += android::base::StringPrintf("%02x", build_id_data[bytes]); |
| 79 | } |
| 80 | |
| 81 | return true; |
| 82 | } else { |
| 83 | // Move past the extra note data. |
| 84 | hdr_size -= sizeof(nhdr); |
Yabin Cui | 03dca28 | 2015-04-14 10:27:54 -0700 | [diff] [blame] | 85 | size_t skip_bytes = NOTE_ALIGN(nhdr.n_namesz) + NOTE_ALIGN(nhdr.n_descsz); |
Christopher Ferris | a21bd93 | 2015-02-27 13:39:47 -0800 | [diff] [blame] | 86 | addr += skip_bytes; |
| 87 | if (hdr_size < skip_bytes) { |
| 88 | break; |
| 89 | } |
| 90 | hdr_size -= skip_bytes; |
| 91 | } |
| 92 | } |
| 93 | } |
| 94 | } |
| 95 | return false; |
| 96 | } |
| 97 | |
| 98 | bool elf_get_build_id(Backtrace* backtrace, uintptr_t addr, std::string* build_id) { |
| 99 | // Read and verify the elf magic number first. |
| 100 | uint8_t e_ident[EI_NIDENT]; |
| 101 | if (backtrace->Read(addr, e_ident, SELFMAG) != SELFMAG) { |
| 102 | return false; |
| 103 | } |
| 104 | |
| 105 | if (memcmp(e_ident, ELFMAG, SELFMAG) != 0) { |
| 106 | return false; |
| 107 | } |
| 108 | |
| 109 | // Read the rest of EI_NIDENT. |
| 110 | if (backtrace->Read(addr + SELFMAG, e_ident + SELFMAG, EI_NIDENT - SELFMAG) != EI_NIDENT - SELFMAG) { |
| 111 | return false; |
| 112 | } |
| 113 | |
| 114 | if (e_ident[EI_CLASS] == ELFCLASS32) { |
| 115 | return get_build_id<Elf32_Ehdr, Elf32_Phdr, Elf32_Nhdr>(backtrace, addr, e_ident, build_id); |
| 116 | } else if (e_ident[EI_CLASS] == ELFCLASS64) { |
| 117 | return get_build_id<Elf64_Ehdr, Elf64_Phdr, Elf64_Nhdr>(backtrace, addr, e_ident, build_id); |
| 118 | } |
| 119 | |
| 120 | return false; |
| 121 | } |