Dmitriy Ivanov | 87a0617 | 2015-02-06 10:56:28 -0800 | [diff] [blame^] | 1 | // Copyright 2014 The Chromium Authors. All rights reserved. |
| 2 | // Use of this source code is governed by a BSD-style license that can be |
| 3 | // found in the LICENSE file. |
| 4 | |
| 5 | // Tool to pack and unpack relative relocations in a shared library. |
| 6 | // |
| 7 | // Packing removes relative relocations from .rel.dyn and writes them |
| 8 | // in a more compact form to .android.rel.dyn. Unpacking does the reverse. |
| 9 | // |
| 10 | // Invoke with -v to trace actions taken when packing or unpacking. |
| 11 | // Invoke with -p to pad removed relocations with R_*_NONE. Suppresses |
| 12 | // shrinking of .rel.dyn. |
| 13 | // See PrintUsage() below for full usage details. |
| 14 | // |
| 15 | // NOTE: Breaks with libelf 0.152, which is buggy. libelf 0.158 works. |
| 16 | |
| 17 | #include <errno.h> |
| 18 | #include <fcntl.h> |
| 19 | #include <getopt.h> |
| 20 | #include <stdio.h> |
| 21 | #include <stdlib.h> |
| 22 | #include <sys/types.h> |
| 23 | #include <unistd.h> |
| 24 | #include <string> |
| 25 | |
| 26 | #include "debug.h" |
| 27 | #include "elf_file.h" |
| 28 | #include "libelf.h" |
| 29 | |
| 30 | namespace { |
| 31 | |
| 32 | void PrintUsage(const char* argv0) { |
| 33 | std::string temporary = argv0; |
| 34 | const size_t last_slash = temporary.find_last_of("/"); |
| 35 | if (last_slash != temporary.npos) { |
| 36 | temporary.erase(0, last_slash + 1); |
| 37 | } |
| 38 | const char* basename = temporary.c_str(); |
| 39 | |
| 40 | printf( |
| 41 | "Usage: %s [-u] [-v] [-p] file\n\n" |
| 42 | "Pack or unpack relative relocations in a shared library.\n\n" |
| 43 | " -u, --unpack unpack previously packed relative relocations\n" |
| 44 | " -v, --verbose trace object file modifications (for debugging)\n" |
| 45 | " -p, --pad do not shrink relocations, but pad (for debugging)\n\n", |
| 46 | basename); |
| 47 | |
| 48 | if (ELF::kMachine == EM_ARM) { |
| 49 | printf( |
| 50 | "Extracts relative relocations from the .rel.dyn section, packs them\n" |
| 51 | "into a more compact format, and stores the packed relocations in\n" |
| 52 | ".android.rel.dyn. Expands .android.rel.dyn to hold the packed\n" |
| 53 | "data, and shrinks .rel.dyn by the amount of unpacked data removed\n" |
| 54 | "from it.\n\n" |
| 55 | "Before being packed, a shared library needs to be prepared by adding\n" |
| 56 | "a null .android.rel.dyn section.\n\n" |
| 57 | "To pack relocations in a shared library:\n\n" |
| 58 | " echo -n 'NULL' >/tmp/small\n" |
| 59 | " arm-linux-androideabi-objcopy \\\n" |
| 60 | " --add-section .android.rel.dyn=/tmp/small \\\n" |
| 61 | " libchrome.<version>.so\n" |
| 62 | " rm /tmp/small\n" |
| 63 | " %s libchrome.<version>.so\n\n" |
| 64 | "To unpack and restore the shared library to its original state:\n\n" |
| 65 | " %s -u libchrome.<version>.so\n" |
| 66 | " arm-linux-androideabi-objcopy \\\n" |
| 67 | " --remove-section=.android.rel.dyn libchrome.<version>.so\n\n", |
| 68 | basename, basename); |
| 69 | } else if (ELF::kMachine == EM_AARCH64) { |
| 70 | printf( |
| 71 | "Extracts relative relocations from the .rela.dyn section, packs them\n" |
| 72 | "into a more compact format, and stores the packed relocations in\n" |
| 73 | ".android.rela.dyn. Expands .android.rela.dyn to hold the packed\n" |
| 74 | "data, and shrinks .rela.dyn by the amount of unpacked data removed\n" |
| 75 | "from it.\n\n" |
| 76 | "Before being packed, a shared library needs to be prepared by adding\n" |
| 77 | "a null .android.rela.dyn section.\n\n" |
| 78 | "To pack relocations in a shared library:\n\n" |
| 79 | " echo -n 'NULL' >/tmp/small\n" |
| 80 | " aarch64-linux-android-objcopy \\\n" |
| 81 | " --add-section .android.rela.dyn=/tmp/small \\\n" |
| 82 | " libchrome.<version>.so\n" |
| 83 | " rm /tmp/small\n" |
| 84 | " %s libchrome.<version>.so\n\n" |
| 85 | "To unpack and restore the shared library to its original state:\n\n" |
| 86 | " %s -u libchrome.<version>.so\n" |
| 87 | " aarch64-linux-android-objcopy \\\n" |
| 88 | " --remove-section=.android.rela.dyn libchrome.<version>.so\n\n", |
| 89 | basename, basename); |
| 90 | } else { |
| 91 | NOTREACHED(); |
| 92 | } |
| 93 | |
| 94 | printf( |
| 95 | "Debug sections are not handled, so packing should not be used on\n" |
| 96 | "shared libraries compiled for debugging or otherwise unstripped.\n"); |
| 97 | } |
| 98 | |
| 99 | } // namespace |
| 100 | |
| 101 | int main(int argc, char* argv[]) { |
| 102 | bool is_unpacking = false; |
| 103 | bool is_verbose = false; |
| 104 | bool is_padding = false; |
| 105 | |
| 106 | static const option options[] = { |
| 107 | {"unpack", 0, 0, 'u'}, {"verbose", 0, 0, 'v'}, {"pad", 0, 0, 'p'}, |
| 108 | {"help", 0, 0, 'h'}, {NULL, 0, 0, 0} |
| 109 | }; |
| 110 | bool has_options = true; |
| 111 | while (has_options) { |
| 112 | int c = getopt_long(argc, argv, "uvph", options, NULL); |
| 113 | switch (c) { |
| 114 | case 'u': |
| 115 | is_unpacking = true; |
| 116 | break; |
| 117 | case 'v': |
| 118 | is_verbose = true; |
| 119 | break; |
| 120 | case 'p': |
| 121 | is_padding = true; |
| 122 | break; |
| 123 | case 'h': |
| 124 | PrintUsage(argv[0]); |
| 125 | return 0; |
| 126 | case '?': |
| 127 | LOG(INFO) << "Try '" << argv[0] << " --help' for more information."; |
| 128 | return 1; |
| 129 | case -1: |
| 130 | has_options = false; |
| 131 | break; |
| 132 | default: |
| 133 | NOTREACHED(); |
| 134 | return 1; |
| 135 | } |
| 136 | } |
| 137 | if (optind != argc - 1) { |
| 138 | LOG(INFO) << "Try '" << argv[0] << " --help' for more information."; |
| 139 | return 1; |
| 140 | } |
| 141 | |
| 142 | if (elf_version(EV_CURRENT) == EV_NONE) { |
| 143 | LOG(WARNING) << "Elf Library is out of date!"; |
| 144 | } |
| 145 | |
| 146 | LOG(INFO) << "Configured for " << ELF::Machine(); |
| 147 | |
| 148 | const char* file = argv[argc - 1]; |
| 149 | const int fd = open(file, O_RDWR); |
| 150 | if (fd == -1) { |
| 151 | LOG(ERROR) << file << ": " << strerror(errno); |
| 152 | return 1; |
| 153 | } |
| 154 | |
| 155 | if (is_verbose) |
| 156 | relocation_packer::Logger::SetVerbose(1); |
| 157 | |
| 158 | relocation_packer::ElfFile elf_file(fd); |
| 159 | elf_file.SetPadding(is_padding); |
| 160 | |
| 161 | bool status; |
| 162 | if (is_unpacking) |
| 163 | status = elf_file.UnpackRelocations(); |
| 164 | else |
| 165 | status = elf_file.PackRelocations(); |
| 166 | |
| 167 | close(fd); |
| 168 | |
| 169 | if (!status) { |
| 170 | LOG(ERROR) << file << ": failed to pack/unpack file"; |
| 171 | return 1; |
| 172 | } |
| 173 | |
| 174 | return 0; |
| 175 | } |