third_party/android_platform/bionic/tools/relocation_packer/src/main.cc

   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 // Invoke with -v to trace actions taken when packing or unpacking.
   8 // Invoke with -p to pad removed relocations with R_*_NONE.  Suppresses
   9 // shrinking of .rel.dyn.
  10 // See PrintUsage() below for full usage details.
  11 //
  12 // NOTE: Breaks with libelf 0.152, which is buggy.  libelf 0.158 works.
  13
  14 #include <errno.h>
  15 #include <fcntl.h>
  16 #include <getopt.h>
  17 #include <stdio.h>
  18 #include <stdlib.h>
  19 #include <sys/types.h>
  20 #include <unistd.h>
  21 #include <string>
  22
  23 #include "debug.h"
  24 #include "elf_file.h"
  25 #include "elf_traits.h"
  26 #include "libelf.h"
  27
  28 #include "nativehelper/ScopedFd.h"
  29
  30 static void PrintUsage(const char* argv0) {
  31   std::string temporary = argv0;
  32   const size_t last_slash = temporary.find_last_of("/");
  33   if (last_slash != temporary.npos) {
  34     temporary.erase(0, last_slash + 1);
  35   }
  36   const char* basename = temporary.c_str();
  37
  38   printf(
  39       "Usage: %s [-u] [-v] [-p] file\n\n"
  40       "Pack or unpack relative relocations in a shared library.\n\n"
  41       "  -u, --unpack   unpack previously packed relative relocations\n"
  42       "  -v, --verbose  trace object file modifications (for debugging)\n"
  43       "  -p, --pad      do not shrink relocations, but pad (for debugging)\n\n",
  44       basename);
  45
  46   printf(
  47       "Debug sections are not handled, so packing should not be used on\n"
  48       "shared libraries compiled for debugging or otherwise unstripped.\n");
  49 }
  50
  51 int main(int argc, char* argv[]) {
  52   bool is_unpacking = false;
  53   bool is_verbose = false;
  54   bool is_padding = false;
  55
  56   static const option options[] = {
  57     {"unpack", 0, 0, 'u'}, {"verbose", 0, 0, 'v'}, {"pad", 0, 0, 'p'},
  58     {"help", 0, 0, 'h'}, {NULL, 0, 0, 0}
  59   };
  60   bool has_options = true;
  61   while (has_options) {
  62     int c = getopt_long(argc, argv, "uvph", options, NULL);
  63     switch (c) {
  64       case 'u':
  65         is_unpacking = true;
  66         break;
  67       case 'v':
  68         is_verbose = true;
  69         break;
  70       case 'p':
  71         is_padding = true;
  72         break;
  73       case 'h':
  74         PrintUsage(argv[0]);
  75         return 0;
  76       case '?':
  77         LOG(INFO) << "Try '" << argv[0] << " --help' for more information.";
  78         return 1;
  79       case -1:
  80         has_options = false;
  81         break;
  82       default:
  83         NOTREACHED();
  84         return 1;
  85     }
  86   }
  87   if (optind != argc - 1) {
  88     LOG(INFO) << "Try '" << argv[0] << " --help' for more information.";
  89     return 1;
  90   }
  91
  92   if (elf_version(EV_CURRENT) == EV_NONE) {
  93     LOG(WARNING) << "Elf Library is out of date!";
  94   }
  95
  96   const char* file = argv[argc - 1];
  97   ScopedFd fd(open(file, O_RDWR));
  98   if (fd.get() == -1) {
  99     LOG(ERROR) << file << ": " << strerror(errno);
 100     return 1;
 101   }
 102
 103   if (is_verbose)
 104     relocation_packer::Logger::SetVerbose(1);
 105
 106   // We need to detect elf class in order to create
 107   // correct implementation
 108   uint8_t e_ident[EI_NIDENT];
 109   if (TEMP_FAILURE_RETRY(read(fd.get(), e_ident, EI_NIDENT) != EI_NIDENT)) {
 110     LOG(ERROR) << file << ": failed to read elf header:" << strerror(errno);
 111     return 1;
 112   }
 113
 114   if (TEMP_FAILURE_RETRY(lseek(fd.get(), 0, SEEK_SET)) != 0) {
 115     LOG(ERROR) << file << ": lseek to 0 failed:" << strerror(errno);
 116     return 1;
 117   }
 118
 119   bool status = false;
 120
 121   if (e_ident[EI_CLASS] == ELFCLASS32) {
 122     relocation_packer::ElfFile<ELF32_traits> elf_file(fd.get());
 123     elf_file.SetPadding(is_padding);
 124
 125     if (is_unpacking) {
 126       status = elf_file.UnpackRelocations();
 127     } else {
 128       status = elf_file.PackRelocations();
 129     }
 130   } else if (e_ident[EI_CLASS] == ELFCLASS64) {
 131     relocation_packer::ElfFile<ELF64_traits> elf_file(fd.get());
 132     elf_file.SetPadding(is_padding);
 133
 134     if (is_unpacking) {
 135       status = elf_file.UnpackRelocations();
 136     } else {
 137       status = elf_file.PackRelocations();
 138     }
 139   } else {
 140     LOG(ERROR) << file << ": unknown ELFCLASS: " << e_ident[EI_CLASS];
 141     return 1;
 142   }
 143
 144   if (!status) {
 145     LOG(ERROR) << file << ": failed to pack/unpack file";
 146     return 1;
 147   }
 148
 149   return 0;
 150 }