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 // 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 "elf_traits.h"
  29 #include "libelf.h"
  30
  31 #include "nativehelper/ScopedFd.h"
  32
  33 static void PrintUsage(const char* argv0) {
  34   std::string temporary = argv0;
  35   const size_t last_slash = temporary.find_last_of("/");
  36   if (last_slash != temporary.npos) {
  37     temporary.erase(0, last_slash + 1);
  38   }
  39   const char* basename = temporary.c_str();
  40
  41   printf(
  42       "Usage: %s [-u] [-v] [-p] file\n\n"
  43       "Pack or unpack relative relocations in a shared library.\n\n"
  44       "  -u, --unpack   unpack previously packed relative relocations\n"
  45       "  -v, --verbose  trace object file modifications (for debugging)\n"
  46       "  -p, --pad      do not shrink relocations, but pad (for debugging)\n\n",
  47       basename);
  48
  49   printf(
  50       "Debug sections are not handled, so packing should not be used on\n"
  51       "shared libraries compiled for debugging or otherwise unstripped.\n");
  52 }
  53
  54 int main(int argc, char* argv[]) {
  55   bool is_unpacking = false;
  56   bool is_verbose = false;
  57   bool is_padding = false;
  58
  59   static const option options[] = {
  60     {"unpack", 0, 0, 'u'}, {"verbose", 0, 0, 'v'}, {"pad", 0, 0, 'p'},
  61     {"help", 0, 0, 'h'}, {NULL, 0, 0, 0}
  62   };
  63   bool has_options = true;
  64   while (has_options) {
  65     int c = getopt_long(argc, argv, "uvph", options, NULL);
  66     switch (c) {
  67       case 'u':
  68         is_unpacking = true;
  69         break;
  70       case 'v':
  71         is_verbose = true;
  72         break;
  73       case 'p':
  74         is_padding = true;
  75         break;
  76       case 'h':
  77         PrintUsage(argv[0]);
  78         return 0;
  79       case '?':
  80         LOG(INFO) << "Try '" << argv[0] << " --help' for more information.";
  81         return 1;
  82       case -1:
  83         has_options = false;
  84         break;
  85       default:
  86         NOTREACHED();
  87         return 1;
  88     }
  89   }
  90   if (optind != argc - 1) {
  91     LOG(INFO) << "Try '" << argv[0] << " --help' for more information.";
  92     return 1;
  93   }
  94
  95   if (elf_version(EV_CURRENT) == EV_NONE) {
  96     LOG(WARNING) << "Elf Library is out of date!";
  97   }
  98
  99   const char* file = argv[argc - 1];
 100   ScopedFd fd(open(file, O_RDWR));
 101   if (fd.get() == -1) {
 102     LOG(ERROR) << file << ": " << strerror(errno);
 103     return 1;
 104   }
 105
 106   if (is_verbose)
 107     relocation_packer::Logger::SetVerbose(1);
 108
 109   // We need to detect elf class in order to create
 110   // correct implementation
 111   uint8_t e_ident[EI_NIDENT];
 112   if (TEMP_FAILURE_RETRY(read(fd.get(), e_ident, EI_NIDENT) != EI_NIDENT)) {
 113     LOG(ERROR) << file << ": failed to read elf header:" << strerror(errno);
 114     return 1;
 115   }
 116
 117   if (TEMP_FAILURE_RETRY(lseek(fd.get(), 0, SEEK_SET)) != 0) {
 118     LOG(ERROR) << file << ": lseek to 0 failed:" << strerror(errno);
 119     return 1;
 120   }
 121
 122   bool status = false;
 123
 124   if (e_ident[EI_CLASS] == ELFCLASS32) {
 125     relocation_packer::ElfFile<ELF32_traits> elf_file(fd.get());
 126     elf_file.SetPadding(is_padding);
 127
 128     if (is_unpacking) {
 129       status = elf_file.UnpackRelocations();
 130     } else {
 131       status = elf_file.PackRelocations();
 132     }
 133   } else if (e_ident[EI_CLASS] == ELFCLASS64) {
 134     relocation_packer::ElfFile<ELF64_traits> elf_file(fd.get());
 135     elf_file.SetPadding(is_padding);
 136
 137     if (is_unpacking) {
 138       status = elf_file.UnpackRelocations();
 139     } else {
 140       status = elf_file.PackRelocations();
 141     }
 142   } else {
 143     LOG(ERROR) << file << ": unknown ELFCLASS: " << e_ident[EI_CLASS];
 144     return 1;
 145   }
 146
 147   if (!status) {
 148     LOG(ERROR) << file << ": failed to pack/unpack file";
 149     return 1;
 150   }
 151
 152   return 0;
 153 }