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// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
// Tool to pack and unpack relative relocations in a shared library.
//
// Packing removes relative relocations from .rel.dyn and writes them
// in a more compact form to .android.rel.dyn. Unpacking does the reverse.
//
// Invoke with -v to trace actions taken when packing or unpacking.
// Invoke with -p to pad removed relocations with R_*_NONE. Suppresses
// shrinking of .rel.dyn.
// See PrintUsage() below for full usage details.
//
// NOTE: Breaks with libelf 0.152, which is buggy. libelf 0.158 works.
#include <errno.h>
#include <fcntl.h>
#include <getopt.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
#include <string>
#include "debug.h"
#include "elf_file.h"
#include "elf_traits.h"
#include "libelf.h"
#include "nativehelper/ScopedFd.h"
static void PrintUsage(const char* argv0) {
std::string temporary = argv0;
const size_t last_slash = temporary.find_last_of("/");
if (last_slash != temporary.npos) {
temporary.erase(0, last_slash + 1);
}
const char* basename = temporary.c_str();
printf(
"Usage: %s [-u] [-v] [-p] file\n\n"
"Pack or unpack relative relocations in a shared library.\n\n"
" -u, --unpack unpack previously packed relative relocations\n"
" -v, --verbose trace object file modifications (for debugging)\n"
" -p, --pad do not shrink relocations, but pad (for debugging)\n\n",
basename);
printf(
"Debug sections are not handled, so packing should not be used on\n"
"shared libraries compiled for debugging or otherwise unstripped.\n");
}
int main(int argc, char* argv[]) {
bool is_unpacking = false;
bool is_verbose = false;
bool is_padding = false;
static const option options[] = {
{"unpack", 0, 0, 'u'}, {"verbose", 0, 0, 'v'}, {"pad", 0, 0, 'p'},
{"help", 0, 0, 'h'}, {NULL, 0, 0, 0}
};
bool has_options = true;
while (has_options) {
int c = getopt_long(argc, argv, "uvph", options, NULL);
switch (c) {
case 'u':
is_unpacking = true;
break;
case 'v':
is_verbose = true;
break;
case 'p':
is_padding = true;
break;
case 'h':
PrintUsage(argv[0]);
return 0;
case '?':
LOG(INFO) << "Try '" << argv[0] << " --help' for more information.";
return 1;
case -1:
has_options = false;
break;
default:
NOTREACHED();
return 1;
}
}
if (optind != argc - 1) {
LOG(INFO) << "Try '" << argv[0] << " --help' for more information.";
return 1;
}
if (elf_version(EV_CURRENT) == EV_NONE) {
LOG(WARNING) << "Elf Library is out of date!";
}
const char* file = argv[argc - 1];
ScopedFd fd(open(file, O_RDWR));
if (fd.get() == -1) {
LOG(ERROR) << file << ": " << strerror(errno);
return 1;
}
if (is_verbose)
relocation_packer::Logger::SetVerbose(1);
// We need to detect elf class in order to create
// correct implementation
uint8_t e_ident[EI_NIDENT];
if (TEMP_FAILURE_RETRY(read(fd.get(), e_ident, EI_NIDENT) != EI_NIDENT)) {
LOG(ERROR) << file << ": failed to read elf header:" << strerror(errno);
return 1;
}
if (TEMP_FAILURE_RETRY(lseek(fd.get(), 0, SEEK_SET)) != 0) {
LOG(ERROR) << file << ": lseek to 0 failed:" << strerror(errno);
return 1;
}
bool status = false;
if (e_ident[EI_CLASS] == ELFCLASS32) {
relocation_packer::ElfFile<ELF32_traits> elf_file(fd.get());
elf_file.SetPadding(is_padding);
if (is_unpacking) {
status = elf_file.UnpackRelocations();
} else {
status = elf_file.PackRelocations();
}
} else if (e_ident[EI_CLASS] == ELFCLASS64) {
relocation_packer::ElfFile<ELF64_traits> elf_file(fd.get());
elf_file.SetPadding(is_padding);
if (is_unpacking) {
status = elf_file.UnpackRelocations();
} else {
status = elf_file.PackRelocations();
}
} else {
LOG(ERROR) << file << ": unknown ELFCLASS: " << e_ident[EI_CLASS];
return 1;
}
if (!status) {
LOG(ERROR) << file << ": failed to pack/unpack file";
return 1;
}
return 0;
}
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