/*
* Copyright (C) 2012 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "elf_file.h"
#include <inttypes.h>
#include <sys/mman.h> // For the PROT_* and MAP_* constants.
#include <sys/types.h>
#include <unistd.h>
#include "android-base/stringprintf.h"
#include "android-base/strings.h"
#include "arch/instruction_set.h"
#include "base/leb128.h"
#include "base/stl_util.h"
#include "base/unix_file/fd_file.h"
#include "base/utils.h"
#include "elf_file_impl.h"
#include "elf_utils.h"
namespace art {
using android::base::StringPrintf;
template <typename ElfTypes>
ElfFileImpl<ElfTypes>::ElfFileImpl(File* file, bool writable,
bool program_header_only,
uint8_t* requested_base)
: writable_(writable),
program_header_only_(program_header_only),
header_(nullptr),
base_address_(nullptr),
program_headers_start_(nullptr),
section_headers_start_(nullptr),
dynamic_program_header_(nullptr),
dynamic_section_start_(nullptr),
symtab_section_start_(nullptr),
dynsym_section_start_(nullptr),
strtab_section_start_(nullptr),
dynstr_section_start_(nullptr),
hash_section_start_(nullptr),
symtab_symbol_table_(nullptr),
dynsym_symbol_table_(nullptr),
requested_base_(requested_base) {
CHECK(file != nullptr);
}
template <typename ElfTypes>
ElfFileImpl<ElfTypes>* ElfFileImpl<ElfTypes>::Open(File* file,
bool writable,
bool program_header_only,
bool low_4gb,
std::string* error_msg,
uint8_t* requested_base) {
std::unique_ptr<ElfFileImpl<ElfTypes>> elf_file(new ElfFileImpl<ElfTypes>
(file, writable, program_header_only, requested_base));
int prot;
int flags;
if (writable) {
prot = PROT_READ | PROT_WRITE;
flags = MAP_SHARED;
} else {
prot = PROT_READ;
flags = MAP_PRIVATE;
}
if (!elf_file->Setup(file, prot, flags, low_4gb, error_msg)) {
return nullptr;
}
return elf_file.release();
}
template <typename ElfTypes>
ElfFileImpl<ElfTypes>* ElfFileImpl<ElfTypes>::Open(File* file,
int prot,
int flags,
bool low_4gb,
std::string* error_msg) {
std::unique_ptr<ElfFileImpl<ElfTypes>> elf_file(new ElfFileImpl<ElfTypes>
(file, (prot & PROT_WRITE) == PROT_WRITE, /*program_header_only*/false,
/*requested_base*/nullptr));
if (!elf_file->Setup(file, prot, flags, low_4gb, error_msg)) {
return nullptr;
}
return elf_file.release();
}
template <typename ElfTypes>
bool ElfFileImpl<ElfTypes>::Setup(File* file,
int prot,
int flags,
bool low_4gb,
std::string* error_msg) {
int64_t temp_file_length = file->GetLength();
if (temp_file_length < 0) {
errno = -temp_file_length;
*error_msg = StringPrintf("Failed to get length of file: '%s' fd=%d: %s",
file->GetPath().c_str(), file->Fd(), strerror(errno));
return false;
}
size_t file_length = static_cast<size_t>(temp_file_length);
if (file_length < sizeof(Elf_Ehdr)) {
*error_msg = StringPrintf("File size of %zd bytes not large enough to contain ELF header of "
"%zd bytes: '%s'", file_length, sizeof(Elf_Ehdr),
file->GetPath().c_str());
return false;
}
if (program_header_only_) {
// first just map ELF header to get program header size information
size_t elf_header_size = sizeof(Elf_Ehdr);
if (!SetMap(file,
MemMap::MapFile(elf_header_size,
prot,
flags,
file->Fd(),
0,
low_4gb,
file->GetPath().c_str(),
error_msg),
error_msg)) {
return false;
}
// then remap to cover program header
size_t program_header_size = header_->e_phoff + (header_->e_phentsize * header_->e_phnum);
if (file_length < program_header_size) {
*error_msg = StringPrintf("File size of %zd bytes not large enough to contain ELF program "
"header of %zd bytes: '%s'", file_length,
sizeof(Elf_Ehdr), file->GetPath().c_str());
return false;
}
if (!SetMap(file,
MemMap::MapFile(program_header_size,
prot,
flags,
file->Fd(),
0,
low_4gb,
file->GetPath().c_str(),
error_msg),
error_msg)) {
*error_msg = StringPrintf("Failed to map ELF program headers: %s", error_msg->c_str());
return false;
}
} else {
// otherwise map entire file
if (!SetMap(file,
MemMap::MapFile(file->GetLength(),
prot,
flags,
file->Fd(),
0,
low_4gb,
file->GetPath().c_str(),
error_msg),
error_msg)) {
*error_msg = StringPrintf("Failed to map ELF file: %s", error_msg->c_str());
return false;
}
}
if (program_header_only_) {
program_headers_start_ = Begin() + GetHeader().e_phoff;
} else {
if (!CheckAndSet(GetHeader().e_phoff, "program headers", &program_headers_start_, error_msg)) {
return false;
}
// Setup section headers.
if (!CheckAndSet(GetHeader().e_shoff, "section headers", §ion_headers_start_, error_msg)) {
return false;
}
// Find shstrtab.
Elf_Shdr* shstrtab_section_header = GetSectionNameStringSection();
if (shstrtab_section_header == nullptr) {
*error_msg = StringPrintf("Failed to find shstrtab section header in ELF file: '%s'",
file->GetPath().c_str());
return false;
}
// Find .dynamic section info from program header
dynamic_program_header_ = FindProgamHeaderByType(PT_DYNAMIC);
if (dynamic_program_header_ == nullptr) {
*error_msg = StringPrintf("Failed to find PT_DYNAMIC program header in ELF file: '%s'",
file->GetPath().c_str());
return false;
}
if (!CheckAndSet(GetDynamicProgramHeader().p_offset, "dynamic section",
reinterpret_cast<uint8_t**>(&dynamic_section_start_), error_msg)) {
return false;
}
// Find other sections from section headers
for (Elf_Word i = 0; i < GetSectionHeaderNum(); i++) {
Elf_Shdr* section_header = GetSectionHeader(i);
if (section_header == nullptr) {
*error_msg = StringPrintf("Failed to find section header for section %d in ELF file: '%s'",
i, file->GetPath().c_str());
return false;
}
switch (section_header->sh_type) {
case SHT_SYMTAB: {
if (!CheckAndSet(section_header->sh_offset, "symtab",
reinterpret_cast<uint8_t**>(&symtab_section_start_), error_msg)) {
return false;
}
break;
}
case SHT_DYNSYM: {
if (!CheckAndSet(section_header->sh_offset, "dynsym",
reinterpret_cast<uint8_t**>(&dynsym_section_start_), error_msg)) {
return false;
}
break;
}
case SHT_STRTAB: {
// TODO: base these off of sh_link from .symtab and .dynsym above
if ((section_header->sh_flags & SHF_ALLOC) != 0) {
// Check that this is named ".dynstr" and ignore otherwise.
const char* header_name = GetString(*shstrtab_section_header, section_header->sh_name);
if (strncmp(".dynstr", header_name, 8) == 0) {
if (!CheckAndSet(section_header->sh_offset, "dynstr",
reinterpret_cast<uint8_t**>(&dynstr_section_start_), error_msg)) {
return false;
}
}
} else {
// Check that this is named ".strtab" and ignore otherwise.
const char* header_name = GetString(*shstrtab_section_header, section_header->sh_name);
if (strncmp(".strtab", header_name, 8) == 0) {
if (!CheckAndSet(section_header->sh_offset, "strtab",
reinterpret_cast<uint8_t**>(&strtab_section_start_), error_msg)) {
return false;
}
}
}
break;
}
case SHT_DYNAMIC: {
if (reinterpret_cast<uint8_t*>(dynamic_section_start_) !=
Begin() + section_header->sh_offset) {
LOG(WARNING) << "Failed to find matching SHT_DYNAMIC for PT_DYNAMIC in "
<< file->GetPath() << ": " << std::hex
<< reinterpret_cast<void*>(dynamic_section_start_)
<< " != " << reinterpret_cast<void*>(Begin() + section_header->sh_offset);
return false;
}
break;
}
case SHT_HASH: {
if (!CheckAndSet(section_header->sh_offset, "hash section",
reinterpret_cast<uint8_t**>(&hash_section_start_), error_msg)) {
return false;
}
break;
}
}
}
// Check for the existence of some sections.
if (!CheckSectionsExist(file, error_msg)) {
return false;
}
}
return true;
}
template <typename ElfTypes>
ElfFileImpl<ElfTypes>::~ElfFileImpl() {
STLDeleteElements(&segments_);
delete symtab_symbol_table_;
delete dynsym_symbol_table_;
}
template <typename ElfTypes>
bool ElfFileImpl<ElfTypes>::CheckAndSet(Elf32_Off offset, const char* label,
uint8_t** target, std::string* error_msg) {
if (Begin() + offset >= End()) {
*error_msg = StringPrintf("Offset %d is out of range for %s in ELF file: '%s'", offset, label,
file_path_.c_str());
return false;
}
*target = Begin() + offset;
return true;
}
template <typename ElfTypes>
bool ElfFileImpl<ElfTypes>::CheckSectionsLinked(const uint8_t* source,
const uint8_t* target) const {
// Only works in whole-program mode, as we need to iterate over the sections.
// Note that we normally can't search by type, as duplicates are allowed for most section types.
if (program_header_only_) {
return true;
}
Elf_Shdr* source_section = nullptr;
Elf_Word target_index = 0;
bool target_found = false;
for (Elf_Word i = 0; i < GetSectionHeaderNum(); i++) {
Elf_Shdr* section_header = GetSectionHeader(i);
if (Begin() + section_header->sh_offset == source) {
// Found the source.
source_section = section_header;
if (target_index) {
break;
}
} else if (Begin() + section_header->sh_offset == target) {
target_index = i;
target_found = true;
if (source_section != nullptr) {
break;
}
}
}
return target_found && source_section != nullptr && source_section->sh_link == target_index;
}
template <typename ElfTypes>
bool ElfFileImpl<ElfTypes>::CheckSectionsExist(File* file, std::string* error_msg) const {
if (!program_header_only_) {
// If in full mode, need section headers.
if (section_headers_start_ == nullptr) {
*error_msg = StringPrintf("No section headers in ELF file: '%s'", file->GetPath().c_str());
return false;
}
}
// This is redundant, but defensive.
if (dynamic_program_header_ == nullptr) {
*error_msg = StringPrintf("Failed to find PT_DYNAMIC program header in ELF file: '%s'",
file->GetPath().c_str());
return false;
}
// Need a dynamic section. This is redundant, but defensive.
if (dynamic_section_start_ == nullptr) {
*error_msg = StringPrintf("Failed to find dynamic section in ELF file: '%s'",
file->GetPath().c_str());
return false;
}
// Symtab validation. These is not really a hard failure, as we are currently not using the
// symtab internally, but it's nice to be defensive.
if (symtab_section_start_ != nullptr) {
// When there's a symtab, there should be a strtab.
if (strtab_section_start_ == nullptr) {
*error_msg = StringPrintf("No strtab for symtab in ELF file: '%s'", file->GetPath().c_str());
return false;
}
// The symtab should link to the strtab.
if (!CheckSectionsLinked(reinterpret_cast<const uint8_t*>(symtab_section_start_),
reinterpret_cast<const uint8_t*>(strtab_section_start_))) {
*error_msg = StringPrintf("Symtab is not linked to the strtab in ELF file: '%s'",
file->GetPath().c_str());
return false;
}
}
// We always need a dynstr & dynsym.
if (dynstr_section_start_ == nullptr) {
*error_msg = StringPrintf("No dynstr in ELF file: '%s'", file->GetPath().c_str());
return false;
}
if (dynsym_section_start_ == nullptr) {
*error_msg = StringPrintf("No dynsym in ELF file: '%s'", file->GetPath().c_str());
return false;
}
// Need a hash section for dynamic symbol lookup.
if (hash_section_start_ == nullptr) {
*error_msg = StringPrintf("Failed to find hash section in ELF file: '%s'",
file->GetPath().c_str());
return false;
}
// And the hash section should be linking to the dynsym.
if (!CheckSectionsLinked(reinterpret_cast<const uint8_t*>(hash_section_start_),
reinterpret_cast<const uint8_t*>(dynsym_section_start_))) {
*error_msg = StringPrintf("Hash section is not linked to the dynstr in ELF file: '%s'",
file->GetPath().c_str());
return false;
}
// We'd also like to confirm a shstrtab in program_header_only_ mode (else Open() does this for
// us). This is usually the last in an oat file, and a good indicator of whether writing was
// successful (or the process crashed and left garbage).
if (program_header_only_) {
// It might not be mapped, but we can compare against the file size.
int64_t offset = static_cast<int64_t>(GetHeader().e_shoff +
(GetHeader().e_shstrndx * GetHeader().e_shentsize));
if (offset >= file->GetLength()) {
*error_msg = StringPrintf("Shstrtab is not in the mapped ELF file: '%s'",
file->GetPath().c_str());
return false;
}
}
return true;
}
template <typename ElfTypes>
bool ElfFileImpl<ElfTypes>::SetMap(File* file, MemMap* map, std::string* error_msg) {
if (map == nullptr) {
// MemMap::Open should have already set an error.
DCHECK(!error_msg->empty());
return false;
}
map_.reset(map);
CHECK(map_.get() != nullptr) << file->GetPath();
CHECK(map_->Begin() != nullptr) << file->GetPath();
header_ = reinterpret_cast<Elf_Ehdr*>(map_->Begin());
if ((ELFMAG0 != header_->e_ident[EI_MAG0])
|| (ELFMAG1 != header_->e_ident[EI_MAG1])
|| (ELFMAG2 != header_->e_ident[EI_MAG2])
|| (ELFMAG3 != header_->e_ident[EI_MAG3])) {
*error_msg = StringPrintf("Failed to find ELF magic value %d %d %d %d in %s, found %d %d %d %d",
ELFMAG0, ELFMAG1, ELFMAG2, ELFMAG3,
file->GetPath().c_str(),
header_->e_ident[EI_MAG0],
header_->e_ident[EI_MAG1],
header_->e_ident[EI_MAG2],
header_->e_ident[EI_MAG3]);
return false;
}
uint8_t elf_class = (sizeof(Elf_Addr) == sizeof(Elf64_Addr)) ? ELFCLASS64 : ELFCLASS32;
if (elf_class != header_->e_ident[EI_CLASS]) {
*error_msg = StringPrintf("Failed to find expected EI_CLASS value %d in %s, found %d",
elf_class,
file->GetPath().c_str(),
header_->e_ident[EI_CLASS]);
return false;
}
if (ELFDATA2LSB != header_->e_ident[EI_DATA]) {
*error_msg = StringPrintf("Failed to find expected EI_DATA value %d in %s, found %d",
ELFDATA2LSB,
file->GetPath().c_str(),
header_->e_ident[EI_CLASS]);
return false;
}
if (EV_CURRENT != header_->e_ident[EI_VERSION]) {
*error_msg = StringPrintf("Failed to find expected EI_VERSION value %d in %s, found %d",
EV_CURRENT,
file->GetPath().c_str(),
header_->e_ident[EI_CLASS]);
return false;
}
if (ET_DYN != header_->e_type) {
*error_msg = StringPrintf("Failed to find expected e_type value %d in %s, found %d",
ET_DYN,
file->GetPath().c_str(),
header_->e_type);
return false;
}
if (EV_CURRENT != header_->e_version) {
*error_msg = StringPrintf("Failed to find expected e_version value %d in %s, found %d",
EV_CURRENT,
file->GetPath().c_str(),
header_->e_version);
return false;
}
if (0 != header_->e_entry) {
*error_msg = StringPrintf("Failed to find expected e_entry value %d in %s, found %d",
0,
file->GetPath().c_str(),
static_cast<int32_t>(header_->e_entry));
return false;
}
if (0 == header_->e_phoff) {
*error_msg = StringPrintf("Failed to find non-zero e_phoff value in %s",
file->GetPath().c_str());
return false;
}
if (0 == header_->e_shoff) {
*error_msg = StringPrintf("Failed to find non-zero e_shoff value in %s",
file->GetPath().c_str());
return false;
}
if (0 == header_->e_ehsize) {
*error_msg = StringPrintf("Failed to find non-zero e_ehsize value in %s",
file->GetPath().c_str());
return false;
}
if (0 == header_->e_phentsize) {
*error_msg = StringPrintf("Failed to find non-zero e_phentsize value in %s",
file->GetPath().c_str());
return false;
}
if (0 == header_->e_phnum) {
*error_msg = StringPrintf("Failed to find non-zero e_phnum value in %s",
file->GetPath().c_str());
return false;
}
if (0 == header_->e_shentsize) {
*error_msg = StringPrintf("Failed to find non-zero e_shentsize value in %s",
file->GetPath().c_str());
return false;
}
if (0 == header_->e_shnum) {
*error_msg = StringPrintf("Failed to find non-zero e_shnum value in %s",
file->GetPath().c_str());
return false;
}
if (0 == header_->e_shstrndx) {
*error_msg = StringPrintf("Failed to find non-zero e_shstrndx value in %s",
file->GetPath().c_str());
return false;
}
if (header_->e_shstrndx >= header_->e_shnum) {
*error_msg = StringPrintf("Failed to find e_shnum value %d less than %d in %s",
header_->e_shstrndx,
header_->e_shnum,
file->GetPath().c_str());
return false;
}
if (!program_header_only_) {
if (header_->e_phoff >= Size()) {
*error_msg = StringPrintf("Failed to find e_phoff value %" PRIu64 " less than %zd in %s",
static_cast<uint64_t>(header_->e_phoff),
Size(),
file->GetPath().c_str());
return false;
}
if (header_->e_shoff >= Size()) {
*error_msg = StringPrintf("Failed to find e_shoff value %" PRIu64 " less than %zd in %s",
static_cast<uint64_t>(header_->e_shoff),
Size(),
file->GetPath().c_str());
return false;
}
}
return true;
}
template <typename ElfTypes>
typename ElfTypes::Ehdr& ElfFileImpl<ElfTypes>::GetHeader() const {
CHECK(header_ != nullptr); // Header has been checked in SetMap. This is a sanity check.
return *header_;
}
template <typename ElfTypes>
uint8_t* ElfFileImpl<ElfTypes>::GetProgramHeadersStart() const {
CHECK(program_headers_start_ != nullptr); // Header has been set in Setup. This is a sanity
// check.
return program_headers_start_;
}
template <typename ElfTypes>
uint8_t* ElfFileImpl<ElfTypes>::GetSectionHeadersStart() const {
CHECK(!program_header_only_); // Only used in "full" mode.
CHECK(section_headers_start_ != nullptr); // Is checked in CheckSectionsExist. Sanity check.
return section_headers_start_;
}
template <typename ElfTypes>
typename ElfTypes::Phdr& ElfFileImpl<ElfTypes>::GetDynamicProgramHeader() const {
CHECK(dynamic_program_header_ != nullptr); // Is checked in CheckSectionsExist. Sanity check.
return *dynamic_program_header_;
}
template <typename ElfTypes>
typename ElfTypes::Dyn* ElfFileImpl<ElfTypes>::GetDynamicSectionStart() const {
CHECK(dynamic_section_start_ != nullptr); // Is checked in CheckSectionsExist. Sanity check.
return dynamic_section_start_;
}
template <typename ElfTypes>
typename ElfTypes::Sym* ElfFileImpl<ElfTypes>::GetSymbolSectionStart(
Elf_Word section_type) const {
CHECK(IsSymbolSectionType(section_type)) << file_path_ << " " << section_type;
switch (section_type) {
case SHT_SYMTAB: {
return symtab_section_start_;
break;
}
case SHT_DYNSYM: {
return dynsym_section_start_;
break;
}
default: {
LOG(FATAL) << section_type;
return nullptr;
}
}
}
template <typename ElfTypes>
const char* ElfFileImpl<ElfTypes>::GetStringSectionStart(
Elf_Word section_type) const {
CHECK(IsSymbolSectionType(section_type)) << file_path_ << " " << section_type;
switch (section_type) {
case SHT_SYMTAB: {
return strtab_section_start_;
}
case SHT_DYNSYM: {
return dynstr_section_start_;
}
default: {
LOG(FATAL) << section_type;
return nullptr;
}
}
}
template <typename ElfTypes>
const char* ElfFileImpl<ElfTypes>::GetString(Elf_Word section_type,
Elf_Word i) const {
CHECK(IsSymbolSectionType(section_type)) << file_path_ << " " << section_type;
if (i == 0) {
return nullptr;
}
const char* string_section_start = GetStringSectionStart(section_type);
if (string_section_start == nullptr) {
return nullptr;
}
return string_section_start + i;
}
// WARNING: The following methods do not check for an error condition (non-existent hash section).
// It is the caller's job to do this.
template <typename ElfTypes>
typename ElfTypes::Word* ElfFileImpl<ElfTypes>::GetHashSectionStart() const {
return hash_section_start_;
}
template <typename ElfTypes>
typename ElfTypes::Word ElfFileImpl<ElfTypes>::GetHashBucketNum() const {
return GetHashSectionStart()[0];
}
template <typename ElfTypes>
typename ElfTypes::Word ElfFileImpl<ElfTypes>::GetHashChainNum() const {
return GetHashSectionStart()[1];
}
template <typename ElfTypes>
typename ElfTypes::Word ElfFileImpl<ElfTypes>::GetHashBucket(size_t i, bool* ok) const {
if (i >= GetHashBucketNum()) {
*ok = false;
return 0;
}
*ok = true;
// 0 is nbucket, 1 is nchain
return GetHashSectionStart()[2 + i];
}
template <typename ElfTypes>
typename ElfTypes::Word ElfFileImpl<ElfTypes>::GetHashChain(size_t i, bool* ok) const {
if (i >= GetHashChainNum()) {
*ok = false;
return 0;
}
*ok = true;
// 0 is nbucket, 1 is nchain, & chains are after buckets
return GetHashSectionStart()[2 + GetHashBucketNum() + i];
}
template <typename ElfTypes>
typename ElfTypes::Word ElfFileImpl<ElfTypes>::GetProgramHeaderNum() const {
return GetHeader().e_phnum;
}
template <typename ElfTypes>
typename ElfTypes::Phdr* ElfFileImpl<ElfTypes>::GetProgramHeader(Elf_Word i) const {
CHECK_LT(i, GetProgramHeaderNum()) << file_path_; // Sanity check for caller.
uint8_t* program_header = GetProgramHeadersStart() + (i * GetHeader().e_phentsize);
if (program_header >= End()) {
return nullptr; // Failure condition.
}
return reinterpret_cast<Elf_Phdr*>(program_header);
}
template <typename ElfTypes>
typename ElfTypes::Phdr* ElfFileImpl<ElfTypes>::FindProgamHeaderByType(Elf_Word type) const {
for (Elf_Word i = 0; i < GetProgramHeaderNum(); i++) {
Elf_Phdr* program_header = GetProgramHeader(i);
if (program_header->p_type == type) {
return program_header;
}
}
return nullptr;
}
template <typename ElfTypes>
typename ElfTypes::Word ElfFileImpl<ElfTypes>::GetSectionHeaderNum() const {
return GetHeader().e_shnum;
}
template <typename ElfTypes>
typename ElfTypes::Shdr* ElfFileImpl<ElfTypes>::GetSectionHeader(Elf_Word i) const {
// Can only access arbitrary sections when we have the whole file, not just program header.
// Even if we Load(), it doesn't bring in all the sections.
CHECK(!program_header_only_) << file_path_;
if (i >= GetSectionHeaderNum()) {
return nullptr; // Failure condition.
}
uint8_t* section_header = GetSectionHeadersStart() + (i * GetHeader().e_shentsize);
if (section_header >= End()) {
return nullptr; // Failure condition.
}
return reinterpret_cast<Elf_Shdr*>(section_header);
}
template <typename ElfTypes>
typename ElfTypes::Shdr* ElfFileImpl<ElfTypes>::FindSectionByType(Elf_Word type) const {
// Can only access arbitrary sections when we have the whole file, not just program header.
// We could change this to switch on known types if they were detected during loading.
CHECK(!program_header_only_) << file_path_;
for (Elf_Word i = 0; i < GetSectionHeaderNum(); i++) {
Elf_Shdr* section_header = GetSectionHeader(i);
if (section_header->sh_type == type) {
return section_header;
}
}
return nullptr;
}
// from bionic
static unsigned elfhash(const char *_name) {
const unsigned char *name = (const unsigned char *) _name;
unsigned h = 0, g;
while (*name) {
h = (h << 4) + *name++;
g = h & 0xf0000000;
h ^= g;
h ^= g >> 24;
}
return h;
}
template <typename ElfTypes>
typename ElfTypes::Shdr* ElfFileImpl<ElfTypes>::GetSectionNameStringSection() const {
return GetSectionHeader(GetHeader().e_shstrndx);
}
template <typename ElfTypes>
const uint8_t* ElfFileImpl<ElfTypes>::FindDynamicSymbolAddress(
const std::string& symbol_name) const {
// Check that we have a hash section.
if (GetHashSectionStart() == nullptr) {
return nullptr; // Failure condition.
}
const Elf_Sym* sym = FindDynamicSymbol(symbol_name);
if (sym != nullptr) {
// TODO: we need to change this to calculate base_address_ in ::Open,
// otherwise it will be wrongly 0 if ::Load has not yet been called.
return base_address_ + sym->st_value;
} else {
return nullptr;
}
}
// WARNING: Only called from FindDynamicSymbolAddress. Elides check for hash section.
template <typename ElfTypes>
const typename ElfTypes::Sym* ElfFileImpl<ElfTypes>::FindDynamicSymbol(
const std::string& symbol_name) const {
if (GetHashBucketNum() == 0) {
// No dynamic symbols at all.
return nullptr;
}
Elf_Word hash = elfhash(symbol_name.c_str());
Elf_Word bucket_index = hash % GetHashBucketNum();
bool ok;
Elf_Word symbol_and_chain_index = GetHashBucket(bucket_index, &ok);
if (!ok) {
return nullptr;
}
while (symbol_and_chain_index != 0 /* STN_UNDEF */) {
Elf_Sym* symbol = GetSymbol(SHT_DYNSYM, symbol_and_chain_index);
if (symbol == nullptr) {
return nullptr; // Failure condition.
}
const char* name = GetString(SHT_DYNSYM, symbol->st_name);
if (symbol_name == name) {
return symbol;
}
symbol_and_chain_index = GetHashChain(symbol_and_chain_index, &ok);
if (!ok) {
return nullptr;
}
}
return nullptr;
}
template <typename ElfTypes>
bool ElfFileImpl<ElfTypes>::IsSymbolSectionType(Elf_Word section_type) {
return ((section_type == SHT_SYMTAB) || (section_type == SHT_DYNSYM));
}
template <typename ElfTypes>
typename ElfTypes::Word ElfFileImpl<ElfTypes>::GetSymbolNum(Elf_Shdr& section_header) const {
CHECK(IsSymbolSectionType(section_header.sh_type))
<< file_path_ << " " << section_header.sh_type;
CHECK_NE(0U, section_header.sh_entsize) << file_path_;
return section_header.sh_size / section_header.sh_entsize;
}
template <typename ElfTypes>
typename ElfTypes::Sym* ElfFileImpl<ElfTypes>::GetSymbol(Elf_Word section_type, Elf_Word i) const {
Elf_Sym* sym_start = GetSymbolSectionStart(section_type);
if (sym_start == nullptr) {
return nullptr;
}
return sym_start + i;
}
template <typename ElfTypes>
typename ElfFileImpl<ElfTypes>::SymbolTable**
ElfFileImpl<ElfTypes>::GetSymbolTable(Elf_Word section_type) {
CHECK(IsSymbolSectionType(section_type)) << file_path_ << " " << section_type;
switch (section_type) {
case SHT_SYMTAB: {
return &symtab_symbol_table_;
}
case SHT_DYNSYM: {
return &dynsym_symbol_table_;
}
default: {
LOG(FATAL) << section_type;
return nullptr;
}
}
}
template <typename ElfTypes>
typename ElfTypes::Sym* ElfFileImpl<ElfTypes>::FindSymbolByName(
Elf_Word section_type, const std::string& symbol_name, bool build_map) {
CHECK(!program_header_only_) << file_path_;
CHECK(IsSymbolSectionType(section_type)) << file_path_ << " " << section_type;
SymbolTable** symbol_table = GetSymbolTable(section_type);
if (*symbol_table != nullptr || build_map) {
if (*symbol_table == nullptr) {
DCHECK(build_map);
*symbol_table = new SymbolTable;
Elf_Shdr* symbol_section = FindSectionByType(section_type);
if (symbol_section == nullptr) {
return nullptr; // Failure condition.
}
Elf_Shdr* string_section = GetSectionHeader(symbol_section->sh_link);
if (string_section == nullptr) {
return nullptr; // Failure condition.
}
for (uint32_t i = 0; i < GetSymbolNum(*symbol_section); i++) {
Elf_Sym* symbol = GetSymbol(section_type, i);
if (symbol == nullptr) {
return nullptr; // Failure condition.
}
unsigned char type = (sizeof(Elf_Addr) == sizeof(Elf64_Addr))
? ELF64_ST_TYPE(symbol->st_info)
: ELF32_ST_TYPE(symbol->st_info);
if (type == STT_NOTYPE) {
continue;
}
const char* name = GetString(*string_section, symbol->st_name);
if (name == nullptr) {
continue;
}
std::pair<typename SymbolTable::iterator, bool> result =
(*symbol_table)->insert(std::make_pair(name, symbol));
if (!result.second) {
// If a duplicate, make sure it has the same logical value. Seen on x86.
if ((symbol->st_value != result.first->second->st_value) ||
(symbol->st_size != result.first->second->st_size) ||
(symbol->st_info != result.first->second->st_info) ||
(symbol->st_other != result.first->second->st_other) ||
(symbol->st_shndx != result.first->second->st_shndx)) {
return nullptr; // Failure condition.
}
}
}
}
CHECK(*symbol_table != nullptr);
typename SymbolTable::const_iterator it = (*symbol_table)->find(symbol_name);
if (it == (*symbol_table)->end()) {
return nullptr;
}
return it->second;
}
// Fall back to linear search
Elf_Shdr* symbol_section = FindSectionByType(section_type);
if (symbol_section == nullptr) {
return nullptr;
}
Elf_Shdr* string_section = GetSectionHeader(symbol_section->sh_link);
if (string_section == nullptr) {
return nullptr;
}
for (uint32_t i = 0; i < GetSymbolNum(*symbol_section); i++) {
Elf_Sym* symbol = GetSymbol(section_type, i);
if (symbol == nullptr) {
return nullptr; // Failure condition.
}
const char* name = GetString(*string_section, symbol->st_name);
if (name == nullptr) {
continue;
}
if (symbol_name == name) {
return symbol;
}
}
return nullptr;
}
template <typename ElfTypes>
typename ElfTypes::Addr ElfFileImpl<ElfTypes>::FindSymbolAddress(
Elf_Word section_type, const std::string& symbol_name, bool build_map) {
Elf_Sym* symbol = FindSymbolByName(section_type, symbol_name, build_map);
if (symbol == nullptr) {
return 0;
}
return symbol->st_value;
}
template <typename ElfTypes>
const char* ElfFileImpl<ElfTypes>::GetString(Elf_Shdr& string_section,
Elf_Word i) const {
CHECK(!program_header_only_) << file_path_;
// TODO: remove this static_cast from enum when using -std=gnu++0x
if (static_cast<Elf_Word>(SHT_STRTAB) != string_section.sh_type) {
return nullptr; // Failure condition.
}
if (i >= string_section.sh_size) {
return nullptr;
}
if (i == 0) {
return nullptr;
}
uint8_t* strings = Begin() + string_section.sh_offset;
uint8_t* string = strings + i;
if (string >= End()) {
return nullptr;
}
return reinterpret_cast<const char*>(string);
}
template <typename ElfTypes>
typename ElfTypes::Word ElfFileImpl<ElfTypes>::GetDynamicNum() const {
return GetDynamicProgramHeader().p_filesz / sizeof(Elf_Dyn);
}
template <typename ElfTypes>
typename ElfTypes::Dyn& ElfFileImpl<ElfTypes>::GetDynamic(Elf_Word i) const {
CHECK_LT(i, GetDynamicNum()) << file_path_;
return *(GetDynamicSectionStart() + i);
}
template <typename ElfTypes>
typename ElfTypes::Dyn* ElfFileImpl<ElfTypes>::FindDynamicByType(Elf_Sword type) const {
for (Elf_Word i = 0; i < GetDynamicNum(); i++) {
Elf_Dyn* dyn = &GetDynamic(i);
if (dyn->d_tag == type) {
return dyn;
}
}
return nullptr;
}
template <typename ElfTypes>
typename ElfTypes::Word ElfFileImpl<ElfTypes>::FindDynamicValueByType(Elf_Sword type) const {
Elf_Dyn* dyn = FindDynamicByType(type);
if (dyn == nullptr) {
return 0;
} else {
return dyn->d_un.d_val;
}
}
template <typename ElfTypes>
typename ElfTypes::Rel* ElfFileImpl<ElfTypes>::GetRelSectionStart(Elf_Shdr& section_header) const {
CHECK(SHT_REL == section_header.sh_type) << file_path_ << " " << section_header.sh_type;
return reinterpret_cast<Elf_Rel*>(Begin() + section_header.sh_offset);
}
template <typename ElfTypes>
typename ElfTypes::Word ElfFileImpl<ElfTypes>::GetRelNum(Elf_Shdr& section_header) const {
CHECK(SHT_REL == section_header.sh_type) << file_path_ << " " << section_header.sh_type;
CHECK_NE(0U, section_header.sh_entsize) << file_path_;
return section_header.sh_size / section_header.sh_entsize;
}
template <typename ElfTypes>
typename ElfTypes::Rel& ElfFileImpl<ElfTypes>::GetRel(Elf_Shdr& section_header, Elf_Word i) const {
CHECK(SHT_REL == section_header.sh_type) << file_path_ << " " << section_header.sh_type;
CHECK_LT(i, GetRelNum(section_header)) << file_path_;
return *(GetRelSectionStart(section_header) + i);
}
template <typename ElfTypes>
typename ElfTypes::Rela* ElfFileImpl<ElfTypes>::GetRelaSectionStart(Elf_Shdr& section_header) const {
CHECK(SHT_RELA == section_header.sh_type) << file_path_ << " " << section_header.sh_type;
return reinterpret_cast<Elf_Rela*>(Begin() + section_header.sh_offset);
}
template <typename ElfTypes>
typename ElfTypes::Word ElfFileImpl<ElfTypes>::GetRelaNum(Elf_Shdr& section_header) const {
CHECK(SHT_RELA == section_header.sh_type) << file_path_ << " " << section_header.sh_type;
return section_header.sh_size / section_header.sh_entsize;
}
template <typename ElfTypes>
typename ElfTypes::Rela& ElfFileImpl<ElfTypes>::GetRela(Elf_Shdr& section_header, Elf_Word i) const {
CHECK(SHT_RELA == section_header.sh_type) << file_path_ << " " << section_header.sh_type;
CHECK_LT(i, GetRelaNum(section_header)) << file_path_;
return *(GetRelaSectionStart(section_header) + i);
}
// Base on bionic phdr_table_get_load_size
template <typename ElfTypes>
bool ElfFileImpl<ElfTypes>::GetLoadedSize(size_t* size, std::string* error_msg) const {
Elf_Addr min_vaddr = static_cast<Elf_Addr>(-1);
Elf_Addr max_vaddr = 0u;
for (Elf_Word i = 0; i < GetProgramHeaderNum(); i++) {
Elf_Phdr* program_header = GetProgramHeader(i);
if (program_header->p_type != PT_LOAD) {
continue;
}
Elf_Addr begin_vaddr = program_header->p_vaddr;
if (begin_vaddr < min_vaddr) {
min_vaddr = begin_vaddr;
}
Elf_Addr end_vaddr = program_header->p_vaddr + program_header->p_memsz;
if (UNLIKELY(begin_vaddr > end_vaddr)) {
std::ostringstream oss;
oss << "Program header #" << i << " has overflow in p_vaddr+p_memsz: 0x" << std::hex
<< program_header->p_vaddr << "+0x" << program_header->p_memsz << "=0x" << end_vaddr
<< " in ELF file \"" << file_path_ << "\"";
*error_msg = oss.str();
*size = static_cast<size_t>(-1);
return false;
}
if (end_vaddr > max_vaddr) {
max_vaddr = end_vaddr;
}
}
min_vaddr = RoundDown(min_vaddr, kPageSize);
max_vaddr = RoundUp(max_vaddr, kPageSize);
CHECK_LT(min_vaddr, max_vaddr) << file_path_;
Elf_Addr loaded_size = max_vaddr - min_vaddr;
// Check that the loaded_size fits in size_t.
if (UNLIKELY(loaded_size > std::numeric_limits<size_t>::max())) {
std::ostringstream oss;
oss << "Loaded size is 0x" << std::hex << loaded_size << " but maximum size_t is 0x"
<< std::numeric_limits<size_t>::max() << " for ELF file \"" << file_path_ << "\"";
*error_msg = oss.str();
*size = static_cast<size_t>(-1);
return false;
}
*size = loaded_size;
return true;
}
template <typename ElfTypes>
bool ElfFileImpl<ElfTypes>::Load(File* file,
bool executable,
bool low_4gb,
std::string* error_msg) {
CHECK(program_header_only_) << file->GetPath();
if (executable) {
InstructionSet elf_ISA = GetInstructionSetFromELF(GetHeader().e_machine, GetHeader().e_flags);
if (elf_ISA != kRuntimeISA) {
std::ostringstream oss;
oss << "Expected ISA " << kRuntimeISA << " but found " << elf_ISA;
*error_msg = oss.str();
return false;
}
}
bool reserved = false;
for (Elf_Word i = 0; i < GetProgramHeaderNum(); i++) {
Elf_Phdr* program_header = GetProgramHeader(i);
if (program_header == nullptr) {
*error_msg = StringPrintf("No program header for entry %d in ELF file %s.",
i, file->GetPath().c_str());
return false;
}
// Record .dynamic header information for later use
if (program_header->p_type == PT_DYNAMIC) {
dynamic_program_header_ = program_header;
continue;
}
// Not something to load, move on.
if (program_header->p_type != PT_LOAD) {
continue;
}
// Found something to load.
// Before load the actual segments, reserve a contiguous chunk
// of required size and address for all segments, but with no
// permissions. We'll then carve that up with the proper
// permissions as we load the actual segments. If p_vaddr is
// non-zero, the segments require the specific address specified,
// which either was specified in the file because we already set
// base_address_ after the first zero segment).
int64_t temp_file_length = file->GetLength();
if (temp_file_length < 0) {
errno = -temp_file_length;
*error_msg = StringPrintf("Failed to get length of file: '%s' fd=%d: %s",
file->GetPath().c_str(), file->Fd(), strerror(errno));
return false;
}
size_t file_length = static_cast<size_t>(temp_file_length);
if (!reserved) {
uint8_t* reserve_base = reinterpret_cast<uint8_t*>(program_header->p_vaddr);
uint8_t* reserve_base_override = reserve_base;
// Override the base (e.g. when compiling with --compile-pic)
if (requested_base_ != nullptr) {
reserve_base_override = requested_base_;
}
std::string reservation_name("ElfFile reservation for ");
reservation_name += file->GetPath();
size_t loaded_size;
if (!GetLoadedSize(&loaded_size, error_msg)) {
DCHECK(!error_msg->empty());
return false;
}
std::unique_ptr<MemMap> reserve(MemMap::MapAnonymous(reservation_name.c_str(),
reserve_base_override,
loaded_size,
PROT_NONE,
low_4gb,
false,
error_msg));
if (reserve.get() == nullptr) {
*error_msg = StringPrintf("Failed to allocate %s: %s",
reservation_name.c_str(), error_msg->c_str());
return false;
}
reserved = true;
// Base address is the difference of actual mapped location and the p_vaddr
base_address_ = reinterpret_cast<uint8_t*>(reinterpret_cast<uintptr_t>(reserve->Begin())
- reinterpret_cast<uintptr_t>(reserve_base));
// By adding the p_vaddr of a section/symbol to base_address_ we will always get the
// dynamic memory address of where that object is actually mapped
//
// TODO: base_address_ needs to be calculated in ::Open, otherwise
// FindDynamicSymbolAddress returns the wrong values until Load is called.
segments_.push_back(reserve.release());
}
// empty segment, nothing to map
if (program_header->p_memsz == 0) {
continue;
}
uint8_t* p_vaddr = base_address_ + program_header->p_vaddr;
int prot = 0;
if (executable && ((program_header->p_flags & PF_X) != 0)) {
prot |= PROT_EXEC;
}
if ((program_header->p_flags & PF_W) != 0) {
prot |= PROT_WRITE;
}
if ((program_header->p_flags & PF_R) != 0) {
prot |= PROT_READ;
}
int flags = 0;
if (writable_) {
prot |= PROT_WRITE;
flags |= MAP_SHARED;
} else {
flags |= MAP_PRIVATE;
}
if (program_header->p_filesz > program_header->p_memsz) {
*error_msg = StringPrintf("Invalid p_filesz > p_memsz (%" PRIu64 " > %" PRIu64 "): %s",
static_cast<uint64_t>(program_header->p_filesz),
static_cast<uint64_t>(program_header->p_memsz),
file->GetPath().c_str());
return false;
}
if (program_header->p_filesz < program_header->p_memsz &&
!IsAligned<kPageSize>(program_header->p_filesz)) {
*error_msg = StringPrintf("Unsupported unaligned p_filesz < p_memsz (%" PRIu64
" < %" PRIu64 "): %s",
static_cast<uint64_t>(program_header->p_filesz),
static_cast<uint64_t>(program_header->p_memsz),
file->GetPath().c_str());
return false;
}
if (file_length < (program_header->p_offset + program_header->p_filesz)) {
*error_msg = StringPrintf("File size of %zd bytes not large enough to contain ELF segment "
"%d of %" PRIu64 " bytes: '%s'", file_length, i,
static_cast<uint64_t>(program_header->p_offset + program_header->p_filesz),
file->GetPath().c_str());
return false;
}
if (program_header->p_filesz != 0u) {
std::unique_ptr<MemMap> segment(
MemMap::MapFileAtAddress(p_vaddr,
program_header->p_filesz,
prot,
flags,
file->Fd(),
program_header->p_offset,
/*low4_gb*/false,
/*reuse*/true, // implies MAP_FIXED
file->GetPath().c_str(),
error_msg));
if (segment.get() == nullptr) {
*error_msg = StringPrintf("Failed to map ELF file segment %d from %s: %s",
i, file->GetPath().c_str(), error_msg->c_str());
return false;
}
if (segment->Begin() != p_vaddr) {
*error_msg = StringPrintf("Failed to map ELF file segment %d from %s at expected address %p, "
"instead mapped to %p",
i, file->GetPath().c_str(), p_vaddr, segment->Begin());
return false;
}
segments_.push_back(segment.release());
}
if (program_header->p_filesz < program_header->p_memsz) {
std::string name = StringPrintf("Zero-initialized segment %" PRIu64 " of ELF file %s",
static_cast<uint64_t>(i), file->GetPath().c_str());
std::unique_ptr<MemMap> segment(
MemMap::MapAnonymous(name.c_str(),
p_vaddr + program_header->p_filesz,
program_header->p_memsz - program_header->p_filesz,
prot, false, true /* reuse */, error_msg));
if (segment == nullptr) {
*error_msg = StringPrintf("Failed to map zero-initialized ELF file segment %d from %s: %s",
i, file->GetPath().c_str(), error_msg->c_str());
return false;
}
if (segment->Begin() != p_vaddr) {
*error_msg = StringPrintf("Failed to map zero-initialized ELF file segment %d from %s "
"at expected address %p, instead mapped to %p",
i, file->GetPath().c_str(), p_vaddr, segment->Begin());
return false;
}
segments_.push_back(segment.release());
}
}
// Now that we are done loading, .dynamic should be in memory to find .dynstr, .dynsym, .hash
uint8_t* dsptr = base_address_ + GetDynamicProgramHeader().p_vaddr;
if ((dsptr < Begin() || dsptr >= End()) && !ValidPointer(dsptr)) {
*error_msg = StringPrintf("dynamic section address invalid in ELF file %s",
file->GetPath().c_str());
return false;
}
dynamic_section_start_ = reinterpret_cast<Elf_Dyn*>(dsptr);
for (Elf_Word i = 0; i < GetDynamicNum(); i++) {
Elf_Dyn& elf_dyn = GetDynamic(i);
uint8_t* d_ptr = base_address_ + elf_dyn.d_un.d_ptr;
switch (elf_dyn.d_tag) {
case DT_HASH: {
if (!ValidPointer(d_ptr)) {
*error_msg = StringPrintf("DT_HASH value %p does not refer to a loaded ELF segment of %s",
d_ptr, file->GetPath().c_str());
return false;
}
hash_section_start_ = reinterpret_cast<Elf_Word*>(d_ptr);
break;
}
case DT_STRTAB: {
if (!ValidPointer(d_ptr)) {
*error_msg = StringPrintf("DT_HASH value %p does not refer to a loaded ELF segment of %s",
d_ptr, file->GetPath().c_str());
return false;
}
dynstr_section_start_ = reinterpret_cast<char*>(d_ptr);
break;
}
case DT_SYMTAB: {
if (!ValidPointer(d_ptr)) {
*error_msg = StringPrintf("DT_HASH value %p does not refer to a loaded ELF segment of %s",
d_ptr, file->GetPath().c_str());
return false;
}
dynsym_section_start_ = reinterpret_cast<Elf_Sym*>(d_ptr);
break;
}
case DT_NULL: {
if (GetDynamicNum() != i+1) {
*error_msg = StringPrintf("DT_NULL found after %d .dynamic entries, "
"expected %d as implied by size of PT_DYNAMIC segment in %s",
i + 1, GetDynamicNum(), file->GetPath().c_str());
return false;
}
break;
}
}
}
// Check for the existence of some sections.
if (!CheckSectionsExist(file, error_msg)) {
return false;
}
return true;
}
template <typename ElfTypes>
bool ElfFileImpl<ElfTypes>::ValidPointer(const uint8_t* start) const {
for (size_t i = 0; i < segments_.size(); ++i) {
const MemMap* segment = segments_[i];
if (segment->Begin() <= start && start < segment->End()) {
return true;
}
}
return false;
}
template <typename ElfTypes>
typename ElfTypes::Shdr* ElfFileImpl<ElfTypes>::FindSectionByName(
const std::string& name) const {
CHECK(!program_header_only_);
Elf_Shdr* shstrtab_sec = GetSectionNameStringSection();
if (shstrtab_sec == nullptr) {
return nullptr;
}
for (uint32_t i = 0; i < GetSectionHeaderNum(); i++) {
Elf_Shdr* shdr = GetSectionHeader(i);
if (shdr == nullptr) {
return nullptr;
}
const char* sec_name = GetString(*shstrtab_sec, shdr->sh_name);
if (sec_name == nullptr) {
continue;
}
if (name == sec_name) {
return shdr;
}
}
return nullptr;
}
template <typename ElfTypes>
bool ElfFileImpl<ElfTypes>::FixupDebugSections(Elf_Addr base_address_delta) {
if (base_address_delta == 0) {
return true;
}
return ApplyOatPatchesTo(".debug_frame", base_address_delta) &&
ApplyOatPatchesTo(".debug_info", base_address_delta) &&
ApplyOatPatchesTo(".debug_line", base_address_delta);
}
template <typename ElfTypes>
bool ElfFileImpl<ElfTypes>::ApplyOatPatchesTo(
const char* target_section_name, Elf_Addr delta) {
auto target_section = FindSectionByName(target_section_name);
if (target_section == nullptr) {
return true;
}
std::string patches_name = target_section_name + std::string(".oat_patches");
auto patches_section = FindSectionByName(patches_name.c_str());
if (patches_section == nullptr) {
LOG(ERROR) << patches_name << " section not found.";
return false;
}
if (patches_section->sh_type != SHT_OAT_PATCH) {
LOG(ERROR) << "Unexpected type of " << patches_name;
return false;
}
ApplyOatPatches(
Begin() + patches_section->sh_offset,
Begin() + patches_section->sh_offset + patches_section->sh_size,
delta,
Begin() + target_section->sh_offset,
Begin() + target_section->sh_offset + target_section->sh_size);
return true;
}
// Apply LEB128 encoded patches to given section.
template <typename ElfTypes>
void ElfFileImpl<ElfTypes>::ApplyOatPatches(
const uint8_t* patches, const uint8_t* patches_end, Elf_Addr delta,
uint8_t* to_patch, const uint8_t* to_patch_end) {
typedef __attribute__((__aligned__(1))) Elf_Addr UnalignedAddress;
while (patches < patches_end) {
to_patch += DecodeUnsignedLeb128(&patches);
DCHECK_LE(patches, patches_end) << "Unexpected end of patch list.";
DCHECK_LT(to_patch, to_patch_end) << "Patch past the end of section.";
*reinterpret_cast<UnalignedAddress*>(to_patch) += delta;
}
}
template <typename ElfTypes>
bool ElfFileImpl<ElfTypes>::Strip(File* file, std::string* error_msg) {
// ELF files produced by MCLinker look roughly like this
//
// +------------+
// | Elf_Ehdr | contains number of Elf_Shdr and offset to first
// +------------+
// | Elf_Phdr | program headers
// | Elf_Phdr |
// | ... |
// | Elf_Phdr |
// +------------+
// | section | mixture of needed and unneeded sections
// +------------+
// | section |
// +------------+
// | ... |
// +------------+
// | section |
// +------------+
// | Elf_Shdr | section headers
// | Elf_Shdr |
// | ... | contains offset to section start
// | Elf_Shdr |
// +------------+
//
// To strip:
// - leave the Elf_Ehdr and Elf_Phdr values in place.
// - walk the sections making a new set of Elf_Shdr section headers for what we want to keep
// - move the sections are keeping up to fill in gaps of sections we want to strip
// - write new Elf_Shdr section headers to end of file, updating Elf_Ehdr
// - truncate rest of file
//
std::vector<Elf_Shdr> section_headers;
std::vector<Elf_Word> section_headers_original_indexes;
section_headers.reserve(GetSectionHeaderNum());
Elf_Shdr* string_section = GetSectionNameStringSection();
CHECK(string_section != nullptr);
for (Elf_Word i = 0; i < GetSectionHeaderNum(); i++) {
Elf_Shdr* sh = GetSectionHeader(i);
CHECK(sh != nullptr);
const char* name = GetString(*string_section, sh->sh_name);
if (name == nullptr) {
CHECK_EQ(0U, i);
section_headers.push_back(*sh);
section_headers_original_indexes.push_back(0);
continue;
}
if (android::base::StartsWith(name, ".debug")
|| (strcmp(name, ".strtab") == 0)
|| (strcmp(name, ".symtab") == 0)) {
continue;
}
section_headers.push_back(*sh);
section_headers_original_indexes.push_back(i);
}
CHECK_NE(0U, section_headers.size());
CHECK_EQ(section_headers.size(), section_headers_original_indexes.size());
// section 0 is the null section, sections start at offset of first section
CHECK(GetSectionHeader(1) != nullptr);
Elf_Off offset = GetSectionHeader(1)->sh_offset;
for (size_t i = 1; i < section_headers.size(); i++) {
Elf_Shdr& new_sh = section_headers[i];
Elf_Shdr* old_sh = GetSectionHeader(section_headers_original_indexes[i]);
CHECK(old_sh != nullptr);
CHECK_EQ(new_sh.sh_name, old_sh->sh_name);
if (old_sh->sh_addralign > 1) {
offset = RoundUp(offset, old_sh->sh_addralign);
}
if (old_sh->sh_offset == offset) {
// already in place
offset += old_sh->sh_size;
continue;
}
// shift section earlier
memmove(Begin() + offset,
Begin() + old_sh->sh_offset,
old_sh->sh_size);
new_sh.sh_offset = offset;
offset += old_sh->sh_size;
}
Elf_Off shoff = offset;
size_t section_headers_size_in_bytes = section_headers.size() * sizeof(Elf_Shdr);
memcpy(Begin() + offset, §ion_headers[0], section_headers_size_in_bytes);
offset += section_headers_size_in_bytes;
GetHeader().e_shnum = section_headers.size();
GetHeader().e_shoff = shoff;
int result = ftruncate(file->Fd(), offset);
if (result != 0) {
*error_msg = StringPrintf("Failed to truncate while stripping ELF file: '%s': %s",
file->GetPath().c_str(), strerror(errno));
return false;
}
return true;
}
static const bool DEBUG_FIXUP = false;
template <typename ElfTypes>
bool ElfFileImpl<ElfTypes>::Fixup(Elf_Addr base_address) {
if (!FixupDynamic(base_address)) {
LOG(WARNING) << "Failed to fixup .dynamic in " << file_path_;
return false;
}
if (!FixupSectionHeaders(base_address)) {
LOG(WARNING) << "Failed to fixup section headers in " << file_path_;
return false;
}
if (!FixupProgramHeaders(base_address)) {
LOG(WARNING) << "Failed to fixup program headers in " << file_path_;
return false;
}
if (!FixupSymbols(base_address, true)) {
LOG(WARNING) << "Failed to fixup .dynsym in " << file_path_;
return false;
}
if (!FixupSymbols(base_address, false)) {
LOG(WARNING) << "Failed to fixup .symtab in " << file_path_;
return false;
}
if (!FixupRelocations(base_address)) {
LOG(WARNING) << "Failed to fixup .rel.dyn in " << file_path_;
return false;
}
static_assert(sizeof(Elf_Off) >= sizeof(base_address), "Potentially losing precision.");
if (!FixupDebugSections(static_cast<Elf_Off>(base_address))) {
LOG(WARNING) << "Failed to fixup debug sections in " << file_path_;
return false;
}
return true;
}
template <typename ElfTypes>
bool ElfFileImpl<ElfTypes>::FixupDynamic(Elf_Addr base_address) {
for (Elf_Word i = 0; i < GetDynamicNum(); i++) {
Elf_Dyn& elf_dyn = GetDynamic(i);
Elf_Word d_tag = elf_dyn.d_tag;
if (IsDynamicSectionPointer(d_tag, GetHeader().e_machine)) {
Elf_Addr d_ptr = elf_dyn.d_un.d_ptr;
if (DEBUG_FIXUP) {
LOG(INFO) << StringPrintf("In %s moving Elf_Dyn[%d] from 0x%" PRIx64 " to 0x%" PRIx64,
file_path_.c_str(), i,
static_cast<uint64_t>(d_ptr),
static_cast<uint64_t>(d_ptr + base_address));
}
d_ptr += base_address;
elf_dyn.d_un.d_ptr = d_ptr;
}
}
return true;
}
template <typename ElfTypes>
bool ElfFileImpl<ElfTypes>::FixupSectionHeaders(Elf_Addr base_address) {
for (Elf_Word i = 0; i < GetSectionHeaderNum(); i++) {
Elf_Shdr* sh = GetSectionHeader(i);
CHECK(sh != nullptr);
// 0 implies that the section will not exist in the memory of the process
if (sh->sh_addr == 0) {
continue;
}
if (DEBUG_FIXUP) {
LOG(INFO) << StringPrintf("In %s moving Elf_Shdr[%d] from 0x%" PRIx64 " to 0x%" PRIx64,
file_path_.c_str(), i,
static_cast<uint64_t>(sh->sh_addr),
static_cast<uint64_t>(sh->sh_addr + base_address));
}
sh->sh_addr += base_address;
}
return true;
}
template <typename ElfTypes>
bool ElfFileImpl<ElfTypes>::FixupProgramHeaders(Elf_Addr base_address) {
// TODO: ELFObjectFile doesn't have give to Elf_Phdr, so we do that ourselves for now.
for (Elf_Word i = 0; i < GetProgramHeaderNum(); i++) {
Elf_Phdr* ph = GetProgramHeader(i);
CHECK(ph != nullptr);
CHECK_EQ(ph->p_vaddr, ph->p_paddr) << file_path_ << " i=" << i;
CHECK((ph->p_align == 0) || (0 == ((ph->p_vaddr - ph->p_offset) & (ph->p_align - 1))))
<< file_path_ << " i=" << i;
if (DEBUG_FIXUP) {
LOG(INFO) << StringPrintf("In %s moving Elf_Phdr[%d] from 0x%" PRIx64 " to 0x%" PRIx64,
file_path_.c_str(), i,
static_cast<uint64_t>(ph->p_vaddr),
static_cast<uint64_t>(ph->p_vaddr + base_address));
}
ph->p_vaddr += base_address;
ph->p_paddr += base_address;
CHECK((ph->p_align == 0) || (0 == ((ph->p_vaddr - ph->p_offset) & (ph->p_align - 1))))
<< file_path_ << " i=" << i;
}
return true;
}
template <typename ElfTypes>
bool ElfFileImpl<ElfTypes>::FixupSymbols(Elf_Addr base_address, bool dynamic) {
Elf_Word section_type = dynamic ? SHT_DYNSYM : SHT_SYMTAB;
// TODO: Unfortunate ELFObjectFile has protected symbol access, so use ElfFile
Elf_Shdr* symbol_section = FindSectionByType(section_type);
if (symbol_section == nullptr) {
// file is missing optional .symtab
CHECK(!dynamic) << file_path_;
return true;
}
for (uint32_t i = 0; i < GetSymbolNum(*symbol_section); i++) {
Elf_Sym* symbol = GetSymbol(section_type, i);
CHECK(symbol != nullptr);
if (symbol->st_value != 0) {
if (DEBUG_FIXUP) {
LOG(INFO) << StringPrintf("In %s moving Elf_Sym[%d] from 0x%" PRIx64 " to 0x%" PRIx64,
file_path_.c_str(), i,
static_cast<uint64_t>(symbol->st_value),
static_cast<uint64_t>(symbol->st_value + base_address));
}
symbol->st_value += base_address;
}
}
return true;
}
template <typename ElfTypes>
bool ElfFileImpl<ElfTypes>::FixupRelocations(Elf_Addr base_address) {
for (Elf_Word i = 0; i < GetSectionHeaderNum(); i++) {
Elf_Shdr* sh = GetSectionHeader(i);
CHECK(sh != nullptr);
if (sh->sh_type == SHT_REL) {
for (uint32_t j = 0; j < GetRelNum(*sh); j++) {
Elf_Rel& rel = GetRel(*sh, j);
if (DEBUG_FIXUP) {
LOG(INFO) << StringPrintf("In %s moving Elf_Rel[%d] from 0x%" PRIx64 " to 0x%" PRIx64,
file_path_.c_str(), j,
static_cast<uint64_t>(rel.r_offset),
static_cast<uint64_t>(rel.r_offset + base_address));
}
rel.r_offset += base_address;
}
} else if (sh->sh_type == SHT_RELA) {
for (uint32_t j = 0; j < GetRelaNum(*sh); j++) {
Elf_Rela& rela = GetRela(*sh, j);
if (DEBUG_FIXUP) {
LOG(INFO) << StringPrintf("In %s moving Elf_Rela[%d] from 0x%" PRIx64 " to 0x%" PRIx64,
file_path_.c_str(), j,
static_cast<uint64_t>(rela.r_offset),
static_cast<uint64_t>(rela.r_offset + base_address));
}
rela.r_offset += base_address;
}
}
}
return true;
}
// Explicit instantiations
template class ElfFileImpl<ElfTypes32>;
template class ElfFileImpl<ElfTypes64>;
ElfFile::ElfFile(ElfFileImpl32* elf32) : elf32_(elf32), elf64_(nullptr) {
}
ElfFile::ElfFile(ElfFileImpl64* elf64) : elf32_(nullptr), elf64_(elf64) {
}
ElfFile::~ElfFile() {
// Should never have 32 and 64-bit impls.
CHECK_NE(elf32_.get() == nullptr, elf64_.get() == nullptr);
}
ElfFile* ElfFile::Open(File* file,
bool writable,
bool program_header_only,
bool low_4gb,
std::string* error_msg,
uint8_t* requested_base) {
if (file->GetLength() < EI_NIDENT) {
*error_msg = StringPrintf("File %s is too short to be a valid ELF file",
file->GetPath().c_str());
return nullptr;
}
std::unique_ptr<MemMap> map(MemMap::MapFile(EI_NIDENT,
PROT_READ,
MAP_PRIVATE,
file->Fd(),
0,
low_4gb,
file->GetPath().c_str(),
error_msg));
if (map == nullptr || map->Size() != EI_NIDENT) {
return nullptr;
}
uint8_t* header = map->Begin();
if (header[EI_CLASS] == ELFCLASS64) {
ElfFileImpl64* elf_file_impl = ElfFileImpl64::Open(file,
writable,
program_header_only,
low_4gb,
error_msg,
requested_base);
if (elf_file_impl == nullptr) {
return nullptr;
}
return new ElfFile(elf_file_impl);
} else if (header[EI_CLASS] == ELFCLASS32) {
ElfFileImpl32* elf_file_impl = ElfFileImpl32::Open(file,
writable,
program_header_only,
low_4gb,
error_msg,
requested_base);
if (elf_file_impl == nullptr) {
return nullptr;
}
return new ElfFile(elf_file_impl);
} else {
*error_msg = StringPrintf("Failed to find expected EI_CLASS value %d or %d in %s, found %d",
ELFCLASS32, ELFCLASS64,
file->GetPath().c_str(),
header[EI_CLASS]);
return nullptr;
}
}
ElfFile* ElfFile::Open(File* file, int mmap_prot, int mmap_flags, std::string* error_msg) {
// low_4gb support not required for this path.
constexpr bool low_4gb = false;
if (file->GetLength() < EI_NIDENT) {
*error_msg = StringPrintf("File %s is too short to be a valid ELF file",
file->GetPath().c_str());
return nullptr;
}
std::unique_ptr<MemMap> map(MemMap::MapFile(EI_NIDENT,
PROT_READ,
MAP_PRIVATE,
file->Fd(),
0,
low_4gb,
file->GetPath().c_str(),
error_msg));
if (map == nullptr || map->Size() != EI_NIDENT) {
return nullptr;
}
uint8_t* header = map->Begin();
if (header[EI_CLASS] == ELFCLASS64) {
ElfFileImpl64* elf_file_impl = ElfFileImpl64::Open(file,
mmap_prot,
mmap_flags,
low_4gb,
error_msg);
if (elf_file_impl == nullptr) {
return nullptr;
}
return new ElfFile(elf_file_impl);
} else if (header[EI_CLASS] == ELFCLASS32) {
ElfFileImpl32* elf_file_impl = ElfFileImpl32::Open(file,
mmap_prot,
mmap_flags,
low_4gb,
error_msg);
if (elf_file_impl == nullptr) {
return nullptr;
}
return new ElfFile(elf_file_impl);
} else {
*error_msg = StringPrintf("Failed to find expected EI_CLASS value %d or %d in %s, found %d",
ELFCLASS32, ELFCLASS64,
file->GetPath().c_str(),
header[EI_CLASS]);
return nullptr;
}
}
#define DELEGATE_TO_IMPL(func, ...) \
if (elf64_.get() != nullptr) { \
return elf64_->func(__VA_ARGS__); \
} else { \
DCHECK(elf32_.get() != nullptr); \
return elf32_->func(__VA_ARGS__); \
}
bool ElfFile::Load(File* file, bool executable, bool low_4gb, std::string* error_msg) {
DELEGATE_TO_IMPL(Load, file, executable, low_4gb, error_msg);
}
const uint8_t* ElfFile::FindDynamicSymbolAddress(const std::string& symbol_name) const {
DELEGATE_TO_IMPL(FindDynamicSymbolAddress, symbol_name);
}
size_t ElfFile::Size() const {
DELEGATE_TO_IMPL(Size);
}
uint8_t* ElfFile::Begin() const {
DELEGATE_TO_IMPL(Begin);
}
uint8_t* ElfFile::End() const {
DELEGATE_TO_IMPL(End);
}
const std::string& ElfFile::GetFilePath() const {
DELEGATE_TO_IMPL(GetFilePath);
}
bool ElfFile::GetSectionOffsetAndSize(const char* section_name, uint64_t* offset,
uint64_t* size) const {
if (elf32_.get() == nullptr) {
CHECK(elf64_.get() != nullptr);
Elf64_Shdr *shdr = elf64_->FindSectionByName(section_name);
if (shdr == nullptr) {
return false;
}
if (offset != nullptr) {
*offset = shdr->sh_offset;
}
if (size != nullptr) {
*size = shdr->sh_size;
}
return true;
} else {
Elf32_Shdr *shdr = elf32_->FindSectionByName(section_name);
if (shdr == nullptr) {
return false;
}
if (offset != nullptr) {
*offset = shdr->sh_offset;
}
if (size != nullptr) {
*size = shdr->sh_size;
}
return true;
}
}
bool ElfFile::HasSection(const std::string& name) const {
if (elf64_.get() != nullptr) {
return elf64_->FindSectionByName(name) != nullptr;
} else {
return elf32_->FindSectionByName(name) != nullptr;
}
}
uint64_t ElfFile::FindSymbolAddress(unsigned section_type,
const std::string& symbol_name,
bool build_map) {
DELEGATE_TO_IMPL(FindSymbolAddress, section_type, symbol_name, build_map);
}
bool ElfFile::GetLoadedSize(size_t* size, std::string* error_msg) const {
DELEGATE_TO_IMPL(GetLoadedSize, size, error_msg);
}
bool ElfFile::Strip(File* file, std::string* error_msg) {
std::unique_ptr<ElfFile> elf_file(ElfFile::Open(file, true, false, /*low_4gb*/false, error_msg));
if (elf_file.get() == nullptr) {
return false;
}
if (elf_file->elf64_.get() != nullptr) {
return elf_file->elf64_->Strip(file, error_msg);
} else {
return elf_file->elf32_->Strip(file, error_msg);
}
}
bool ElfFile::Fixup(uint64_t base_address) {
if (elf64_.get() != nullptr) {
return elf64_->Fixup(static_cast<Elf64_Addr>(base_address));
} else {
DCHECK(elf32_.get() != nullptr);
CHECK(IsUint<32>(base_address)) << std::hex << base_address;
return elf32_->Fixup(static_cast<Elf32_Addr>(base_address));
}
DELEGATE_TO_IMPL(Fixup, base_address);
}
} // namespace art