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android / platform / art / 98d43cb / . / runtime / elf_file.cc
blob: 6179b5e8d1bf698e0d2b236028786a5a4fc3fcf6 [file] [log] [blame]
/*
* 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 <sys/types.h>
#include <unistd.h>
#include "base/logging.h"
#include "base/stringprintf.h"
#include "base/stl_util.h"
#include "dwarf.h"
#include "leb128.h"
#include "utils.h"
#include "instruction_set.h"
namespace art {
// -------------------------------------------------------------------
// Binary GDB JIT Interface as described in
// http://sourceware.org/gdb/onlinedocs/gdb/Declarations.html
extern "C" {
typedef enum {
JIT_NOACTION = 0,
JIT_REGISTER_FN,
JIT_UNREGISTER_FN
} JITAction;
struct JITCodeEntry {
JITCodeEntry* next_;
JITCodeEntry* prev_;
const byte *symfile_addr_;
uint64_t symfile_size_;
};
struct JITDescriptor {
uint32_t version_;
uint32_t action_flag_;
JITCodeEntry* relevant_entry_;
JITCodeEntry* first_entry_;
};
// GDB will place breakpoint into this function.
// To prevent GCC from inlining or removing it we place noinline attribute
// and inline assembler statement inside.
void __attribute__((noinline)) __jit_debug_register_code() {
__asm__("");
}
// GDB will inspect contents of this descriptor.
// Static initialization is necessary to prevent GDB from seeing
// uninitialized descriptor.
JITDescriptor __jit_debug_descriptor = { 1, JIT_NOACTION, nullptr, nullptr };
}
static JITCodeEntry* CreateCodeEntry(const byte *symfile_addr,
uintptr_t symfile_size) {
JITCodeEntry* entry = new JITCodeEntry;
entry->symfile_addr_ = symfile_addr;
entry->symfile_size_ = symfile_size;
entry->prev_ = nullptr;
// TODO: Do we need a lock here?
entry->next_ = __jit_debug_descriptor.first_entry_;
if (entry->next_ != nullptr) {
entry->next_->prev_ = entry;
}
__jit_debug_descriptor.first_entry_ = entry;
__jit_debug_descriptor.relevant_entry_ = entry;
__jit_debug_descriptor.action_flag_ = JIT_REGISTER_FN;
__jit_debug_register_code();
return entry;
}
static void UnregisterCodeEntry(JITCodeEntry* entry) {
// TODO: Do we need a lock here?
if (entry->prev_ != nullptr) {
entry->prev_->next_ = entry->next_;
} else {
__jit_debug_descriptor.first_entry_ = entry->next_;
}
if (entry->next_ != nullptr) {
entry->next_->prev_ = entry->prev_;
}
__jit_debug_descriptor.relevant_entry_ = entry;
__jit_debug_descriptor.action_flag_ = JIT_UNREGISTER_FN;
__jit_debug_register_code();
delete entry;
}
ElfFile::ElfFile(File* file, bool writable, bool program_header_only)
: file_(file),
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),
jit_elf_image_(nullptr),
jit_gdb_entry_(nullptr) {
CHECK(file != nullptr);
}
ElfFile* ElfFile::Open(File* file, bool writable, bool program_header_only,
std::string* error_msg) {
std::unique_ptr<ElfFile> elf_file(new ElfFile(file, writable, program_header_only));
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(prot, flags, error_msg)) {
return nullptr;
}
return elf_file.release();
}
ElfFile* ElfFile::Open(File* file, int prot, int flags, std::string* error_msg) {
std::unique_ptr<ElfFile> elf_file(new ElfFile(file, (prot & PROT_WRITE) == PROT_WRITE, false));
if (!elf_file->Setup(prot, flags, error_msg)) {
return nullptr;
}
return elf_file.release();
}
bool ElfFile::Setup(int prot, int flags, 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(Elf32_Ehdr)) {
*error_msg = StringPrintf("File size of %zd bytes not large enough to contain ELF header of "
"%zd bytes: '%s'", file_length, sizeof(Elf32_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(Elf32_Ehdr);
if (!SetMap(MemMap::MapFile(elf_header_size, prot, flags, file_->Fd(), 0,
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(Elf32_Ehdr), file_->GetPath().c_str());
return false;
}
if (!SetMap(MemMap::MapFile(program_header_size, prot, flags, file_->Fd(), 0,
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(MemMap::MapFile(file_->GetLength(), prot, flags, file_->Fd(), 0,
file_->GetPath().c_str(), error_msg),
error_msg)) {
*error_msg = StringPrintf("Failed to map ELF file: %s", error_msg->c_str());
return false;
}
}
// Either way, the program header is relative to the elf header
program_headers_start_ = Begin() + GetHeader().e_phoff;
if (!program_header_only_) {
// Setup section headers.
section_headers_start_ = Begin() + GetHeader().e_shoff;
// 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;
}
dynamic_section_start_
= reinterpret_cast<Elf32_Dyn*>(Begin() + GetDynamicProgramHeader().p_offset);
// Find other sections from section headers
for (Elf32_Word i = 0; i < GetSectionHeaderNum(); i++) {
Elf32_Shdr& section_header = GetSectionHeader(i);
byte* section_addr = Begin() + section_header.sh_offset;
switch (section_header.sh_type) {
case SHT_SYMTAB: {
symtab_section_start_ = reinterpret_cast<Elf32_Sym*>(section_addr);
break;
}
case SHT_DYNSYM: {
dynsym_section_start_ = reinterpret_cast<Elf32_Sym*>(section_addr);
break;
}
case SHT_STRTAB: {
// TODO: base these off of sh_link from .symtab and .dynsym above
if ((section_header.sh_flags & SHF_ALLOC) != 0) {
dynstr_section_start_ = reinterpret_cast<char*>(section_addr);
} else {
strtab_section_start_ = reinterpret_cast<char*>(section_addr);
}
break;
}
case SHT_DYNAMIC: {
if (reinterpret_cast<byte*>(dynamic_section_start_) != section_addr) {
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*>(section_addr);
return false;
}
break;
}
case SHT_HASH: {
hash_section_start_ = reinterpret_cast<Elf32_Word*>(section_addr);
break;
}
}
}
}
return true;
}
ElfFile::~ElfFile() {
STLDeleteElements(&segments_);
delete symtab_symbol_table_;
delete dynsym_symbol_table_;
delete jit_elf_image_;
if (jit_gdb_entry_) {
UnregisterCodeEntry(jit_gdb_entry_);
}
}
bool ElfFile::SetMap(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<Elf32_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;
}
if (ELFCLASS32 != header_->e_ident[EI_CLASS]) {
*error_msg = StringPrintf("Failed to find expected EI_CLASS value %d in %s, found %d",
ELFCLASS32,
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(),
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 %d less than %zd in %s",
header_->e_phoff,
Size(),
file_->GetPath().c_str());
return false;
}
if (header_->e_shoff >= Size()) {
*error_msg = StringPrintf("Failed to find e_shoff value %d less than %zd in %s",
header_->e_shoff,
Size(),
file_->GetPath().c_str());
return false;
}
}
return true;
}
Elf32_Ehdr& ElfFile::GetHeader() const {
CHECK(header_ != nullptr);
return *header_;
}
byte* ElfFile::GetProgramHeadersStart() const {
CHECK(program_headers_start_ != nullptr);
return program_headers_start_;
}
byte* ElfFile::GetSectionHeadersStart() const {
CHECK(section_headers_start_ != nullptr);
return section_headers_start_;
}
Elf32_Phdr& ElfFile::GetDynamicProgramHeader() const {
CHECK(dynamic_program_header_ != nullptr);
return *dynamic_program_header_;
}
Elf32_Dyn* ElfFile::GetDynamicSectionStart() const {
CHECK(dynamic_section_start_ != nullptr);
return dynamic_section_start_;
}
Elf32_Sym* ElfFile::GetSymbolSectionStart(Elf32_Word section_type) const {
CHECK(IsSymbolSectionType(section_type)) << file_->GetPath() << " " << section_type;
Elf32_Sym* symbol_section_start;
switch (section_type) {
case SHT_SYMTAB: {
symbol_section_start = symtab_section_start_;
break;
}
case SHT_DYNSYM: {
symbol_section_start = dynsym_section_start_;
break;
}
default: {
LOG(FATAL) << section_type;
symbol_section_start = nullptr;
}
}
CHECK(symbol_section_start != nullptr);
return symbol_section_start;
}
const char* ElfFile::GetStringSectionStart(Elf32_Word section_type) const {
CHECK(IsSymbolSectionType(section_type)) << file_->GetPath() << " " << section_type;
const char* string_section_start;
switch (section_type) {
case SHT_SYMTAB: {
string_section_start = strtab_section_start_;
break;
}
case SHT_DYNSYM: {
string_section_start = dynstr_section_start_;
break;
}
default: {
LOG(FATAL) << section_type;
string_section_start = nullptr;
}
}
CHECK(string_section_start != nullptr);
return string_section_start;
}
const char* ElfFile::GetString(Elf32_Word section_type, Elf32_Word i) const {
CHECK(IsSymbolSectionType(section_type)) << file_->GetPath() << " " << section_type;
if (i == 0) {
return nullptr;
}
const char* string_section_start = GetStringSectionStart(section_type);
const char* string = string_section_start + i;
return string;
}
Elf32_Word* ElfFile::GetHashSectionStart() const {
CHECK(hash_section_start_ != nullptr);
return hash_section_start_;
}
Elf32_Word ElfFile::GetHashBucketNum() const {
return GetHashSectionStart()[0];
}
Elf32_Word ElfFile::GetHashChainNum() const {
return GetHashSectionStart()[1];
}
Elf32_Word ElfFile::GetHashBucket(size_t i) const {
CHECK_LT(i, GetHashBucketNum());
// 0 is nbucket, 1 is nchain
return GetHashSectionStart()[2 + i];
}
Elf32_Word ElfFile::GetHashChain(size_t i) const {
CHECK_LT(i, GetHashChainNum());
// 0 is nbucket, 1 is nchain, & chains are after buckets
return GetHashSectionStart()[2 + GetHashBucketNum() + i];
}
Elf32_Word ElfFile::GetProgramHeaderNum() const {
return GetHeader().e_phnum;
}
Elf32_Phdr& ElfFile::GetProgramHeader(Elf32_Word i) const {
CHECK_LT(i, GetProgramHeaderNum()) << file_->GetPath();
byte* program_header = GetProgramHeadersStart() + (i * GetHeader().e_phentsize);
CHECK_LT(program_header, End()) << file_->GetPath();
return *reinterpret_cast<Elf32_Phdr*>(program_header);
}
Elf32_Phdr* ElfFile::FindProgamHeaderByType(Elf32_Word type) const {
for (Elf32_Word i = 0; i < GetProgramHeaderNum(); i++) {
Elf32_Phdr& program_header = GetProgramHeader(i);
if (program_header.p_type == type) {
return &program_header;
}
}
return nullptr;
}
Elf32_Word ElfFile::GetSectionHeaderNum() const {
return GetHeader().e_shnum;
}
Elf32_Shdr& ElfFile::GetSectionHeader(Elf32_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_->GetPath();
CHECK_LT(i, GetSectionHeaderNum()) << file_->GetPath();
byte* section_header = GetSectionHeadersStart() + (i * GetHeader().e_shentsize);
CHECK_LT(section_header, End()) << file_->GetPath();
return *reinterpret_cast<Elf32_Shdr*>(section_header);
}
Elf32_Shdr* ElfFile::FindSectionByType(Elf32_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_->GetPath();
for (Elf32_Word i = 0; i < GetSectionHeaderNum(); i++) {
Elf32_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;
}
Elf32_Shdr& ElfFile::GetSectionNameStringSection() const {
return GetSectionHeader(GetHeader().e_shstrndx);
}
const byte* ElfFile::FindDynamicSymbolAddress(const std::string& symbol_name) const {
const Elf32_Sym* sym = FindDynamicSymbol(symbol_name);
if (sym != nullptr) {
return base_address_ + sym->st_value;
} else {
return nullptr;
}
}
const Elf32_Sym* ElfFile::FindDynamicSymbol(const std::string& symbol_name) const {
Elf32_Word hash = elfhash(symbol_name.c_str());
Elf32_Word bucket_index = hash % GetHashBucketNum();
Elf32_Word symbol_and_chain_index = GetHashBucket(bucket_index);
while (symbol_and_chain_index != 0 /* STN_UNDEF */) {
Elf32_Sym& symbol = GetSymbol(SHT_DYNSYM, symbol_and_chain_index);
const char* name = GetString(SHT_DYNSYM, symbol.st_name);
if (symbol_name == name) {
return &symbol;
}
symbol_and_chain_index = GetHashChain(symbol_and_chain_index);
}
return nullptr;
}
bool ElfFile::IsSymbolSectionType(Elf32_Word section_type) {
return ((section_type == SHT_SYMTAB) || (section_type == SHT_DYNSYM));
}
Elf32_Word ElfFile::GetSymbolNum(Elf32_Shdr& section_header) const {
CHECK(IsSymbolSectionType(section_header.sh_type))
<< file_->GetPath() << " " << section_header.sh_type;
CHECK_NE(0U, section_header.sh_entsize) << file_->GetPath();
return section_header.sh_size / section_header.sh_entsize;
}
Elf32_Sym& ElfFile::GetSymbol(Elf32_Word section_type,
Elf32_Word i) const {
return *(GetSymbolSectionStart(section_type) + i);
}
ElfFile::SymbolTable** ElfFile::GetSymbolTable(Elf32_Word section_type) {
CHECK(IsSymbolSectionType(section_type)) << file_->GetPath() << " " << 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;
}
}
}
Elf32_Sym* ElfFile::FindSymbolByName(Elf32_Word section_type,
const std::string& symbol_name,
bool build_map) {
CHECK(!program_header_only_) << file_->GetPath();
CHECK(IsSymbolSectionType(section_type)) << file_->GetPath() << " " << 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;
Elf32_Shdr* symbol_section = FindSectionByType(section_type);
CHECK(symbol_section != nullptr) << file_->GetPath();
Elf32_Shdr& string_section = GetSectionHeader(symbol_section->sh_link);
for (uint32_t i = 0; i < GetSymbolNum(*symbol_section); i++) {
Elf32_Sym& symbol = GetSymbol(section_type, i);
unsigned char type = 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<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.
CHECK_EQ(symbol.st_value, result.first->second->st_value);
CHECK_EQ(symbol.st_size, result.first->second->st_size);
CHECK_EQ(symbol.st_info, result.first->second->st_info);
CHECK_EQ(symbol.st_other, result.first->second->st_other);
CHECK_EQ(symbol.st_shndx, result.first->second->st_shndx);
}
}
}
CHECK(*symbol_table != nullptr);
SymbolTable::const_iterator it = (*symbol_table)->find(symbol_name);
if (it == (*symbol_table)->end()) {
return nullptr;
}
return it->second;
}
// Fall back to linear search
Elf32_Shdr* symbol_section = FindSectionByType(section_type);
CHECK(symbol_section != nullptr) << file_->GetPath();
Elf32_Shdr& string_section = GetSectionHeader(symbol_section->sh_link);
for (uint32_t i = 0; i < GetSymbolNum(*symbol_section); i++) {
Elf32_Sym& symbol = GetSymbol(section_type, i);
const char* name = GetString(string_section, symbol.st_name);
if (name == nullptr) {
continue;
}
if (symbol_name == name) {
return &symbol;
}
}
return nullptr;
}
Elf32_Addr ElfFile::FindSymbolAddress(Elf32_Word section_type,
const std::string& symbol_name,
bool build_map) {
Elf32_Sym* symbol = FindSymbolByName(section_type, symbol_name, build_map);
if (symbol == nullptr) {
return 0;
}
return symbol->st_value;
}
const char* ElfFile::GetString(Elf32_Shdr& string_section, Elf32_Word i) const {
CHECK(!program_header_only_) << file_->GetPath();
// TODO: remove this static_cast from enum when using -std=gnu++0x
CHECK_EQ(static_cast<Elf32_Word>(SHT_STRTAB), string_section.sh_type) << file_->GetPath();
CHECK_LT(i, string_section.sh_size) << file_->GetPath();
if (i == 0) {
return nullptr;
}
byte* strings = Begin() + string_section.sh_offset;
byte* string = strings + i;
CHECK_LT(string, End()) << file_->GetPath();
return reinterpret_cast<const char*>(string);
}
Elf32_Word ElfFile::GetDynamicNum() const {
return GetDynamicProgramHeader().p_filesz / sizeof(Elf32_Dyn);
}
Elf32_Dyn& ElfFile::GetDynamic(Elf32_Word i) const {
CHECK_LT(i, GetDynamicNum()) << file_->GetPath();
return *(GetDynamicSectionStart() + i);
}
Elf32_Dyn* ElfFile::FindDynamicByType(Elf32_Sword type) const {
for (Elf32_Word i = 0; i < GetDynamicNum(); i++) {
Elf32_Dyn* dyn = &GetDynamic(i);
if (dyn->d_tag == type) {
return dyn;
}
}
return NULL;
}
Elf32_Word ElfFile::FindDynamicValueByType(Elf32_Sword type) const {
Elf32_Dyn* dyn = FindDynamicByType(type);
if (dyn == NULL) {
return 0;
} else {
return dyn->d_un.d_val;
}
}
Elf32_Rel* ElfFile::GetRelSectionStart(Elf32_Shdr& section_header) const {
CHECK(SHT_REL == section_header.sh_type) << file_->GetPath() << " " << section_header.sh_type;
return reinterpret_cast<Elf32_Rel*>(Begin() + section_header.sh_offset);
}
Elf32_Word ElfFile::GetRelNum(Elf32_Shdr& section_header) const {
CHECK(SHT_REL == section_header.sh_type) << file_->GetPath() << " " << section_header.sh_type;
CHECK_NE(0U, section_header.sh_entsize) << file_->GetPath();
return section_header.sh_size / section_header.sh_entsize;
}
Elf32_Rel& ElfFile::GetRel(Elf32_Shdr& section_header, Elf32_Word i) const {
CHECK(SHT_REL == section_header.sh_type) << file_->GetPath() << " " << section_header.sh_type;
CHECK_LT(i, GetRelNum(section_header)) << file_->GetPath();
return *(GetRelSectionStart(section_header) + i);
}
Elf32_Rela* ElfFile::GetRelaSectionStart(Elf32_Shdr& section_header) const {
CHECK(SHT_RELA == section_header.sh_type) << file_->GetPath() << " " << section_header.sh_type;
return reinterpret_cast<Elf32_Rela*>(Begin() + section_header.sh_offset);
}
Elf32_Word ElfFile::GetRelaNum(Elf32_Shdr& section_header) const {
CHECK(SHT_RELA == section_header.sh_type) << file_->GetPath() << " " << section_header.sh_type;
return section_header.sh_size / section_header.sh_entsize;
}
Elf32_Rela& ElfFile::GetRela(Elf32_Shdr& section_header, Elf32_Word i) const {
CHECK(SHT_RELA == section_header.sh_type) << file_->GetPath() << " " << section_header.sh_type;
CHECK_LT(i, GetRelaNum(section_header)) << file_->GetPath();
return *(GetRelaSectionStart(section_header) + i);
}
// Base on bionic phdr_table_get_load_size
size_t ElfFile::GetLoadedSize() const {
Elf32_Addr min_vaddr = 0xFFFFFFFFu;
Elf32_Addr max_vaddr = 0x00000000u;
for (Elf32_Word i = 0; i < GetProgramHeaderNum(); i++) {
Elf32_Phdr& program_header = GetProgramHeader(i);
if (program_header.p_type != PT_LOAD) {
continue;
}
Elf32_Addr begin_vaddr = program_header.p_vaddr;
if (begin_vaddr < min_vaddr) {
min_vaddr = begin_vaddr;
}
Elf32_Addr end_vaddr = program_header.p_vaddr + program_header.p_memsz;
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_->GetPath();
size_t loaded_size = max_vaddr - min_vaddr;
return loaded_size;
}
bool ElfFile::Load(bool executable, std::string* error_msg) {
CHECK(program_header_only_) << file_->GetPath();
if (executable) {
InstructionSet elf_ISA = kNone;
switch (GetHeader().e_machine) {
case EM_ARM: {
elf_ISA = kArm;
break;
}
case EM_AARCH64: {
elf_ISA = kArm64;
break;
}
case EM_386: {
elf_ISA = kX86;
break;
}
case EM_X86_64: {
elf_ISA = kX86_64;
break;
}
case EM_MIPS: {
elf_ISA = kMips;
break;
}
}
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 (Elf32_Word i = 0; i < GetProgramHeaderNum(); i++) {
Elf32_Phdr& program_header = GetProgramHeader(i);
// 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) {
byte* reserve_base = ((program_header.p_vaddr != 0) ?
reinterpret_cast<byte*>(program_header.p_vaddr) : nullptr);
std::string reservation_name("ElfFile reservation for ");
reservation_name += file_->GetPath();
std::unique_ptr<MemMap> reserve(MemMap::MapAnonymous(reservation_name.c_str(),
reserve_base,
GetLoadedSize(), PROT_NONE, 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;
if (reserve_base == nullptr) {
base_address_ = reserve->Begin();
}
segments_.push_back(reserve.release());
}
// empty segment, nothing to map
if (program_header.p_memsz == 0) {
continue;
}
byte* 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 (file_length < (program_header.p_offset + program_header.p_memsz)) {
*error_msg = StringPrintf("File size of %zd bytes not large enough to contain ELF segment "
"%d of %d bytes: '%s'", file_length, i,
program_header.p_offset + program_header.p_memsz,
file_->GetPath().c_str());
return false;
}
std::unique_ptr<MemMap> segment(MemMap::MapFileAtAddress(p_vaddr,
program_header.p_memsz,
prot, flags, file_->Fd(),
program_header.p_offset,
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());
}
// Now that we are done loading, .dynamic should be in memory to find .dynstr, .dynsym, .hash
dynamic_section_start_
= reinterpret_cast<Elf32_Dyn*>(base_address_ + GetDynamicProgramHeader().p_vaddr);
for (Elf32_Word i = 0; i < GetDynamicNum(); i++) {
Elf32_Dyn& elf_dyn = GetDynamic(i);
byte* 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<Elf32_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<Elf32_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;
}
}
}
// Use GDB JIT support to do stack backtrace, etc.
if (executable) {
GdbJITSupport();
}
return true;
}
bool ElfFile::ValidPointer(const byte* 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;
}
Elf32_Shdr* ElfFile::FindSectionByName(const std::string& name) const {
CHECK(!program_header_only_);
Elf32_Shdr& shstrtab_sec = GetSectionNameStringSection();
for (uint32_t i = 0; i < GetSectionHeaderNum(); i++) {
Elf32_Shdr& shdr = GetSectionHeader(i);
const char* sec_name = GetString(shstrtab_sec, shdr.sh_name);
if (sec_name == nullptr) {
continue;
}
if (name == sec_name) {
return &shdr;
}
}
return nullptr;
}
struct PACKED(1) FDE {
uint32_t raw_length_;
uint32_t GetLength() {
return raw_length_ + sizeof(raw_length_);
}
uint32_t CIE_pointer;
uint32_t initial_location;
uint32_t address_range;
uint8_t instructions[0];
};
static FDE* NextFDE(FDE* frame) {
byte* fde_bytes = reinterpret_cast<byte*>(frame);
fde_bytes += frame->GetLength();
return reinterpret_cast<FDE*>(fde_bytes);
}
static bool IsFDE(FDE* frame) {
return frame->CIE_pointer != 0;
}
// TODO This only works for 32-bit Elf Files.
static bool FixupEHFrame(uintptr_t text_start, byte* eh_frame, size_t eh_frame_size) {
FDE* last_frame = reinterpret_cast<FDE*>(eh_frame + eh_frame_size);
FDE* frame = NextFDE(reinterpret_cast<FDE*>(eh_frame));
for (; frame < last_frame; frame = NextFDE(frame)) {
if (!IsFDE(frame)) {
return false;
}
frame->initial_location += text_start;
}
return true;
}
struct PACKED(1) DebugInfoHeader {
uint32_t unit_length; // TODO 32-bit specific size
uint16_t version;
uint32_t debug_abbrev_offset; // TODO 32-bit specific size
uint8_t address_size;
};
// Returns -1 if it is variable length, which we will just disallow for now.
static int32_t FormLength(uint32_t att) {
switch (att) {
case DW_FORM_data1:
case DW_FORM_flag:
case DW_FORM_flag_present:
case DW_FORM_ref1:
return 1;
case DW_FORM_data2:
case DW_FORM_ref2:
return 2;
case DW_FORM_addr: // TODO 32-bit only
case DW_FORM_ref_addr: // TODO 32-bit only
case DW_FORM_sec_offset: // TODO 32-bit only
case DW_FORM_strp: // TODO 32-bit only
case DW_FORM_data4:
case DW_FORM_ref4:
return 4;
case DW_FORM_data8:
case DW_FORM_ref8:
case DW_FORM_ref_sig8:
return 8;
case DW_FORM_block:
case DW_FORM_block1:
case DW_FORM_block2:
case DW_FORM_block4:
case DW_FORM_exprloc:
case DW_FORM_indirect:
case DW_FORM_ref_udata:
case DW_FORM_sdata:
case DW_FORM_string:
case DW_FORM_udata:
default:
return -1;
}
}
class DebugTag {
public:
const uint32_t index_;
~DebugTag() {}
// Creates a new tag and moves data pointer up to the start of the next one.
// nullptr means error.
static DebugTag* Create(const byte** data_pointer) {
const byte* data = *data_pointer;
uint32_t index = DecodeUnsignedLeb128(&data);
std::unique_ptr<DebugTag> tag(new DebugTag(index));
tag->size_ = static_cast<uint32_t>(
reinterpret_cast<uintptr_t>(data) - reinterpret_cast<uintptr_t>(*data_pointer));
// skip the abbrev
tag->tag_ = DecodeUnsignedLeb128(&data);
tag->has_child_ = (*data == 0);
data++;
while (true) {
uint32_t attr = DecodeUnsignedLeb128(&data);
uint32_t form = DecodeUnsignedLeb128(&data);
if (attr == 0 && form == 0) {
break;
} else if (attr == 0 || form == 0) {
// Bad abbrev.
return nullptr;
}
int32_t size = FormLength(form);
if (size == -1) {
return nullptr;
}
tag->AddAttribute(attr, static_cast<uint32_t>(size));
}
*data_pointer = data;
return tag.release();
}
uint32_t GetSize() const {
return size_;
}
bool HasChild() {
return has_child_;
}
uint32_t GetTagNumber() {
return tag_;
}
// Gets the offset of a particular attribute in this tag structure.
// Interpretation of the data is left to the consumer. 0 is returned if the
// tag does not contain the attribute.
uint32_t GetOffsetOf(uint32_t dwarf_attribute) const {
auto it = off_map_.find(dwarf_attribute);
if (it == off_map_.end()) {
return 0;
} else {
return it->second;
}
}
// Gets the size of attribute
uint32_t GetAttrSize(uint32_t dwarf_attribute) const {
auto it = size_map_.find(dwarf_attribute);
if (it == size_map_.end()) {
return 0;
} else {
return it->second;
}
}
private:
explicit DebugTag(uint32_t index) : index_(index) {}
void AddAttribute(uint32_t type, uint32_t attr_size) {
off_map_.insert(std::pair<uint32_t, uint32_t>(type, size_));
size_map_.insert(std::pair<uint32_t, uint32_t>(type, attr_size));
size_ += attr_size;
}
std::map<uint32_t, uint32_t> off_map_;
std::map<uint32_t, uint32_t> size_map_;
uint32_t size_;
uint32_t tag_;
bool has_child_;
};
class DebugAbbrev {
public:
~DebugAbbrev() {}
static DebugAbbrev* Create(const byte* dbg_abbrev, size_t dbg_abbrev_size) {
std::unique_ptr<DebugAbbrev> abbrev(new DebugAbbrev);
const byte* last = dbg_abbrev + dbg_abbrev_size;
while (dbg_abbrev < last) {
std::unique_ptr<DebugTag> tag(DebugTag::Create(&dbg_abbrev));
if (tag.get() == nullptr) {
return nullptr;
} else {
abbrev->tags_.insert(std::pair<uint32_t, uint32_t>(tag->index_, abbrev->tag_list_.size()));
abbrev->tag_list_.push_back(std::move(tag));
}
}
return abbrev.release();
}
DebugTag* ReadTag(const byte* entry) {
uint32_t tag_num = DecodeUnsignedLeb128(&entry);
auto it = tags_.find(tag_num);
if (it == tags_.end()) {
return nullptr;
} else {
CHECK_GT(tag_list_.size(), it->second);
return tag_list_.at(it->second).get();
}
}
private:
DebugAbbrev() {}
std::map<uint32_t, uint32_t> tags_;
std::vector<std::unique_ptr<DebugTag>> tag_list_;
};
class DebugInfoIterator {
public:
static DebugInfoIterator* Create(DebugInfoHeader* header, size_t frame_size,
DebugAbbrev* abbrev) {
std::unique_ptr<DebugInfoIterator> iter(new DebugInfoIterator(header, frame_size, abbrev));
if (iter->GetCurrentTag() == nullptr) {
return nullptr;
} else {
return iter.release();
}
}
~DebugInfoIterator() {}
// Moves to the next DIE. Returns false if at last entry.
// TODO Handle variable length attributes.
bool next() {
if (current_entry_ == nullptr || current_tag_ == nullptr) {
return false;
}
current_entry_ += current_tag_->GetSize();
if (current_entry_ >= last_entry_) {
current_entry_ = nullptr;
return false;
}
current_tag_ = abbrev_->ReadTag(current_entry_);
if (current_tag_ == nullptr) {
current_entry_ = nullptr;
return false;
} else {
return true;
}
}
const DebugTag* GetCurrentTag() {
return const_cast<DebugTag*>(current_tag_);
}
byte* GetPointerToField(uint8_t dwarf_field) {
if (current_tag_ == nullptr || current_entry_ == nullptr || current_entry_ >= last_entry_) {
return nullptr;
}
uint32_t off = current_tag_->GetOffsetOf(dwarf_field);
if (off == 0) {
// tag does not have that field.
return nullptr;
} else {
DCHECK_LT(off, current_tag_->GetSize());
return current_entry_ + off;
}
}
private:
DebugInfoIterator(DebugInfoHeader* header, size_t frame_size, DebugAbbrev* abbrev)
: abbrev_(abbrev),
last_entry_(reinterpret_cast<byte*>(header) + frame_size),
current_entry_(reinterpret_cast<byte*>(header) + sizeof(DebugInfoHeader)),
current_tag_(abbrev_->ReadTag(current_entry_)) {}
DebugAbbrev* abbrev_;
byte* last_entry_;
byte* current_entry_;
DebugTag* current_tag_;
};
static bool FixupDebugInfo(uint32_t text_start, DebugInfoIterator* iter) {
do {
if (iter->GetCurrentTag()->GetAttrSize(DW_AT_low_pc) != sizeof(int32_t) ||
iter->GetCurrentTag()->GetAttrSize(DW_AT_high_pc) != sizeof(int32_t)) {
return false;
}
uint32_t* PC_low = reinterpret_cast<uint32_t*>(iter->GetPointerToField(DW_AT_low_pc));
uint32_t* PC_high = reinterpret_cast<uint32_t*>(iter->GetPointerToField(DW_AT_high_pc));
if (PC_low != nullptr && PC_high != nullptr) {
*PC_low += text_start;
*PC_high += text_start;
}
} while (iter->next());
return true;
}
static bool FixupDebugSections(const byte* dbg_abbrev, size_t dbg_abbrev_size,
uintptr_t text_start,
byte* dbg_info, size_t dbg_info_size,
byte* eh_frame, size_t eh_frame_size) {
std::unique_ptr<DebugAbbrev> abbrev(DebugAbbrev::Create(dbg_abbrev, dbg_abbrev_size));
if (abbrev.get() == nullptr) {
return false;
}
std::unique_ptr<DebugInfoIterator> iter(
DebugInfoIterator::Create(reinterpret_cast<DebugInfoHeader*>(dbg_info),
dbg_info_size, abbrev.get()));
if (iter.get() == nullptr) {
return false;
}
return FixupDebugInfo(text_start, iter.get())
&& FixupEHFrame(text_start, eh_frame, eh_frame_size);
}
void ElfFile::GdbJITSupport() {
// We only get here if we only are mapping the program header.
DCHECK(program_header_only_);
// Well, we need the whole file to do this.
std::string error_msg;
// Make it MAP_PRIVATE so we can just give it to gdb if all the necessary
// sections are there.
std::unique_ptr<ElfFile> all_ptr(Open(const_cast<File*>(file_), PROT_READ | PROT_WRITE,
MAP_PRIVATE, &error_msg));
if (all_ptr.get() == nullptr) {
return;
}
ElfFile& all = *all_ptr;
// Do we have interesting sections?
const Elf32_Shdr* debug_info = all.FindSectionByName(".debug_info");
const Elf32_Shdr* debug_abbrev = all.FindSectionByName(".debug_abbrev");
const Elf32_Shdr* eh_frame = all.FindSectionByName(".eh_frame");
const Elf32_Shdr* debug_str = all.FindSectionByName(".debug_str");
const Elf32_Shdr* strtab_sec = all.FindSectionByName(".strtab");
const Elf32_Shdr* symtab_sec = all.FindSectionByName(".symtab");
Elf32_Shdr* text_sec = all.FindSectionByName(".text");
if (debug_info == nullptr || debug_abbrev == nullptr || eh_frame == nullptr ||
debug_str == nullptr || text_sec == nullptr || strtab_sec == nullptr ||
symtab_sec == nullptr) {
return;
}
// We need to add in a strtab and symtab to the image.
// all is MAP_PRIVATE so it can be written to freely.
// We also already have strtab and symtab so we are fine there.
Elf32_Ehdr& elf_hdr = all.GetHeader();
elf_hdr.e_entry = 0;
elf_hdr.e_phoff = 0;
elf_hdr.e_phnum = 0;
elf_hdr.e_phentsize = 0;
elf_hdr.e_type = ET_EXEC;
text_sec->sh_type = SHT_NOBITS;
text_sec->sh_offset = 0;
if (!FixupDebugSections(
all.Begin() + debug_abbrev->sh_offset, debug_abbrev->sh_size, text_sec->sh_addr,
all.Begin() + debug_info->sh_offset, debug_info->sh_size,
all.Begin() + eh_frame->sh_offset, eh_frame->sh_size)) {
LOG(ERROR) << "Failed to load GDB data";
return;
}
jit_gdb_entry_ = CreateCodeEntry(all.Begin(), all.Size());
gdb_file_mapping_.reset(all_ptr.release());
}
} // namespace art