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android / platform / art / c6301bc / . / runtime / elf_file.cc
blob: 0df8211c57f74ea866ff7b0e9be1a9b33cd2452c [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 "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_(NULL),
base_address_(NULL),
program_headers_start_(NULL),
section_headers_start_(NULL),
dynamic_program_header_(NULL),
dynamic_section_start_(NULL),
symtab_section_start_(NULL),
dynsym_section_start_(NULL),
strtab_section_start_(NULL),
dynstr_section_start_(NULL),
hash_section_start_(NULL),
symtab_symbol_table_(NULL),
dynsym_symbol_table_(NULL),
jit_elf_image_(NULL),
jit_gdb_entry_(NULL) {
CHECK(file != NULL);
}
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));
if (!elf_file->Setup(error_msg)) {
return nullptr;
}
return elf_file.release();
}
bool ElfFile::Setup(std::string* error_msg) {
int prot;
int flags;
if (writable_) {
prot = PROT_READ | PROT_WRITE;
flags = MAP_SHARED;
} else {
prot = PROT_READ;
flags = MAP_PRIVATE;
}
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_ == NULL) {
*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 == NULL) {
// MemMap::Open should have already set an error.
DCHECK(!error_msg->empty());
return false;
}
map_.reset(map);
CHECK(map_.get() != NULL) << file_->GetPath();
CHECK(map_->Begin() != NULL) << 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_ != NULL);
return *header_;
}
byte* ElfFile::GetProgramHeadersStart() const {
CHECK(program_headers_start_ != NULL);
return program_headers_start_;
}
byte* ElfFile::GetSectionHeadersStart() const {
CHECK(section_headers_start_ != NULL);
return section_headers_start_;
}
Elf32_Phdr& ElfFile::GetDynamicProgramHeader() const {
CHECK(dynamic_program_header_ != NULL);
return *dynamic_program_header_;
}
Elf32_Dyn* ElfFile::GetDynamicSectionStart() const {
CHECK(dynamic_section_start_ != NULL);
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 = NULL;
}
}
CHECK(symbol_section_start != NULL);
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 = NULL;
}
}
CHECK(string_section_start != NULL);
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 NULL;
}
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_ != NULL);
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 NULL;
}
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 NULL;
}
// 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 {
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 base_address_ + symbol.st_value;
}
symbol_and_chain_index = GetHashChain(symbol_and_chain_index);
}
return NULL;
}
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 NULL;
}
}
}
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 != NULL || build_map) {
if (*symbol_table == NULL) {
DCHECK(build_map);
*symbol_table = new SymbolTable;
Elf32_Shdr* symbol_section = FindSectionByType(section_type);
CHECK(symbol_section != NULL) << 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 == NULL) {
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 != NULL);
SymbolTable::const_iterator it = (*symbol_table)->find(symbol_name);
if (it == (*symbol_table)->end()) {
return NULL;
}
return it->second;
}
// Fall back to linear search
Elf32_Shdr* symbol_section = FindSectionByType(section_type);
CHECK(symbol_section != NULL) << 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 == NULL) {
continue;
}
if (symbol_name == name) {
return &symbol;
}
}
return NULL;
}
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 == NULL) {
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 NULL;
}
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_Word ElfFile::FindDynamicValueByType(Elf32_Sword type) const {
for (Elf32_Word i = 0; i < GetDynamicNum(); i++) {
Elf32_Dyn& elf_dyn = GetDynamic(i);
if (elf_dyn.d_tag == type) {
return elf_dyn.d_un.d_val;
}
}
return 0;
}
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;
}
}
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.
// If p_vaddr is zero, it must be the first loadable segment,
// since they must be in order. Since it is zero, there isn't a
// specific address requested, so first request a contiguous chunk
// of required size 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 (program_header.p_vaddr == 0) {
std::string reservation_name("ElfFile reservation for ");
reservation_name += file_->GetPath();
std::unique_ptr<MemMap> reserve(MemMap::MapAnonymous(reservation_name.c_str(),
NULL, 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;
}
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;
}
static bool check_section_name(ElfFile& file, int section_num, const char *name) {
Elf32_Shdr& section_header = file.GetSectionHeader(section_num);
const char *section_name = file.GetString(SHT_SYMTAB, section_header.sh_name);
return strcmp(name, section_name) == 0;
}
static void IncrementUint32(byte *p, uint32_t increment) {
uint32_t *u = reinterpret_cast<uint32_t *>(p);
*u += increment;
}
static void RoundAndClear(byte *image, uint32_t& offset, int pwr2) {
uint32_t mask = pwr2 - 1;
while (offset & mask) {
image[offset++] = 0;
}
}
// Simple macro to bump a point to a section header to the next one.
#define BUMP_SHENT(sp) \
sp = reinterpret_cast<Elf32_Shdr *> (\
reinterpret_cast<byte*>(sp) + elf_hdr.e_shentsize);\
offset += elf_hdr.e_shentsize
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;
std::unique_ptr<ElfFile> ptr(Open(const_cast<File*>(file_), false, false, &error_msg));
ElfFile& all = *ptr;
// Do we have interesting sections?
// Is this an OAT file with interesting sections?
if (all.GetSectionHeaderNum() != kExpectedSectionsInOATFile) {
return;
}
if (!check_section_name(all, 8, ".debug_info") ||
!check_section_name(all, 9, ".debug_abbrev") ||
!check_section_name(all, 10, ".debug_frame") ||
!check_section_name(all, 11, ".debug_str")) {
return;
}
#ifdef __LP64__
if (true) {
return; // No ELF debug support in 64bit.
}
#endif
// This is not needed if we have no .text segment.
uint32_t text_start_addr = 0;
for (uint32_t i = 0; i < segments_.size(); i++) {
if (segments_[i]->GetProtect() & PROT_EXEC) {
// We found the .text section.
text_start_addr = PointerToLowMemUInt32(segments_[i]->Begin());
break;
}
}
if (text_start_addr == 0U) {
return;
}
// Okay, we are good enough. Fake up an ELF image and tell GDB about it.
// We need some extra space for the debug and string sections, the ELF header, and the
// section header.
uint32_t needed_size = KB;
for (Elf32_Word i = 1; i < all.GetSectionHeaderNum(); i++) {
Elf32_Shdr& section_header = all.GetSectionHeader(i);
if (section_header.sh_addr == 0 && section_header.sh_type != SHT_DYNSYM) {
// Debug section: we need it.
needed_size += section_header.sh_size;
} else if (section_header.sh_type == SHT_STRTAB &&
strcmp(".shstrtab",
all.GetString(SHT_SYMTAB, section_header.sh_name)) == 0) {
// We also need the shared string table.
needed_size += section_header.sh_size;
// We also need the extra strings .symtab\0.strtab\0
needed_size += 16;
}
}
// Start creating our image.
jit_elf_image_ = new byte[needed_size];
// Create the Elf Header by copying the old one
Elf32_Ehdr& elf_hdr =
*reinterpret_cast<Elf32_Ehdr*>(jit_elf_image_);
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;
uint32_t offset = sizeof(Elf32_Ehdr);
// Copy the debug sections and string table.
uint32_t debug_offsets[kExpectedSectionsInOATFile];
memset(debug_offsets, '\0', sizeof debug_offsets);
Elf32_Shdr *text_header = nullptr;
int extra_shstrtab_entries = -1;
int text_section_index = -1;
int section_index = 1;
for (Elf32_Word i = 1; i < kExpectedSectionsInOATFile; i++) {
Elf32_Shdr& section_header = all.GetSectionHeader(i);
// Round up to multiple of 4, ensuring zero fill.
RoundAndClear(jit_elf_image_, offset, 4);
if (section_header.sh_addr == 0 && section_header.sh_type != SHT_DYNSYM) {
// Debug section: we need it. Unfortunately, it wasn't mapped in.
debug_offsets[i] = offset;
// Read it from the file.
lseek(file_->Fd(), section_header.sh_offset, SEEK_SET);
read(file_->Fd(), jit_elf_image_ + offset, section_header.sh_size);
offset += section_header.sh_size;
section_index++;
offset += 16;
} else if (section_header.sh_type == SHT_STRTAB &&
strcmp(".shstrtab",
all.GetString(SHT_SYMTAB, section_header.sh_name)) == 0) {
// We also need the shared string table.
debug_offsets[i] = offset;
// Read it from the file.
lseek(file_->Fd(), section_header.sh_offset, SEEK_SET);
read(file_->Fd(), jit_elf_image_ + offset, section_header.sh_size);
offset += section_header.sh_size;
// We also need the extra strings .symtab\0.strtab\0
extra_shstrtab_entries = section_header.sh_size;
memcpy(jit_elf_image_+offset, ".symtab\0.strtab\0", 16);
offset += 16;
section_index++;
} else if (section_header.sh_flags & SHF_EXECINSTR) {
DCHECK(strcmp(".text", all.GetString(SHT_SYMTAB,
section_header.sh_name)) == 0);
text_header = &section_header;
text_section_index = section_index++;
}
}
DCHECK(text_header != nullptr);
DCHECK_NE(extra_shstrtab_entries, -1);
// We now need to update the addresses for debug_info and debug_frame to get to the
// correct offset within the .text section.
byte *p = jit_elf_image_+debug_offsets[8];
byte *end = p + all.GetSectionHeader(8).sh_size;
// For debug_info; patch compilation using low_pc @ offset 13, high_pc at offset 17.
IncrementUint32(p + 13, text_start_addr);
IncrementUint32(p + 17, text_start_addr);
// Now fix the low_pc, high_pc for each method address.
// First method starts at offset 0x15, each subsequent method is 1+3*4 bytes further.
for (p += 0x15; p < end; p += 1 /* attr# */ + 3 * sizeof(uint32_t) /* addresses */) {
IncrementUint32(p + 1 + sizeof(uint32_t), text_start_addr);
IncrementUint32(p + 1 + 2 * sizeof(uint32_t), text_start_addr);
}
// Now we have to handle the debug_frame method start addresses
p = jit_elf_image_+debug_offsets[10];
end = p + all.GetSectionHeader(10).sh_size;
// Skip past the CIE.
p += *reinterpret_cast<uint32_t *>(p) + 4;
// And walk the FDEs.
for (; p < end; p += *reinterpret_cast<uint32_t *>(p) + sizeof(uint32_t)) {
IncrementUint32(p + 2 * sizeof(uint32_t), text_start_addr);
}
// Create the data for the symbol table.
const int kSymbtabAlignment = 16;
RoundAndClear(jit_elf_image_, offset, kSymbtabAlignment);
uint32_t symtab_offset = offset;
// First entry is empty.
memset(jit_elf_image_+offset, 0, sizeof(Elf32_Sym));
offset += sizeof(Elf32_Sym);
// Symbol 1 is the real .text section.
Elf32_Sym& sym_ent = *reinterpret_cast<Elf32_Sym*>(jit_elf_image_+offset);
sym_ent.st_name = 1; /* .text */
sym_ent.st_value = text_start_addr;
sym_ent.st_size = text_header->sh_size;
SetBindingAndType(&sym_ent, STB_LOCAL, STT_SECTION);
sym_ent.st_other = 0;
sym_ent.st_shndx = text_section_index;
offset += sizeof(Elf32_Sym);
// Create the data for the string table.
RoundAndClear(jit_elf_image_, offset, kSymbtabAlignment);
const int kTextStringSize = 7;
uint32_t strtab_offset = offset;
memcpy(jit_elf_image_+offset, "\0.text", kTextStringSize);
offset += kTextStringSize;
// Create the section header table.
// Round up to multiple of kSymbtabAlignment, ensuring zero fill.
RoundAndClear(jit_elf_image_, offset, kSymbtabAlignment);
elf_hdr.e_shoff = offset;
Elf32_Shdr *sp =
reinterpret_cast<Elf32_Shdr *>(jit_elf_image_ + offset);
// Copy the first empty index.
*sp = all.GetSectionHeader(0);
BUMP_SHENT(sp);
elf_hdr.e_shnum = 1;
for (Elf32_Word i = 1; i < kExpectedSectionsInOATFile; i++) {
Elf32_Shdr& section_header = all.GetSectionHeader(i);
if (section_header.sh_addr == 0 && section_header.sh_type != SHT_DYNSYM) {
// Debug section: we need it.
*sp = section_header;
sp->sh_offset = debug_offsets[i];
sp->sh_addr = 0;
elf_hdr.e_shnum++;
BUMP_SHENT(sp);
} else if (section_header.sh_type == SHT_STRTAB &&
strcmp(".shstrtab",
all.GetString(SHT_SYMTAB, section_header.sh_name)) == 0) {
// We also need the shared string table.
*sp = section_header;
sp->sh_offset = debug_offsets[i];
sp->sh_size += 16; /* sizeof ".symtab\0.strtab\0" */
sp->sh_addr = 0;
elf_hdr.e_shstrndx = elf_hdr.e_shnum;
elf_hdr.e_shnum++;
BUMP_SHENT(sp);
}
}
// Add a .text section for the matching code section.
*sp = *text_header;
sp->sh_type = SHT_NOBITS;
sp->sh_offset = 0;
sp->sh_addr = text_start_addr;
elf_hdr.e_shnum++;
BUMP_SHENT(sp);
// .symtab section: Need an empty index and the .text entry
sp->sh_name = extra_shstrtab_entries;
sp->sh_type = SHT_SYMTAB;
sp->sh_flags = 0;
sp->sh_addr = 0;
sp->sh_offset = symtab_offset;
sp->sh_size = 2 * sizeof(Elf32_Sym);
sp->sh_link = elf_hdr.e_shnum + 1; // Link to .strtab section.
sp->sh_info = 0;
sp->sh_addralign = 16;
sp->sh_entsize = sizeof(Elf32_Sym);
elf_hdr.e_shnum++;
BUMP_SHENT(sp);
// .strtab section: Enough for .text\0.
sp->sh_name = extra_shstrtab_entries + 8;
sp->sh_type = SHT_STRTAB;
sp->sh_flags = 0;
sp->sh_addr = 0;
sp->sh_offset = strtab_offset;
sp->sh_size = kTextStringSize;
sp->sh_link = 0;
sp->sh_info = 0;
sp->sh_addralign = 16;
sp->sh_entsize = 0;
elf_hdr.e_shnum++;
BUMP_SHENT(sp);
// We now have enough information to tell GDB about our file.
jit_gdb_entry_ = CreateCodeEntry(jit_elf_image_, offset);
}
} // namespace art