This source file includes following definitions.
- ElfBind
- ElfType
- ElfBind
- ElfType
- ElfBind
- ElfType
- GetTableElement
- GetNumSymbols
- ElfW
- ElfW
- ElfW
- GetDynstr
- GetSymAddr
- ElfW
- ElfW
- GetVerstr
- Init
- LookupSymbol
- LookupSymbolByAddress
- image_
- begin
- end
- Update
#include "base/elf_mem_image.h"
#ifdef HAVE_ELF_MEM_IMAGE
#include <stddef.h>
#include "base/logging.h"
#define VERSYM_VERSION 0x7fff
namespace base {
namespace {
template <int N> class ElfClass {
public:
static const int kElfClass = -1;
static int ElfBind(const ElfW(Sym) *) {
CHECK(false);
return 0;
}
static int ElfType(const ElfW(Sym) *) {
CHECK(false);
return 0;
}
};
template <> class ElfClass<32> {
public:
static const int kElfClass = ELFCLASS32;
static int ElfBind(const ElfW(Sym) *symbol) {
return ELF32_ST_BIND(symbol->st_info);
}
static int ElfType(const ElfW(Sym) *symbol) {
return ELF32_ST_TYPE(symbol->st_info);
}
};
template <> class ElfClass<64> {
public:
static const int kElfClass = ELFCLASS64;
static int ElfBind(const ElfW(Sym) *symbol) {
return ELF64_ST_BIND(symbol->st_info);
}
static int ElfType(const ElfW(Sym) *symbol) {
return ELF64_ST_TYPE(symbol->st_info);
}
};
typedef ElfClass<__WORDSIZE> CurrentElfClass;
template <class T>
const T* GetTableElement(const ElfW(Ehdr) *ehdr,
ElfW(Off) table_offset,
ElfW(Word) element_size,
size_t index) {
return reinterpret_cast<const T*>(reinterpret_cast<const char *>(ehdr)
+ table_offset
+ index * element_size);
}
}
const void *const ElfMemImage::kInvalidBase =
reinterpret_cast<const void *>(~0L);
ElfMemImage::ElfMemImage(const void *base) {
CHECK(base != kInvalidBase);
Init(base);
}
int ElfMemImage::GetNumSymbols() const {
if (!hash_) {
return 0;
}
return hash_[1];
}
const ElfW(Sym) *ElfMemImage::GetDynsym(int index) const {
CHECK_LT(index, GetNumSymbols());
return dynsym_ + index;
}
const ElfW(Versym) *ElfMemImage::GetVersym(int index) const {
CHECK_LT(index, GetNumSymbols());
return versym_ + index;
}
const ElfW(Phdr) *ElfMemImage::GetPhdr(int index) const {
CHECK_LT(index, ehdr_->e_phnum);
return GetTableElement<ElfW(Phdr)>(ehdr_,
ehdr_->e_phoff,
ehdr_->e_phentsize,
index);
}
const char *ElfMemImage::GetDynstr(ElfW(Word) offset) const {
CHECK_LT(offset, strsize_);
return dynstr_ + offset;
}
const void *ElfMemImage::GetSymAddr(const ElfW(Sym) *sym) const {
if (sym->st_shndx == SHN_UNDEF || sym->st_shndx >= SHN_LORESERVE) {
return reinterpret_cast<const void *>(sym->st_value);
}
CHECK_LT(link_base_, sym->st_value);
return GetTableElement<char>(ehdr_, 0, 1, sym->st_value) - link_base_;
}
const ElfW(Verdef) *ElfMemImage::GetVerdef(int index) const {
CHECK_LE(index, verdefnum_);
const ElfW(Verdef) *version_definition = verdef_;
while (version_definition->vd_ndx < index && version_definition->vd_next) {
const char *const version_definition_as_char =
reinterpret_cast<const char *>(version_definition);
version_definition =
reinterpret_cast<const ElfW(Verdef) *>(version_definition_as_char +
version_definition->vd_next);
}
return version_definition->vd_ndx == index ? version_definition : NULL;
}
const ElfW(Verdaux) *ElfMemImage::GetVerdefAux(
const ElfW(Verdef) *verdef) const {
return reinterpret_cast<const ElfW(Verdaux) *>(verdef+1);
}
const char *ElfMemImage::GetVerstr(ElfW(Word) offset) const {
CHECK_LT(offset, strsize_);
return dynstr_ + offset;
}
void ElfMemImage::Init(const void *base) {
ehdr_ = NULL;
dynsym_ = NULL;
dynstr_ = NULL;
versym_ = NULL;
verdef_ = NULL;
hash_ = NULL;
strsize_ = 0;
verdefnum_ = 0;
link_base_ = ~0L;
if (!base) {
return;
}
const intptr_t base_as_uintptr_t = reinterpret_cast<uintptr_t>(base);
const bool fake_vdso = ((base_as_uintptr_t & 1) != 0);
base = reinterpret_cast<const void *>(base_as_uintptr_t & ~1);
const char *const base_as_char = reinterpret_cast<const char *>(base);
if (base_as_char[EI_MAG0] != ELFMAG0 || base_as_char[EI_MAG1] != ELFMAG1 ||
base_as_char[EI_MAG2] != ELFMAG2 || base_as_char[EI_MAG3] != ELFMAG3) {
RAW_DCHECK(false, "no ELF magic");
return;
}
int elf_class = base_as_char[EI_CLASS];
if (elf_class != CurrentElfClass::kElfClass) {
DCHECK_EQ(elf_class, CurrentElfClass::kElfClass);
return;
}
switch (base_as_char[EI_DATA]) {
case ELFDATA2LSB: {
if (__LITTLE_ENDIAN != __BYTE_ORDER) {
DCHECK_EQ(__LITTLE_ENDIAN, __BYTE_ORDER);
return;
}
break;
}
case ELFDATA2MSB: {
if (__BIG_ENDIAN != __BYTE_ORDER) {
DCHECK_EQ(__BIG_ENDIAN, __BYTE_ORDER);
return;
}
break;
}
default: {
RAW_DCHECK(false, "unexpected data encoding");
return;
}
}
ehdr_ = reinterpret_cast<const ElfW(Ehdr) *>(base);
const ElfW(Phdr) *dynamic_program_header = NULL;
for (int i = 0; i < ehdr_->e_phnum; ++i) {
const ElfW(Phdr) *const program_header = GetPhdr(i);
switch (program_header->p_type) {
case PT_LOAD:
if (link_base_ == ~0L) {
link_base_ = program_header->p_vaddr;
}
break;
case PT_DYNAMIC:
dynamic_program_header = program_header;
break;
}
}
if (link_base_ == ~0L || !dynamic_program_header) {
RAW_DCHECK(~0L != link_base_, "no PT_LOADs in VDSO");
RAW_DCHECK(dynamic_program_header, "no PT_DYNAMIC in VDSO");
Init(0);
return;
}
ptrdiff_t relocation =
base_as_char - reinterpret_cast<const char *>(link_base_);
ElfW(Dyn) *dynamic_entry =
reinterpret_cast<ElfW(Dyn) *>(dynamic_program_header->p_vaddr +
relocation);
for (; dynamic_entry->d_tag != DT_NULL; ++dynamic_entry) {
ElfW(Xword) value = dynamic_entry->d_un.d_val;
if (fake_vdso) {
if (dynamic_entry->d_tag == DT_VERDEF) {
value += relocation;
}
} else {
value += relocation;
}
switch (dynamic_entry->d_tag) {
case DT_HASH:
hash_ = reinterpret_cast<ElfW(Word) *>(value);
break;
case DT_SYMTAB:
dynsym_ = reinterpret_cast<ElfW(Sym) *>(value);
break;
case DT_STRTAB:
dynstr_ = reinterpret_cast<const char *>(value);
break;
case DT_VERSYM:
versym_ = reinterpret_cast<ElfW(Versym) *>(value);
break;
case DT_VERDEF:
verdef_ = reinterpret_cast<ElfW(Verdef) *>(value);
break;
case DT_VERDEFNUM:
verdefnum_ = dynamic_entry->d_un.d_val;
break;
case DT_STRSZ:
strsize_ = dynamic_entry->d_un.d_val;
break;
default:
break;
}
}
if (!hash_ || !dynsym_ || !dynstr_ || !versym_ ||
!verdef_ || !verdefnum_ || !strsize_) {
RAW_DCHECK(hash_, "invalid VDSO (no DT_HASH)");
RAW_DCHECK(dynsym_, "invalid VDSO (no DT_SYMTAB)");
RAW_DCHECK(dynstr_, "invalid VDSO (no DT_STRTAB)");
RAW_DCHECK(versym_, "invalid VDSO (no DT_VERSYM)");
RAW_DCHECK(verdef_, "invalid VDSO (no DT_VERDEF)");
RAW_DCHECK(verdefnum_, "invalid VDSO (no DT_VERDEFNUM)");
RAW_DCHECK(strsize_, "invalid VDSO (no DT_STRSZ)");
Init(0);
return;
}
}
bool ElfMemImage::LookupSymbol(const char *name,
const char *version,
int type,
SymbolInfo *info) const {
for (SymbolIterator it = begin(); it != end(); ++it) {
if (strcmp(it->name, name) == 0 && strcmp(it->version, version) == 0 &&
CurrentElfClass::ElfType(it->symbol) == type) {
if (info) {
*info = *it;
}
return true;
}
}
return false;
}
bool ElfMemImage::LookupSymbolByAddress(const void *address,
SymbolInfo *info_out) const {
for (SymbolIterator it = begin(); it != end(); ++it) {
const char *const symbol_start =
reinterpret_cast<const char *>(it->address);
const char *const symbol_end = symbol_start + it->symbol->st_size;
if (symbol_start <= address && address < symbol_end) {
if (info_out) {
if (CurrentElfClass::ElfBind(it->symbol) == STB_GLOBAL) {
*info_out = *it;
return true;
} else {
*info_out = *it;
}
} else {
return true;
}
}
}
return false;
}
ElfMemImage::SymbolIterator::SymbolIterator(const void *const image, int index)
: index_(index), image_(image) {
}
const ElfMemImage::SymbolInfo *ElfMemImage::SymbolIterator::operator->() const {
return &info_;
}
const ElfMemImage::SymbolInfo& ElfMemImage::SymbolIterator::operator*() const {
return info_;
}
bool ElfMemImage::SymbolIterator::operator==(const SymbolIterator &rhs) const {
return this->image_ == rhs.image_ && this->index_ == rhs.index_;
}
bool ElfMemImage::SymbolIterator::operator!=(const SymbolIterator &rhs) const {
return !(*this == rhs);
}
ElfMemImage::SymbolIterator &ElfMemImage::SymbolIterator::operator++() {
this->Update(1);
return *this;
}
ElfMemImage::SymbolIterator ElfMemImage::begin() const {
SymbolIterator it(this, 0);
it.Update(0);
return it;
}
ElfMemImage::SymbolIterator ElfMemImage::end() const {
return SymbolIterator(this, GetNumSymbols());
}
void ElfMemImage::SymbolIterator::Update(int increment) {
const ElfMemImage *image = reinterpret_cast<const ElfMemImage *>(image_);
CHECK(image->IsPresent() || increment == 0);
if (!image->IsPresent()) {
return;
}
index_ += increment;
if (index_ >= image->GetNumSymbols()) {
index_ = image->GetNumSymbols();
return;
}
const ElfW(Sym) *symbol = image->GetDynsym(index_);
const ElfW(Versym) *version_symbol = image->GetVersym(index_);
CHECK(symbol && version_symbol);
const char *const symbol_name = image->GetDynstr(symbol->st_name);
const ElfW(Versym) version_index = version_symbol[0] & VERSYM_VERSION;
const ElfW(Verdef) *version_definition = NULL;
const char *version_name = "";
if (symbol->st_shndx == SHN_UNDEF) {
} else {
version_definition = image->GetVerdef(version_index);
}
if (version_definition) {
CHECK_LE(1, version_definition->vd_cnt);
CHECK_LE(version_definition->vd_cnt, 2);
const ElfW(Verdaux) *version_aux = image->GetVerdefAux(version_definition);
version_name = image->GetVerstr(version_aux->vda_name);
}
info_.name = symbol_name;
info_.version = version_name;
info_.address = image->GetSymAddr(symbol);
info_.symbol = symbol;
}
}
#endif