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/*
* Copyright (C) 2017 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.h>
#include <stdint.h>
#include <memory>
#include <string>
#include "ElfInterface.h"
#include "Memory.h"
#include "Regs.h"
template <typename EhdrType, typename PhdrType, typename ShdrType>
bool ElfInterface::ReadAllHeaders() {
EhdrType ehdr;
if (!memory_->Read(0, &ehdr, sizeof(ehdr))) {
return false;
}
if (!ReadProgramHeaders<EhdrType, PhdrType>(ehdr)) {
return false;
}
return ReadSectionHeaders<EhdrType, ShdrType>(ehdr);
}
template <typename EhdrType, typename PhdrType>
bool ElfInterface::ReadProgramHeaders(const EhdrType& ehdr) {
uint64_t offset = ehdr.e_phoff;
for (size_t i = 0; i < ehdr.e_phnum; i++, offset += ehdr.e_phentsize) {
PhdrType phdr;
if (!memory_->ReadField(offset, &phdr, &phdr.p_type, sizeof(phdr.p_type))) {
return false;
}
if (HandleType(offset, phdr.p_type)) {
continue;
}
switch (phdr.p_type) {
case PT_LOAD:
{
// Get the flags first, if this isn't an executable header, ignore it.
if (!memory_->ReadField(offset, &phdr, &phdr.p_flags, sizeof(phdr.p_flags))) {
return false;
}
if ((phdr.p_flags & PF_X) == 0) {
continue;
}
if (!memory_->ReadField(offset, &phdr, &phdr.p_vaddr, sizeof(phdr.p_vaddr))) {
return false;
}
if (!memory_->ReadField(offset, &phdr, &phdr.p_offset, sizeof(phdr.p_offset))) {
return false;
}
if (!memory_->ReadField(offset, &phdr, &phdr.p_memsz, sizeof(phdr.p_memsz))) {
return false;
}
pt_loads_[phdr.p_offset] = LoadInfo{phdr.p_offset, phdr.p_vaddr,
static_cast<size_t>(phdr.p_memsz)};
if (phdr.p_offset == 0) {
load_bias_ = phdr.p_vaddr;
}
break;
}
case PT_GNU_EH_FRAME:
if (!memory_->ReadField(offset, &phdr, &phdr.p_offset, sizeof(phdr.p_offset))) {
return false;
}
eh_frame_offset_ = phdr.p_offset;
if (!memory_->ReadField(offset, &phdr, &phdr.p_memsz, sizeof(phdr.p_memsz))) {
return false;
}
eh_frame_size_ = phdr.p_memsz;
break;
case PT_DYNAMIC:
if (!memory_->ReadField(offset, &phdr, &phdr.p_offset, sizeof(phdr.p_offset))) {
return false;
}
dynamic_offset_ = phdr.p_offset;
if (!memory_->ReadField(offset, &phdr, &phdr.p_memsz, sizeof(phdr.p_memsz))) {
return false;
}
dynamic_size_ = phdr.p_memsz;
break;
}
}
return true;
}
template <typename EhdrType, typename ShdrType>
bool ElfInterface::ReadSectionHeaders(const EhdrType& ehdr) {
uint64_t offset = ehdr.e_shoff;
uint64_t sec_offset = 0;
uint64_t sec_size = 0;
// Get the location of the section header names.
// If something is malformed in the header table data, we aren't going
// to terminate, we'll simply ignore this part.
ShdrType shdr;
if (ehdr.e_shstrndx < ehdr.e_shnum) {
uint64_t sh_offset = offset + ehdr.e_shstrndx * ehdr.e_shentsize;
if (memory_->ReadField(sh_offset, &shdr, &shdr.sh_offset, sizeof(shdr.sh_offset)) &&
memory_->ReadField(sh_offset, &shdr, &shdr.sh_size, sizeof(shdr.sh_size))) {
sec_offset = shdr.sh_offset;
sec_size = shdr.sh_size;
}
}
// Skip the first header, it's always going to be NULL.
for (size_t i = 1; i < ehdr.e_shnum; i++, offset += ehdr.e_shentsize) {
if (!memory_->ReadField(offset, &shdr, &shdr.sh_type, sizeof(shdr.sh_type))) {
return false;
}
if (shdr.sh_type == SHT_PROGBITS) {
// Look for the .debug_frame and .gnu_debugdata.
if (!memory_->ReadField(offset, &shdr, &shdr.sh_name, sizeof(shdr.sh_name))) {
return false;
}
if (shdr.sh_name < sec_size) {
std::string name;
if (memory_->ReadString(sec_offset + shdr.sh_name, &name)) {
if (name == ".debug_frame") {
if (memory_->ReadField(offset, &shdr, &shdr.sh_offset, sizeof(shdr.sh_offset)) &&
memory_->ReadField(offset, &shdr, &shdr.sh_size, sizeof(shdr.sh_size))) {
debug_frame_offset_ = shdr.sh_offset;
debug_frame_size_ = shdr.sh_size;
}
} else if (name == ".gnu_debugdata") {
if (memory_->ReadField(offset, &shdr, &shdr.sh_offset, sizeof(shdr.sh_offset)) &&
memory_->ReadField(offset, &shdr, &shdr.sh_size, sizeof(shdr.sh_size))) {
gnu_debugdata_offset_ = shdr.sh_offset;
gnu_debugdata_size_ = shdr.sh_size;
}
}
}
}
}
}
return true;
}
template <typename DynType>
bool ElfInterface::GetSonameWithTemplate(std::string* soname) {
if (soname_type_ == SONAME_INVALID) {
return false;
}
if (soname_type_ == SONAME_VALID) {
*soname = soname_;
return true;
}
soname_type_ = SONAME_INVALID;
uint64_t soname_offset = 0;
uint64_t strtab_offset = 0;
uint64_t strtab_size = 0;
// Find the soname location from the dynamic headers section.
DynType dyn;
uint64_t offset = dynamic_offset_;
uint64_t max_offset = offset + dynamic_size_;
for (uint64_t offset = dynamic_offset_; offset < max_offset; offset += sizeof(DynType)) {
if (!memory_->Read(offset, &dyn, sizeof(dyn))) {
return false;
}
if (dyn.d_tag == DT_STRTAB) {
strtab_offset = dyn.d_un.d_ptr;
} else if (dyn.d_tag == DT_STRSZ) {
strtab_size = dyn.d_un.d_val;
} else if (dyn.d_tag == DT_SONAME) {
soname_offset = dyn.d_un.d_val;
} else if (dyn.d_tag == DT_NULL) {
break;
}
}
soname_offset += strtab_offset;
if (soname_offset >= strtab_offset + strtab_size) {
return false;
}
if (!memory_->ReadString(soname_offset, &soname_)) {
return false;
}
soname_type_ = SONAME_VALID;
*soname = soname_;
return true;
}
bool ElfInterface::Step(uint64_t, Regs*, Memory*) {
return false;
}
// Instantiate all of the needed template functions.
template bool ElfInterface::ReadAllHeaders<Elf32_Ehdr, Elf32_Phdr, Elf32_Shdr>();
template bool ElfInterface::ReadAllHeaders<Elf64_Ehdr, Elf64_Phdr, Elf64_Shdr>();
template bool ElfInterface::ReadProgramHeaders<Elf32_Ehdr, Elf32_Phdr>(const Elf32_Ehdr&);
template bool ElfInterface::ReadProgramHeaders<Elf64_Ehdr, Elf64_Phdr>(const Elf64_Ehdr&);
template bool ElfInterface::ReadSectionHeaders<Elf32_Ehdr, Elf32_Shdr>(const Elf32_Ehdr&);
template bool ElfInterface::ReadSectionHeaders<Elf64_Ehdr, Elf64_Shdr>(const Elf64_Ehdr&);
template bool ElfInterface::GetSonameWithTemplate<Elf32_Dyn>(std::string*);
template bool ElfInterface::GetSonameWithTemplate<Elf64_Dyn>(std::string*);