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platform_system_core/libunwindstack/ElfInterface.cpp

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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 <7zCrc.h>
#include <Xz.h>
#include <XzCrc64.h>
#include <unwindstack/DwarfSection.h>
#include <unwindstack/ElfInterface.h>
#include <unwindstack/Log.h>
#include <unwindstack/Memory.h>
#include <unwindstack/Regs.h>
#include "DwarfDebugFrame.h"
#include "DwarfEhFrame.h"
#include "Symbols.h"
namespace unwindstack {
ElfInterface::~ElfInterface() {
for (auto symbol : symbols_) {
delete symbol;
}
}
Memory* ElfInterface::CreateGnuDebugdataMemory() {
if (gnu_debugdata_offset_ == 0 || gnu_debugdata_size_ == 0) {
return nullptr;
}
// TODO: Only call these initialization functions once.
CrcGenerateTable();
Crc64GenerateTable();
std::vector<uint8_t> src(gnu_debugdata_size_);
if (!memory_->Read(gnu_debugdata_offset_, src.data(), gnu_debugdata_size_)) {
gnu_debugdata_offset_ = 0;
gnu_debugdata_size_ = static_cast<uint64_t>(-1);
return nullptr;
}
ISzAlloc alloc;
CXzUnpacker state;
alloc.Alloc = [](void*, size_t size) { return malloc(size); };
alloc.Free = [](void*, void* ptr) { return free(ptr); };
XzUnpacker_Construct(&state, &alloc);
std::unique_ptr<MemoryBuffer> dst(new MemoryBuffer);
int return_val;
size_t src_offset = 0;
size_t dst_offset = 0;
ECoderStatus status;
dst->Resize(5 * gnu_debugdata_size_);
do {
size_t src_remaining = src.size() - src_offset;
size_t dst_remaining = dst->Size() - dst_offset;
if (dst_remaining < 2 * gnu_debugdata_size_) {
dst->Resize(dst->Size() + 2 * gnu_debugdata_size_);
dst_remaining += 2 * gnu_debugdata_size_;
}
return_val = XzUnpacker_Code(&state, dst->GetPtr(dst_offset), &dst_remaining, &src[src_offset],
&src_remaining, CODER_FINISH_ANY, &status);
src_offset += src_remaining;
dst_offset += dst_remaining;
} while (return_val == SZ_OK && status == CODER_STATUS_NOT_FINISHED);
XzUnpacker_Free(&state);
if (return_val != SZ_OK || !XzUnpacker_IsStreamWasFinished(&state)) {
gnu_debugdata_offset_ = 0;
gnu_debugdata_size_ = static_cast<uint64_t>(-1);
return nullptr;
}
// Shrink back down to the exact size.
dst->Resize(dst_offset);
return dst.release();
}
template <typename AddressType>
void ElfInterface::InitHeadersWithTemplate() {
if (eh_frame_offset_ != 0) {
eh_frame_.reset(new DwarfEhFrame<AddressType>(memory_));
if (!eh_frame_->Init(eh_frame_offset_, eh_frame_size_)) {
eh_frame_.reset(nullptr);
eh_frame_offset_ = 0;
eh_frame_size_ = static_cast<uint64_t>(-1);
}
}
if (debug_frame_offset_ != 0) {
debug_frame_.reset(new DwarfDebugFrame<AddressType>(memory_));
if (!debug_frame_->Init(debug_frame_offset_, debug_frame_size_)) {
debug_frame_.reset(nullptr);
debug_frame_offset_ = 0;
debug_frame_size_ = static_cast<uint64_t>(-1);
}
}
}
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;
}
// We could still potentially unwind without the section header
// information, so ignore any errors.
if (!ReadSectionHeaders<EhdrType, ShdrType>(ehdr)) {
log(0, "Malformed section header found, ignoring...");
}
return true;
}
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.
offset += ehdr.e_shentsize;
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_SYMTAB || shdr.sh_type == SHT_DYNSYM) {
if (!memory_->Read(offset, &shdr, sizeof(shdr))) {
return false;
}
// Need to go get the information about the section that contains
// the string terminated names.
ShdrType str_shdr;
if (shdr.sh_link >= ehdr.e_shnum) {
return false;
}
uint64_t str_offset = ehdr.e_shoff + shdr.sh_link * ehdr.e_shentsize;
if (!memory_->ReadField(str_offset, &str_shdr, &str_shdr.sh_type, sizeof(str_shdr.sh_type))) {
return false;
}
if (str_shdr.sh_type != SHT_STRTAB) {
return false;
}
if (!memory_->ReadField(str_offset, &str_shdr, &str_shdr.sh_offset,
sizeof(str_shdr.sh_offset))) {
return false;
}
if (!memory_->ReadField(str_offset, &str_shdr, &str_shdr.sh_size, sizeof(str_shdr.sh_size))) {
return false;
}
symbols_.push_back(new Symbols(shdr.sh_offset, shdr.sh_size, shdr.sh_entsize,
str_shdr.sh_offset, str_shdr.sh_size));
} else if (shdr.sh_type == SHT_PROGBITS && sec_size != 0) {
// 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)) {
uint64_t* offset_ptr = nullptr;
uint64_t* size_ptr = nullptr;
if (name == ".debug_frame") {
offset_ptr = &debug_frame_offset_;
size_ptr = &debug_frame_size_;
} else if (name == ".gnu_debugdata") {
offset_ptr = &gnu_debugdata_offset_;
size_ptr = &gnu_debugdata_size_;
}
if (offset_ptr != nullptr &&
memory_->ReadField(offset, &shdr, &shdr.sh_offset, sizeof(shdr.sh_offset)) &&
memory_->ReadField(offset, &shdr, &shdr.sh_size, sizeof(shdr.sh_size))) {
*offset_ptr = shdr.sh_offset;
*size_ptr = 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;
}
template <typename SymType>
bool ElfInterface::GetFunctionNameWithTemplate(uint64_t addr, std::string* name,
uint64_t* func_offset) {
if (symbols_.empty()) {
return false;
}
for (const auto symbol : symbols_) {
if (symbol->GetName<SymType>(addr, load_bias_, memory_, name, func_offset)) {
return true;
}
}
return false;
}
bool ElfInterface::Step(uint64_t pc, Regs* regs, Memory* process_memory, bool* finished) {
// Need to subtract off the load_bias to get the correct pc.
if (pc < load_bias_) {
return false;
}
pc -= load_bias_;
// Try the eh_frame first.
DwarfSection* eh_frame = eh_frame_.get();
if (eh_frame != nullptr && eh_frame->Step(pc, regs, process_memory, finished)) {
return true;
}
// Try the debug_frame next.
DwarfSection* debug_frame = debug_frame_.get();
if (debug_frame != nullptr && debug_frame->Step(pc, regs, process_memory, finished)) {
return true;
}
return false;
}
// This is an estimation of the size of the elf file using the location
// of the section headers and size. This assumes that the section headers
// are at the end of the elf file. If the elf has a load bias, the size
// will be too large, but this is acceptable.
template <typename EhdrType>
void ElfInterface::GetMaxSizeWithTemplate(Memory* memory, uint64_t* size) {
EhdrType ehdr;
if (!memory->Read(0, &ehdr, sizeof(ehdr))) {
return;
}
if (ehdr.e_shnum == 0) {
return;
}
*size = ehdr.e_shoff + ehdr.e_shentsize * ehdr.e_shnum;
}
// Instantiate all of the needed template functions.
template void ElfInterface::InitHeadersWithTemplate<uint32_t>();
template void ElfInterface::InitHeadersWithTemplate<uint64_t>();
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*);
template bool ElfInterface::GetFunctionNameWithTemplate<Elf32_Sym>(uint64_t, std::string*,
uint64_t*);
template bool ElfInterface::GetFunctionNameWithTemplate<Elf64_Sym>(uint64_t, std::string*,
uint64_t*);
template void ElfInterface::GetMaxSizeWithTemplate<Elf32_Ehdr>(Memory*, uint64_t*);
template void ElfInterface::GetMaxSizeWithTemplate<Elf64_Ehdr>(Memory*, uint64_t*);
} // namespace unwindstack
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