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platform_system_core/libunwindstack/ElfInterface.cpp
Christopher Ferris 4cc36d2b43 Fix handling of load bias values. 
It turns out that for the dwarf information, if a FDE indicates it's pc
relative, then pc has to be incremented by the load bias. If not, then
it should not be incremented.

Previously, the code always subtracted load bias values from pcs, and assumed
that all fdes were incremented by load bias values. The new code actually
reads the fdes and adjusted the pcs in the fde and in the eh frame hdr so
that load bias values are already handled properly.

In addition, add dumping of arm exidx values in unwind_reg_info. This allowed
verifying that the debug frame in those elf files was being handled properly.

Added a new unit test that only has a debug frame that has a non-zero load
bias and has fde entries that do not have pc relative encoding.

Fix a couple of other small bugs.

Bug: 109824792

Test: All libbacktrace/libunwindstack unit tests pass.
Test: Ran ART 137-cfi test and 004-ThreadStress.
Test: Verify that displaying the fde start and end pc actually match the
Test: real data for fde that have pc relative set, and that don't.
Test: Verified that the unwind information for arm exidx matches the
Test: debug frame data.

Change-Id: I707555286b5cb05df9f25489e8c5ede753cfe0fb
2018-06-11 18:53:55 -07:00

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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 <utility>
#include <7zCrc.h>
#include <Xz.h>
#include <XzCrc64.h>
#include <unwindstack/DwarfError.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 "DwarfEhFrameWithHdr.h"
#include "Symbols.h"
namespace unwindstack {
ElfInterface::~ElfInterface() {
for (auto symbol : symbols_) {
delete symbol;
}
}
bool ElfInterface::IsValidPc(uint64_t pc) {
if (!pt_loads_.empty()) {
for (auto& entry : pt_loads_) {
uint64_t start = entry.second.table_offset;
uint64_t end = start + entry.second.table_size;
if (pc >= start && pc < end) {
return true;
}
}
return false;
}
// No PT_LOAD data, look for a fde for this pc in the section data.
if (debug_frame_ != nullptr && debug_frame_->GetFdeFromPc(pc) != nullptr) {
return true;
}
if (eh_frame_ != nullptr && eh_frame_->GetFdeFromPc(pc) != nullptr) {
return true;
}
return false;
}
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_->ReadFully(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 = [](ISzAllocPtr, size_t size) { return malloc(size); };
alloc.Free = [](ISzAllocPtr, 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, true, 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(uint64_t load_bias) {
if (eh_frame_hdr_offset_ != 0) {
eh_frame_.reset(new DwarfEhFrameWithHdr<AddressType>(memory_));
if (!eh_frame_->Init(eh_frame_hdr_offset_, eh_frame_hdr_size_, load_bias)) {
eh_frame_.reset(nullptr);
}
}
if (eh_frame_.get() == nullptr && eh_frame_offset_ != 0) {
// If there is an eh_frame section without an eh_frame_hdr section,
// or using the frame hdr object failed to init.
eh_frame_.reset(new DwarfEhFrame<AddressType>(memory_));
if (!eh_frame_->Init(eh_frame_offset_, eh_frame_size_, load_bias)) {
eh_frame_.reset(nullptr);
}
}
if (eh_frame_.get() == nullptr) {
eh_frame_hdr_offset_ = 0;
eh_frame_hdr_size_ = static_cast<uint64_t>(-1);
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_, load_bias)) {
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(uint64_t* load_bias) {
EhdrType ehdr;
if (!memory_->ReadFully(0, &ehdr, sizeof(ehdr))) {
last_error_.code = ERROR_MEMORY_INVALID;
last_error_.address = 0;
return false;
}
if (!ReadProgramHeaders<EhdrType, PhdrType>(ehdr, load_bias)) {
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>
uint64_t ElfInterface::GetLoadBias(Memory* memory) {
EhdrType ehdr;
if (!memory->Read(0, &ehdr, sizeof(ehdr))) {
return false;
}
uint64_t offset = ehdr.e_phoff;
for (size_t i = 0; i < ehdr.e_phnum; i++, offset += ehdr.e_phentsize) {
PhdrType phdr;
if (!memory->Read(offset, &phdr, sizeof(phdr))) {
return 0;
}
if (phdr.p_type == PT_LOAD && phdr.p_offset == 0) {
return phdr.p_vaddr;
}
}
return 0;
}
template <typename EhdrType, typename PhdrType>
bool ElfInterface::ReadProgramHeaders(const EhdrType& ehdr, uint64_t* load_bias) {
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))) {
last_error_.code = ERROR_MEMORY_INVALID;
last_error_.address =
offset + reinterpret_cast<uintptr_t>(&phdr.p_type) - reinterpret_cast<uintptr_t>(&phdr);
return false;
}
if (HandleType(offset, phdr.p_type, *load_bias)) {
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))) {
last_error_.code = ERROR_MEMORY_INVALID;
last_error_.address = offset + reinterpret_cast<uintptr_t>(&phdr.p_flags) -
reinterpret_cast<uintptr_t>(&phdr);
return false;
}
if ((phdr.p_flags & PF_X) == 0) {
continue;
}
if (!memory_->ReadField(offset, &phdr, &phdr.p_vaddr, sizeof(phdr.p_vaddr))) {
last_error_.code = ERROR_MEMORY_INVALID;
last_error_.address = offset + reinterpret_cast<uintptr_t>(&phdr.p_vaddr) -
reinterpret_cast<uintptr_t>(&phdr);
return false;
}
if (!memory_->ReadField(offset, &phdr, &phdr.p_offset, sizeof(phdr.p_offset))) {
last_error_.code = ERROR_MEMORY_INVALID;
last_error_.address = offset + reinterpret_cast<uintptr_t>(&phdr.p_offset) -
reinterpret_cast<uintptr_t>(&phdr);
return false;
}
if (!memory_->ReadField(offset, &phdr, &phdr.p_memsz, sizeof(phdr.p_memsz))) {
last_error_.code = ERROR_MEMORY_INVALID;
last_error_.address = offset + reinterpret_cast<uintptr_t>(&phdr.p_memsz) -
reinterpret_cast<uintptr_t>(&phdr);
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))) {
last_error_.code = ERROR_MEMORY_INVALID;
last_error_.address = offset + reinterpret_cast<uintptr_t>(&phdr.p_offset) -
reinterpret_cast<uintptr_t>(&phdr);
return false;
}
// This is really the pointer to the .eh_frame_hdr section.
eh_frame_hdr_offset_ = phdr.p_offset;
if (!memory_->ReadField(offset, &phdr, &phdr.p_memsz, sizeof(phdr.p_memsz))) {
last_error_.code = ERROR_MEMORY_INVALID;
last_error_.address = offset + reinterpret_cast<uintptr_t>(&phdr.p_memsz) -
reinterpret_cast<uintptr_t>(&phdr);
return false;
}
eh_frame_hdr_size_ = phdr.p_memsz;
break;
case PT_DYNAMIC:
if (!memory_->ReadField(offset, &phdr, &phdr.p_offset, sizeof(phdr.p_offset))) {
last_error_.code = ERROR_MEMORY_INVALID;
last_error_.address = offset + reinterpret_cast<uintptr_t>(&phdr.p_offset) -
reinterpret_cast<uintptr_t>(&phdr);
return false;
}
dynamic_offset_ = phdr.p_offset;
if (!memory_->ReadField(offset, &phdr, &phdr.p_vaddr, sizeof(phdr.p_vaddr))) {
last_error_.code = ERROR_MEMORY_INVALID;
last_error_.address = offset + reinterpret_cast<uintptr_t>(&phdr.p_vaddr) -
reinterpret_cast<uintptr_t>(&phdr);
return false;
}
dynamic_vaddr_ = phdr.p_vaddr;
if (!memory_->ReadField(offset, &phdr, &phdr.p_memsz, sizeof(phdr.p_memsz))) {
last_error_.code = ERROR_MEMORY_INVALID;
last_error_.address = offset + reinterpret_cast<uintptr_t>(&phdr.p_memsz) -
reinterpret_cast<uintptr_t>(&phdr);
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_->Read(offset, &shdr, sizeof(shdr))) {
last_error_.code = ERROR_MEMORY_INVALID;
last_error_.address = offset;
return false;
}
if (shdr.sh_type == SHT_SYMTAB || shdr.sh_type == SHT_DYNSYM) {
// 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) {
last_error_.code = ERROR_UNWIND_INFO;
return false;
}
uint64_t str_offset = ehdr.e_shoff + shdr.sh_link * ehdr.e_shentsize;
if (!memory_->Read(str_offset, &str_shdr, sizeof(str_shdr))) {
last_error_.code = ERROR_MEMORY_INVALID;
last_error_.address = str_offset;
return false;
}
if (str_shdr.sh_type != SHT_STRTAB) {
last_error_.code = ERROR_UNWIND_INFO;
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 (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_;
} else if (name == ".eh_frame") {
offset_ptr = &eh_frame_offset_;
size_ptr = &eh_frame_size_;
} else if (eh_frame_hdr_offset_ == 0 && name == ".eh_frame_hdr") {
offset_ptr = &eh_frame_hdr_offset_;
size_ptr = &eh_frame_hdr_size_;
}
if (offset_ptr != nullptr) {
*offset_ptr = shdr.sh_offset;
*size_ptr = shdr.sh_size;
}
}
}
} else if (shdr.sh_type == SHT_STRTAB) {
// In order to read soname, keep track of address to offset mapping.
strtabs_.push_back(std::make_pair<uint64_t, uint64_t>(static_cast<uint64_t>(shdr.sh_addr),
static_cast<uint64_t>(shdr.sh_offset)));
}
}
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_addr = 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_->ReadFully(offset, &dyn, sizeof(dyn))) {
last_error_.code = ERROR_MEMORY_INVALID;
last_error_.address = offset;
return false;
}
if (dyn.d_tag == DT_STRTAB) {
strtab_addr = 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;
}
}
// Need to map the strtab address to the real offset.
for (const auto& entry : strtabs_) {
if (entry.first == strtab_addr) {
soname_offset = entry.second + soname_offset;
if (soname_offset >= entry.second + strtab_size) {
return false;
}
if (!memory_->ReadString(soname_offset, &soname_)) {
return false;
}
soname_type_ = SONAME_VALID;
*soname = soname_;
return true;
}
}
return false;
}
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, memory_, name, func_offset)) {
return true;
}
}
return false;
}
template <typename SymType>
bool ElfInterface::GetGlobalVariableWithTemplate(const std::string& name, uint64_t* memory_address) {
if (symbols_.empty()) {
return false;
}
for (const auto symbol : symbols_) {
if (symbol->GetGlobal<SymType>(memory_, name, memory_address)) {
return true;
}
}
return false;
}
bool ElfInterface::Step(uint64_t pc, Regs* regs, Memory* process_memory, bool* finished) {
last_error_.code = ERROR_NONE;
last_error_.address = 0;
// Try the debug_frame first since it contains the most specific unwind
// information.
DwarfSection* debug_frame = debug_frame_.get();
if (debug_frame != nullptr && debug_frame->Step(pc, regs, process_memory, finished)) {
return true;
}
// Try the eh_frame next.
DwarfSection* eh_frame = eh_frame_.get();
if (eh_frame != nullptr && eh_frame->Step(pc, regs, process_memory, finished)) {
return true;
}
if (gnu_debugdata_interface_ != nullptr &&
gnu_debugdata_interface_->Step(pc, regs, process_memory, finished)) {
return true;
}
// Set the error code based on the first error encountered.
DwarfSection* section = nullptr;
if (debug_frame_ != nullptr) {
section = debug_frame_.get();
} else if (eh_frame_ != nullptr) {
section = eh_frame_.get();
} else if (gnu_debugdata_interface_ != nullptr) {
last_error_ = gnu_debugdata_interface_->last_error();
return false;
} else {
return false;
}
// Convert the DWARF ERROR to an external error.
DwarfErrorCode code = section->LastErrorCode();
switch (code) {
case DWARF_ERROR_NONE:
last_error_.code = ERROR_NONE;
break;
case DWARF_ERROR_MEMORY_INVALID:
last_error_.code = ERROR_MEMORY_INVALID;
last_error_.address = section->LastErrorAddress();
break;
case DWARF_ERROR_ILLEGAL_VALUE:
case DWARF_ERROR_ILLEGAL_STATE:
case DWARF_ERROR_STACK_INDEX_NOT_VALID:
case DWARF_ERROR_TOO_MANY_ITERATIONS:
case DWARF_ERROR_CFA_NOT_DEFINED:
case DWARF_ERROR_NO_FDES:
last_error_.code = ERROR_UNWIND_INFO;
break;
case DWARF_ERROR_NOT_IMPLEMENTED:
case DWARF_ERROR_UNSUPPORTED_VERSION:
last_error_.code = ERROR_UNSUPPORTED;
break;
}
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->ReadFully(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>(uint64_t);
template void ElfInterface::InitHeadersWithTemplate<uint64_t>(uint64_t);
template bool ElfInterface::ReadAllHeaders<Elf32_Ehdr, Elf32_Phdr, Elf32_Shdr>(uint64_t*);
template bool ElfInterface::ReadAllHeaders<Elf64_Ehdr, Elf64_Phdr, Elf64_Shdr>(uint64_t*);
template bool ElfInterface::ReadProgramHeaders<Elf32_Ehdr, Elf32_Phdr>(const Elf32_Ehdr&, uint64_t*);
template bool ElfInterface::ReadProgramHeaders<Elf64_Ehdr, Elf64_Phdr>(const Elf64_Ehdr&, uint64_t*);
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 bool ElfInterface::GetGlobalVariableWithTemplate<Elf32_Sym>(const std::string&, uint64_t*);
template bool ElfInterface::GetGlobalVariableWithTemplate<Elf64_Sym>(const std::string&, uint64_t*);
template void ElfInterface::GetMaxSizeWithTemplate<Elf32_Ehdr>(Memory*, uint64_t*);
template void ElfInterface::GetMaxSizeWithTemplate<Elf64_Ehdr>(Memory*, uint64_t*);
template uint64_t ElfInterface::GetLoadBias<Elf32_Ehdr, Elf32_Phdr>(Memory*);
template uint64_t ElfInterface::GetLoadBias<Elf64_Ehdr, Elf64_Phdr>(Memory*);
} // namespace unwindstack
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