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revng-revng/binaryfile.cpp
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Alessandro Di Federico d8f13c799d Detect try/catch landing pads 
Landing pads are basically the `catch` blocks in C++ `try`/`catch`
statements. So far we were missing them since they are encoded in a
particular way in a way similar to DWARF debugging information in the
`.eh_frame` and, more specifically, in the `.gcc_except_table` sections
of ELF programs.

This commit parses these sections so that the basic blocks associated to
landing pads are correctly identified. Personality functions are
detected too. A test is also introduced to assess the effectiveness of
our code.
2017-03-31 10:10:16 +02:00

630 lines
20 KiB
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/// \file binaryfile.cpp
/// \brief
//
// This file is distributed under the MIT License. See LICENSE.md for details.
//
// Standard includes
#include <string>
#include <tuple>
#include <utility>
// LLVM includes
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/Triple.h"
#include "llvm/Object/ELF.h"
#include "llvm/Object/ObjectFile.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/Dwarf.h"
#include "llvm/Support/ELF.h"
#include "llvm/Support/Endian.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/LEB128.h"
// Local includes
#include "binaryfile.h"
#include "debug.h"
// using directives
using namespace llvm;
using std::make_pair;
BinaryFile::BinaryFile(std::string FilePath, bool UseSections) {
auto BinaryOrErr = object::createBinary(FilePath);
assert(BinaryOrErr && "Couldn't open the input file");
BinaryHandle = std::move(BinaryOrErr.get());
auto *TheBinary = cast<object::ObjectFile>(BinaryHandle.getBinary());
// TODO: QEMU should provide this information
unsigned InstructionAlignment = 0;
StringRef SyscallHelper = "";
StringRef SyscallNumberRegister = "";
ArrayRef<uint64_t> NoReturnSyscalls = { };
unsigned DelaySlotSize = 0;
switch (TheBinary->getArch()) {
case Triple::x86_64:
InstructionAlignment = 1;
SyscallHelper = "helper_syscall";
SyscallNumberRegister = "rax";
NoReturnSyscalls = {
0xe7, // exit_group
0x3c, // exit
0x3b // execve
};
break;
case Triple::arm:
InstructionAlignment = 4;
SyscallHelper = "helper_exception_with_syndrome";
SyscallNumberRegister = "r7";
NoReturnSyscalls = {
0xf8, // exit_group
0x1, // exit
0xb // execve
};
break;
case Triple::mips:
InstructionAlignment = 4;
SyscallHelper = "helper_raise_exception";
SyscallNumberRegister = "v0";
NoReturnSyscalls = {
0x1096, // exit_group
0xfa1, // exit
0xfab // execve
};
DelaySlotSize = 1;
break;
default:
assert(false);
}
TheArchitecture = Architecture(TheBinary->getArch(),
InstructionAlignment,
1,
TheBinary->isLittleEndian(),
TheBinary->getBytesInAddress() * 8,
SyscallHelper,
SyscallNumberRegister,
NoReturnSyscalls,
DelaySlotSize);
assert(TheBinary->getFileFormatName().startswith("ELF")
&& "Only the ELF file format is currently supported");
if (TheArchitecture.pointerSize() == 32) {
if (TheArchitecture.isLittleEndian()) {
parseELF<object::ELF32LE>(TheBinary, UseSections);
} else {
parseELF<object::ELF32BE>(TheBinary, UseSections);
}
} else if (TheArchitecture.pointerSize() == 64) {
if (TheArchitecture.isLittleEndian()) {
parseELF<object::ELF64LE>(TheBinary, UseSections);
} else {
parseELF<object::ELF64BE>(TheBinary, UseSections);
}
} else {
assert("Unexpect address size");
}
}
template<typename T>
void BinaryFile::parseELF(object::ObjectFile *TheBinary, bool UseSections) {
// Parse the ELF file
std::error_code EC;
object::ELFFile<T> TheELF(TheBinary->getData(), EC);
assert(!EC && "Error while loading the ELF file");
// Look for static or dynamic symbols
using Elf_ShdrPtr = decltype(&(*TheELF.sections().begin()));
Elf_ShdrPtr SymtabShdr = nullptr;
Optional<uint64_t> EHFrameAddress;
Optional<uint64_t> EHFrameSize;
Optional<uint64_t> EHFrameHdrAddress;
for (auto &Section : TheELF.sections()){
auto Name = TheELF.getSectionName(&Section);
if (Name) {
if (*Name == ".symtab") {
// .symtab might override .dynsym
SymtabShdr = &Section;
} else if (SymtabShdr == nullptr && *Name == ".dynsym") {
SymtabShdr = &Section;
} else if (*Name == ".eh_frame") {
assert(!EHFrameAddress && "Duplicate .eh_frame");
EHFrameAddress = static_cast<uint64_t>(Section.sh_addr);
EHFrameSize = static_cast<uint64_t>(Section.sh_size);
}
}
}
// If we found a symbol table
if (SymtabShdr != nullptr && SymtabShdr->sh_link != 0) {
// Obtain a reference to the string table
auto *Strtab = TheELF.getSection(SymtabShdr->sh_link).get();
auto StrtabArray = TheELF.getSectionContents(Strtab).get();
StringRef StrtabContent(reinterpret_cast<const char *>(StrtabArray.data()),
StrtabArray.size());
// Collect symbol names
for (auto &Symbol : TheELF.symbols(SymtabShdr)) {
Symbols.push_back({
Symbol.getName(StrtabContent).get(),
Symbol.st_value,
Symbol.st_size
});
}
}
const auto *ElfHeader = TheELF.getHeader();
EntryPoint = static_cast<uint64_t>(ElfHeader->e_entry);
ProgramHeaders.Count = ElfHeader->e_phnum;
ProgramHeaders.Size = ElfHeader->e_phentsize;
// Loop over the program headers looking for PT_LOAD segments, read them out
// and create a global variable for each one of them (writable or read-only),
// assign them a section and output information about them in the linking info
// CSV
using Elf_Phdr = const typename object::ELFFile<T>::Elf_Phdr;
for (Elf_Phdr &ProgramHeader : TheELF.program_headers()) {
switch (ProgramHeader.p_type) {
case ELF::PT_LOAD:
{
SegmentInfo Segment;
auto Start = ProgramHeader.p_vaddr;
Segment.StartVirtualAddress = Start;
Segment.EndVirtualAddress = Start + ProgramHeader.p_memsz;
Segment.IsReadable = ProgramHeader.p_flags & ELF::PF_R;
Segment.IsWriteable = ProgramHeader.p_flags & ELF::PF_W;
Segment.IsExecutable = ProgramHeader.p_flags & ELF::PF_X;
auto ActualAddress = TheELF.base() + ProgramHeader.p_offset;
Segment.Data = ArrayRef<uint8_t>(ActualAddress, ProgramHeader.p_filesz);
// If it's an executable segment, and we've been asked so, register
// which sections actually contain code
if (UseSections && Segment.IsExecutable) {
using Elf_Shdr = const typename object::ELFFile<T>::Elf_Shdr;
auto Inserter = std::back_inserter(Segment.ExecutableSections);
for (Elf_Shdr &SectionHeader : TheELF.sections()) {
if (SectionHeader.sh_flags & ELF::SHF_EXECINSTR) {
auto SectionStart = SectionHeader.sh_addr;
auto SectionEnd = SectionStart + SectionHeader.sh_size;
Inserter = make_pair(SectionStart, SectionEnd);
}
}
}
Segments.push_back(Segment);
// Check if it's the segment containing the program headers
auto ProgramHeaderStart = ProgramHeader.p_offset;
auto ProgramHeaderEnd = ProgramHeader.p_offset + ProgramHeader.p_filesz;
if (ProgramHeaderStart <= ElfHeader->e_phoff
&& ElfHeader->e_phoff < ProgramHeaderEnd) {
auto PhdrAddress = static_cast<uint64_t>(ProgramHeader.p_vaddr
+ ElfHeader->e_phoff
- ProgramHeader.p_offset);
ProgramHeaders.Address = PhdrAddress;
}
}
break;
case ELF::PT_GNU_EH_FRAME:
assert(!EHFrameHdrAddress);
EHFrameHdrAddress = ProgramHeader.p_vaddr;
break;
}
}
Optional<uint64_t> FDEsCount;
if (EHFrameHdrAddress) {
uint64_t Address;
std::tie(Address, FDEsCount) = ehFrameFromEhFrameHdr<T>(*EHFrameHdrAddress);
if (EHFrameAddress) {
assert(*EHFrameAddress == Address);
}
EHFrameAddress = Address;
}
if (EHFrameAddress)
parseEHFrame<T>(*EHFrameAddress, FDEsCount, EHFrameSize);
}
//
// .eh_frame-related functions
//
template<typename E>
class DwarfReader {
public:
DwarfReader(ArrayRef<uint8_t> Buffer, uint64_t Address) :
Address(Address),
Start(Buffer.data()),
Cursor(Buffer.data()),
End(Buffer.data() + Buffer.size()) { }
template<typename T>
T readNext() {
assert(Cursor + sizeof(T) <= End);
T Result = Endianess<T, E>::read(Cursor);
Cursor += sizeof(T);
return Result;
}
uint8_t readNextU8() { return readNext<uint8_t>(); }
uint16_t readNextU16() { return readNext<uint16_t>(); }
uint32_t readNextU32() { return readNext<uint32_t>(); }
uint64_t readNextU64() { return readNext<uint64_t>(); }
uint64_t readNextU() {
if (is64())
return readNextU64();
else
return readNextU32();
}
uint64_t readULEB128() {
unsigned Length;
uint64_t Result = decodeULEB128(Cursor, &Length);
Cursor += Length;
assert(Cursor <= End);
return Result;
}
int64_t readSLEB128() {
unsigned Length;
int64_t Result = decodeSLEB128(Cursor, &Length);
Cursor += Length;
assert(Cursor <= End);
return Result;
}
Pointer readPointer(unsigned Encoding, uint64_t Base=0) {
assert((Encoding & ~(0x70 | 0x0F | dwarf::DW_EH_PE_indirect)) == 0);
if ((Encoding & 0x70) == dwarf::DW_EH_PE_pcrel)
Base = Address + (Cursor - Start);
unsigned Format = Encoding & 0x0F;
switch (Format) {
case dwarf::DW_EH_PE_uleb128:
return readPointerInternal(readULEB128(), Encoding, Base);
case dwarf::DW_EH_PE_sleb128:
return readPointerInternal(readSLEB128(), Encoding, Base);
case dwarf::DW_EH_PE_absptr:
if (is64())
return readPointerInternal(readNext<uint64_t>(), Encoding, Base);
else
return readPointerInternal(readNext<uint32_t>(), Encoding, Base);
case dwarf::DW_EH_PE_signed:
if (is64())
return readPointerInternal(readNext<int64_t>(), Encoding, Base);
else
return readPointerInternal(readNext<int32_t>(), Encoding, Base);
case dwarf::DW_EH_PE_udata2:
return readPointerInternal(readNext<uint16_t>(), Encoding, Base);
case dwarf::DW_EH_PE_sdata2:
return readPointerInternal(readNext<int16_t>(), Encoding, Base);
case dwarf::DW_EH_PE_udata4:
return readPointerInternal(readNext<uint32_t>(), Encoding, Base);
case dwarf::DW_EH_PE_sdata4:
return readPointerInternal(readNext<int32_t>(), Encoding, Base);
case dwarf::DW_EH_PE_udata8:
return readPointerInternal(readNext<uint64_t>(), Encoding, Base);
case dwarf::DW_EH_PE_sdata8:
return readPointerInternal(readNext<int64_t>(), Encoding, Base);
default:
llvm_unreachable("Unknown Encoding");
}
}
void moveTo(uint64_t Offset) {
const uint8_t *NewCursor = Start + Offset;
assert(NewCursor >= Cursor && NewCursor <= End);
Cursor = NewCursor;
}
bool eof() const { return Cursor >= End; }
uint64_t offset() const { return Cursor - Start; }
private:
template<typename T>
Pointer readPointerInternal(T Value, unsigned Encoding, uint64_t Base) {
uint64_t Result = Value;
if (Value != 0) {
int EncodingRelative = Encoding & 0x70;
assert(EncodingRelative == 0 || EncodingRelative == 0x10);
Result = Base;
if (std::numeric_limits<T>::is_signed)
Result += static_cast<int64_t>(Value);
else
Result += static_cast<uint64_t>(Value);
}
return Pointer(Encoding & dwarf::DW_EH_PE_indirect, Result);
}
bool is64() const;
private:
uint64_t Address;
const uint8_t *Start;
const uint8_t *Cursor;
const uint8_t *End;
};
template<> bool DwarfReader<object::ELF32BE>::is64() const { return false; }
template<> bool DwarfReader<object::ELF32LE>::is64() const { return false; }
template<> bool DwarfReader<object::ELF64BE>::is64() const { return true; }
template<> bool DwarfReader<object::ELF64LE>::is64() const { return true; }
template<typename T>
std::pair<uint64_t, uint64_t>
BinaryFile::ehFrameFromEhFrameHdr(uint64_t EHFrameHdrAddress) {
auto R = getAddressData(EHFrameHdrAddress);
assert(R && ".eh_frame_hdr section not available in any segment");
llvm::ArrayRef<uint8_t> EHFrameHdr = *R;
DwarfReader<T> EHFrameHdrReader(EHFrameHdr, EHFrameHdrAddress);
uint64_t VersionNumber = EHFrameHdrReader.readNextU8();
assert(VersionNumber == 1);
// ExceptionFrameEncoding
uint64_t ExceptionFrameEncoding = EHFrameHdrReader.readNextU8();
// FDEsCountEncoding
unsigned FDEsCountEncoding = EHFrameHdrReader.readNextU8();
// LookupTableEncoding
EHFrameHdrReader.readNextU8();
Pointer EHFramePointer = EHFrameHdrReader.readPointer(ExceptionFrameEncoding);
Pointer FDEsCountPointer = EHFrameHdrReader.readPointer(FDEsCountEncoding);
return { getPointer<T>(EHFramePointer), getPointer<T>(FDEsCountPointer) };
}
template<typename T>
void BinaryFile::parseEHFrame(uint64_t EHFrameAddress,
Optional<uint64_t> FDEsCount,
Optional<uint64_t> EHFrameSize) {
assert(FDEsCount || EHFrameSize);
auto R = getAddressData(EHFrameAddress);
// Sometimes the .eh_frame section is present but not mapped in memory. This
// means it cannot be used at runtime, therefore we can ignore it.
if (!R)
return;
llvm::ArrayRef<uint8_t> EHFrame = *R;
DwarfReader<T> EHFrameReader(EHFrame, EHFrameAddress);
// A few fields of the CIE are used when decoding the FDE's. This struct
// will cache those fields we need so that we don't have to decode it
// repeatedly for each FDE that references it.
struct DecodedCIE {
Optional<uint32_t> FDEPointerEncoding;
Optional<uint32_t> LSDAPointerEncoding;
bool hasAugmentationLength;
};
// Map from the start offset of the CIE to the cached data for that CIE.
DenseMap<uint64_t, DecodedCIE> CachedCIEs;
unsigned FDEIndex = 0;
while (!EHFrameReader.eof()
&& ((FDEsCount && FDEIndex < *FDEsCount)
|| (EHFrameSize && EHFrameReader.offset() < *EHFrameSize))) {
uint64_t StartOffset = EHFrameReader.offset();
// Read the length of the entry
uint64_t Length = EHFrameReader.readNextU32();
if (Length == 0xffffffff)
Length = EHFrameReader.readNextU64();
// Compute the end offset of the entry
uint64_t OffsetAfterLength = EHFrameReader.offset();
uint64_t EndOffset = OffsetAfterLength + Length;
// Zero-sized entry, skip it
if (Length == 0) {
assert(EHFrameReader.offset() == EndOffset);
continue;
}
// Get the entry ID, 0 means it's a CIE, otherwise it's a FDE
uint32_t ID = EHFrameReader.readNextU32();
if (ID == 0) {
// This is a CIE
DBG("ehframe", dbg << "New CIE\n");
// Ensure the version is the one we expect
uint32_t Version = EHFrameReader.readNextU8();
assert(Version == 1);
// Parse a null terminated augmentation string
SmallString<8> AugmentationString;
for (uint8_t Char = EHFrameReader.readNextU8();
Char != 0;
Char = EHFrameReader.readNextU8())
AugmentationString.push_back(Char);
// Optionally parse the EH data if the augmentation string says it's
// there
if (StringRef(AugmentationString).count("eh") != 0)
EHFrameReader.readNextU();
// CodeAlignmentFactor
EHFrameReader.readULEB128();
// DataAlignmentFactor
EHFrameReader.readULEB128();
// ReturnAddressRegister
EHFrameReader.readNextU8();
Optional<uint64_t> AugmentationLength;
Optional<uint32_t> LSDAPointerEncoding;
Optional<uint32_t> PersonalityEncoding;
Optional<uint32_t> FDEPointerEncoding;
if (!AugmentationString.empty() && AugmentationString.front() == 'z') {
AugmentationLength = EHFrameReader.readULEB128();
// Walk the augmentation string to get all the augmentation data.
for (unsigned i = 1, e = AugmentationString.size(); i != e; ++i) {
char Char = AugmentationString[i];
switch (Char) {
case 'e':
assert((i + 1) != e && AugmentationString[i + 1] == 'h' &&
"Expected 'eh' in augmentation string");
break;
case 'L':
// This is the only information we really care about, all the rest
// is processed just so we can get here
assert(!LSDAPointerEncoding && "Duplicate LSDA encoding");
LSDAPointerEncoding = EHFrameReader.readNextU8();
break;
case 'P': {
assert(!PersonalityEncoding && "Duplicate personality");
PersonalityEncoding = EHFrameReader.readNextU8();
// Personality
Pointer Personality;
Personality = EHFrameReader.readPointer(*PersonalityEncoding);
uint64_t PersonalityPtr = getPointer<T>(Personality);
DBG("ehframe", {
dbg << "Personality function: " << PersonalityPtr << "\n";
});
// TODO: technically this is not a landing pad
LandingPads.insert(PersonalityPtr);
break;
}
case 'R':
assert(!FDEPointerEncoding && "Duplicate FDE encoding");
FDEPointerEncoding = EHFrameReader.readNextU8();
break;
case 'z':
llvm_unreachable("'z' must be first in the augmentation string");
}
}
}
// Cache this entry
CachedCIEs[StartOffset] = {
FDEPointerEncoding,
LSDAPointerEncoding,
AugmentationLength.hasValue()
};
} else {
// This is an FDE
FDEIndex++;
// The CIE pointer for an FDE is the same location as the ID which we
// already read
uint64_t CIEOffset = OffsetAfterLength - ID;
// Ensure we already met this CIE
auto CIEIt = CachedCIEs.find(CIEOffset);
assert(CIEIt != CachedCIEs.end()
&& "Couldn't find CIE at offset in to __eh_frame section");
// Ensure we have at least the pointer encoding
const DecodedCIE &CIE = CIEIt->getSecond();
assert(CIE.FDEPointerEncoding &&
"FDE references CIE which did not set pointer encoding");
// PCBegin
auto PCBeginPointer = EHFrameReader.readPointer(*CIE.FDEPointerEncoding);
uint64_t PCBegin = getPointer<T>(PCBeginPointer);
DBG("ehframe", dbg << "PCBegin: " << std::hex << PCBegin << "\n");
// PCRange
EHFrameReader.readPointer(*CIE.FDEPointerEncoding);
if (CIE.hasAugmentationLength)
EHFrameReader.readULEB128();
// Decode the LSDA if the CIE augmentation string said we should.
if (CIE.LSDAPointerEncoding) {
auto LSDAPointer = EHFrameReader.readPointer(*CIE.LSDAPointerEncoding);
parseLSDA<T>(PCBegin, getPointer<T>(LSDAPointer));
}
}
// Skip all the remaining parts
EHFrameReader.moveTo(EndOffset);
}
}
template<typename T>
void BinaryFile::parseLSDA(uint64_t FDEStart, uint64_t LSDAAddress) {
DBG("ehframe", dbg << "LSDAAddress: " << std::hex << LSDAAddress << "\n");
auto R = getAddressData(LSDAAddress);
assert(R && "LSDA not available in any segment");
llvm::ArrayRef<uint8_t> LSDA = *R;
DwarfReader<T> LSDAReader(LSDA, LSDAAddress);
uint32_t LandingPadBaseEncoding = LSDAReader.readNextU8();
uint64_t LandingPadBase = 0;
if (LandingPadBaseEncoding != dwarf::DW_EH_PE_omit) {
auto LandingPadBasePointer = LSDAReader.readPointer(LandingPadBaseEncoding);
LandingPadBase = getPointer<T>(LandingPadBasePointer);
} else {
LandingPadBase = FDEStart;
}
DBG("ehframe",
dbg << "LandingPadBase: " << std::hex << LandingPadBase << "\n");
uint32_t TypeTableEncoding = LSDAReader.readNextU8();
if (TypeTableEncoding != dwarf::DW_EH_PE_omit)
LSDAReader.readULEB128();
uint32_t CallSiteTableEncoding = LSDAReader.readNextU8();
uint64_t CallSiteTableLength = LSDAReader.readULEB128();
uint64_t CallSiteTableEnd = LSDAReader.offset() + CallSiteTableLength;
while (LSDAReader.offset() < CallSiteTableEnd) {
// InstructionStart
LSDAReader.readPointer(CallSiteTableEncoding);
// InstructionEnd
LSDAReader.readPointer(CallSiteTableEncoding);
// LandingPad
Pointer LandingPadPointer = LSDAReader.readPointer(CallSiteTableEncoding,
LandingPadBase);
uint64_t LandingPad = getPointer<T>(LandingPadPointer);
// Action
LSDAReader.readULEB128();
if (LandingPad != 0) {
DBG("ehframe", {
if (LandingPads.count(LandingPad) == 0)
dbg << "New landing pad found: " << std::hex << LandingPad << "\n";
});
LandingPads.insert(LandingPad);
}
}
}
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