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//===-- RuntimeDyldELF.cpp - Run-time dynamic linker for MC-JIT -*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// Implementation of ELF support for the MC-JIT runtime dynamic linker.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "dyld"
#include "llvm/ADT/OwningPtr.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/IntervalMap.h"
#include "RuntimeDyldELF.h"
#include "llvm/Object/ObjectFile.h"
#include "llvm/Support/ELF.h"
#include "llvm/ADT/Triple.h"
#include "llvm/Object/ELF.h"
#include "JITRegistrar.h"
using namespace llvm;
using namespace llvm::object;
namespace {
template<support::endianness target_endianness, bool is64Bits>
class DyldELFObject : public ELFObjectFile<target_endianness, is64Bits> {
LLVM_ELF_IMPORT_TYPES(target_endianness, is64Bits)
typedef Elf_Shdr_Impl<target_endianness, is64Bits> Elf_Shdr;
typedef Elf_Sym_Impl<target_endianness, is64Bits> Elf_Sym;
typedef Elf_Rel_Impl<target_endianness, is64Bits, false> Elf_Rel;
typedef Elf_Rel_Impl<target_endianness, is64Bits, true> Elf_Rela;
typedef typename ELFObjectFile<target_endianness, is64Bits>::
Elf_Ehdr Elf_Ehdr;
typedef typename ELFDataTypeTypedefHelper<
target_endianness, is64Bits>::value_type addr_type;
protected:
// This duplicates the 'Data' member in the 'Binary' base class
// but it is necessary to workaround a bug in gcc 4.2
MemoryBuffer *InputData;
public:
DyldELFObject(MemoryBuffer *Object, error_code &ec);
void updateSectionAddress(const SectionRef &Sec, uint64_t Addr);
void updateSymbolAddress(const SymbolRef &Sym, uint64_t Addr);
const MemoryBuffer& getBuffer() const { return *InputData; }
// Methods for type inquiry through isa, cast, and dyn_cast
static inline bool classof(const Binary *v) {
return (isa<ELFObjectFile<target_endianness, is64Bits> >(v)
&& classof(cast<ELFObjectFile<target_endianness, is64Bits> >(v)));
}
static inline bool classof(
const ELFObjectFile<target_endianness, is64Bits> *v) {
return v->isDyldType();
}
static inline bool classof(const DyldELFObject *v) {
return true;
}
};
template<support::endianness target_endianness, bool is64Bits>
class ELFObjectImage : public ObjectImage {
protected:
DyldELFObject<target_endianness, is64Bits> *DyldObj;
bool Registered;
public:
ELFObjectImage(DyldELFObject<target_endianness, is64Bits> *Obj)
: ObjectImage(Obj),
DyldObj(Obj),
Registered(false) {}
virtual ~ELFObjectImage() {
if (Registered)
deregisterWithDebugger();
}
// Subclasses can override these methods to update the image with loaded
// addresses for sections and common symbols
virtual void updateSectionAddress(const SectionRef &Sec, uint64_t Addr)
{
DyldObj->updateSectionAddress(Sec, Addr);
}
virtual void updateSymbolAddress(const SymbolRef &Sym, uint64_t Addr)
{
DyldObj->updateSymbolAddress(Sym, Addr);
}
virtual void registerWithDebugger()
{
JITRegistrar::getGDBRegistrar().registerObject(DyldObj->getBuffer());
Registered = true;
}
virtual void deregisterWithDebugger()
{
JITRegistrar::getGDBRegistrar().deregisterObject(DyldObj->getBuffer());
}
};
template<support::endianness target_endianness, bool is64Bits>
DyldELFObject<target_endianness, is64Bits>::DyldELFObject(MemoryBuffer *Object,
error_code &ec)
: ELFObjectFile<target_endianness, is64Bits>(Object, ec),
InputData(Object) {
this->isDyldELFObject = true;
}
template<support::endianness target_endianness, bool is64Bits>
void DyldELFObject<target_endianness, is64Bits>::updateSectionAddress(
const SectionRef &Sec,
uint64_t Addr) {
DataRefImpl ShdrRef = Sec.getRawDataRefImpl();
Elf_Shdr *shdr = const_cast<Elf_Shdr*>(
reinterpret_cast<const Elf_Shdr *>(ShdrRef.p));
// This assumes the address passed in matches the target address bitness
// The template-based type cast handles everything else.
shdr->sh_addr = static_cast<addr_type>(Addr);
}
template<support::endianness target_endianness, bool is64Bits>
void DyldELFObject<target_endianness, is64Bits>::updateSymbolAddress(
const SymbolRef &SymRef,
uint64_t Addr) {
Elf_Sym *sym = const_cast<Elf_Sym*>(
ELFObjectFile<target_endianness, is64Bits>::
getSymbol(SymRef.getRawDataRefImpl()));
// This assumes the address passed in matches the target address bitness
// The template-based type cast handles everything else.
sym->st_value = static_cast<addr_type>(Addr);
}
} // namespace
namespace llvm {
ObjectImage *RuntimeDyldELF::createObjectImage(
const MemoryBuffer *ConstInputBuffer) {
MemoryBuffer *InputBuffer = const_cast<MemoryBuffer*>(ConstInputBuffer);
std::pair<unsigned char, unsigned char> Ident = getElfArchType(InputBuffer);
error_code ec;
if (Ident.first == ELF::ELFCLASS32 && Ident.second == ELF::ELFDATA2LSB) {
DyldELFObject<support::little, false> *Obj =
new DyldELFObject<support::little, false>(InputBuffer, ec);
return new ELFObjectImage<support::little, false>(Obj);
}
else if (Ident.first == ELF::ELFCLASS32 && Ident.second == ELF::ELFDATA2MSB) {
DyldELFObject<support::big, false> *Obj =
new DyldELFObject<support::big, false>(InputBuffer, ec);
return new ELFObjectImage<support::big, false>(Obj);
}
else if (Ident.first == ELF::ELFCLASS64 && Ident.second == ELF::ELFDATA2MSB) {
DyldELFObject<support::big, true> *Obj =
new DyldELFObject<support::big, true>(InputBuffer, ec);
return new ELFObjectImage<support::big, true>(Obj);
}
else if (Ident.first == ELF::ELFCLASS64 && Ident.second == ELF::ELFDATA2LSB) {
DyldELFObject<support::little, true> *Obj =
new DyldELFObject<support::little, true>(InputBuffer, ec);
return new ELFObjectImage<support::little, true>(Obj);
}
else
llvm_unreachable("Unexpected ELF format");
}
void RuntimeDyldELF::handleObjectLoaded(ObjectImage *Obj)
{
Obj->registerWithDebugger();
// Save the loaded object. It will deregister itself when deleted
LoadedObject = Obj;
}
RuntimeDyldELF::~RuntimeDyldELF() {
if (LoadedObject)
delete LoadedObject;
}
void RuntimeDyldELF::resolveX86_64Relocation(uint8_t *LocalAddress,
uint64_t FinalAddress,
uint64_t Value,
uint32_t Type,
int64_t Addend) {
switch (Type) {
default:
llvm_unreachable("Relocation type not implemented yet!");
break;
case ELF::R_X86_64_64: {
uint64_t *Target = (uint64_t*)(LocalAddress);
*Target = Value + Addend;
break;
}
case ELF::R_X86_64_32:
case ELF::R_X86_64_32S: {
Value += Addend;
// FIXME: Handle the possibility of this assertion failing
assert((Type == ELF::R_X86_64_32 && !(Value & 0xFFFFFFFF00000000ULL)) ||
(Type == ELF::R_X86_64_32S &&
(Value & 0xFFFFFFFF00000000ULL) == 0xFFFFFFFF00000000ULL));
uint32_t TruncatedAddr = (Value & 0xFFFFFFFF);
uint32_t *Target = reinterpret_cast<uint32_t*>(LocalAddress);
*Target = TruncatedAddr;
break;
}
case ELF::R_X86_64_PC32: {
uint32_t *Placeholder = reinterpret_cast<uint32_t*>(LocalAddress);
int64_t RealOffset = *Placeholder + Value + Addend - FinalAddress;
assert(RealOffset <= 214783647 && RealOffset >= -214783648);
int32_t TruncOffset = (RealOffset & 0xFFFFFFFF);
*Placeholder = TruncOffset;
break;
}
}
}
void RuntimeDyldELF::resolveX86Relocation(uint8_t *LocalAddress,
uint32_t FinalAddress,
uint32_t Value,
uint32_t Type,
int32_t Addend) {
switch (Type) {
case ELF::R_386_32: {
uint32_t *Target = (uint32_t*)(LocalAddress);
uint32_t Placeholder = *Target;
*Target = Placeholder + Value + Addend;
break;
}
case ELF::R_386_PC32: {
uint32_t *Placeholder = reinterpret_cast<uint32_t*>(LocalAddress);
uint32_t RealOffset = *Placeholder + Value + Addend - FinalAddress;
*Placeholder = RealOffset;
break;
}
default:
// There are other relocation types, but it appears these are the
// only ones currently used by the LLVM ELF object writer
llvm_unreachable("Relocation type not implemented yet!");
break;
}
}
void RuntimeDyldELF::resolveARMRelocation(uint8_t *LocalAddress,
uint32_t FinalAddress,
uint32_t Value,
uint32_t Type,
int32_t Addend) {
// TODO: Add Thumb relocations.
uint32_t* TargetPtr = (uint32_t*)LocalAddress;
Value += Addend;
DEBUG(dbgs() << "resolveARMRelocation, LocalAddress: " << LocalAddress
<< " FinalAddress: " << format("%p",FinalAddress)
<< " Value: " << format("%x",Value)
<< " Type: " << format("%x",Type)
<< " Addend: " << format("%x",Addend)
<< "\n");
switch(Type) {
default:
llvm_unreachable("Not implemented relocation type!");
// Just write 32bit value to relocation address
case ELF::R_ARM_ABS32 :
*TargetPtr = Value;
break;
// Write first 16 bit of 32 bit value to the mov instruction.
// Last 4 bit should be shifted.
case ELF::R_ARM_MOVW_ABS_NC :
Value = Value & 0xFFFF;
*TargetPtr |= Value & 0xFFF;
*TargetPtr |= ((Value >> 12) & 0xF) << 16;
break;
// Write last 16 bit of 32 bit value to the mov instruction.
// Last 4 bit should be shifted.
case ELF::R_ARM_MOVT_ABS :
Value = (Value >> 16) & 0xFFFF;
*TargetPtr |= Value & 0xFFF;
*TargetPtr |= ((Value >> 12) & 0xF) << 16;
break;
// Write 24 bit relative value to the branch instruction.
case ELF::R_ARM_PC24 : // Fall through.
case ELF::R_ARM_CALL : // Fall through.
case ELF::R_ARM_JUMP24 :
int32_t RelValue = static_cast<int32_t>(Value - FinalAddress - 8);
RelValue = (RelValue & 0x03FFFFFC) >> 2;
*TargetPtr &= 0xFF000000;
*TargetPtr |= RelValue;
break;
}
}
void RuntimeDyldELF::resolveRelocation(uint8_t *LocalAddress,
uint64_t FinalAddress,
uint64_t Value,
uint32_t Type,
int64_t Addend) {
switch (Arch) {
case Triple::x86_64:
resolveX86_64Relocation(LocalAddress, FinalAddress, Value, Type, Addend);
break;
case Triple::x86:
resolveX86Relocation(LocalAddress, (uint32_t)(FinalAddress & 0xffffffffL),
(uint32_t)(Value & 0xffffffffL), Type,
(uint32_t)(Addend & 0xffffffffL));
break;
case Triple::arm: // Fall through.
case Triple::thumb:
resolveARMRelocation(LocalAddress, (uint32_t)(FinalAddress & 0xffffffffL),
(uint32_t)(Value & 0xffffffffL), Type,
(uint32_t)(Addend & 0xffffffffL));
break;
default: llvm_unreachable("Unsupported CPU type!");
}
}
void RuntimeDyldELF::processRelocationRef(const ObjRelocationInfo &Rel,
ObjectImage &Obj,
ObjSectionToIDMap &ObjSectionToID,
LocalSymbolMap &Symbols,
StubMap &Stubs) {
uint32_t RelType = (uint32_t)(Rel.Type & 0xffffffffL);
intptr_t Addend = (intptr_t)Rel.AdditionalInfo;
RelocationValueRef Value;
StringRef TargetName;
const SymbolRef &Symbol = Rel.Symbol;
Symbol.getName(TargetName);
DEBUG(dbgs() << "\t\tRelType: " << RelType
<< " Addend: " << Addend
<< " TargetName: " << TargetName
<< "\n");
// First look the symbol in object file symbols.
LocalSymbolMap::iterator lsi = Symbols.find(TargetName.data());
if (lsi != Symbols.end()) {
Value.SectionID = lsi->second.first;
Value.Addend = lsi->second.second;
} else {
// Second look the symbol in global symbol table.
StringMap<SymbolLoc>::iterator gsi = SymbolTable.find(TargetName.data());
if (gsi != SymbolTable.end()) {
Value.SectionID = gsi->second.first;
Value.Addend = gsi->second.second;
} else {
SymbolRef::Type SymType;
Symbol.getType(SymType);
switch (SymType) {
case SymbolRef::ST_Debug: {
// TODO: Now ELF SymbolRef::ST_Debug = STT_SECTION, it's not obviously
// and can be changed by another developers. Maybe best way is add
// a new symbol type ST_Section to SymbolRef and use it.
section_iterator si = Obj.end_sections();
Symbol.getSection(si);
if (si == Obj.end_sections())
llvm_unreachable("Symbol section not found, bad object file format!");
DEBUG(dbgs() << "\t\tThis is section symbol\n");
Value.SectionID = findOrEmitSection(Obj, (*si), true, ObjSectionToID);
Value.Addend = Addend;
break;
}
case SymbolRef::ST_Unknown: {
Value.SymbolName = TargetName.data();
Value.Addend = Addend;
break;
}
default:
llvm_unreachable("Unresolved symbol type!");
break;
}
}
}
DEBUG(dbgs() << "\t\tRel.SectionID: " << Rel.SectionID
<< " Rel.Offset: " << Rel.Offset
<< "\n");
if (Arch == Triple::arm &&
(RelType == ELF::R_ARM_PC24 ||
RelType == ELF::R_ARM_CALL ||
RelType == ELF::R_ARM_JUMP24)) {
// This is an ARM branch relocation, need to use a stub function.
DEBUG(dbgs() << "\t\tThis is an ARM branch relocation.");
SectionEntry &Section = Sections[Rel.SectionID];
uint8_t *Target = Section.Address + Rel.Offset;
// Look up for existing stub.
StubMap::const_iterator i = Stubs.find(Value);
if (i != Stubs.end()) {
resolveRelocation(Target, (uint64_t)Target, (uint64_t)Section.Address +
i->second, RelType, 0);
DEBUG(dbgs() << " Stub function found\n");
} else {
// Create a new stub function.
DEBUG(dbgs() << " Create a new stub function\n");
Stubs[Value] = Section.StubOffset;
uint8_t *StubTargetAddr = createStubFunction(Section.Address +
Section.StubOffset);
AddRelocation(Value, Rel.SectionID,
StubTargetAddr - Section.Address, ELF::R_ARM_ABS32);
resolveRelocation(Target, (uint64_t)Target, (uint64_t)Section.Address +
Section.StubOffset, RelType, 0);
Section.StubOffset += getMaxStubSize();
}
} else
AddRelocation(Value, Rel.SectionID, Rel.Offset, RelType);
}
bool RuntimeDyldELF::isCompatibleFormat(const MemoryBuffer *InputBuffer) const {
StringRef Magic = InputBuffer->getBuffer().slice(0, ELF::EI_NIDENT);
return (memcmp(Magic.data(), ELF::ElfMagic, strlen(ELF::ElfMagic))) == 0;
}
} // namespace llvm