blob: f52d22ce22608bd32634e1b476c88cf272aa17e7 [file] [log] [blame]
//===-- RuntimeDyldImpl.h - 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.
// Interface for the implementations of runtime dynamic linker facilities.
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/ADT/Triple.h"
#include "llvm/ExecutionEngine/ObjectImage.h"
#include "llvm/ExecutionEngine/RuntimeDyld.h"
#include "llvm/Object/ObjectFile.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/Format.h"
#include "llvm/Support/Host.h"
#include "llvm/Support/Mutex.h"
#include "llvm/Support/SwapByteOrder.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Support/system_error.h"
#include <map>
using namespace llvm;
using namespace llvm::object;
namespace llvm {
class ObjectBuffer;
class Twine;
/// SectionEntry - represents a section emitted into memory by the dynamic
/// linker.
class SectionEntry {
/// Name - section name.
StringRef Name;
/// Address - address in the linker's memory where the section resides.
uint8_t *Address;
/// Size - section size. Doesn't include the stubs.
size_t Size;
/// LoadAddress - the address of the section in the target process's memory.
/// Used for situations in which JIT-ed code is being executed in the address
/// space of a separate process. If the code executes in the same address
/// space where it was JIT-ed, this just equals Address.
uint64_t LoadAddress;
/// StubOffset - used for architectures with stub functions for far
/// relocations (like ARM).
uintptr_t StubOffset;
/// ObjAddress - address of the section in the in-memory object file. Used
/// for calculating relocations in some object formats (like MachO).
uintptr_t ObjAddress;
SectionEntry(StringRef name, uint8_t *address, size_t size,
uintptr_t objAddress)
: Name(name), Address(address), Size(size),
LoadAddress((uintptr_t)address), StubOffset(size),
ObjAddress(objAddress) {}
/// RelocationEntry - used to represent relocations internally in the dynamic
/// linker.
class RelocationEntry {
/// SectionID - the section this relocation points to.
unsigned SectionID;
/// Offset - offset into the section.
uint64_t Offset;
/// RelType - relocation type.
uint32_t RelType;
/// Addend - the relocation addend encoded in the instruction itself. Also
/// used to make a relocation section relative instead of symbol relative.
int64_t Addend;
/// SymOffset - Section offset of the relocation entry's symbol (used for GOT
/// lookup).
uint64_t SymOffset;
/// True if this is a PCRel relocation (MachO specific).
bool IsPCRel;
/// The size of this relocation (MachO specific).
unsigned Size;
RelocationEntry(unsigned id, uint64_t offset, uint32_t type, int64_t addend)
: SectionID(id), Offset(offset), RelType(type), Addend(addend),
SymOffset(0), IsPCRel(false), Size(0) {}
RelocationEntry(unsigned id, uint64_t offset, uint32_t type, int64_t addend,
uint64_t symoffset)
: SectionID(id), Offset(offset), RelType(type), Addend(addend),
SymOffset(symoffset), IsPCRel(false), Size(0) {}
RelocationEntry(unsigned id, uint64_t offset, uint32_t type, int64_t addend,
bool IsPCRel, unsigned Size)
: SectionID(id), Offset(offset), RelType(type), Addend(addend),
SymOffset(0), IsPCRel(IsPCRel), Size(Size) {}
class RelocationValueRef {
unsigned SectionID;
uint64_t Offset;
int64_t Addend;
const char *SymbolName;
RelocationValueRef() : SectionID(0), Offset(0), Addend(0),
SymbolName(nullptr) {}
inline bool operator==(const RelocationValueRef &Other) const {
return SectionID == Other.SectionID && Offset == Other.Offset &&
Addend == Other.Addend && SymbolName == Other.SymbolName;
inline bool operator<(const RelocationValueRef &Other) const {
if (SectionID != Other.SectionID)
return SectionID < Other.SectionID;
if (Offset != Other.Offset)
return Offset < Other.Offset;
if (Addend != Other.Addend)
return Addend < Other.Addend;
return SymbolName < Other.SymbolName;
class RuntimeDyldImpl {
// The MemoryManager to load objects into.
RTDyldMemoryManager *MemMgr;
// A list of all sections emitted by the dynamic linker. These sections are
// referenced in the code by means of their index in this list - SectionID.
typedef SmallVector<SectionEntry, 64> SectionList;
SectionList Sections;
typedef unsigned SID; // Type for SectionIDs
// Keep a map of sections from object file to the SectionID which
// references it.
typedef std::map<SectionRef, unsigned> ObjSectionToIDMap;
// A global symbol table for symbols from all loaded modules. Maps the
// symbol name to a (SectionID, offset in section) pair.
typedef std::pair<unsigned, uintptr_t> SymbolLoc;
typedef StringMap<SymbolLoc> SymbolTableMap;
SymbolTableMap GlobalSymbolTable;
// Pair representing the size and alignment requirement for a common symbol.
typedef std::pair<unsigned, unsigned> CommonSymbolInfo;
// Keep a map of common symbols to their info pairs
typedef std::map<SymbolRef, CommonSymbolInfo> CommonSymbolMap;
// For each symbol, keep a list of relocations based on it. Anytime
// its address is reassigned (the JIT re-compiled the function, e.g.),
// the relocations get re-resolved.
// The symbol (or section) the relocation is sourced from is the Key
// in the relocation list where it's stored.
typedef SmallVector<RelocationEntry, 64> RelocationList;
// Relocations to sections already loaded. Indexed by SectionID which is the
// source of the address. The target where the address will be written is
// SectionID/Offset in the relocation itself.
DenseMap<unsigned, RelocationList> Relocations;
// Relocations to external symbols that are not yet resolved. Symbols are
// external when they aren't found in the global symbol table of all loaded
// modules. This map is indexed by symbol name.
StringMap<RelocationList> ExternalSymbolRelocations;
typedef std::map<RelocationValueRef, uintptr_t> StubMap;
Triple::ArchType Arch;
bool IsTargetLittleEndian;
// True if all sections should be passed to the memory manager, false if only
// sections containing relocations should be. Defaults to 'false'.
bool ProcessAllSections;
// This mutex prevents simultaneously loading objects from two different
// threads. This keeps us from having to protect individual data structures
// and guarantees that section allocation requests to the memory manager
// won't be interleaved between modules. It is also used in mapSectionAddress
// and resolveRelocations to protect write access to internal data structures.
// loadObject may be called on the same thread during the handling of of
// processRelocations, and that's OK. The handling of the relocation lists
// is written in such a way as to work correctly if new elements are added to
// the end of the list while the list is being processed.
sys::Mutex lock;
virtual unsigned getMaxStubSize() = 0;
virtual unsigned getStubAlignment() = 0;
bool HasError;
std::string ErrorStr;
// Set the error state and record an error string.
bool Error(const Twine &Msg) {
ErrorStr = Msg.str();
HasError = true;
return true;
uint64_t getSectionLoadAddress(unsigned SectionID) {
return Sections[SectionID].LoadAddress;
uint8_t *getSectionAddress(unsigned SectionID) {
return (uint8_t *)Sections[SectionID].Address;
void writeInt16BE(uint8_t *Addr, uint16_t Value) {
if (IsTargetLittleEndian)
Value = sys::SwapByteOrder(Value);
*Addr = (Value >> 8) & 0xFF;
*(Addr + 1) = Value & 0xFF;
void writeInt32BE(uint8_t *Addr, uint32_t Value) {
if (IsTargetLittleEndian)
Value = sys::SwapByteOrder(Value);
*Addr = (Value >> 24) & 0xFF;
*(Addr + 1) = (Value >> 16) & 0xFF;
*(Addr + 2) = (Value >> 8) & 0xFF;
*(Addr + 3) = Value & 0xFF;
void writeInt64BE(uint8_t *Addr, uint64_t Value) {
if (IsTargetLittleEndian)
Value = sys::SwapByteOrder(Value);
*Addr = (Value >> 56) & 0xFF;
*(Addr + 1) = (Value >> 48) & 0xFF;
*(Addr + 2) = (Value >> 40) & 0xFF;
*(Addr + 3) = (Value >> 32) & 0xFF;
*(Addr + 4) = (Value >> 24) & 0xFF;
*(Addr + 5) = (Value >> 16) & 0xFF;
*(Addr + 6) = (Value >> 8) & 0xFF;
*(Addr + 7) = Value & 0xFF;
/// \brief Given the common symbols discovered in the object file, emit a
/// new section for them and update the symbol mappings in the object and
/// symbol table.
void emitCommonSymbols(ObjectImage &Obj, const CommonSymbolMap &CommonSymbols,
uint64_t TotalSize, SymbolTableMap &SymbolTable);
/// \brief Emits section data from the object file to the MemoryManager.
/// \param IsCode if it's true then allocateCodeSection() will be
/// used for emits, else allocateDataSection() will be used.
/// \return SectionID.
unsigned emitSection(ObjectImage &Obj, const SectionRef &Section,
bool IsCode);
/// \brief Find Section in LocalSections. If the secton is not found - emit
/// it and store in LocalSections.
/// \param IsCode if it's true then allocateCodeSection() will be
/// used for emmits, else allocateDataSection() will be used.
/// \return SectionID.
unsigned findOrEmitSection(ObjectImage &Obj, const SectionRef &Section,
bool IsCode, ObjSectionToIDMap &LocalSections);
// \brief Add a relocation entry that uses the given section.
void addRelocationForSection(const RelocationEntry &RE, unsigned SectionID);
// \brief Add a relocation entry that uses the given symbol. This symbol may
// be found in the global symbol table, or it may be external.
void addRelocationForSymbol(const RelocationEntry &RE, StringRef SymbolName);
/// \brief Emits long jump instruction to Addr.
/// \return Pointer to the memory area for emitting target address.
uint8_t *createStubFunction(uint8_t *Addr);
/// \brief Resolves relocations from Relocs list with address from Value.
void resolveRelocationList(const RelocationList &Relocs, uint64_t Value);
/// \brief A object file specific relocation resolver
/// \param RE The relocation to be resolved
/// \param Value Target symbol address to apply the relocation action
virtual void resolveRelocation(const RelocationEntry &RE, uint64_t Value) = 0;
/// \brief Parses one or more object file relocations (some object files use
/// relocation pairs) and stores it to Relocations or SymbolRelocations
/// (this depends on the object file type).
/// \return Iterator to the next relocation that needs to be parsed.
virtual relocation_iterator
processRelocationRef(unsigned SectionID, relocation_iterator RelI,
ObjectImage &Obj, ObjSectionToIDMap &ObjSectionToID,
const SymbolTableMap &Symbols, StubMap &Stubs) = 0;
/// \brief Resolve relocations to external symbols.
void resolveExternalSymbols();
/// \brief Update GOT entries for external symbols.
// The base class does nothing. ELF overrides this.
virtual void updateGOTEntries(StringRef Name, uint64_t Addr) {}
// \brief Compute an upper bound of the memory that is required to load all
// sections
void computeTotalAllocSize(ObjectImage &Obj, uint64_t &CodeSize,
uint64_t &DataSizeRO, uint64_t &DataSizeRW);
// \brief Compute the stub buffer size required for a section
unsigned computeSectionStubBufSize(ObjectImage &Obj,
const SectionRef &Section);
RuntimeDyldImpl(RTDyldMemoryManager *mm)
: MemMgr(mm), ProcessAllSections(false), HasError(false) {}
virtual ~RuntimeDyldImpl();
void setProcessAllSections(bool ProcessAllSections) {
this->ProcessAllSections = ProcessAllSections;
ObjectImage *loadObject(ObjectImage *InputObject);
void *getSymbolAddress(StringRef Name) {
// FIXME: Just look up as a function for now. Overly simple of course.
// Work in progress.
SymbolTableMap::const_iterator pos = GlobalSymbolTable.find(Name);
if (pos == GlobalSymbolTable.end())
return nullptr;
SymbolLoc Loc = pos->second;
return getSectionAddress(Loc.first) + Loc.second;
uint64_t getSymbolLoadAddress(StringRef Name) {
// FIXME: Just look up as a function for now. Overly simple of course.
// Work in progress.
SymbolTableMap::const_iterator pos = GlobalSymbolTable.find(Name);
if (pos == GlobalSymbolTable.end())
return 0;
SymbolLoc Loc = pos->second;
return getSectionLoadAddress(Loc.first) + Loc.second;
void resolveRelocations();
void reassignSectionAddress(unsigned SectionID, uint64_t Addr);
void mapSectionAddress(const void *LocalAddress, uint64_t TargetAddress);
// Is the linker in an error state?
bool hasError() { return HasError; }
// Mark the error condition as handled and continue.
void clearError() { HasError = false; }
// Get the error message.
StringRef getErrorString() { return ErrorStr; }
virtual bool isCompatibleFormat(const ObjectBuffer *Buffer) const = 0;
virtual bool isCompatibleFile(const ObjectFile *Obj) const = 0;
virtual void registerEHFrames();
virtual void deregisterEHFrames();
virtual void finalizeLoad(ObjSectionToIDMap &SectionMap) {}
} // end namespace llvm