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//===-- RuntimeDyldImpl.h - Run-time dynamic linker for MC-JIT --*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// Interface for the implementations of runtime dynamic linker facilities.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_LIB_EXECUTIONENGINE_RUNTIMEDYLD_RUNTIMEDYLDIMPL_H
#define LLVM_LIB_EXECUTIONENGINE_RUNTIMEDYLD_RUNTIMEDYLDIMPL_H
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/ADT/Triple.h"
#include "llvm/ExecutionEngine/RTDyldMemoryManager.h"
#include "llvm/ExecutionEngine/RuntimeDyld.h"
#include "llvm/ExecutionEngine/RuntimeDyldChecker.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 <map>
#include <system_error>
#include <unordered_map>
using namespace llvm;
using namespace llvm::object;
namespace llvm {
class Twine;
#define UNIMPLEMENTED_RELOC(RelType) \
case RelType: \
return make_error<RuntimeDyldError>("Unimplemented relocation: " #RelType)
/// SectionEntry - represents a section emitted into memory by the dynamic
/// linker.
class SectionEntry {
/// Name - section name.
std::string 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;
/// The total amount of space allocated for this section. This includes the
/// section size and the maximum amount of space that the stubs can occupy.
size_t AllocationSize;
/// ObjAddress - address of the section in the in-memory object file. Used
/// for calculating relocations in some object formats (like MachO).
uintptr_t ObjAddress;
public:
SectionEntry(StringRef name, uint8_t *address, size_t size,
size_t allocationSize, uintptr_t objAddress)
: Name(name), Address(address), Size(size),
LoadAddress(reinterpret_cast<uintptr_t>(address)), StubOffset(size),
AllocationSize(allocationSize), ObjAddress(objAddress) {
// AllocationSize is used only in asserts, prevent an "unused private field"
// warning:
(void)AllocationSize;
}
StringRef getName() const { return Name; }
uint8_t *getAddress() const { return Address; }
/// Return the address of this section with an offset.
uint8_t *getAddressWithOffset(unsigned OffsetBytes) const {
assert(OffsetBytes <= AllocationSize && "Offset out of bounds!");
return Address + OffsetBytes;
}
size_t getSize() const { return Size; }
uint64_t getLoadAddress() const { return LoadAddress; }
void setLoadAddress(uint64_t LA) { LoadAddress = LA; }
/// Return the load address of this section with an offset.
uint64_t getLoadAddressWithOffset(unsigned OffsetBytes) const {
assert(OffsetBytes <= AllocationSize && "Offset out of bounds!");
return LoadAddress + OffsetBytes;
}
uintptr_t getStubOffset() const { return StubOffset; }
void advanceStubOffset(unsigned StubSize) {
StubOffset += StubSize;
assert(StubOffset <= AllocationSize && "Not enough space allocated!");
}
uintptr_t getObjAddress() const { return ObjAddress; }
};
/// RelocationEntry - used to represent relocations internally in the dynamic
/// linker.
class RelocationEntry {
public:
/// 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;
struct SectionPair {
uint32_t SectionA;
uint32_t SectionB;
};
/// SymOffset - Section offset of the relocation entry's symbol (used for GOT
/// lookup).
union {
uint64_t SymOffset;
SectionPair Sections;
};
/// True if this is a PCRel relocation (MachO specific).
bool IsPCRel;
/// The size of this relocation (MachO specific).
unsigned Size;
// ARM (MachO and COFF) specific.
bool IsTargetThumbFunc = false;
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), IsTargetThumbFunc(false) {}
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),
IsTargetThumbFunc(false) {}
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), IsTargetThumbFunc(false) {}
RelocationEntry(unsigned id, uint64_t offset, uint32_t type, int64_t addend,
unsigned SectionA, uint64_t SectionAOffset, unsigned SectionB,
uint64_t SectionBOffset, bool IsPCRel, unsigned Size)
: SectionID(id), Offset(offset), RelType(type),
Addend(SectionAOffset - SectionBOffset + addend), IsPCRel(IsPCRel),
Size(Size), IsTargetThumbFunc(false) {
Sections.SectionA = SectionA;
Sections.SectionB = SectionB;
}
RelocationEntry(unsigned id, uint64_t offset, uint32_t type, int64_t addend,
unsigned SectionA, uint64_t SectionAOffset, unsigned SectionB,
uint64_t SectionBOffset, bool IsPCRel, unsigned Size,
bool IsTargetThumbFunc)
: SectionID(id), Offset(offset), RelType(type),
Addend(SectionAOffset - SectionBOffset + addend), IsPCRel(IsPCRel),
Size(Size), IsTargetThumbFunc(IsTargetThumbFunc) {
Sections.SectionA = SectionA;
Sections.SectionB = SectionB;
}
};
class RelocationValueRef {
public:
unsigned SectionID;
uint64_t Offset;
int64_t Addend;
const char *SymbolName;
bool IsStubThumb = false;
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 &&
IsStubThumb == Other.IsStubThumb;
}
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;
if (IsStubThumb != Other.IsStubThumb)
return IsStubThumb < Other.IsStubThumb;
return SymbolName < Other.SymbolName;
}
};
/// Symbol info for RuntimeDyld.
class SymbolTableEntry {
public:
SymbolTableEntry() = default;
SymbolTableEntry(unsigned SectionID, uint64_t Offset, JITSymbolFlags Flags)
: Offset(Offset), SectionID(SectionID), Flags(Flags) {}
unsigned getSectionID() const { return SectionID; }
uint64_t getOffset() const { return Offset; }
void setOffset(uint64_t NewOffset) { Offset = NewOffset; }
JITSymbolFlags getFlags() const { return Flags; }
private:
uint64_t Offset = 0;
unsigned SectionID = 0;
JITSymbolFlags Flags = JITSymbolFlags::None;
};
typedef StringMap<SymbolTableEntry> RTDyldSymbolTable;
class RuntimeDyldImpl {
friend class RuntimeDyld::LoadedObjectInfo;
protected:
static const unsigned AbsoluteSymbolSection = ~0U;
// The MemoryManager to load objects into.
RuntimeDyld::MemoryManager &MemMgr;
// The symbol resolver to use for external symbols.
JITSymbolResolver &Resolver;
// 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
#define RTDYLD_INVALID_SECTION_ID ((RuntimeDyldImpl::SID)(-1))
// 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.
RTDyldSymbolTable GlobalSymbolTable;
// Keep a map of common symbols to their info pairs
typedef std::vector<SymbolRef> CommonSymbolList;
// 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.
std::unordered_map<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;
bool IsMipsO32ABI;
bool IsMipsN32ABI;
bool IsMipsN64ABI;
// 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;
using NotifyStubEmittedFunction =
RuntimeDyld::NotifyStubEmittedFunction;
NotifyStubEmittedFunction NotifyStubEmitted;
virtual unsigned getMaxStubSize() const = 0;
virtual unsigned getStubAlignment() = 0;
bool HasError;
std::string ErrorStr;
void writeInt16BE(uint8_t *Addr, uint16_t Value) {
if (IsTargetLittleEndian)
sys::swapByteOrder(Value);
*Addr = (Value >> 8) & 0xFF;
*(Addr + 1) = Value & 0xFF;
}
void writeInt32BE(uint8_t *Addr, uint32_t Value) {
if (IsTargetLittleEndian)
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)
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;
}
virtual void setMipsABI(const ObjectFile &Obj) {
IsMipsO32ABI = false;
IsMipsN32ABI = false;
IsMipsN64ABI = false;
}
/// Endian-aware read Read the least significant Size bytes from Src.
uint64_t readBytesUnaligned(uint8_t *Src, unsigned Size) const;
/// Endian-aware write. Write the least significant Size bytes from Value to
/// Dst.
void writeBytesUnaligned(uint64_t Value, uint8_t *Dst, unsigned Size) const;
/// Generate JITSymbolFlags from a libObject symbol.
virtual Expected<JITSymbolFlags> getJITSymbolFlags(const SymbolRef &Sym);
/// Modify the given target address based on the given symbol flags.
/// This can be used by subclasses to tweak addresses based on symbol flags,
/// For example: the MachO/ARM target uses it to set the low bit if the target
/// is a thumb symbol.
virtual uint64_t modifyAddressBasedOnFlags(uint64_t Addr,
JITSymbolFlags Flags) const {
return Addr;
}
/// 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.
Error emitCommonSymbols(const ObjectFile &Obj,
CommonSymbolList &CommonSymbols, uint64_t CommonSize,
uint32_t CommonAlign);
/// 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.
Expected<unsigned> emitSection(const ObjectFile &Obj,
const SectionRef &Section,
bool IsCode);
/// 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.
Expected<unsigned> findOrEmitSection(const ObjectFile &Obj,
const SectionRef &Section, bool IsCode,
ObjSectionToIDMap &LocalSections);
// Add a relocation entry that uses the given section.
void addRelocationForSection(const RelocationEntry &RE, unsigned SectionID);
// 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);
/// Emits long jump instruction to Addr.
/// \return Pointer to the memory area for emitting target address.
uint8_t *createStubFunction(uint8_t *Addr, unsigned AbiVariant = 0);
/// Resolves relocations from Relocs list with address from Value.
void resolveRelocationList(const RelocationList &Relocs, uint64_t Value);
/// 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;
/// 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 Expected<relocation_iterator>
processRelocationRef(unsigned SectionID, relocation_iterator RelI,
const ObjectFile &Obj, ObjSectionToIDMap &ObjSectionToID,
StubMap &Stubs) = 0;
void applyExternalSymbolRelocations(
const StringMap<JITEvaluatedSymbol> ExternalSymbolMap);
/// Resolve relocations to external symbols.
Error resolveExternalSymbols();
// Compute an upper bound of the memory that is required to load all
// sections
Error computeTotalAllocSize(const ObjectFile &Obj,
uint64_t &CodeSize, uint32_t &CodeAlign,
uint64_t &RODataSize, uint32_t &RODataAlign,
uint64_t &RWDataSize, uint32_t &RWDataAlign);
// Compute GOT size
unsigned computeGOTSize(const ObjectFile &Obj);
// Compute the stub buffer size required for a section
unsigned computeSectionStubBufSize(const ObjectFile &Obj,
const SectionRef &Section);
// Implementation of the generic part of the loadObject algorithm.
Expected<ObjSectionToIDMap> loadObjectImpl(const object::ObjectFile &Obj);
// Return size of Global Offset Table (GOT) entry
virtual size_t getGOTEntrySize() { return 0; }
// Return true if the relocation R may require allocating a GOT entry.
virtual bool relocationNeedsGot(const RelocationRef &R) const {
return false;
}
// Return true if the relocation R may require allocating a stub.
virtual bool relocationNeedsStub(const RelocationRef &R) const {
return true; // Conservative answer
}
public:
RuntimeDyldImpl(RuntimeDyld::MemoryManager &MemMgr,
JITSymbolResolver &Resolver)
: MemMgr(MemMgr), Resolver(Resolver),
ProcessAllSections(false), HasError(false) {
}
virtual ~RuntimeDyldImpl();
void setProcessAllSections(bool ProcessAllSections) {
this->ProcessAllSections = ProcessAllSections;
}
virtual std::unique_ptr<RuntimeDyld::LoadedObjectInfo>
loadObject(const object::ObjectFile &Obj) = 0;
uint64_t getSectionLoadAddress(unsigned SectionID) const {
return Sections[SectionID].getLoadAddress();
}
uint8_t *getSectionAddress(unsigned SectionID) const {
return Sections[SectionID].getAddress();
}
StringRef getSectionContent(unsigned SectionID) const {
return StringRef(reinterpret_cast<char *>(Sections[SectionID].getAddress()),
Sections[SectionID].getStubOffset() + getMaxStubSize());
}
uint8_t* getSymbolLocalAddress(StringRef Name) const {
// FIXME: Just look up as a function for now. Overly simple of course.
// Work in progress.
RTDyldSymbolTable::const_iterator pos = GlobalSymbolTable.find(Name);
if (pos == GlobalSymbolTable.end())
return nullptr;
const auto &SymInfo = pos->second;
// Absolute symbols do not have a local address.
if (SymInfo.getSectionID() == AbsoluteSymbolSection)
return nullptr;
return getSectionAddress(SymInfo.getSectionID()) + SymInfo.getOffset();
}
unsigned getSymbolSectionID(StringRef Name) const {
auto GSTItr = GlobalSymbolTable.find(Name);
if (GSTItr == GlobalSymbolTable.end())
return ~0U;
return GSTItr->second.getSectionID();
}
JITEvaluatedSymbol getSymbol(StringRef Name) const {
// FIXME: Just look up as a function for now. Overly simple of course.
// Work in progress.
RTDyldSymbolTable::const_iterator pos = GlobalSymbolTable.find(Name);
if (pos == GlobalSymbolTable.end())
return nullptr;
const auto &SymEntry = pos->second;
uint64_t SectionAddr = 0;
if (SymEntry.getSectionID() != AbsoluteSymbolSection)
SectionAddr = getSectionLoadAddress(SymEntry.getSectionID());
uint64_t TargetAddr = SectionAddr + SymEntry.getOffset();
// FIXME: Have getSymbol should return the actual address and the client
// modify it based on the flags. This will require clients to be
// aware of the target architecture, which we should build
// infrastructure for.
TargetAddr = modifyAddressBasedOnFlags(TargetAddr, SymEntry.getFlags());
return JITEvaluatedSymbol(TargetAddr, SymEntry.getFlags());
}
std::map<StringRef, JITEvaluatedSymbol> getSymbolTable() const {
std::map<StringRef, JITEvaluatedSymbol> Result;
for (auto &KV : GlobalSymbolTable) {
auto SectionID = KV.second.getSectionID();
uint64_t SectionAddr = 0;
if (SectionID != AbsoluteSymbolSection)
SectionAddr = getSectionLoadAddress(SectionID);
Result[KV.first()] =
JITEvaluatedSymbol(SectionAddr + KV.second.getOffset(), KV.second.getFlags());
}
return Result;
}
void resolveRelocations();
void resolveLocalRelocations();
static void finalizeAsync(std::unique_ptr<RuntimeDyldImpl> This,
unique_function<void(Error)> OnEmitted,
std::unique_ptr<MemoryBuffer> UnderlyingBuffer);
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 isCompatibleFile(const ObjectFile &Obj) const = 0;
void setNotifyStubEmitted(NotifyStubEmittedFunction NotifyStubEmitted) {
this->NotifyStubEmitted = std::move(NotifyStubEmitted);
}
virtual void registerEHFrames();
void deregisterEHFrames();
virtual Error finalizeLoad(const ObjectFile &ObjImg,
ObjSectionToIDMap &SectionMap) {
return Error::success();
}
};
} // end namespace llvm
#endif