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//===- JITSymbol.h - JIT symbol abstraction ---------------------*- C++ -*-===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// Abstraction for target process addresses.
#include <algorithm>
#include <cassert>
#include <cstddef>
#include <cstdint>
#include <functional>
#include <map>
#include <set>
#include <string>
#include "llvm/ADT/BitmaskEnum.h"
#include "llvm/ADT/FunctionExtras.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Support/Error.h"
namespace llvm {
class GlobalValue;
namespace object {
class SymbolRef;
} // end namespace object
/// Represents an address in the target process's address space.
using JITTargetAddress = uint64_t;
/// Convert a JITTargetAddress to a pointer.
/// Note: This is a raw cast of the address bit pattern to the given pointer
/// type. When casting to a function pointer in order to execute JIT'd code
/// jitTargetAddressToFunction should be preferred, as it will also perform
/// pointer signing on targets that require it.
template <typename T> T jitTargetAddressToPointer(JITTargetAddress Addr) {
static_assert(std::is_pointer<T>::value, "T must be a pointer type");
uintptr_t IntPtr = static_cast<uintptr_t>(Addr);
assert(IntPtr == Addr && "JITTargetAddress value out of range for uintptr_t");
return reinterpret_cast<T>(IntPtr);
/// Convert a JITTargetAddress to a callable function pointer.
/// Casts the given address to a callable function pointer. This operation
/// will perform pointer signing for platforms that require it (e.g. arm64e).
template <typename T> T jitTargetAddressToFunction(JITTargetAddress Addr) {
std::is_pointer<T>::value &&
std::is_function<typename std::remove_pointer<T>::type>::value,
"T must be a function pointer type");
return jitTargetAddressToPointer<T>(Addr);
/// Convert a pointer to a JITTargetAddress.
template <typename T> JITTargetAddress pointerToJITTargetAddress(T *Ptr) {
return static_cast<JITTargetAddress>(reinterpret_cast<uintptr_t>(Ptr));
/// Flags for symbols in the JIT.
class JITSymbolFlags {
using UnderlyingType = uint8_t;
using TargetFlagsType = uint8_t;
enum FlagNames : UnderlyingType {
None = 0,
HasError = 1U << 0,
Weak = 1U << 1,
Common = 1U << 2,
Absolute = 1U << 3,
Exported = 1U << 4,
Callable = 1U << 5,
LLVM_MARK_AS_BITMASK_ENUM(/* LargestValue = */ Callable)
/// Default-construct a JITSymbolFlags instance.
JITSymbolFlags() = default;
/// Construct a JITSymbolFlags instance from the given flags.
JITSymbolFlags(FlagNames Flags) : Flags(Flags) {}
/// Construct a JITSymbolFlags instance from the given flags and target
/// flags.
JITSymbolFlags(FlagNames Flags, TargetFlagsType TargetFlags)
: TargetFlags(TargetFlags), Flags(Flags) {}
/// Implicitly convert to bool. Returs true if any flag is set.
explicit operator bool() const { return Flags != None || TargetFlags != 0; }
/// Compare for equality.
bool operator==(const JITSymbolFlags &RHS) const {
return Flags == RHS.Flags && TargetFlags == RHS.TargetFlags;
/// Bitwise AND-assignment for FlagNames.
JITSymbolFlags &operator&=(const FlagNames &RHS) {
Flags &= RHS;
return *this;
/// Bitwise OR-assignment for FlagNames.
JITSymbolFlags &operator|=(const FlagNames &RHS) {
Flags |= RHS;
return *this;
/// Return true if there was an error retrieving this symbol.
bool hasError() const {
return (Flags & HasError) == HasError;
/// Returns true if the Weak flag is set.
bool isWeak() const {
return (Flags & Weak) == Weak;
/// Returns true if the Common flag is set.
bool isCommon() const {
return (Flags & Common) == Common;
/// Returns true if the symbol isn't weak or common.
bool isStrong() const {
return !isWeak() && !isCommon();
/// Returns true if the Exported flag is set.
bool isExported() const {
return (Flags & Exported) == Exported;
/// Returns true if the given symbol is known to be callable.
bool isCallable() const { return (Flags & Callable) == Callable; }
/// Get the underlying flags value as an integer.
UnderlyingType getRawFlagsValue() const {
return static_cast<UnderlyingType>(Flags);
/// Return a reference to the target-specific flags.
TargetFlagsType& getTargetFlags() { return TargetFlags; }
/// Return a reference to the target-specific flags.
const TargetFlagsType& getTargetFlags() const { return TargetFlags; }
/// Construct a JITSymbolFlags value based on the flags of the given global
/// value.
static JITSymbolFlags fromGlobalValue(const GlobalValue &GV);
/// Construct a JITSymbolFlags value based on the flags of the given libobject
/// symbol.
static Expected<JITSymbolFlags>
fromObjectSymbol(const object::SymbolRef &Symbol);
TargetFlagsType TargetFlags = 0;
FlagNames Flags = None;
inline JITSymbolFlags operator&(const JITSymbolFlags &LHS,
const JITSymbolFlags::FlagNames &RHS) {
JITSymbolFlags Tmp = LHS;
Tmp &= RHS;
return Tmp;
inline JITSymbolFlags operator|(const JITSymbolFlags &LHS,
const JITSymbolFlags::FlagNames &RHS) {
JITSymbolFlags Tmp = LHS;
Tmp |= RHS;
return Tmp;
/// ARM-specific JIT symbol flags.
/// FIXME: This should be moved into a target-specific header.
class ARMJITSymbolFlags {
ARMJITSymbolFlags() = default;
enum FlagNames {
None = 0,
Thumb = 1 << 0
operator JITSymbolFlags::TargetFlagsType&() { return Flags; }
static ARMJITSymbolFlags fromObjectSymbol(const object::SymbolRef &Symbol);
JITSymbolFlags::TargetFlagsType Flags = 0;
/// Represents a symbol that has been evaluated to an address already.
class JITEvaluatedSymbol {
JITEvaluatedSymbol() = default;
/// Create a 'null' symbol.
JITEvaluatedSymbol(std::nullptr_t) {}
/// Create a symbol for the given address and flags.
JITEvaluatedSymbol(JITTargetAddress Address, JITSymbolFlags Flags)
: Address(Address), Flags(Flags) {}
/// An evaluated symbol converts to 'true' if its address is non-zero.
explicit operator bool() const { return Address != 0; }
/// Return the address of this symbol.
JITTargetAddress getAddress() const { return Address; }
/// Return the flags for this symbol.
JITSymbolFlags getFlags() const { return Flags; }
/// Set the flags for this symbol.
void setFlags(JITSymbolFlags Flags) { this->Flags = std::move(Flags); }
JITTargetAddress Address = 0;
JITSymbolFlags Flags;
/// Represents a symbol in the JIT.
class JITSymbol {
using GetAddressFtor = unique_function<Expected<JITTargetAddress>()>;
/// Create a 'null' symbol, used to represent a "symbol not found"
/// result from a successful (non-erroneous) lookup.
: CachedAddr(0) {}
/// Create a JITSymbol representing an error in the symbol lookup
/// process (e.g. a network failure during a remote lookup).
JITSymbol(Error Err)
: Err(std::move(Err)), Flags(JITSymbolFlags::HasError) {}
/// Create a symbol for a definition with a known address.
JITSymbol(JITTargetAddress Addr, JITSymbolFlags Flags)
: CachedAddr(Addr), Flags(Flags) {}
/// Construct a JITSymbol from a JITEvaluatedSymbol.
JITSymbol(JITEvaluatedSymbol Sym)
: CachedAddr(Sym.getAddress()), Flags(Sym.getFlags()) {}
/// Create a symbol for a definition that doesn't have a known address
/// yet.
/// @param GetAddress A functor to materialize a definition (fixing the
/// address) on demand.
/// This constructor allows a JIT layer to provide a reference to a symbol
/// definition without actually materializing the definition up front. The
/// user can materialize the definition at any time by calling the getAddress
/// method.
JITSymbol(GetAddressFtor GetAddress, JITSymbolFlags Flags)
: GetAddress(std::move(GetAddress)), CachedAddr(0), Flags(Flags) {}
JITSymbol(const JITSymbol&) = delete;
JITSymbol& operator=(const JITSymbol&) = delete;
JITSymbol(JITSymbol &&Other)
: GetAddress(std::move(Other.GetAddress)), Flags(std::move(Other.Flags)) {
if (Flags.hasError())
Err = std::move(Other.Err);
CachedAddr = std::move(Other.CachedAddr);
JITSymbol& operator=(JITSymbol &&Other) {
GetAddress = std::move(Other.GetAddress);
Flags = std::move(Other.Flags);
if (Flags.hasError())
Err = std::move(Other.Err);
CachedAddr = std::move(Other.CachedAddr);
return *this;
~JITSymbol() {
if (Flags.hasError())
/// Returns true if the symbol exists, false otherwise.
explicit operator bool() const {
return !Flags.hasError() && (CachedAddr || GetAddress);
/// Move the error field value out of this JITSymbol.
Error takeError() {
if (Flags.hasError())
return std::move(Err);
return Error::success();
/// Get the address of the symbol in the target address space. Returns
/// '0' if the symbol does not exist.
Expected<JITTargetAddress> getAddress() {
assert(!Flags.hasError() && "getAddress called on error value");
if (GetAddress) {
if (auto CachedAddrOrErr = GetAddress()) {
GetAddress = nullptr;
CachedAddr = *CachedAddrOrErr;
assert(CachedAddr && "Symbol could not be materialized.");
} else
return CachedAddrOrErr.takeError();
return CachedAddr;
JITSymbolFlags getFlags() const { return Flags; }
GetAddressFtor GetAddress;
union {
JITTargetAddress CachedAddr;
Error Err;
JITSymbolFlags Flags;
/// Symbol resolution interface.
/// Allows symbol flags and addresses to be looked up by name.
/// Symbol queries are done in bulk (i.e. you request resolution of a set of
/// symbols, rather than a single one) to reduce IPC overhead in the case of
/// remote JITing, and expose opportunities for parallel compilation.
class JITSymbolResolver {
using LookupSet = std::set<StringRef>;
using LookupResult = std::map<StringRef, JITEvaluatedSymbol>;
using OnResolvedFunction = unique_function<void(Expected<LookupResult>)>;
virtual ~JITSymbolResolver() = default;
/// Returns the fully resolved address and flags for each of the given
/// symbols.
/// This method will return an error if any of the given symbols can not be
/// resolved, or if the resolution process itself triggers an error.
virtual void lookup(const LookupSet &Symbols,
OnResolvedFunction OnResolved) = 0;
/// Returns the subset of the given symbols that should be materialized by
/// the caller. Only weak/common symbols should be looked up, as strong
/// definitions are implicitly always part of the caller's responsibility.
virtual Expected<LookupSet>
getResponsibilitySet(const LookupSet &Symbols) = 0;
virtual void anchor();
/// Legacy symbol resolution interface.
class LegacyJITSymbolResolver : public JITSymbolResolver {
/// Performs lookup by, for each symbol, first calling
/// findSymbolInLogicalDylib and if that fails calling
/// findSymbol.
void lookup(const LookupSet &Symbols, OnResolvedFunction OnResolved) final;
/// Performs flags lookup by calling findSymbolInLogicalDylib and
/// returning the flags value for that symbol.
Expected<LookupSet> getResponsibilitySet(const LookupSet &Symbols) final;
/// This method returns the address of the specified symbol if it exists
/// within the logical dynamic library represented by this JITSymbolResolver.
/// Unlike findSymbol, queries through this interface should return addresses
/// for hidden symbols.
/// This is of particular importance for the Orc JIT APIs, which support lazy
/// compilation by breaking up modules: Each of those broken out modules
/// must be able to resolve hidden symbols provided by the others. Clients
/// writing memory managers for MCJIT can usually ignore this method.
/// This method will be queried by RuntimeDyld when checking for previous
/// definitions of common symbols.
virtual JITSymbol findSymbolInLogicalDylib(const std::string &Name) = 0;
/// This method returns the address of the specified function or variable.
/// It is used to resolve symbols during module linking.
/// If the returned symbol's address is equal to ~0ULL then RuntimeDyld will
/// skip all relocations for that symbol, and the client will be responsible
/// for handling them manually.
virtual JITSymbol findSymbol(const std::string &Name) = 0;
virtual void anchor();
} // end namespace llvm