RuntimeDyld.h

Go to the documentation of this file.

//===- RuntimeDyld.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 runtime dynamic linker facilities of the MC-JIT.
//
//===----------------------------------------------------------------------===//
 
#ifndef LLVM_EXECUTIONENGINE_RUNTIMEDYLD_H
#define LLVM_EXECUTIONENGINE_RUNTIMEDYLD_H
 
#include "llvm/ADT/FunctionExtras.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/DebugInfo/DIContext.h"
#include "llvm/ExecutionEngine/JITSymbol.h"
#include "llvm/Object/ObjectFile.h"
#include "llvm/Support/Error.h"
#include <algorithm>
#include <cassert>
#include <cstddef>
#include <cstdint>
#include <map>
#include <memory>
#include <string>
#include <system_error>
 
namespace llvm {
 
namespace object {
 
template <typename T> class OwningBinary;
 
} // end namespace object
 
/// Base class for errors originating in RuntimeDyld, e.g. missing relocation
/// support.
class RuntimeDyldError : public ErrorInfo<RuntimeDyldError> {
public:
  static char ID;
 
  RuntimeDyldError(std::string ErrMsg) : ErrMsg(std::move(ErrMsg)) {}
 
  void log(raw_ostream &OS) const override;
  const std::string &getErrorMessage() const { return ErrMsg; }
  std::error_code convertToErrorCode() const override;
 
private:
  std::string ErrMsg;
};
 
class RuntimeDyldImpl;
 
class RuntimeDyld {
protected:
  // Change the address associated with a section when resolving relocations.
  // Any relocations already associated with the symbol will be re-resolved.
  void reassignSectionAddress(unsigned SectionID, uint64_t Addr);
 
public:
  using NotifyStubEmittedFunction = std::function<void(
      StringRef FileName, StringRef SectionName, StringRef SymbolName,
      unsigned SectionID, uint32_t StubOffset)>;
 
  /// Information about the loaded object.
  class LoadedObjectInfo : public llvm::LoadedObjectInfo {
    friend class RuntimeDyldImpl;
 
  public:
    using ObjSectionToIDMap = std::map<object::SectionRef, unsigned>;
 
    LoadedObjectInfo(RuntimeDyldImpl &RTDyld, ObjSectionToIDMap ObjSecToIDMap)
        : RTDyld(RTDyld), ObjSecToIDMap(std::move(ObjSecToIDMap)) {}
 
    virtual object::OwningBinary<object::ObjectFile>
    getObjectForDebug(const object::ObjectFile &Obj) const = 0;
 
    uint64_t
    getSectionLoadAddress(const object::SectionRef &Sec) const override;
 
  protected:
    virtual void anchor();
 
    RuntimeDyldImpl &RTDyld;
    ObjSectionToIDMap ObjSecToIDMap;
  };
 
  /// Memory Management.
  class MemoryManager {
    friend class RuntimeDyld;
 
  public:
    MemoryManager() = default;
    virtual ~MemoryManager() = default;
 
    /// Allocate a memory block of (at least) the given size suitable for
    /// executable code. The SectionID is a unique identifier assigned by the
    /// RuntimeDyld instance, and optionally recorded by the memory manager to
    /// access a loaded section.
    virtual uint8_t *allocateCodeSection(uintptr_t Size, unsigned Alignment,
                                         unsigned SectionID,
                                         StringRef SectionName) = 0;
 
    /// Allocate a memory block of (at least) the given size suitable for data.
    /// The SectionID is a unique identifier assigned by the JIT engine, and
    /// optionally recorded by the memory manager to access a loaded section.
    virtual uint8_t *allocateDataSection(uintptr_t Size, unsigned Alignment,
                                         unsigned SectionID,
                                         StringRef SectionName,
                                         bool IsReadOnly) = 0;
 
    /// Inform the memory manager about the total amount of memory required to
    /// allocate all sections to be loaded:
    /// \p CodeSize - the total size of all code sections
    /// \p DataSizeRO - the total size of all read-only data sections
    /// \p DataSizeRW - the total size of all read-write data sections
    ///
    /// Note that by default the callback is disabled. To enable it
    /// redefine the method needsToReserveAllocationSpace to return true.
    virtual void reserveAllocationSpace(uintptr_t CodeSize, uint32_t CodeAlign,
                                        uintptr_t RODataSize,
                                        uint32_t RODataAlign,
                                        uintptr_t RWDataSize,
                                        uint32_t RWDataAlign) {}
 
    /// Override to return true to enable the reserveAllocationSpace callback.
    virtual bool needsToReserveAllocationSpace() { return false; }
 
    /// Register the EH frames with the runtime so that c++ exceptions work.
    ///
    /// \p Addr parameter provides the local address of the EH frame section
    /// data, while \p LoadAddr provides the address of the data in the target
    /// address space.  If the section has not been remapped (which will usually
    /// be the case for local execution) these two values will be the same.
    virtual void registerEHFrames(uint8_t *Addr, uint64_t LoadAddr,
                                  size_t Size) = 0;
    virtual void deregisterEHFrames() = 0;
 
    /// This method is called when object loading is complete and section page
    /// permissions can be applied.  It is up to the memory manager implementation
    /// to decide whether or not to act on this method.  The memory manager will
    /// typically allocate all sections as read-write and then apply specific
    /// permissions when this method is called.  Code sections cannot be executed
    /// until this function has been called.  In addition, any cache coherency
    /// operations needed to reliably use the memory are also performed.
    ///
    /// Returns true if an error occurred, false otherwise.
    virtual bool finalizeMemory(std::string *ErrMsg = nullptr) = 0;
 
    /// This method is called after an object has been loaded into memory but
    /// before relocations are applied to the loaded sections.
    ///
    /// Memory managers which are preparing code for execution in an external
    /// address space can use this call to remap the section addresses for the
    /// newly loaded object.
    ///
    /// For clients that do not need access to an ExecutionEngine instance this
    /// method should be preferred to its cousin
    /// MCJITMemoryManager::notifyObjectLoaded as this method is compatible with
    /// ORC JIT stacks.
    virtual void notifyObjectLoaded(RuntimeDyld &RTDyld,
                                    const object::ObjectFile &Obj) {}
 
  private:
    virtual void anchor();
 
    bool FinalizationLocked = false;
  };
 
  /// Construct a RuntimeDyld instance.
  RuntimeDyld(MemoryManager &MemMgr, JITSymbolResolver &Resolver);
  RuntimeDyld(const RuntimeDyld &) = delete;
  RuntimeDyld &operator=(const RuntimeDyld &) = delete;
  ~RuntimeDyld();
 
  /// Add the referenced object file to the list of objects to be loaded and
  /// relocated.
  std::unique_ptr<LoadedObjectInfo> loadObject(const object::ObjectFile &O);
 
  /// Get the address of our local copy of the symbol. This may or may not
  /// be the address used for relocation (clients can copy the data around
  /// and resolve relocatons based on where they put it).
  void *getSymbolLocalAddress(StringRef Name) const;
 
  /// Get the section ID for the section containing the given symbol.
  unsigned getSymbolSectionID(StringRef Name) const;
 
  /// Get the target address and flags for the named symbol.
  /// This address is the one used for relocation.
  JITEvaluatedSymbol getSymbol(StringRef Name) const;
 
  /// Returns a copy of the symbol table. This can be used by on-finalized
  /// callbacks to extract the symbol table before throwing away the
  /// RuntimeDyld instance. Because the map keys (StringRefs) are backed by
  /// strings inside the RuntimeDyld instance, the map should be processed
  /// before the RuntimeDyld instance is discarded.
  std::map<StringRef, JITEvaluatedSymbol> getSymbolTable() const;
 
  /// Resolve the relocations for all symbols we currently know about.
  void resolveRelocations();
 
  /// Map a section to its target address space value.
  /// Map the address of a JIT section as returned from the memory manager
  /// to the address in the target process as the running code will see it.
  /// This is the address which will be used for relocation resolution.
  void mapSectionAddress(const void *LocalAddress, uint64_t TargetAddress);
 
  /// Returns the section's working memory.
  StringRef getSectionContent(unsigned SectionID) const;
 
  /// If the section was loaded, return the section's load address,
  /// otherwise return None.
  uint64_t getSectionLoadAddress(unsigned SectionID) const;
 
  /// Set the NotifyStubEmitted callback. This is used for debugging
  /// purposes. A callback is made for each stub that is generated.
  void setNotifyStubEmitted(NotifyStubEmittedFunction NotifyStubEmitted) {
    this->NotifyStubEmitted = std::move(NotifyStubEmitted);
  }
 
  /// Register any EH frame sections that have been loaded but not previously
  /// registered with the memory manager.  Note, RuntimeDyld is responsible
  /// for identifying the EH frame and calling the memory manager with the
  /// EH frame section data.  However, the memory manager itself will handle
  /// the actual target-specific EH frame registration.
  void registerEHFrames();
 
  void deregisterEHFrames();
 
  bool hasError();
  StringRef getErrorString();
 
  /// By default, only sections that are "required for execution" are passed to
  /// the RTDyldMemoryManager, and other sections are discarded. Passing 'true'
  /// to this method will cause RuntimeDyld to pass all sections to its
  /// memory manager regardless of whether they are "required to execute" in the
  /// usual sense. This is useful for inspecting metadata sections that may not
  /// contain relocations, E.g. Debug info, stackmaps.
  ///
  /// Must be called before the first object file is loaded.
  void setProcessAllSections(bool ProcessAllSections) {
    assert(!Dyld && "setProcessAllSections must be called before loadObject.");
    this->ProcessAllSections = ProcessAllSections;
  }
 
  /// Perform all actions needed to make the code owned by this RuntimeDyld
  /// instance executable:
  ///
  /// 1) Apply relocations.
  /// 2) Register EH frames.
  /// 3) Update memory permissions*.
  ///
  /// * Finalization is potentially recursive**, and the 3rd step will only be
  ///   applied by the outermost call to finalize. This allows different
  ///   RuntimeDyld instances to share a memory manager without the innermost
  ///   finalization locking the memory and causing relocation fixup errors in
  ///   outer instances.
  ///
  /// ** Recursive finalization occurs when one RuntimeDyld instances needs the
  ///   address of a symbol owned by some other instance in order to apply
  ///   relocations.
  ///
  void finalizeWithMemoryManagerLocking();
 
private:
  friend void jitLinkForORC(
      object::OwningBinary<object::ObjectFile> O,
      RuntimeDyld::MemoryManager &MemMgr, JITSymbolResolver &Resolver,
      bool ProcessAllSections,
      unique_function<Error(const object::ObjectFile &Obj, LoadedObjectInfo &,
                            std::map<StringRef, JITEvaluatedSymbol>)>
          OnLoaded,
      unique_function<void(object::OwningBinary<object::ObjectFile> O,
                           std::unique_ptr<LoadedObjectInfo>, Error)>
          OnEmitted);
 
  // RuntimeDyldImpl is the actual class. RuntimeDyld is just the public
  // interface.
  std::unique_ptr<RuntimeDyldImpl> Dyld;
  MemoryManager &MemMgr;
  JITSymbolResolver &Resolver;
  bool ProcessAllSections;
  NotifyStubEmittedFunction NotifyStubEmitted;
};
 
// Asynchronous JIT link for ORC.
//
// Warning: This API is experimental and probably should not be used by anyone
// but ORC's RTDyldObjectLinkingLayer2. Internally it constructs a RuntimeDyld
// instance and uses continuation passing to perform the fix-up and finalize
// steps asynchronously.
void jitLinkForORC(
    object::OwningBinary<object::ObjectFile> O,
    RuntimeDyld::MemoryManager &MemMgr, JITSymbolResolver &Resolver,
    bool ProcessAllSections,
    unique_function<Error(const object::ObjectFile &Obj,
                          RuntimeDyld::LoadedObjectInfo &,
                          std::map<StringRef, JITEvaluatedSymbol>)>
        OnLoaded,
    unique_function<void(object::OwningBinary<object::ObjectFile>,
                         std::unique_ptr<RuntimeDyld::LoadedObjectInfo>, Error)>
        OnEmitted);
 
} // end namespace llvm
 
#endif // LLVM_EXECUTIONENGINE_RUNTIMEDYLD_H