//===- SectionMemoryManager.h - Memory manager for MCJIT/RtDyld -*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains the declaration of a section-based memory manager used by
// the MCJIT execution engine and RuntimeDyld.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_EXECUTIONENGINE_SECTIONMEMORYMANAGER_H
#define LLVM_EXECUTIONENGINE_SECTIONMEMORYMANAGER_H

#include "llvm/ADT/SmallVector.h"
#include "llvm/ExecutionEngine/JITMemoryManager.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/Memory.h"

namespace llvm {

/// This is a simple memory manager which implements the methods called by
/// the RuntimeDyld class to allocate memory for section-based loading of
/// objects, usually those generated by the MCJIT execution engine.
///
/// This memory manager allocates all section memory as read-write.  The
/// RuntimeDyld will copy JITed section memory into these allocated blocks
/// and perform any necessary linking and relocations.
///
/// Any client using this memory manager MUST ensure that section-specific
/// page permissions have been applied before attempting to execute functions
/// in the JITed object.  Permissions can be applied either by calling
/// MCJIT::finalizeObject or by calling SectionMemoryManager::applyPermissions
/// directly.  Clients of MCJIT should call MCJIT::finalizeObject.
class SectionMemoryManager : public JITMemoryManager {
  SectionMemoryManager(const SectionMemoryManager&) LLVM_DELETED_FUNCTION;
  void operator=(const SectionMemoryManager&) LLVM_DELETED_FUNCTION;

public:
  SectionMemoryManager() { }
  virtual ~SectionMemoryManager();

  /// \brief Allocates a memory block of (at least) the given size suitable for
  /// executable code.
  ///
  /// The value of \p Alignment must be a power of two.  If \p Alignment is zero
  /// a default alignment of 16 will be used.
  virtual uint8_t *allocateCodeSection(uintptr_t Size, unsigned Alignment,
                                       unsigned SectionID);

  /// \brief Allocates a memory block of (at least) the given size suitable for
  /// executable code.
  ///
  /// The value of \p Alignment must be a power of two.  If \p Alignment is zero
  /// a default alignment of 16 will be used.
  virtual uint8_t *allocateDataSection(uintptr_t Size, unsigned Alignment,
                                       unsigned SectionID,
                                       bool isReadOnly);

  /// \brief Applies section-specific memory permissions.
  ///
  /// 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.
  ///
  /// \returns true if an error occurred, false otherwise.
  virtual bool applyPermissions(std::string *ErrMsg = 0);

  void registerEHFrames(StringRef SectionData);

  /// This method returns the address of the specified function. As such it is
  /// only useful for resolving library symbols, not code generated symbols.
  ///
  /// If \p AbortOnFailure is false and no function with the given name is
  /// found, this function returns a null pointer. Otherwise, it prints a
  /// message to stderr and aborts.
  virtual void *getPointerToNamedFunction(const std::string &Name,
                                          bool AbortOnFailure = true);

  /// \brief Invalidate instruction cache for code sections.
  ///
  /// Some platforms with separate data cache and instruction cache require
  /// explicit cache flush, otherwise JIT code manipulations (like resolved
  /// relocations) will get to the data cache but not to the instruction cache.
  ///
  /// This method is called from applyPermissions.
  virtual void invalidateInstructionCache();

private:
  struct MemoryGroup {
      SmallVector<sys::MemoryBlock, 16> AllocatedMem;
      SmallVector<sys::MemoryBlock, 16> FreeMem;
      sys::MemoryBlock Near;
  };

  uint8_t *allocateSection(MemoryGroup &MemGroup, uintptr_t Size,
                           unsigned Alignment);

  error_code applyMemoryGroupPermissions(MemoryGroup &MemGroup,
                                         unsigned Permissions);

  MemoryGroup CodeMem;
  MemoryGroup RWDataMem;
  MemoryGroup RODataMem;

public:
  ///
  /// Functions below are not used by MCJIT or RuntimeDyld, but must be
  /// implemented because they are declared as pure virtuals in the base class.
  ///

  virtual void setMemoryWritable() {
    llvm_unreachable("Unexpected call!");
  }
  virtual void setMemoryExecutable() {
    llvm_unreachable("Unexpected call!");
  }
  virtual void setPoisonMemory(bool poison) {
    llvm_unreachable("Unexpected call!");
  }
  virtual void AllocateGOT() {
    llvm_unreachable("Unexpected call!");
  }
  virtual uint8_t *getGOTBase() const {
    llvm_unreachable("Unexpected call!");
    return 0;
  }
  virtual uint8_t *startFunctionBody(const Function *F,
                                     uintptr_t &ActualSize){
    llvm_unreachable("Unexpected call!");
    return 0;
  }
  virtual uint8_t *allocateStub(const GlobalValue *F, unsigned StubSize,
                                unsigned Alignment) {
    llvm_unreachable("Unexpected call!");
    return 0;
  }
  virtual void endFunctionBody(const Function *F, uint8_t *FunctionStart,
                               uint8_t *FunctionEnd) {
    llvm_unreachable("Unexpected call!");
  }
  virtual uint8_t *allocateSpace(intptr_t Size, unsigned Alignment) {
    llvm_unreachable("Unexpected call!");
    return 0;
  }
  virtual uint8_t *allocateGlobal(uintptr_t Size, unsigned Alignment) {
    llvm_unreachable("Unexpected call!");
    return 0;
  }
  virtual void deallocateFunctionBody(void *Body) {
    llvm_unreachable("Unexpected call!");
  }
  virtual uint8_t *startExceptionTable(const Function *F,
                                       uintptr_t &ActualSize) {
    llvm_unreachable("Unexpected call!");
    return 0;
  }
  virtual void endExceptionTable(const Function *F, uint8_t *TableStart,
                                 uint8_t *TableEnd, uint8_t *FrameRegister) {
    llvm_unreachable("Unexpected call!");
  }
  virtual void deallocateExceptionTable(void *ET) {
    llvm_unreachable("Unexpected call!");
  }
};

}

#endif // LLVM_EXECUTION_ENGINE_SECTION_MEMORY_MANAGER_H