//===- SectionMemoryManager.h - Memory manager for MCJIT/RtDyld -*- 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
//
//===----------------------------------------------------------------------===//
//
// 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/RTDyldMemoryManager.h"
#include "llvm/Support/Memory.h"
#include <cstdint>
#include <string>
#include <system_error>
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::finalizeMemory
/// directly. Clients of MCJIT should call MCJIT::finalizeObject.
class SectionMemoryManager : public RTDyldMemoryManager {
public:
/// This enum describes the various reasons to allocate pages from
/// allocateMappedMemory.
enum class AllocationPurpose {
Code,
ROData,
RWData,
};
/// Implementations of this interface are used by SectionMemoryManager to
/// request pages from the operating system.
class MemoryMapper {
public:
/// This method attempts to allocate \p NumBytes bytes of virtual memory for
/// \p Purpose. \p NearBlock may point to an existing allocation, in which
/// case an attempt is made to allocate more memory near the existing block.
/// The actual allocated address is not guaranteed to be near the requested
/// address. \p Flags is used to set the initial protection flags for the
/// block of the memory. \p EC [out] returns an object describing any error
/// that occurs.
///
/// This method may allocate more than the number of bytes requested. The
/// actual number of bytes allocated is indicated in the returned
/// MemoryBlock.
///
/// The start of the allocated block must be aligned with the system
/// allocation granularity (64K on Windows, page size on Linux). If the
/// address following \p NearBlock is not so aligned, it will be rounded up
/// to the next allocation granularity boundary.
///
/// \r a non-null MemoryBlock if the function was successful, otherwise a
/// null MemoryBlock with \p EC describing the error.
virtual sys::MemoryBlock
allocateMappedMemory(AllocationPurpose Purpose, size_t NumBytes,
const sys::MemoryBlock *const NearBlock,
unsigned Flags, std::error_code &EC) = 0;
/// This method sets the protection flags for a block of memory to the state
/// specified by \p Flags. The behavior is not specified if the memory was
/// not allocated using the allocateMappedMemory method.
/// \p Block describes the memory block to be protected.
/// \p Flags specifies the new protection state to be assigned to the block.
///
/// If \p Flags is MF_WRITE, the actual behavior varies with the operating
/// system (i.e. MF_READ | MF_WRITE on Windows) and the target architecture
/// (i.e. MF_WRITE -> MF_READ | MF_WRITE on i386).
///
/// \r error_success if the function was successful, or an error_code
/// describing the failure if an error occurred.
virtual std::error_code protectMappedMemory(const sys::MemoryBlock &Block,
unsigned Flags) = 0;
/// This method releases a block of memory that was allocated with the
/// allocateMappedMemory method. It should not be used to release any memory
/// block allocated any other way.
/// \p Block describes the memory to be released.
///
/// \r error_success if the function was successful, or an error_code
/// describing the failure if an error occurred.
virtual std::error_code releaseMappedMemory(sys::MemoryBlock &M) = 0;
virtual ~MemoryMapper();
};
/// Creates a SectionMemoryManager instance with \p MM as the associated
/// memory mapper. If \p MM is nullptr then a default memory mapper is used
/// that directly calls into the operating system.
SectionMemoryManager(MemoryMapper *MM = nullptr);
SectionMemoryManager(const SectionMemoryManager &) = delete;
void operator=(const SectionMemoryManager &) = delete;
~SectionMemoryManager() override;
/// 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.
uint8_t *allocateCodeSection(uintptr_t Size, unsigned Alignment,
unsigned SectionID,
StringRef SectionName) override;
/// 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.
uint8_t *allocateDataSection(uintptr_t Size, unsigned Alignment,
unsigned SectionID, StringRef SectionName,
bool isReadOnly) override;
/// Update section-specific memory permissions and other attributes.
///
/// 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.
bool finalizeMemory(std::string *ErrMsg = nullptr) override;
/// 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 finalizeMemory.
virtual void invalidateInstructionCache();
private:
struct FreeMemBlock {
// The actual block of free memory
sys::MemoryBlock Free;
// If there is a pending allocation from the same reservation right before
// this block, store it's index in PendingMem, to be able to update the
// pending region if part of this block is allocated, rather than having to
// create a new one
unsigned PendingPrefixIndex;
};
struct MemoryGroup {
// PendingMem contains all blocks of memory (subblocks of AllocatedMem)
// which have not yet had their permissions applied, but have been given
// out to the user. FreeMem contains all block of memory, which have
// neither had their permissions applied, nor been given out to the user.
SmallVector<sys::MemoryBlock, 16> PendingMem;
SmallVector<FreeMemBlock, 16> FreeMem;
// All memory blocks that have been requested from the system
SmallVector<sys::MemoryBlock, 16> AllocatedMem;
sys::MemoryBlock Near;
};
uint8_t *allocateSection(AllocationPurpose Purpose, uintptr_t Size,
unsigned Alignment);
std::error_code applyMemoryGroupPermissions(MemoryGroup &MemGroup,
unsigned Permissions);
void anchor() override;
MemoryGroup CodeMem;
MemoryGroup RWDataMem;
MemoryGroup RODataMem;
MemoryMapper &MMapper;
};
} // end namespace llvm
#endif // LLVM_EXECUTIONENGINE_SECTIONMEMORYMANAGER_H