//===- 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 #include #include 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 PendingMem; SmallVector FreeMem; // All memory blocks that have been requested from the system SmallVector 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_EXECUTION_ENGINE_SECTION_MEMORY_MANAGER_H