1 //===- SectionMemoryManager.h - Memory manager for MCJIT/RtDyld -*- C++ -*-===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // This file contains the declaration of a section-based memory manager used by 10 // the MCJIT execution engine and RuntimeDyld. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #ifndef LLVM_EXECUTIONENGINE_SECTIONMEMORYMANAGER_H 15 #define LLVM_EXECUTIONENGINE_SECTIONMEMORYMANAGER_H 16 17 #include "llvm/ADT/SmallVector.h" 18 #include "llvm/ADT/StringRef.h" 19 #include "llvm/ExecutionEngine/RTDyldMemoryManager.h" 20 #include "llvm/Support/Memory.h" 21 #include <cstdint> 22 #include <string> 23 #include <system_error> 24 25 namespace llvm { 26 27 /// This is a simple memory manager which implements the methods called by 28 /// the RuntimeDyld class to allocate memory for section-based loading of 29 /// objects, usually those generated by the MCJIT execution engine. 30 /// 31 /// This memory manager allocates all section memory as read-write. The 32 /// RuntimeDyld will copy JITed section memory into these allocated blocks 33 /// and perform any necessary linking and relocations. 34 /// 35 /// Any client using this memory manager MUST ensure that section-specific 36 /// page permissions have been applied before attempting to execute functions 37 /// in the JITed object. Permissions can be applied either by calling 38 /// MCJIT::finalizeObject or by calling SectionMemoryManager::finalizeMemory 39 /// directly. Clients of MCJIT should call MCJIT::finalizeObject. 40 class SectionMemoryManager : public RTDyldMemoryManager { 41 public: 42 /// This enum describes the various reasons to allocate pages from 43 /// allocateMappedMemory. 44 enum class AllocationPurpose { 45 Code, 46 ROData, 47 RWData, 48 }; 49 50 /// Implementations of this interface are used by SectionMemoryManager to 51 /// request pages from the operating system. 52 class MemoryMapper { 53 public: 54 /// This method attempts to allocate \p NumBytes bytes of virtual memory for 55 /// \p Purpose. \p NearBlock may point to an existing allocation, in which 56 /// case an attempt is made to allocate more memory near the existing block. 57 /// The actual allocated address is not guaranteed to be near the requested 58 /// address. \p Flags is used to set the initial protection flags for the 59 /// block of the memory. \p EC [out] returns an object describing any error 60 /// that occurs. 61 /// 62 /// This method may allocate more than the number of bytes requested. The 63 /// actual number of bytes allocated is indicated in the returned 64 /// MemoryBlock. 65 /// 66 /// The start of the allocated block must be aligned with the system 67 /// allocation granularity (64K on Windows, page size on Linux). If the 68 /// address following \p NearBlock is not so aligned, it will be rounded up 69 /// to the next allocation granularity boundary. 70 /// 71 /// \r a non-null MemoryBlock if the function was successful, otherwise a 72 /// null MemoryBlock with \p EC describing the error. 73 virtual sys::MemoryBlock 74 allocateMappedMemory(AllocationPurpose Purpose, size_t NumBytes, 75 const sys::MemoryBlock *const NearBlock, 76 unsigned Flags, std::error_code &EC) = 0; 77 78 /// This method sets the protection flags for a block of memory to the state 79 /// specified by \p Flags. The behavior is not specified if the memory was 80 /// not allocated using the allocateMappedMemory method. 81 /// \p Block describes the memory block to be protected. 82 /// \p Flags specifies the new protection state to be assigned to the block. 83 /// 84 /// If \p Flags is MF_WRITE, the actual behavior varies with the operating 85 /// system (i.e. MF_READ | MF_WRITE on Windows) and the target architecture 86 /// (i.e. MF_WRITE -> MF_READ | MF_WRITE on i386). 87 /// 88 /// \r error_success if the function was successful, or an error_code 89 /// describing the failure if an error occurred. 90 virtual std::error_code protectMappedMemory(const sys::MemoryBlock &Block, 91 unsigned Flags) = 0; 92 93 /// This method releases a block of memory that was allocated with the 94 /// allocateMappedMemory method. It should not be used to release any memory 95 /// block allocated any other way. 96 /// \p Block describes the memory to be released. 97 /// 98 /// \r error_success if the function was successful, or an error_code 99 /// describing the failure if an error occurred. 100 virtual std::error_code releaseMappedMemory(sys::MemoryBlock &M) = 0; 101 102 virtual ~MemoryMapper(); 103 }; 104 105 /// Creates a SectionMemoryManager instance with \p MM as the associated 106 /// memory mapper. If \p MM is nullptr then a default memory mapper is used 107 /// that directly calls into the operating system. 108 SectionMemoryManager(MemoryMapper *MM = nullptr); 109 SectionMemoryManager(const SectionMemoryManager &) = delete; 110 void operator=(const SectionMemoryManager &) = delete; 111 ~SectionMemoryManager() override; 112 113 /// Allocates a memory block of (at least) the given size suitable for 114 /// executable code. 115 /// 116 /// The value of \p Alignment must be a power of two. If \p Alignment is zero 117 /// a default alignment of 16 will be used. 118 uint8_t *allocateCodeSection(uintptr_t Size, unsigned Alignment, 119 unsigned SectionID, 120 StringRef SectionName) override; 121 122 /// Allocates a memory block of (at least) the given size suitable for 123 /// executable code. 124 /// 125 /// The value of \p Alignment must be a power of two. If \p Alignment is zero 126 /// a default alignment of 16 will be used. 127 uint8_t *allocateDataSection(uintptr_t Size, unsigned Alignment, 128 unsigned SectionID, StringRef SectionName, 129 bool isReadOnly) override; 130 131 /// Update section-specific memory permissions and other attributes. 132 /// 133 /// This method is called when object loading is complete and section page 134 /// permissions can be applied. It is up to the memory manager implementation 135 /// to decide whether or not to act on this method. The memory manager will 136 /// typically allocate all sections as read-write and then apply specific 137 /// permissions when this method is called. Code sections cannot be executed 138 /// until this function has been called. In addition, any cache coherency 139 /// operations needed to reliably use the memory are also performed. 140 /// 141 /// \returns true if an error occurred, false otherwise. 142 bool finalizeMemory(std::string *ErrMsg = nullptr) override; 143 144 /// Invalidate instruction cache for code sections. 145 /// 146 /// Some platforms with separate data cache and instruction cache require 147 /// explicit cache flush, otherwise JIT code manipulations (like resolved 148 /// relocations) will get to the data cache but not to the instruction cache. 149 /// 150 /// This method is called from finalizeMemory. 151 virtual void invalidateInstructionCache(); 152 153 private: 154 struct FreeMemBlock { 155 // The actual block of free memory 156 sys::MemoryBlock Free; 157 // If there is a pending allocation from the same reservation right before 158 // this block, store it's index in PendingMem, to be able to update the 159 // pending region if part of this block is allocated, rather than having to 160 // create a new one 161 unsigned PendingPrefixIndex; 162 }; 163 164 struct MemoryGroup { 165 // PendingMem contains all blocks of memory (subblocks of AllocatedMem) 166 // which have not yet had their permissions applied, but have been given 167 // out to the user. FreeMem contains all block of memory, which have 168 // neither had their permissions applied, nor been given out to the user. 169 SmallVector<sys::MemoryBlock, 16> PendingMem; 170 SmallVector<FreeMemBlock, 16> FreeMem; 171 172 // All memory blocks that have been requested from the system 173 SmallVector<sys::MemoryBlock, 16> AllocatedMem; 174 175 sys::MemoryBlock Near; 176 }; 177 178 uint8_t *allocateSection(AllocationPurpose Purpose, uintptr_t Size, 179 unsigned Alignment); 180 181 std::error_code applyMemoryGroupPermissions(MemoryGroup &MemGroup, 182 unsigned Permissions); 183 184 void anchor() override; 185 186 MemoryGroup CodeMem; 187 MemoryGroup RWDataMem; 188 MemoryGroup RODataMem; 189 MemoryMapper &MMapper; 190 }; 191 192 } // end namespace llvm 193 194 #endif // LLVM_EXECUTION_ENGINE_SECTION_MEMORY_MANAGER_H 195