1 //===- SectionMemoryManager.h - Memory manager for MCJIT/RtDyld -*- C++ -*-===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This file contains the declaration of a section-based memory manager used by 11 // the MCJIT execution engine and RuntimeDyld. 12 // 13 //===----------------------------------------------------------------------===// 14 15 #ifndef LLVM_EXECUTIONENGINE_SECTIONMEMORYMANAGER_H 16 #define LLVM_EXECUTIONENGINE_SECTIONMEMORYMANAGER_H 17 18 #include "llvm/ADT/SmallVector.h" 19 #include "llvm/ADT/StringRef.h" 20 #include "llvm/ExecutionEngine/RTDyldMemoryManager.h" 21 #include "llvm/Support/Memory.h" 22 #include <cstdint> 23 #include <string> 24 #include <system_error> 25 26 namespace llvm { 27 28 /// This is a simple memory manager which implements the methods called by 29 /// the RuntimeDyld class to allocate memory for section-based loading of 30 /// objects, usually those generated by the MCJIT execution engine. 31 /// 32 /// This memory manager allocates all section memory as read-write. The 33 /// RuntimeDyld will copy JITed section memory into these allocated blocks 34 /// and perform any necessary linking and relocations. 35 /// 36 /// Any client using this memory manager MUST ensure that section-specific 37 /// page permissions have been applied before attempting to execute functions 38 /// in the JITed object. Permissions can be applied either by calling 39 /// MCJIT::finalizeObject or by calling SectionMemoryManager::finalizeMemory 40 /// directly. Clients of MCJIT should call MCJIT::finalizeObject. 41 class SectionMemoryManager : public RTDyldMemoryManager { 42 public: 43 /// This enum describes the various reasons to allocate pages from 44 /// allocateMappedMemory. 45 enum class AllocationPurpose { 46 Code, 47 ROData, 48 RWData, 49 }; 50 51 /// Implementations of this interface are used by SectionMemoryManager to 52 /// request pages from the operating system. 53 class MemoryMapper { 54 public: 55 /// This method attempts to allocate \p NumBytes bytes of virtual memory for 56 /// \p Purpose. \p NearBlock may point to an existing allocation, in which 57 /// case an attempt is made to allocate more memory near the existing block. 58 /// The actual allocated address is not guaranteed to be near the requested 59 /// address. \p Flags is used to set the initial protection flags for the 60 /// block of the memory. \p EC [out] returns an object describing any error 61 /// that occurs. 62 /// 63 /// This method may allocate more than the number of bytes requested. The 64 /// actual number of bytes allocated is indicated in the returned 65 /// MemoryBlock. 66 /// 67 /// The start of the allocated block must be aligned with the system 68 /// allocation granularity (64K on Windows, page size on Linux). If the 69 /// address following \p NearBlock is not so aligned, it will be rounded up 70 /// to the next allocation granularity boundary. 71 /// 72 /// \r a non-null MemoryBlock if the function was successful, otherwise a 73 /// null MemoryBlock with \p EC describing the error. 74 virtual sys::MemoryBlock 75 allocateMappedMemory(AllocationPurpose Purpose, size_t NumBytes, 76 const sys::MemoryBlock *const NearBlock, 77 unsigned Flags, std::error_code &EC) = 0; 78 79 /// This method sets the protection flags for a block of memory to the state 80 /// specified by \p Flags. The behavior is not specified if the memory was 81 /// not allocated using the allocateMappedMemory method. 82 /// \p Block describes the memory block to be protected. 83 /// \p Flags specifies the new protection state to be assigned to the block. 84 /// 85 /// If \p Flags is MF_WRITE, the actual behavior varies with the operating 86 /// system (i.e. MF_READ | MF_WRITE on Windows) and the target architecture 87 /// (i.e. MF_WRITE -> MF_READ | MF_WRITE on i386). 88 /// 89 /// \r error_success if the function was successful, or an error_code 90 /// describing the failure if an error occurred. 91 virtual std::error_code protectMappedMemory(const sys::MemoryBlock &Block, 92 unsigned Flags) = 0; 93 94 /// This method releases a block of memory that was allocated with the 95 /// allocateMappedMemory method. It should not be used to release any memory 96 /// block allocated any other way. 97 /// \p Block describes the memory to be released. 98 /// 99 /// \r error_success if the function was successful, or an error_code 100 /// describing the failure if an error occurred. 101 virtual std::error_code releaseMappedMemory(sys::MemoryBlock &M) = 0; 102 103 virtual ~MemoryMapper(); 104 }; 105 106 /// Creates a SectionMemoryManager instance with \p MM as the associated 107 /// memory mapper. If \p MM is nullptr then a default memory mapper is used 108 /// that directly calls into the operating system. 109 SectionMemoryManager(MemoryMapper *MM = nullptr); 110 SectionMemoryManager(const SectionMemoryManager &) = delete; 111 void operator=(const SectionMemoryManager &) = delete; 112 ~SectionMemoryManager() override; 113 114 /// Allocates a memory block of (at least) the given size suitable for 115 /// executable code. 116 /// 117 /// The value of \p Alignment must be a power of two. If \p Alignment is zero 118 /// a default alignment of 16 will be used. 119 uint8_t *allocateCodeSection(uintptr_t Size, unsigned Alignment, 120 unsigned SectionID, 121 StringRef SectionName) override; 122 123 /// Allocates a memory block of (at least) the given size suitable for 124 /// executable code. 125 /// 126 /// The value of \p Alignment must be a power of two. If \p Alignment is zero 127 /// a default alignment of 16 will be used. 128 uint8_t *allocateDataSection(uintptr_t Size, unsigned Alignment, 129 unsigned SectionID, StringRef SectionName, 130 bool isReadOnly) override; 131 132 /// Update section-specific memory permissions and other attributes. 133 /// 134 /// This method is called when object loading is complete and section page 135 /// permissions can be applied. It is up to the memory manager implementation 136 /// to decide whether or not to act on this method. The memory manager will 137 /// typically allocate all sections as read-write and then apply specific 138 /// permissions when this method is called. Code sections cannot be executed 139 /// until this function has been called. In addition, any cache coherency 140 /// operations needed to reliably use the memory are also performed. 141 /// 142 /// \returns true if an error occurred, false otherwise. 143 bool finalizeMemory(std::string *ErrMsg = nullptr) override; 144 145 /// Invalidate instruction cache for code sections. 146 /// 147 /// Some platforms with separate data cache and instruction cache require 148 /// explicit cache flush, otherwise JIT code manipulations (like resolved 149 /// relocations) will get to the data cache but not to the instruction cache. 150 /// 151 /// This method is called from finalizeMemory. 152 virtual void invalidateInstructionCache(); 153 154 private: 155 struct FreeMemBlock { 156 // The actual block of free memory 157 sys::MemoryBlock Free; 158 // If there is a pending allocation from the same reservation right before 159 // this block, store it's index in PendingMem, to be able to update the 160 // pending region if part of this block is allocated, rather than having to 161 // create a new one 162 unsigned PendingPrefixIndex; 163 }; 164 165 struct MemoryGroup { 166 // PendingMem contains all blocks of memory (subblocks of AllocatedMem) 167 // which have not yet had their permissions applied, but have been given 168 // out to the user. FreeMem contains all block of memory, which have 169 // neither had their permissions applied, nor been given out to the user. 170 SmallVector<sys::MemoryBlock, 16> PendingMem; 171 SmallVector<FreeMemBlock, 16> FreeMem; 172 173 // All memory blocks that have been requested from the system 174 SmallVector<sys::MemoryBlock, 16> AllocatedMem; 175 176 sys::MemoryBlock Near; 177 }; 178 179 uint8_t *allocateSection(AllocationPurpose Purpose, uintptr_t Size, 180 unsigned Alignment); 181 182 std::error_code applyMemoryGroupPermissions(MemoryGroup &MemGroup, 183 unsigned Permissions); 184 185 void anchor() override; 186 187 MemoryGroup CodeMem; 188 MemoryGroup RWDataMem; 189 MemoryGroup RODataMem; 190 MemoryMapper &MMapper; 191 }; 192 193 } // end namespace llvm 194 195 #endif // LLVM_EXECUTION_ENGINE_SECTION_MEMORY_MANAGER_H 196
