1 //===- llvm/Support/Memory.h - Memory Support --------------------*- 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 declares the llvm::sys::Memory class. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #ifndef LLVM_SUPPORT_MEMORY_H 15 #define LLVM_SUPPORT_MEMORY_H 16 17 #include "llvm/Support/DataTypes.h" 18 #include <string> 19 #include <system_error> 20 21 namespace llvm { 22 namespace sys { 23 24 /// This class encapsulates the notion of a memory block which has an address 25 /// and a size. It is used by the Memory class (a friend) as the result of 26 /// various memory allocation operations. 27 /// @see Memory 28 /// @brief Memory block abstraction. 29 class MemoryBlock { 30 public: 31 MemoryBlock() : Address(nullptr), Size(0) { } 32 MemoryBlock(void *addr, size_t size) : Address(addr), Size(size) { } 33 void *base() const { return Address; } 34 size_t size() const { return Size; } 35 private: 36 void *Address; ///< Address of first byte of memory area 37 size_t Size; ///< Size, in bytes of the memory area 38 friend class Memory; 39 }; 40 41 /// This class provides various memory handling functions that manipulate 42 /// MemoryBlock instances. 43 /// @since 1.4 44 /// @brief An abstraction for memory operations. 45 class Memory { 46 public: 47 enum ProtectionFlags { 48 MF_READ = 0x1000000, 49 MF_WRITE = 0x2000000, 50 MF_EXEC = 0x4000000 51 }; 52 53 /// This method allocates a block of memory that is suitable for loading 54 /// dynamically generated code (e.g. JIT). An attempt to allocate 55 /// \p NumBytes bytes of virtual memory is made. 56 /// \p NearBlock may point to an existing allocation in which case 57 /// 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. 60 /// \p Flags is used to set the initial protection flags for the block 61 /// of the memory. 62 /// \p EC [out] returns an object describing any error that occurs. 63 /// 64 /// This method may allocate more than the number of bytes requested. The 65 /// actual number of bytes allocated is indicated in the returned 66 /// MemoryBlock. 67 /// 68 /// The start of the allocated block must be aligned with the 69 /// system allocation granularity (64K on Windows, page size on Linux). 70 /// If the address following \p NearBlock is not so aligned, it will be 71 /// rounded up to the next allocation granularity boundary. 72 /// 73 /// \r a non-null MemoryBlock if the function was successful, 74 /// otherwise a null MemoryBlock is with \p EC describing the error. 75 /// 76 /// @brief Allocate mapped memory. 77 static MemoryBlock allocateMappedMemory(size_t NumBytes, 78 const MemoryBlock *const NearBlock, 79 unsigned Flags, 80 std::error_code &EC); 81 82 /// This method releases a block of memory that was allocated with the 83 /// allocateMappedMemory method. It should not be used to release any 84 /// memory block allocated any other way. 85 /// \p Block describes the memory to be released. 86 /// 87 /// \r error_success if the function was successful, or an error_code 88 /// describing the failure if an error occurred. 89 /// 90 /// @brief Release mapped memory. 91 static std::error_code releaseMappedMemory(MemoryBlock &Block); 92 93 /// This method sets the protection flags for a block of memory to the 94 /// state specified by /p Flags. The behavior is not specified if the 95 /// memory was not allocated using the allocateMappedMemory method. 96 /// \p Block describes the memory block to be protected. 97 /// \p Flags specifies the new protection state to be assigned to the block. 98 /// \p ErrMsg [out] returns a string describing any error that occurred. 99 /// 100 /// If \p Flags is MF_WRITE, the actual behavior varies 101 /// with the operating system (i.e. MF_READ | MF_WRITE on Windows) and the 102 /// target architecture (i.e. MF_WRITE -> MF_READ | MF_WRITE on i386). 103 /// 104 /// \r error_success if the function was successful, or an error_code 105 /// describing the failure if an error occurred. 106 /// 107 /// @brief Set memory protection state. 108 static std::error_code protectMappedMemory(const MemoryBlock &Block, 109 unsigned Flags); 110 111 /// This method allocates a block of Read/Write/Execute memory that is 112 /// suitable for executing dynamically generated code (e.g. JIT). An 113 /// attempt to allocate \p NumBytes bytes of virtual memory is made. 114 /// \p NearBlock may point to an existing allocation in which case 115 /// an attempt is made to allocate more memory near the existing block. 116 /// 117 /// On success, this returns a non-null memory block, otherwise it returns 118 /// a null memory block and fills in *ErrMsg. 119 /// 120 /// @brief Allocate Read/Write/Execute memory. 121 static MemoryBlock AllocateRWX(size_t NumBytes, 122 const MemoryBlock *NearBlock, 123 std::string *ErrMsg = nullptr); 124 125 /// This method releases a block of Read/Write/Execute memory that was 126 /// allocated with the AllocateRWX method. It should not be used to 127 /// release any memory block allocated any other way. 128 /// 129 /// On success, this returns false, otherwise it returns true and fills 130 /// in *ErrMsg. 131 /// @brief Release Read/Write/Execute memory. 132 static bool ReleaseRWX(MemoryBlock &block, std::string *ErrMsg = nullptr); 133 134 135 /// InvalidateInstructionCache - Before the JIT can run a block of code 136 /// that has been emitted it must invalidate the instruction cache on some 137 /// platforms. 138 static void InvalidateInstructionCache(const void *Addr, size_t Len); 139 140 /// setExecutable - Before the JIT can run a block of code, it has to be 141 /// given read and executable privilege. Return true if it is already r-x 142 /// or the system is able to change its previlege. 143 static bool setExecutable(MemoryBlock &M, std::string *ErrMsg = nullptr); 144 145 /// setWritable - When adding to a block of code, the JIT may need 146 /// to mark a block of code as RW since the protections are on page 147 /// boundaries, and the JIT internal allocations are not page aligned. 148 static bool setWritable(MemoryBlock &M, std::string *ErrMsg = nullptr); 149 150 /// setRangeExecutable - Mark the page containing a range of addresses 151 /// as executable. 152 static bool setRangeExecutable(const void *Addr, size_t Size); 153 154 /// setRangeWritable - Mark the page containing a range of addresses 155 /// as writable. 156 static bool setRangeWritable(const void *Addr, size_t Size); 157 }; 158 } 159 } 160 161 #endif 162
