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
21namespace llvm {
22namespace 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