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