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
24namespace 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.
39class SectionMemoryManager : public RTDyldMemoryManager {
40public:
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
152private:
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};
190
191} // end namespace llvm
192
193#endif // LLVM_EXECUTIONENGINE_SECTIONMEMORYMANAGER_H
194