1 //===- SectionMemoryManager.cpp - Memory manager for MCJIT/RtDyld *- C++ -*-==//
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
7 //===----------------------------------------------------------------------===//
9 // This file implements the section-based memory manager used by the MCJIT
10 // execution engine and RuntimeDyld
12 //===----------------------------------------------------------------------===//
14 #include "llvm/ExecutionEngine/SectionMemoryManager.h"
15 #include "llvm/Config/config.h"
16 #include "llvm/Support/MathExtras.h"
17 #include "llvm/Support/Process.h"
21 uint8_t *SectionMemoryManager::allocateDataSection(uintptr_t Size,
24 StringRef SectionName,
27 return allocateSection(SectionMemoryManager::AllocationPurpose::ROData,
29 return allocateSection(SectionMemoryManager::AllocationPurpose::RWData, Size,
33 uint8_t *SectionMemoryManager::allocateCodeSection(uintptr_t Size,
36 StringRef SectionName) {
37 return allocateSection(SectionMemoryManager::AllocationPurpose::Code, Size,
41 uint8_t *SectionMemoryManager::allocateSection(
42 SectionMemoryManager::AllocationPurpose Purpose, uintptr_t Size,
47 assert(!(Alignment & (Alignment - 1)) && "Alignment must be a power of two.");
49 uintptr_t RequiredSize = Alignment * ((Size + Alignment - 1) / Alignment + 1);
52 MemoryGroup &MemGroup = [&]() -> MemoryGroup & {
54 case AllocationPurpose::Code:
56 case AllocationPurpose::ROData:
58 case AllocationPurpose::RWData:
61 llvm_unreachable("Unknown SectionMemoryManager::AllocationPurpose");
64 // Look in the list of free memory regions and use a block there if one
66 for (FreeMemBlock &FreeMB : MemGroup.FreeMem) {
67 if (FreeMB.Free.allocatedSize() >= RequiredSize) {
68 Addr = (uintptr_t)FreeMB.Free.base();
69 uintptr_t EndOfBlock = Addr + FreeMB.Free.allocatedSize();
71 Addr = (Addr + Alignment - 1) & ~(uintptr_t)(Alignment - 1);
73 if (FreeMB.PendingPrefixIndex == (unsigned)-1) {
74 // The part of the block we're giving out to the user is now pending
75 MemGroup.PendingMem.push_back(sys::MemoryBlock((void *)Addr, Size));
77 // Remember this pending block, such that future allocations can just
78 // modify it rather than creating a new one
79 FreeMB.PendingPrefixIndex = MemGroup.PendingMem.size() - 1;
81 sys::MemoryBlock &PendingMB =
82 MemGroup.PendingMem[FreeMB.PendingPrefixIndex];
83 PendingMB = sys::MemoryBlock(PendingMB.base(),
84 Addr + Size - (uintptr_t)PendingMB.base());
87 // Remember how much free space is now left in this block
89 sys::MemoryBlock((void *)(Addr + Size), EndOfBlock - Addr - Size);
90 return (uint8_t *)Addr;
94 // No pre-allocated free block was large enough. Allocate a new memory region.
95 // Note that all sections get allocated as read-write. The permissions will
96 // be updated later based on memory group.
98 // FIXME: It would be useful to define a default allocation size (or add
99 // it as a constructor parameter) to minimize the number of allocations.
101 // FIXME: Initialize the Near member for each memory group to avoid
104 sys::MemoryBlock MB = MMapper.allocateMappedMemory(
105 Purpose, RequiredSize, &MemGroup.Near,
106 sys::Memory::MF_READ | sys::Memory::MF_WRITE, ec);
108 // FIXME: Add error propagation to the interface.
112 // Save this address as the basis for our next request
115 // Remember that we allocated this memory
116 MemGroup.AllocatedMem.push_back(MB);
117 Addr = (uintptr_t)MB.base();
118 uintptr_t EndOfBlock = Addr + MB.allocatedSize();
120 // Align the address.
121 Addr = (Addr + Alignment - 1) & ~(uintptr_t)(Alignment - 1);
123 // The part of the block we're giving out to the user is now pending
124 MemGroup.PendingMem.push_back(sys::MemoryBlock((void *)Addr, Size));
126 // The allocateMappedMemory may allocate much more memory than we need. In
127 // this case, we store the unused memory as a free memory block.
128 unsigned FreeSize = EndOfBlock - Addr - Size;
131 FreeMB.Free = sys::MemoryBlock((void *)(Addr + Size), FreeSize);
132 FreeMB.PendingPrefixIndex = (unsigned)-1;
133 MemGroup.FreeMem.push_back(FreeMB);
136 // Return aligned address
137 return (uint8_t *)Addr;
140 bool SectionMemoryManager::finalizeMemory(std::string *ErrMsg) {
141 // FIXME: Should in-progress permissions be reverted if an error occurs?
144 // Make code memory executable.
145 ec = applyMemoryGroupPermissions(CodeMem,
146 sys::Memory::MF_READ | sys::Memory::MF_EXEC);
149 *ErrMsg = ec.message();
154 // Make read-only data memory read-only.
155 ec = applyMemoryGroupPermissions(RODataMem,
156 sys::Memory::MF_READ | sys::Memory::MF_EXEC);
159 *ErrMsg = ec.message();
164 // Read-write data memory already has the correct permissions
166 // Some platforms with separate data cache and instruction cache require
167 // explicit cache flush, otherwise JIT code manipulations (like resolved
168 // relocations) will get to the data cache but not to the instruction cache.
169 invalidateInstructionCache();
174 static sys::MemoryBlock trimBlockToPageSize(sys::MemoryBlock M) {
175 static const size_t PageSize = sys::Process::getPageSizeEstimate();
177 size_t StartOverlap =
178 (PageSize - ((uintptr_t)M.base() % PageSize)) % PageSize;
180 size_t TrimmedSize = M.allocatedSize();
181 TrimmedSize -= StartOverlap;
182 TrimmedSize -= TrimmedSize % PageSize;
184 sys::MemoryBlock Trimmed((void *)((uintptr_t)M.base() + StartOverlap),
187 assert(((uintptr_t)Trimmed.base() % PageSize) == 0);
188 assert((Trimmed.allocatedSize() % PageSize) == 0);
189 assert(M.base() <= Trimmed.base() &&
190 Trimmed.allocatedSize() <= M.allocatedSize());
196 SectionMemoryManager::applyMemoryGroupPermissions(MemoryGroup &MemGroup,
197 unsigned Permissions) {
198 for (sys::MemoryBlock &MB : MemGroup.PendingMem)
199 if (std::error_code EC = MMapper.protectMappedMemory(MB, Permissions))
202 MemGroup.PendingMem.clear();
204 // Now go through free blocks and trim any of them that don't span the entire
205 // page because one of the pending blocks may have overlapped it.
206 for (FreeMemBlock &FreeMB : MemGroup.FreeMem) {
207 FreeMB.Free = trimBlockToPageSize(FreeMB.Free);
208 // We cleared the PendingMem list, so all these pointers are now invalid
209 FreeMB.PendingPrefixIndex = (unsigned)-1;
212 // Remove all blocks which are now empty
213 MemGroup.FreeMem.erase(remove_if(MemGroup.FreeMem,
214 [](FreeMemBlock &FreeMB) {
215 return FreeMB.Free.allocatedSize() == 0;
217 MemGroup.FreeMem.end());
219 return std::error_code();
222 void SectionMemoryManager::invalidateInstructionCache() {
223 for (sys::MemoryBlock &Block : CodeMem.PendingMem)
224 sys::Memory::InvalidateInstructionCache(Block.base(),
225 Block.allocatedSize());
228 SectionMemoryManager::~SectionMemoryManager() {
229 for (MemoryGroup *Group : {&CodeMem, &RWDataMem, &RODataMem}) {
230 for (sys::MemoryBlock &Block : Group->AllocatedMem)
231 MMapper.releaseMappedMemory(Block);
235 SectionMemoryManager::MemoryMapper::~MemoryMapper() {}
237 void SectionMemoryManager::anchor() {}
240 // Trivial implementation of SectionMemoryManager::MemoryMapper that just calls
242 class DefaultMMapper final : public SectionMemoryManager::MemoryMapper {
245 allocateMappedMemory(SectionMemoryManager::AllocationPurpose Purpose,
246 size_t NumBytes, const sys::MemoryBlock *const NearBlock,
247 unsigned Flags, std::error_code &EC) override {
248 return sys::Memory::allocateMappedMemory(NumBytes, NearBlock, Flags, EC);
251 std::error_code protectMappedMemory(const sys::MemoryBlock &Block,
252 unsigned Flags) override {
253 return sys::Memory::protectMappedMemory(Block, Flags);
256 std::error_code releaseMappedMemory(sys::MemoryBlock &M) override {
257 return sys::Memory::releaseMappedMemory(M);
261 DefaultMMapper DefaultMMapperInstance;
264 SectionMemoryManager::SectionMemoryManager(MemoryMapper *MM)
265 : MMapper(MM ? *MM : DefaultMMapperInstance) {}