LLVM  3.7.0
SectionMemoryManager.cpp
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1 //===- SectionMemoryManager.cpp - Memory manager for MCJIT/RtDyld *- 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 implements the section-based memory manager used by the MCJIT
11 // execution engine and RuntimeDyld
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "llvm/Config/config.h"
18 
19 namespace llvm {
20 
22  unsigned Alignment,
23  unsigned SectionID,
24  StringRef SectionName,
25  bool IsReadOnly) {
26  if (IsReadOnly)
27  return allocateSection(RODataMem, Size, Alignment);
28  return allocateSection(RWDataMem, Size, Alignment);
29 }
30 
32  unsigned Alignment,
33  unsigned SectionID,
34  StringRef SectionName) {
35  return allocateSection(CodeMem, Size, Alignment);
36 }
37 
38 uint8_t *SectionMemoryManager::allocateSection(MemoryGroup &MemGroup,
39  uintptr_t Size,
40  unsigned Alignment) {
41  if (!Alignment)
42  Alignment = 16;
43 
44  assert(!(Alignment & (Alignment - 1)) && "Alignment must be a power of two.");
45 
46  uintptr_t RequiredSize = Alignment * ((Size + Alignment - 1)/Alignment + 1);
47  uintptr_t Addr = 0;
48 
49  // Look in the list of free memory regions and use a block there if one
50  // is available.
51  for (int i = 0, e = MemGroup.FreeMem.size(); i != e; ++i) {
52  sys::MemoryBlock &MB = MemGroup.FreeMem[i];
53  if (MB.size() >= RequiredSize) {
54  Addr = (uintptr_t)MB.base();
55  uintptr_t EndOfBlock = Addr + MB.size();
56  // Align the address.
57  Addr = (Addr + Alignment - 1) & ~(uintptr_t)(Alignment - 1);
58  // Store cutted free memory block.
59  MemGroup.FreeMem[i] = sys::MemoryBlock((void*)(Addr + Size),
60  EndOfBlock - Addr - Size);
61  return (uint8_t*)Addr;
62  }
63  }
64 
65  // No pre-allocated free block was large enough. Allocate a new memory region.
66  // Note that all sections get allocated as read-write. The permissions will
67  // be updated later based on memory group.
68  //
69  // FIXME: It would be useful to define a default allocation size (or add
70  // it as a constructor parameter) to minimize the number of allocations.
71  //
72  // FIXME: Initialize the Near member for each memory group to avoid
73  // interleaving.
74  std::error_code ec;
75  sys::MemoryBlock MB = sys::Memory::allocateMappedMemory(RequiredSize,
76  &MemGroup.Near,
79  ec);
80  if (ec) {
81  // FIXME: Add error propagation to the interface.
82  return nullptr;
83  }
84 
85  // Save this address as the basis for our next request
86  MemGroup.Near = MB;
87 
88  MemGroup.AllocatedMem.push_back(MB);
89  Addr = (uintptr_t)MB.base();
90  uintptr_t EndOfBlock = Addr + MB.size();
91 
92  // Align the address.
93  Addr = (Addr + Alignment - 1) & ~(uintptr_t)(Alignment - 1);
94 
95  // The allocateMappedMemory may allocate much more memory than we need. In
96  // this case, we store the unused memory as a free memory block.
97  unsigned FreeSize = EndOfBlock-Addr-Size;
98  if (FreeSize > 16)
99  MemGroup.FreeMem.push_back(sys::MemoryBlock((void*)(Addr + Size), FreeSize));
100 
101  // Return aligned address
102  return (uint8_t*)Addr;
103 }
104 
105 bool SectionMemoryManager::finalizeMemory(std::string *ErrMsg)
106 {
107  // FIXME: Should in-progress permissions be reverted if an error occurs?
108  std::error_code ec;
109 
110  // Don't allow free memory blocks to be used after setting protection flags.
111  CodeMem.FreeMem.clear();
112 
113  // Make code memory executable.
114  ec = applyMemoryGroupPermissions(CodeMem,
116  if (ec) {
117  if (ErrMsg) {
118  *ErrMsg = ec.message();
119  }
120  return true;
121  }
122 
123  // Don't allow free memory blocks to be used after setting protection flags.
124  RODataMem.FreeMem.clear();
125 
126  // Make read-only data memory read-only.
127  ec = applyMemoryGroupPermissions(RODataMem,
129  if (ec) {
130  if (ErrMsg) {
131  *ErrMsg = ec.message();
132  }
133  return true;
134  }
135 
136  // Read-write data memory already has the correct permissions
137 
138  // Some platforms with separate data cache and instruction cache require
139  // explicit cache flush, otherwise JIT code manipulations (like resolved
140  // relocations) will get to the data cache but not to the instruction cache.
142 
143  return false;
144 }
145 
146 std::error_code
147 SectionMemoryManager::applyMemoryGroupPermissions(MemoryGroup &MemGroup,
148  unsigned Permissions) {
149 
150  for (int i = 0, e = MemGroup.AllocatedMem.size(); i != e; ++i) {
151  std::error_code ec;
152  ec =
153  sys::Memory::protectMappedMemory(MemGroup.AllocatedMem[i], Permissions);
154  if (ec) {
155  return ec;
156  }
157  }
158 
159  return std::error_code();
160 }
161 
163  for (int i = 0, e = CodeMem.AllocatedMem.size(); i != e; ++i)
164  sys::Memory::InvalidateInstructionCache(CodeMem.AllocatedMem[i].base(),
165  CodeMem.AllocatedMem[i].size());
166 }
167 
169  for (unsigned i = 0, e = CodeMem.AllocatedMem.size(); i != e; ++i)
170  sys::Memory::releaseMappedMemory(CodeMem.AllocatedMem[i]);
171  for (unsigned i = 0, e = RWDataMem.AllocatedMem.size(); i != e; ++i)
172  sys::Memory::releaseMappedMemory(RWDataMem.AllocatedMem[i]);
173  for (unsigned i = 0, e = RODataMem.AllocatedMem.size(); i != e; ++i)
174  sys::Memory::releaseMappedMemory(RODataMem.AllocatedMem[i]);
175 }
176 
177 } // namespace llvm
178 
static std::error_code releaseMappedMemory(MemoryBlock &Block)
This method releases a block of memory that was allocated with the allocateMappedMemory method...
static MemoryBlock allocateMappedMemory(size_t NumBytes, const MemoryBlock *const NearBlock, unsigned Flags, std::error_code &EC)
This method allocates a block of memory that is suitable for loading dynamically generated code (e...
static void InvalidateInstructionCache(const void *Addr, size_t Len)
InvalidateInstructionCache - Before the JIT can run a block of code that has been emitted it must inv...
virtual void invalidateInstructionCache()
Invalidate instruction cache for code sections.
uint8_t * allocateCodeSection(uintptr_t Size, unsigned Alignment, unsigned SectionID, StringRef SectionName) override
Allocates a memory block of (at least) the given size suitable for executable code.
uint8_t * allocateDataSection(uintptr_t Size, unsigned Alignment, unsigned SectionID, StringRef SectionName, bool isReadOnly) override
Allocates a memory block of (at least) the given size suitable for executable code.
size_t size() const
Definition: Memory.h:34
This class encapsulates the notion of a memory block which has an address and a size.
Definition: Memory.h:29
void * base() const
Definition: Memory.h:33
bool finalizeMemory(std::string *ErrMsg=nullptr) override
Update section-specific memory permissions and other attributes.
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:40
static std::error_code protectMappedMemory(const MemoryBlock &Block, unsigned Flags)
This method sets the protection flags for a block of memory to the state specified by /p Flags...