SectionMemoryManager.cpp revision 36b56886974eae4f9c5ebc96befd3e7bfe5de338 
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"
16#include "llvm/ExecutionEngine/SectionMemoryManager.h"
17#include "llvm/Support/MathExtras.h"
18
19namespace llvm {
20
21uint8_t *SectionMemoryManager::allocateDataSection(uintptr_t Size,
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
31uint8_t *SectionMemoryManager::allocateCodeSection(uintptr_t Size,
32                                                   unsigned Alignment,
33                                                   unsigned SectionID,
34                                                   StringRef SectionName) {
35  return allocateSection(CodeMem, Size, Alignment);
36}
37
38uint8_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  error_code ec;
75  sys::MemoryBlock MB = sys::Memory::allocateMappedMemory(RequiredSize,
76                                                          &MemGroup.Near,
77                                                          sys::Memory::MF_READ |
78                                                            sys::Memory::MF_WRITE,
79                                                          ec);
80  if (ec) {
81    // FIXME: Add error propagation to the interface.
82    return NULL;
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
105bool SectionMemoryManager::finalizeMemory(std::string *ErrMsg)
106{
107  // FIXME: Should in-progress permissions be reverted if an error occurs?
108  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,
115                                   sys::Memory::MF_READ | sys::Memory::MF_EXEC);
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,
128                                   sys::Memory::MF_READ | sys::Memory::MF_EXEC);
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.
141  invalidateInstructionCache();
142
143  return false;
144}
145
146error_code SectionMemoryManager::applyMemoryGroupPermissions(MemoryGroup &MemGroup,
147                                                             unsigned Permissions) {
148
149  for (int i = 0, e = MemGroup.AllocatedMem.size(); i != e; ++i) {
150      error_code ec;
151      ec = sys::Memory::protectMappedMemory(MemGroup.AllocatedMem[i],
152                                            Permissions);
153      if (ec) {
154        return ec;
155      }
156  }
157
158  return error_code::success();
159}
160
161void SectionMemoryManager::invalidateInstructionCache() {
162  for (int i = 0, e = CodeMem.AllocatedMem.size(); i != e; ++i)
163    sys::Memory::InvalidateInstructionCache(CodeMem.AllocatedMem[i].base(),
164                                            CodeMem.AllocatedMem[i].size());
165}
166
167SectionMemoryManager::~SectionMemoryManager() {
168  for (unsigned i = 0, e = CodeMem.AllocatedMem.size(); i != e; ++i)
169    sys::Memory::releaseMappedMemory(CodeMem.AllocatedMem[i]);
170  for (unsigned i = 0, e = RWDataMem.AllocatedMem.size(); i != e; ++i)
171    sys::Memory::releaseMappedMemory(RWDataMem.AllocatedMem[i]);
172  for (unsigned i = 0, e = RODataMem.AllocatedMem.size(); i != e; ++i)
173    sys::Memory::releaseMappedMemory(RODataMem.AllocatedMem[i]);
174}
175
176} // namespace llvm
177
178