Memory.inc revision 355940 
1//===- Win32/Memory.cpp - Win32 Memory Implementation -----------*- 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 provides the Win32 specific implementation of various Memory
10// management utilities
11//
12//===----------------------------------------------------------------------===//
13
14#include "llvm/Support/DataTypes.h"
15#include "llvm/Support/ErrorHandling.h"
16#include "llvm/Support/Process.h"
17#include "llvm/Support/WindowsError.h"
18
19// The Windows.h header must be the last one included.
20#include "WindowsSupport.h"
21
22namespace {
23
24DWORD getWindowsProtectionFlags(unsigned Flags) {
25  switch (Flags & llvm::sys::Memory::MF_RWE_MASK) {
26  // Contrary to what you might expect, the Windows page protection flags
27  // are not a bitwise combination of RWX values
28  case llvm::sys::Memory::MF_READ:
29    return PAGE_READONLY;
30  case llvm::sys::Memory::MF_WRITE:
31    // Note: PAGE_WRITE is not supported by VirtualProtect
32    return PAGE_READWRITE;
33  case llvm::sys::Memory::MF_READ|llvm::sys::Memory::MF_WRITE:
34    return PAGE_READWRITE;
35  case llvm::sys::Memory::MF_READ|llvm::sys::Memory::MF_EXEC:
36    return PAGE_EXECUTE_READ;
37  case llvm::sys::Memory::MF_READ |
38         llvm::sys::Memory::MF_WRITE |
39         llvm::sys::Memory::MF_EXEC:
40    return PAGE_EXECUTE_READWRITE;
41  case llvm::sys::Memory::MF_EXEC:
42    return PAGE_EXECUTE;
43  default:
44    llvm_unreachable("Illegal memory protection flag specified!");
45  }
46  // Provide a default return value as required by some compilers.
47  return PAGE_NOACCESS;
48}
49
50// While we'd be happy to allocate single pages, the Windows allocation
51// granularity may be larger than a single page (in practice, it is 64K)
52// so mapping less than that will create an unreachable fragment of memory.
53size_t getAllocationGranularity() {
54  SYSTEM_INFO  Info;
55  ::GetSystemInfo(&Info);
56  if (Info.dwPageSize > Info.dwAllocationGranularity)
57    return Info.dwPageSize;
58  else
59    return Info.dwAllocationGranularity;
60}
61
62// Large/huge memory pages need explicit process permissions in order to be
63// used. See https://blogs.msdn.microsoft.com/oldnewthing/20110128-00/?p=11643
64// Also large pages need to be manually enabled on your OS. If all this is
65// sucessfull, we return the minimal large memory page size.
66static size_t enableProcessLargePages() {
67  HANDLE Token = 0;
68  size_t LargePageMin = GetLargePageMinimum();
69  if (LargePageMin)
70    OpenProcessToken(GetCurrentProcess(), TOKEN_ADJUST_PRIVILEGES | TOKEN_QUERY,
71                     &Token);
72  if (!Token)
73    return 0;
74  LUID Luid;
75  if (!LookupPrivilegeValue(0, SE_LOCK_MEMORY_NAME, &Luid)) {
76    CloseHandle(Token);
77    return 0;
78  }
79  TOKEN_PRIVILEGES TP{};
80  TP.PrivilegeCount = 1;
81  TP.Privileges[0].Luid = Luid;
82  TP.Privileges[0].Attributes = SE_PRIVILEGE_ENABLED;
83  if (!AdjustTokenPrivileges(Token, FALSE, &TP, 0, 0, 0)) {
84    CloseHandle(Token);
85    return 0;
86  }
87  DWORD E = GetLastError();
88  CloseHandle(Token);
89  if (E == ERROR_SUCCESS)
90    return LargePageMin;
91  return 0;
92}
93
94} // namespace
95
96namespace llvm {
97namespace sys {
98
99//===----------------------------------------------------------------------===//
100//=== WARNING: Implementation here must contain only Win32 specific code
101//===          and must not be UNIX code
102//===----------------------------------------------------------------------===//
103
104MemoryBlock Memory::allocateMappedMemory(size_t NumBytes,
105                                         const MemoryBlock *const NearBlock,
106                                         unsigned Flags,
107                                         std::error_code &EC) {
108  EC = std::error_code();
109  if (NumBytes == 0)
110    return MemoryBlock();
111
112  static size_t DefaultGranularity = getAllocationGranularity();
113  static size_t LargePageGranularity = enableProcessLargePages();
114
115  DWORD AllocType = MEM_RESERVE | MEM_COMMIT;
116  bool HugePages = false;
117  size_t Granularity = DefaultGranularity;
118
119  if ((Flags & MF_HUGE_HINT) && LargePageGranularity > 0) {
120    AllocType |= MEM_LARGE_PAGES;
121    HugePages = true;
122    Granularity = LargePageGranularity;
123  }
124
125  size_t NumBlocks = (NumBytes + Granularity - 1) / Granularity;
126
127  uintptr_t Start = NearBlock ? reinterpret_cast<uintptr_t>(NearBlock->base()) +
128                                NearBlock->allocatedSize()
129                           : 0;
130
131  // If the requested address is not aligned to the allocation granularity,
132  // round up to get beyond NearBlock. VirtualAlloc would have rounded down.
133  if (Start && Start % Granularity != 0)
134    Start += Granularity - Start % Granularity;
135
136  DWORD Protect = getWindowsProtectionFlags(Flags);
137
138  size_t AllocSize = NumBlocks * Granularity;
139  void *PA = ::VirtualAlloc(reinterpret_cast<void *>(Start),
140                            AllocSize, AllocType, Protect);
141  if (PA == NULL) {
142    if (NearBlock || HugePages) {
143      // Try again without the NearBlock hint and without large memory pages
144      return allocateMappedMemory(NumBytes, NULL, Flags & ~MF_HUGE_HINT, EC);
145    }
146    EC = mapWindowsError(::GetLastError());
147    return MemoryBlock();
148  }
149
150  MemoryBlock Result;
151  Result.Address = PA;
152  Result.AllocatedSize = AllocSize;
153  Result.Flags = (Flags & ~MF_HUGE_HINT) | (HugePages ? MF_HUGE_HINT : 0);
154
155  if (Flags & MF_EXEC)
156    Memory::InvalidateInstructionCache(Result.Address, AllocSize);
157
158  return Result;
159}
160
161  std::error_code Memory::releaseMappedMemory(MemoryBlock &M) {
162  if (M.Address == 0 || M.AllocatedSize == 0)
163    return std::error_code();
164
165  if (!VirtualFree(M.Address, 0, MEM_RELEASE))
166    return mapWindowsError(::GetLastError());
167
168  M.Address = 0;
169  M.AllocatedSize = 0;
170
171  return std::error_code();
172}
173
174  std::error_code Memory::protectMappedMemory(const MemoryBlock &M,
175                                       unsigned Flags) {
176  if (M.Address == 0 || M.AllocatedSize == 0)
177    return std::error_code();
178
179  DWORD Protect = getWindowsProtectionFlags(Flags);
180
181  DWORD OldFlags;
182  if (!VirtualProtect(M.Address, M.AllocatedSize, Protect, &OldFlags))
183    return mapWindowsError(::GetLastError());
184
185  if (Flags & MF_EXEC)
186    Memory::InvalidateInstructionCache(M.Address, M.AllocatedSize);
187
188  return std::error_code();
189}
190
191/// InvalidateInstructionCache - Before the JIT can run a block of code
192/// that has been emitted it must invalidate the instruction cache on some
193/// platforms.
194void Memory::InvalidateInstructionCache(
195    const void *Addr, size_t Len) {
196  FlushInstructionCache(GetCurrentProcess(), Addr, Len);
197}
198
199} // namespace sys
200} // namespace llvm
201