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//===- Win32/Memory.cpp - Win32 Memory Implementation -----------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file provides the Win32 specific implementation of various Memory
// management utilities
//
//===----------------------------------------------------------------------===//
#include "llvm/Support/DataTypes.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/Process.h"
#include "llvm/Support/WindowsError.h"
// The Windows.h header must be the last one included.
#include "WindowsSupport.h"
static DWORD getWindowsProtectionFlags(unsigned Flags) {
switch (Flags & llvm::sys::Memory::MF_RWE_MASK) {
// Contrary to what you might expect, the Windows page protection flags
// are not a bitwise combination of RWX values
case llvm::sys::Memory::MF_READ:
return PAGE_READONLY;
case llvm::sys::Memory::MF_WRITE:
// Note: PAGE_WRITE is not supported by VirtualProtect
return PAGE_READWRITE;
case llvm::sys::Memory::MF_READ|llvm::sys::Memory::MF_WRITE:
return PAGE_READWRITE;
case llvm::sys::Memory::MF_READ|llvm::sys::Memory::MF_EXEC:
return PAGE_EXECUTE_READ;
case llvm::sys::Memory::MF_READ |
llvm::sys::Memory::MF_WRITE |
llvm::sys::Memory::MF_EXEC:
return PAGE_EXECUTE_READWRITE;
case llvm::sys::Memory::MF_EXEC:
return PAGE_EXECUTE;
default:
llvm_unreachable("Illegal memory protection flag specified!");
}
// Provide a default return value as required by some compilers.
return PAGE_NOACCESS;
}
// While we'd be happy to allocate single pages, the Windows allocation
// granularity may be larger than a single page (in practice, it is 64K)
// so mapping less than that will create an unreachable fragment of memory.
static size_t getAllocationGranularity() {
SYSTEM_INFO Info;
::GetSystemInfo(&Info);
if (Info.dwPageSize > Info.dwAllocationGranularity)
return Info.dwPageSize;
else
return Info.dwAllocationGranularity;
}
// Large/huge memory pages need explicit process permissions in order to be
// used. See https://blogs.msdn.microsoft.com/oldnewthing/20110128-00/?p=11643
// Also large pages need to be manually enabled on your OS. If all this is
// sucessfull, we return the minimal large memory page size.
static size_t enableProcessLargePages() {
HANDLE Token = 0;
size_t LargePageMin = GetLargePageMinimum();
if (LargePageMin)
OpenProcessToken(GetCurrentProcess(), TOKEN_ADJUST_PRIVILEGES | TOKEN_QUERY,
&Token);
if (!Token)
return 0;
LUID Luid;
if (!LookupPrivilegeValue(0, SE_LOCK_MEMORY_NAME, &Luid)) {
CloseHandle(Token);
return 0;
}
TOKEN_PRIVILEGES TP{};
TP.PrivilegeCount = 1;
TP.Privileges[0].Luid = Luid;
TP.Privileges[0].Attributes = SE_PRIVILEGE_ENABLED;
if (!AdjustTokenPrivileges(Token, FALSE, &TP, 0, 0, 0)) {
CloseHandle(Token);
return 0;
}
DWORD E = GetLastError();
CloseHandle(Token);
if (E == ERROR_SUCCESS)
return LargePageMin;
return 0;
}
namespace llvm {
namespace sys {
//===----------------------------------------------------------------------===//
//=== WARNING: Implementation here must contain only Win32 specific code
//=== and must not be UNIX code
//===----------------------------------------------------------------------===//
MemoryBlock Memory::allocateMappedMemory(size_t NumBytes,
const MemoryBlock *const NearBlock,
unsigned Flags,
std::error_code &EC) {
EC = std::error_code();
if (NumBytes == 0)
return MemoryBlock();
static size_t DefaultGranularity = getAllocationGranularity();
static size_t LargePageGranularity = enableProcessLargePages();
DWORD AllocType = MEM_RESERVE | MEM_COMMIT;
bool HugePages = false;
size_t Granularity = DefaultGranularity;
if ((Flags & MF_HUGE_HINT) && LargePageGranularity > 0) {
AllocType |= MEM_LARGE_PAGES;
HugePages = true;
Granularity = LargePageGranularity;
}
size_t NumBlocks = (NumBytes + Granularity - 1) / Granularity;
uintptr_t Start = NearBlock ? reinterpret_cast<uintptr_t>(NearBlock->base()) +
NearBlock->allocatedSize()
: 0;
// If the requested address is not aligned to the allocation granularity,
// round up to get beyond NearBlock. VirtualAlloc would have rounded down.
if (Start && Start % Granularity != 0)
Start += Granularity - Start % Granularity;
DWORD Protect = getWindowsProtectionFlags(Flags);
size_t AllocSize = NumBlocks * Granularity;
void *PA = ::VirtualAlloc(reinterpret_cast<void *>(Start),
AllocSize, AllocType, Protect);
if (PA == NULL) {
if (NearBlock || HugePages) {
// Try again without the NearBlock hint and without large memory pages
return allocateMappedMemory(NumBytes, NULL, Flags & ~MF_HUGE_HINT, EC);
}
EC = mapWindowsError(::GetLastError());
return MemoryBlock();
}
MemoryBlock Result;
Result.Address = PA;
Result.AllocatedSize = AllocSize;
Result.Flags = (Flags & ~MF_HUGE_HINT) | (HugePages ? MF_HUGE_HINT : 0);
if (Flags & MF_EXEC)
Memory::InvalidateInstructionCache(Result.Address, AllocSize);
return Result;
}
std::error_code Memory::releaseMappedMemory(MemoryBlock &M) {
if (M.Address == 0 || M.AllocatedSize == 0)
return std::error_code();
if (!VirtualFree(M.Address, 0, MEM_RELEASE))
return mapWindowsError(::GetLastError());
M.Address = 0;
M.AllocatedSize = 0;
return std::error_code();
}
std::error_code Memory::protectMappedMemory(const MemoryBlock &M,
unsigned Flags) {
if (M.Address == 0 || M.AllocatedSize == 0)
return std::error_code();
DWORD Protect = getWindowsProtectionFlags(Flags);
DWORD OldFlags;
if (!VirtualProtect(M.Address, M.AllocatedSize, Protect, &OldFlags))
return mapWindowsError(::GetLastError());
if (Flags & MF_EXEC)
Memory::InvalidateInstructionCache(M.Address, M.AllocatedSize);
return std::error_code();
}
/// InvalidateInstructionCache - Before the JIT can run a block of code
/// that has been emitted it must invalidate the instruction cache on some
/// platforms.
void Memory::InvalidateInstructionCache(
const void *Addr, size_t Len) {
FlushInstructionCache(GetCurrentProcess(), Addr, Len);
}
} // namespace sys
} // namespace llvm
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