LPVOID PreReservedVirtualAllocWrapper::EnsurePreReservedRegionInternal()
{
LPVOID startAddress = preReservedStartAddress;
if (startAddress != nullptr)
{
return startAddress;
}
//PreReserve a (bigger) segment
size_t bytes = PreReservedAllocationSegmentCount * AutoSystemInfo::Data.GetAllocationGranularityPageSize();
if (PHASE_FORCE1(Js::PreReservedHeapAllocPhase))
{
//This code is used where CFG is not available, but still PreReserve optimization for CFG can be tested
startAddress = VirtualAlloc(NULL, bytes, MEM_RESERVE, PAGE_READWRITE);
PreReservedHeapTrace(_u("Reserving PreReservedSegment For the first time(CFG Non-Enabled). Address: 0x%p\n"), preReservedStartAddress);
preReservedStartAddress = startAddress;
return startAddress;
}
#if defined(_CONTROL_FLOW_GUARD)
bool supportPreReservedRegion = true;
#if !TARGET_64
#if _M_IX86
// We want to restrict the number of prereserved segment for 32-bit process so that we don't use up the address space
// Note: numPreReservedSegment is for the whole process, and access and update to it is not protected by a global lock.
// So we may allocate more than the maximum some of the time if multiple thread check it simutaniously and allocate pass the limit.
// It doesn't affect functionally, and it should be OK if we exceed.
if (PreReservedVirtualAllocWrapper::numPreReservedSegment > PreReservedVirtualAllocWrapper::MaxPreReserveSegment)
{
supportPreReservedRegion = false;
}
#else
// TODO: fast check for prereserved segment is not implementated in ARM yet, so it is only enabled for x86
supportPreReservedRegion = false;
#endif // _M_IX86
#endif
if (AutoSystemInfo::Data.IsCFGEnabled() && supportPreReservedRegion)
{
startAddress = VirtualAlloc(NULL, bytes, MEM_RESERVE, PAGE_READWRITE);
PreReservedHeapTrace(_u("Reserving PreReservedSegment For the first time(CFG Enabled). Address: 0x%p\n"), preReservedStartAddress);
preReservedStartAddress = startAddress;
#if !TARGET_64
if (startAddress)
{
InterlockedIncrement(&PreReservedVirtualAllocWrapper::numPreReservedSegment);
}
#endif
}
#endif
return startAddress;
}
BOOL
PreReservedVirtualAllocWrapper::Free(LPVOID lpAddress, size_t dwSize, DWORD dwFreeType)
{
{
AutoCriticalSection autocs(&this->cs);
if (dwSize == 0)
{
Assert(false);
return FALSE;
}
if (preReservedStartAddress == nullptr)
{
Assert(false);
return FALSE;
}
Assert(dwSize % AutoSystemInfo::PageSize == 0);
#pragma warning(suppress: 6250)
#pragma warning(suppress: 28160) // Calling VirtualFreeEx without the MEM_RELEASE flag frees memory but not address descriptors (VADs)
BOOL success = VirtualFree(lpAddress, dwSize, MEM_DECOMMIT);
size_t requestedNumOfSegments = dwSize / AutoSystemInfo::Data.GetAllocationGranularityPageSize();
Assert(requestedNumOfSegments <= MAXUINT32);
if (success)
{
PreReservedHeapTrace(_u("MEM_DECOMMIT: Address: 0x%p of size: 0x%x bytes\n"), lpAddress, dwSize);
}
if (success && (dwFreeType & MEM_RELEASE) != 0)
{
Assert((uintptr_t) lpAddress >= (uintptr_t) preReservedStartAddress);
AssertMsg(((uintptr_t)lpAddress & (AutoSystemInfo::Data.GetAllocationGranularityPageCount() - 1)) == 0, "Not aligned with Allocation Granularity?");
AssertMsg(dwSize % AutoSystemInfo::Data.GetAllocationGranularityPageSize() == 0, "Release size should match the allocation granularity size");
Assert(requestedNumOfSegments != 0);
BVIndex freeSegmentsBVIndex = (BVIndex) (((uintptr_t) lpAddress - (uintptr_t) preReservedStartAddress) / AutoSystemInfo::Data.GetAllocationGranularityPageSize());
AssertMsg(freeSegmentsBVIndex < PreReservedAllocationSegmentCount, "Invalid Index ?");
freeSegments.SetRange(freeSegmentsBVIndex, static_cast<uint>(requestedNumOfSegments));
PreReservedHeapTrace(_u("MEM_RELEASE: Address: 0x%p of size: 0x%x * 0x%x bytes\n"), lpAddress, requestedNumOfSegments, AutoSystemInfo::Data.GetAllocationGranularityPageSize());
}
return success;
}
}
PreReservedVirtualAllocWrapper::~PreReservedVirtualAllocWrapper()
{
if (IsPreReservedRegionPresent())
{
BOOL success = VirtualFree(preReservedStartAddress, 0, MEM_RELEASE);
PreReservedHeapTrace(_u("MEM_RELEASE the PreReservedSegment. Start Address: 0x%p, Size: 0x%x * 0x%x bytes"), preReservedStartAddress, PreReservedAllocationSegmentCount,
AutoSystemInfo::Data.GetAllocationGranularityPageSize());
if (!success)
{
// OOP JIT TODO: check if we need to cleanup the context related to this content process
}
#if !TARGET_64 && _CONTROL_FLOW_GUARD
Assert(numPreReservedSegment > 0);
InterlockedDecrement(&PreReservedVirtualAllocWrapper::numPreReservedSegment);
#endif
}
}
PreReservedVirtualAllocWrapper::~PreReservedVirtualAllocWrapper()
{
Assert(this);
if (IsPreReservedRegionPresent())
{
BOOL success = VirtualFree(preReservedStartAddress, 0, MEM_RELEASE);
PreReservedHeapTrace(_u("MEM_RELEASE the PreReservedSegment. Start Address: 0x%p, Size: 0x%x * 0x%x bytes"), preReservedStartAddress, PreReservedAllocationSegmentCount,
AutoSystemInfo::Data.GetAllocationGranularityPageSize());
if (!success)
{
Assert(false);
}
#if !_M_X64_OR_ARM64 && _CONTROL_FLOW_GUARD
Assert(numPreReservedSegment > 0);
InterlockedDecrement(&PreReservedVirtualAllocWrapper::numPreReservedSegment);
#endif
}
}
LPVOID PreReservedVirtualAllocWrapper::Alloc(LPVOID lpAddress, size_t dwSize, DWORD allocationType, DWORD protectFlags, bool isCustomHeapAllocation)
{
Assert(this);
AssertMsg(isCustomHeapAllocation, "PreReservation used for allocations other than CustomHeap?");
AssertMsg(AutoSystemInfo::Data.IsCFGEnabled() || PHASE_FORCE1(Js::PreReservedHeapAllocPhase), "PreReservation without CFG ?");
Assert(dwSize != 0);
{
AutoCriticalSection autocs(&this->cs);
//Return nullptr, if no space to Reserve
if (EnsurePreReservedRegionInternal() == nullptr)
{
PreReservedHeapTrace(_u("No space to pre-reserve memory with %d pages. Returning NULL\n"), PreReservedAllocationSegmentCount * AutoSystemInfo::Data.GetAllocationGranularityPageCount());
return nullptr;
}
char * addressToReserve = nullptr;
uint freeSegmentsBVIndex = BVInvalidIndex;
size_t requestedNumOfSegments = dwSize / (AutoSystemInfo::Data.GetAllocationGranularityPageSize());
Assert(requestedNumOfSegments <= MAXUINT32);
if (lpAddress == nullptr)
{
Assert(requestedNumOfSegments != 0);
AssertMsg(dwSize % AutoSystemInfo::Data.GetAllocationGranularityPageSize() == 0, "dwSize should be aligned with Allocation Granularity");
do
{
freeSegmentsBVIndex = freeSegments.GetNextBit(freeSegmentsBVIndex + 1);
//Return nullptr, if we don't have free/decommit pages to allocate
if ((freeSegments.Length() - freeSegmentsBVIndex < requestedNumOfSegments) ||
freeSegmentsBVIndex == BVInvalidIndex)
{
PreReservedHeapTrace(_u("No more space to commit in PreReserved Memory region.\n"));
return nullptr;
}
} while (!freeSegments.TestRange(freeSegmentsBVIndex, static_cast<uint>(requestedNumOfSegments)));
uint offset = freeSegmentsBVIndex * AutoSystemInfo::Data.GetAllocationGranularityPageSize();
addressToReserve = (char*) preReservedStartAddress + offset;
//Check if the region is not already in MEM_COMMIT state.
MEMORY_BASIC_INFORMATION memBasicInfo;
size_t bytes = VirtualQuery(addressToReserve, &memBasicInfo, sizeof(memBasicInfo));
if (bytes == 0
|| memBasicInfo.RegionSize < requestedNumOfSegments * AutoSystemInfo::Data.GetAllocationGranularityPageSize()
|| memBasicInfo.State == MEM_COMMIT
)
{
CustomHeap_BadPageState_fatal_error((ULONG_PTR)this);
return nullptr;
}
}
else
{
//Check If the lpAddress is within the range of the preReserved Memory Region
Assert(((char*) lpAddress) >= (char*) preReservedStartAddress || ((char*) lpAddress + dwSize) < GetPreReservedEndAddress());
addressToReserve = (char*) lpAddress;
freeSegmentsBVIndex = (uint) ((addressToReserve - (char*) preReservedStartAddress) / AutoSystemInfo::Data.GetAllocationGranularityPageSize());
#if DBG
uint numOfSegments = (uint)ceil((double)dwSize / (double)AutoSystemInfo::Data.GetAllocationGranularityPageSize());
Assert(numOfSegments != 0);
Assert(freeSegmentsBVIndex + numOfSegments - 1 < freeSegments.Length());
Assert(!freeSegments.TestRange(freeSegmentsBVIndex, numOfSegments));
#endif
}
AssertMsg(freeSegmentsBVIndex < PreReservedAllocationSegmentCount, "Invalid BitVector index calculation?");
AssertMsg(dwSize % AutoSystemInfo::PageSize == 0, "COMMIT is managed at AutoSystemInfo::PageSize granularity");
char * allocatedAddress = nullptr;
if ((allocationType & MEM_COMMIT) != 0)
{
#if defined(ENABLE_JIT_CLAMP)
AutoEnableDynamicCodeGen enableCodeGen;
#endif
#if defined(_CONTROL_FLOW_GUARD)
if (AutoSystemInfo::Data.IsCFGEnabled())
{
DWORD oldProtect = 0;
DWORD allocProtectFlags = 0;
if (AutoSystemInfo::Data.IsCFGEnabled())
{
allocProtectFlags = PAGE_EXECUTE_RW_TARGETS_INVALID;
}
else
{
allocProtectFlags = PAGE_EXECUTE_READWRITE;
}
allocatedAddress = (char *)VirtualAlloc(addressToReserve, dwSize, MEM_COMMIT, allocProtectFlags);
AssertMsg(allocatedAddress != nullptr, "If no space to allocate, then how did we fetch this address from the tracking bit vector?");
VirtualProtect(allocatedAddress, dwSize, protectFlags, &oldProtect);
AssertMsg(oldProtect == (PAGE_EXECUTE_READWRITE), "CFG Bitmap gets allocated and bits will be set to invalid only upon passing these flags.");
}
else
#endif
{
allocatedAddress = (char *)VirtualAlloc(addressToReserve, dwSize, MEM_COMMIT, protectFlags);
}
}
else
{
// Just return the uncommitted address if we didn't ask to commit it.
allocatedAddress = addressToReserve;
}
// Keep track of the committed pages within the preReserved Memory Region
if (lpAddress == nullptr && allocatedAddress != nullptr)
{
Assert(allocatedAddress == addressToReserve);
Assert(requestedNumOfSegments != 0);
freeSegments.ClearRange(freeSegmentsBVIndex, static_cast<uint>(requestedNumOfSegments));
}
PreReservedHeapTrace(_u("MEM_COMMIT: StartAddress: 0x%p of size: 0x%x * 0x%x bytes \n"), allocatedAddress, requestedNumOfSegments, AutoSystemInfo::Data.GetAllocationGranularityPageSize());
return allocatedAddress;
}
}