Function EraVirtualFreeEx

projects/WinDurango.KernelX/src/kernelx.cpp:353–392

        if (!hMap)
        {
            SetLastError(ERROR_OUTOFMEMORY);
            return nullptr;
        }

        for (SIZE_T dwOffset = 0; dwOffset < dwSize; dwOffset += dwPageSize)
        {
            LPVOID PageAddress = (LPBYTE)lpAddress + dwOffset;
            MapViewOfFile3(hMap, hProcess, PageAddress, dwOffset, dwPageSize, MEM_REPLACE_PLACEHOLDER, PAGE_READWRITE,
                           nullptr, 0);
            VirtualAlloc2(hProcess, PageAddress, dwPageSize, MEM_COMMIT, flProtect & PAGE_MASK, nullptr, 0);
        }

        CloseHandle(hMap);
    }

    return lpAddress;
}

EXTERN_C LPVOID __stdcall EraVirtualAlloc(LPVOID lpAddress, SIZE_T dwSize, DWORD flAllocationType, DWORD flProtect)
{
    return EraVirtualAllocEx(GetCurrentProcess(), lpAddress, dwSize, flAllocationType, flProtect);
}

EXTERN_C BOOL __stdcall EraVirtualFreeEx(HANDLE hProcess, LPVOID lpAddress, SIZE_T dwSize, DWORD dwFreeType)
{
    LPVOID AllocationBase;
    MAPPABLE_MEM Mappable;
    AcquireSRWLockShared(&XwpMappableLock);
    AllocationBase = MappableQuery(lpAddress, &Mappable);
    ReleaseSRWLockShared(&XwpMappableLock);

    // If we have a mappable allocation, we need to ensure it is unmapped first.
    if (AllocationBase)
    {
        ULONG_PTR PageSize = Mappable.Is4MBPages ? PAGE_SIZE_4MB : PAGE_SIZE_64K;
        ULONG_PTR BasePage = (ULONG_PTR)lpAddress & ~(PageSize - 1);

        if (dwFreeType == MEM_RELEASE && (AllocationBase != lpAddress || dwSize))
            return FALSE;

        if (dwFreeType == MEM_RELEASE || (dwFreeType == MEM_DECOMMIT && !dwSize))
            dwSize = Mappable.RegionSize - ((ULONG_PTR)BasePage - (ULONG_PTR)AllocationBase);