private nint AllocateSinglePageNearAddress(nint targetAddr)
{
var sysInfo = new NativeImport.NativeStructs.SYSTEM_INFO();
NativeImport.GetSystemInfo(ref sysInfo);
nuint pageSize = sysInfo.dwPageSize;
nuint startAddr = ((nuint)targetAddr & ~(pageSize - 1));
nuint minAddr = (nuint)Math.Min((long)(startAddr - 0x7FFFFF00), sysInfo.lpMinimumApplicationAddress.ToInt64());
nuint maxAddr = (nuint)Math.Min((long)(startAddr - 0x7FFFFF00), sysInfo.lpMaximumApplicationAddress.ToInt64());
nuint startPage = (startAddr - (startAddr % pageSize));
nuint pageOffset = 1;
while (true)
{
nuint byteOffset = pageOffset * pageSize;
nuint highAddr = startPage + byteOffset;
nuint lowAddr = (startPage > byteOffset) ? startPage - byteOffset : 0;
bool needsExit = highAddr > maxAddr && lowAddr < minAddr;
if (highAddr < maxAddr)
{
IntPtr outAddr = NativeImport.VirtualAlloc((nint)highAddr, pageSize, NativeImport.NativeStructs.AllocationType.Commit | NativeImport.NativeStructs.AllocationType.Reserve,
NativeImport.NativeStructs.MemoryProtection.ExecuteReadWrite);
if (outAddr != IntPtr.Zero)
{
return(outAddr);
}
}
if (lowAddr > minAddr)
{
IntPtr outAddr = NativeImport.VirtualAlloc((nint)lowAddr, pageSize, NativeImport.NativeStructs.AllocationType.Commit | NativeImport.NativeStructs.AllocationType.Reserve,
NativeImport.NativeStructs.MemoryProtection.ExecuteReadWrite);
if (outAddr != IntPtr.Zero)
{
return(outAddr);
}
}
pageOffset++;
if (needsExit)
{
break;
}
}
return(0);
}
