My aim is to communicate with a driver that would create a segment memory with a specified protection level, so my user-level application can copy some protected code there and execute it in that protection level. In x86 this is possible with the aid of a callgate.
Can it be done in x64 ? If one has resources on this, please post.
Although I'm not a specialist in such a delicate matter, I'd like to suggest you to read the AMD Architecture Programmer's Manual Volume #2 "System Programming". If this information about an x64-callgates is exist, it is in that document.