Comment by immibis
6 months ago
There's still something on the platform that you can call without extra indirection in the way on your side of the handoff. That is true on all platforms; whether it's an INT or SYSCALL instruction or a CALL or JMP instruction is irrelevant.
If it's a CALL instruction into a user-space DLL, that's still an extra indirection.
Kind of like the syscall dispatch table on the Linux kernel side, right? After you issue the handoff instruction and it becomes the operating system's problem, there's still more code before you get to the code that does the thing you wanted.