Re: [PATCH] x86/entry/64: randomize kernel stack offset upon syscall

[Ingo Molnar]

* Reshetova, Elena <elena.reshetova@xxxxxxxxx> wrote:

> CONFIG_PAGE_TABLE_ISOLATION=n:
> 
> base:                                  Simple syscall: 0.0510 microseconds
> get_random_bytes(4096 bytes buffer):   Simple syscall: 0.0597 microseconds
> 
> So, pure speed wise get_random_bytes() with 1 page per-cpu buffer wins. 

It still adds +17% overhead to the system call path, which is sad.
Why is it so expensive?

Thanks,

	Ingo