Re: [PATCH] sched/x86: Save [ER]FLAGS on context switch

Thomas Gleixner
2019-02-19T11:38:53Z

On Tue, 19 Feb 2019, Peter Zijlstra wrote:

> On Tue, Feb 19, 2019 at 10:04:09AM +0100, Peter Zijlstra wrote:
> > > Does that make more sense?
> >
> > It appears to me you're going about it backwards.
>
> So how about you do a GCC plugin that verifies limits on code-gen
> between user_access_begin/user_access_end() ?
>
> - No CALL/RET
> - implies user_access_end() happens
> - implies no fentry hooks
> - No __preempt_count frobbing
> - No tracepoints
> - ...
>
> That way you put the burden on the special code, not on the rest of the
> kernel.

And then you have kprobes ....