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

[Thomas Gleixner]

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 ....