Re: [RFC] ftrace: Add support to keep some functions out of ftrace

Peter Zijlstra
2022-08-15T15:49:12Z

On Mon, Aug 15, 2022 at 08:35:53AM -0700, Alexei Starovoitov wrote:
> On Mon, Aug 15, 2022 at 8:28 AM Peter Zijlstra <peterz@infradead.org> wrote:
> >
> > On Mon, Aug 15, 2022 at 08:17:42AM -0700, Alexei Starovoitov wrote:
> > > It's hiding a fake function from ftrace, since it's not a function
> > > and ftrace infra shouldn't show it tracing logs.
> > > In other words it's a _notrace_ function with nop5.
> >
> > Then make it a notrace function with a nop5 in it. That isn't hard.
>
> That's exactly what we're trying to do.

All the while claiming ftrace is broken while it is not.

> Jiri's patch is one way to achieve that.

Fairly horrible way.

> What is your suggestion?

Mailed it already.

> Move it from C to asm ?

Would be much better than proposed IMO.

> Make it naked function with explicit inline asm?

Can be made to work but is iffy because the compiler can do horrible
things with placing the asm().