Using ftrace

[Glenn Washburn]

On Tue, 31 Jan 2023 08:22:45 +0100 (CET)
Richard Weinberger <richard at nod.at> wrote:

> ----- Ursprüngliche Mail -----
> > Von: "Anton Ivanov" <anton.ivanov at kot-begemot.co.uk>
> > On 31/01/2023 04:17, Glenn Washburn wrote:
> >> I'm trying to use the ftrace facility within UML. It appears as
> >> though it exists in the menuconfig, but I can't seem to get the
> >> kernel to recognize the tracefs filesystem. I'm wondering if
> >> someone can confirm that either ftrace does or does not work in
> >> UML.
> > 
> > I have not used it. We have not had any requests related to it
> > either
> > 
> > I will look into it.
> 
> Tracing itself should work. But function tracing is not supported.
> You'll get tracefs as soon you select one tracer (such as
> CONFIG_IRQSOFF_TRACER).

Okay, that makes sense. Yes, I was really asking about function
tracing.

> Adding function (and function graph) tracing to UML is possible but a
> bit of work. You need to find a way to implement all of ftraces
> mcount hooks for UML.

Sounds like more than I want to invest at this point. I'll get on
without it for the time being. Thanks for the confirmation. 

Glenn