Using ftrace

[Richard Weinberger]

----- 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).

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.

Thanks,
//richard