Re: [patch 4/8] x86/entry: Move irq tracing on syscall entry to C-code

[Andy Lutomirski]

> On Mar 1, 2020, at 2:16 AM, Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
> 
> ïSteven Rostedt <rostedt@xxxxxxxxxxx> writes:
> 
>> On Sat, 29 Feb 2020 11:25:24 -0800
>> Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote:
>> 
>>>> While the tracer itself seems to handle this correctly, what about
>>>> things like BPF programs which can be attached to tracepoints and
>>>> function trace entries?  
>>> 
>>> I think that everything using the tracing code, including BPF, should
>>> either do its own rcuidle stuff or explicitly not execute if weâre
>>> not in CONTEXT_KERNEL.  That is, we probably need to patch BPF.
>> 
>> That's basically the route we are taking.
> 
> Ok, but for the time being anything before/after CONTEXT_KERNEL is unsafe
> except trace_hardirq_off/on() as those trace functions do not allow to
> attach anything AFAICT.

Can you point to whatever makes those particular functions special?  I failed to follow the macro maze.

> 
> Thanks,
> 
>        tglx