linux-kernel - Re: [PATCH 0/4] tracing: improve symbolic printing

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Message-ID: <2f749ade-7821-00fa-ba34-e2d25cbad441@oracle.com>
Date:   Wed, 4 Oct 2023 22:35:07 +0100
From:   Alan Maguire <alan.maguire@...cle.com>
To:     Steven Rostedt <rostedt@...dmis.org>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     Johannes Berg <johannes@...solutions.net>,
        linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
        netdev@...r.kernel.org, linux-wireless@...r.kernel.org
Subject: Re: [PATCH 0/4] tracing: improve symbolic printing

On 04/10/2023 18:29, Steven Rostedt wrote:
> On Wed, 4 Oct 2023 09:54:31 -0700
> Jakub Kicinski <kuba@...nel.org> wrote:
> 
>> On Wed, 4 Oct 2023 12:35:24 -0400 Steven Rostedt wrote:
>>>> Potentially naive question - the trace point holds enum skb_drop_reason.
>>>> The user space can get the names from BTF. Can we not teach user space
>>>> to generically look up names of enums in BTF?    
>>>
>>> That puts a hard requirement to include BTF in builds where it was not
>>> needed before. I really do not want to build with BTF just to get access to
>>> these symbols. And since this is used by the embedded world, and BTF is
>>> extremely bloated, the short answer is "No".  
>>
>> Dunno. BTF is there most of the time. It could make the life of
>> majority of the users far more pleasant.
> 
> BTF isn't there for a lot of developers working in embedded who use this
> code. Most my users that I deal with have minimal environments, so BTF is a
> showstopper.

One thing we've heard from some embedded folks [1] is that having
kernel BTF loadable as a separate module (rather than embedded in
vmlinux) would help, as there are size limits on vmlinux that they can
workaround by having modules on a different partition. We're hoping
to get that working soon. I was wondering if you see other issues around
BTF adoption for embedded systems that we could put on the to-do list?
Not necessarily for this particular use-case (since there are
complications with trace data as you describe), but just trying to make
sure we can remove barriers to BTF adoption where possible.

Thanks!

Alan

[1]
https://lore.kernel.org/bpf/CAHBbfcUkr6fTm2X9GNsFNqV75fTG=aBQXFx_8Ayk+4hk7heB-g@mail.gmail.com/

> 
>>
>> I hope we can at least agree that the current methods of generating 
>> the string arrays at C level are... aesthetically displeasing.
> 
> I don't know, I kinda like it ;-)
> 
> -- Steve
>