netdev - Re: [PATCH bpf-next 1/2] bpf: switch most helper return values from 32-bit int to 64-bit long

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Date:   Thu, 18 Jun 2020 17:39:29 -0700
From:   John Fastabend <john.fastabend@...il.com>
To:     John Fastabend <john.fastabend@...il.com>,
        Andrii Nakryiko <andrii.nakryiko@...il.com>,
        John Fastabend <john.fastabend@...il.com>
Cc:     Andrii Nakryiko <andriin@...com>, bpf <bpf@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Kernel Team <kernel-team@...com>
Subject: Re: [PATCH bpf-next 1/2] bpf: switch most helper return values from
 32-bit int to 64-bit long

John Fastabend wrote:
> Andrii Nakryiko wrote:
> > On Thu, Jun 18, 2020 at 11:58 AM John Fastabend
> > <john.fastabend@...il.com> wrote:

[...]

> > That would be great. Self-tests do work, but having more testing with
> > real-world application would certainly help as well.
> 
> Thanks for all the follow up.
> 
> I ran the change through some CI on my side and it passed so I can
> complain about a few shifts here and there or just update my code or
> just not change the return types on my side but I'm convinced its OK
> in most cases and helps in some so...
> 
> Acked-by: John Fastabend <john.fastabend@...il.com>

I'll follow this up with a few more selftests to capture a couple of our
patterns. These changes are subtle and I worry a bit that additional
<<,s>> pattern could have the potential to break something.

Another one we didn't discuss that I found in our code base is feeding
the output of a probe_* helper back into the size field (after some
alu ops) of subsequent probe_* call. Unfortunately, the tests I ran
today didn't cover that case.

I'll put it on the list tomorrow and encode these in selftests. I'll
let the mainainers decide if they want to wait for those or not.