netdev - Re: [PATCH 5/5] bpf: Allow to resolve bpf trampoline in unwind

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Message-ID: <20200203195826.GB1535545@krava>
Date:   Mon, 3 Feb 2020 20:58:26 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Björn Töpel <bjorn.topel@...el.com>
Cc:     Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>, netdev@...r.kernel.org,
        bpf@...r.kernel.org, Andrii Nakryiko <andriin@...com>,
        Yonghong Song <yhs@...com>, Martin KaFai Lau <kafai@...com>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        David Miller <davem@...hat.com>
Subject: Re: [PATCH 5/5] bpf: Allow to resolve bpf trampoline in unwind

On Mon, Jan 13, 2020 at 01:37:28PM +0100, Jiri Olsa wrote:
> On Mon, Jan 13, 2020 at 01:31:38PM +0100, Björn Töpel wrote:
> > On 2020-01-13 13:21, Björn Töpel wrote:
> > > 
> > > On 2020-01-13 10:43, Jiri Olsa wrote:
> > > > hi,
> > > > attached patch seems to work for me (trampoline usecase), but I
> > > > don't know
> > > > how to test it for dispatcher.. also I need to check if we need to
> > > > decrease
> > > > BPF_TRAMP_MAX or BPF_DISPATCHER_MAX, it might take more time;-)
> > > > 
> > > 
> > > Thanks for working on it! I'll take the patch for a spin.
> > > 
> > > To test the dispatcher, just run XDP!
> > > 
> > > With your change, the BPF_DISPATCHER_MAX is still valid. 48 entries =>
> > > 1890B which is < (BPF_IMAGE_SIZE / 2).
> 
> great
> 
> > > 
> > 
> > ...and FWIW, it would be nice with bpf_dispatcher_<...> entries in kallsyms
> 
> ok so it'd be 'bpf_dispatcher_<name>'

hi,
so the only dispatcher is currently defined as:
  DEFINE_BPF_DISPATCHER(bpf_dispatcher_xdp)

with the bpf_dispatcher_<name> logic it shows in kallsyms as:
  ffffffffa0450000 t bpf_dispatcher_bpf_dispatcher_xdp    [bpf]

to fix that, would you guys preffer having:
  DEFINE_BPF_DISPATCHER(xdp) 

or using the full dispatcher name as kallsyms name?
which would require some discipline for future dispatcher names ;-)

thanks,
jirka