linux-kernel - Re: [PATCH bpf-next v2 1/7] bpf: Refactor trampoline update code

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Message-ID: <20200304151107.GA9984@chromium.org>
Date:   Wed, 4 Mar 2020 16:11:07 +0100
From:   KP Singh <kpsingh@...omium.org>
To:     Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc:     linux-security-module@...r.kernel.org,
        open list <linux-kernel@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Paul Turner <pjt@...gle.com>, Jann Horn <jannh@...gle.com>,
        Florent Revest <revest@...omium.org>,
        Brendan Jackman <jackmanb@...omium.org>
Subject: Re: [PATCH bpf-next v2 1/7] bpf: Refactor trampoline update code

On 03-Mär 20:49, Andrii Nakryiko wrote:
> On Tue, Mar 3, 2020 at 5:56 PM KP Singh <kpsingh@...omium.org> wrote:
> >
> > From: KP Singh <kpsingh@...gle.com>
> >
> > As we need to introduce a third type of attachment for trampolines, the
> > flattened signature of arch_prepare_bpf_trampoline gets even more
> > complicated.
> >
> > Refactor the prog and count argument to arch_prepare_bpf_trampoline to
> > use bpf_tramp_progs to simplify the addition and accounting for new
> > attachment types.
> >
> > Signed-off-by: KP Singh <kpsingh@...gle.com>
> > ---
> 
> See note about const-ification of trampoline and naming suggestion,
> but looks good overall:
> 
> Acked-by: Andrii Nakryiko <andriin@...com>
> 
> > +static struct bpf_tramp_progs *
> > +bpf_trampoline_update_progs(struct bpf_trampoline *tr, int *total)
> 
> reading the code again, seems like bpf_trampoline_update_progs is
> really more like bpf_trampoline_get_progs, no? It doesn't modify
> trampoline itself, so might as well mark tr as const pointer.

Makes sense. I will send a v3 with these some minor fixes by EOD ZRH.

- KP

> 
> 
> > +{
> > +       struct bpf_tramp_progs *tprogs;
> > +       struct bpf_prog **progs;
> > +       struct bpf_prog_aux *aux;
> > +       int kind;
> > +
> 
> [...]