linux-kernel - Re: [PATCH RFC 2/5] bpf: Use file object build id in stackmap

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Date:   Thu, 9 Feb 2023 14:19:05 +0100
From:   Jiri Olsa <olsajiri@...il.com>
To:     Hao Luo <haoluo@...gle.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Andrii Nakryiko <andrii@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        bpf@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-perf-users@...r.kernel.org, Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Daniel Borkmann <daniel@...earbox.net>
Subject: Re: [PATCH RFC 2/5] bpf: Use file object build id in stackmap

On Wed, Feb 08, 2023 at 11:23:13PM -0800, Hao Luo wrote:
> On Wed, Feb 1, 2023 at 5:58 AM Jiri Olsa <jolsa@...nel.org> wrote:
> >
> > Use build id from file object in stackmap if it's available.
> >
> > Signed-off-by: Jiri Olsa <jolsa@...nel.org>
> > ---
> 
> Can we insert the lookup from vma->vm_file in build_id_parse() rather
> than its callers?

that might simplify also the perf code.. we might need to rename
it though.. maybe build_id_read(vma,...), I'll check

thanks,
jirka

> 
> >  kernel/bpf/stackmap.c | 8 ++++++++
> >  1 file changed, 8 insertions(+)
> >
> > diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
> > index aecea7451b61..944cb260a42c 100644
> > --- a/kernel/bpf/stackmap.c
> > +++ b/kernel/bpf/stackmap.c
> > @@ -156,7 +156,15 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
> >                         goto build_id_valid;
> >                 }
> >                 vma = find_vma(current->mm, ips[i]);
> > +#ifdef CONFIG_FILE_BUILD_ID
> > +               if (vma && vma->vm_file && vma->vm_file->f_bid) {
> > +                       memcpy(id_offs[i].build_id,
> > +                              vma->vm_file->f_bid->data,
> > +                              vma->vm_file->f_bid->sz);
> > +               } else {
> > +#else
> >                 if (!vma || build_id_parse(vma, id_offs[i].build_id, NULL)) {
> > +#endif
> >                         /* per entry fall back to ips */
> >                         id_offs[i].status = BPF_STACK_BUILD_ID_IP;
> >                         id_offs[i].ip = ips[i];
> > --
> > 2.39.1
> >