netdev - Re: [PATCH 09/11] bpf: Add d

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Date:   Tue, 23 Jun 2020 11:58:33 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Jiri Olsa <jolsa@...nel.org>, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Martin KaFai Lau <kafai@...com>,
        David Miller <davem@...hat.com>,
        John Fastabend <john.fastabend@...il.com>,
        Wenbo Zhang <ethercflow@...il.com>,
        KP Singh <kpsingh@...omium.org>,
        Andrii Nakryiko <andriin@...com>,
        Brendan Gregg <bgregg@...flix.com>,
        Florent Revest <revest@...omium.org>,
        Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH 09/11] bpf: Add d_path helper

On Tue, Jun 23, 2020 at 3:02 AM Jiri Olsa <jolsa@...hat.com> wrote:
>
> On Mon, Jun 22, 2020 at 12:18:19PM -0700, Andrii Nakryiko wrote:
> > On Mon, Jun 22, 2020 at 2:02 AM Jiri Olsa <jolsa@...hat.com> wrote:
> > >
> > > On Fri, Jun 19, 2020 at 11:25:27AM -0700, Andrii Nakryiko wrote:
> > >
> > > SNIP
> > >
> > > > > > >  /* integer value in 'imm' field of BPF_CALL instruction selects which helper
> > > > > > >   * function eBPF program intends to call
> > > > > > > diff --git a/kernel/bpf/btf_ids.c b/kernel/bpf/btf_ids.c
> > > > > > > index d8d0df162f04..853c8fd59b06 100644
> > > > > > > --- a/kernel/bpf/btf_ids.c
> > > > > > > +++ b/kernel/bpf/btf_ids.c
> > > > > > > @@ -13,3 +13,14 @@ BTF_ID(struct, seq_file)
> > > > > > >
> > > > > > >  BTF_ID_LIST(bpf_xdp_output_btf_ids)
> > > > > > >  BTF_ID(struct, xdp_buff)
> > > > > > > +
> > > > > > > +BTF_ID_LIST(bpf_d_path_btf_ids)
> > > > > > > +BTF_ID(struct, path)
> > > > > > > +
> > > > > > > +BTF_WHITELIST_ENTRY(btf_whitelist_d_path)
> > > > > > > +BTF_ID(func, vfs_truncate)
> > > > > > > +BTF_ID(func, vfs_fallocate)
> > > > > > > +BTF_ID(func, dentry_open)
> > > > > > > +BTF_ID(func, vfs_getattr)
> > > > > > > +BTF_ID(func, filp_close)
> > > > > > > +BTF_WHITELIST_END(btf_whitelist_d_path)
> > > > > >
> > > > > > Oh, so that's why you added btf_ids.c. Do you think centralizing all
> > > > > > those BTF ID lists in one file is going to be more convenient? I lean
> > > > > > towards keeping them closer to where they are used, as it was with all
> > > > > > those helper BTF IDS. But I wonder what others think...
> > > > >
> > > > > either way works for me, but then BTF_ID_* macros needs to go
> > > > > to include/linux/btf_ids.h header right?
> > > > >
> > > >
> > > > given it's internal API, I'd probably just put it in
> > > > include/linux/btf.h or include/linux/bpf.h, don't think we need extra
> > > > header just for these
> > >
> > > actually, I might end up with extra header, so it's possible
> > > to add selftest for this
> > >
> >
> > How does extra header help with selftest?
>
> to create binary with various lists defined like we do in kernel
> using the same macros..  and check they are properly made/sorted
>

So the problem here is that selftests don't have access to internal
(non-UAPI) linux/bpf.h header, right? Ok, that's a fair point.

> jirka
>