netdev - Re: [PATCH] libbpf: Make bpf/bpf

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Date:   Thu, 9 Apr 2020 14:31:11 +0900
From:   Yoshiki Komachi <komachi.yoshiki@...il.com>
To:     Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Andrii Nakryiko <andriin@...com>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH] libbpf: Make bpf/bpf_helpers.h self-contained

2020年4月7日(火) 15:52 Andrii Nakryiko <andrii.nakryiko@...il.com>:
>
> On Mon, Apr 6, 2020 at 11:29 PM Yoshiki Komachi
> <komachi.yoshiki@...il.com> wrote:
> >
> > I tried to compile a bpf program including bpf_helpers.h, however it
> > resulted in failure as below:
> >
> >   # clang -I./linux/tools/lib/ -I/lib/modules/$(uname -r)/build/include/ \
> >     -O2 -Wall -target bpf -emit-llvm -c bpf_prog.c -o bpf_prog.bc
> >   ...
> >   In file included from linux/tools/lib/bpf/bpf_helpers.h:5:
> >   linux/tools/lib/bpf/bpf_helper_defs.h:56:82: error: unknown type name '__u64'
> >   ...
> >
> > This is because bpf_helpers.h depends on linux/types.h and it is not
> > self-contained. This has been like this long time, but since bpf_helpers.h
> > was moved from selftests private file to libbpf header file, IMO it
> > should include linux/types.h by itself.
> >
> > Fixes: e01a75c15969 ("libbpf: Move bpf_{helpers, helper_defs, endian, tracing}.h into libbpf")
> > Signed-off-by: Yoshiki Komachi <komachi.yoshiki@...il.com>
> > ---
> >  tools/lib/bpf/bpf_helpers.h | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h
> > index f69cc208778a..d9288e695eb1 100644
> > --- a/tools/lib/bpf/bpf_helpers.h
> > +++ b/tools/lib/bpf/bpf_helpers.h
> > @@ -2,6 +2,7 @@
> >  #ifndef __BPF_HELPERS__
> >  #define __BPF_HELPERS__
> >
> > +#include <linux/types.h>
> >  #include "bpf_helper_defs.h"
>
> It's actually intentional, so that bpf_helpers.h can be used together
> with auto-generated (from BTF) vmlinux.h (which will have all the
> __u64 and other typedefs).

Thanks for kind comments, and I found out that it’s not wrong but intentional.

However users (like me) may not be aware of it at this point, because
there is no related statement as far as I know. Instead of my previous
proposal, we should add some comments (e.g., this header needs to
include either auto-generated (from BTF) vmlinux.h or linux/types.h
before using) to bpf_helpers.h header, IMO.

> >
> >  #define __uint(name, val) int (*name)[val]
> > --
> > 2.24.1
> >