linux-kernel - Re: [PATCH] libbpf: Fix up generation of bpf_helper

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Message-ID: <CAADnVQLFVH000BJM4cN29kcC+KKDmVek3jaen3cZz2=12jP58g@mail.gmail.com>
Date:   Wed, 27 Nov 2019 17:20:17 -0800
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
Cc:     Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Stanislav Fomichev <sdf@...ichev.me>,
        Andrii Nakryiko <andrii.nakryiko@...il.com>,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        Andrii Nakryiko <andriin@...com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jiri Olsa <jolsa@...nel.org>, Martin KaFai Lau <kafai@...com>,
        Namhyung Kim <namhyung@...nel.org>, bpf <bpf@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>,
        linux-perf-users@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Quentin Monnet <quentin.monnet@...ronome.com>
Subject: Re: [PATCH] libbpf: Fix up generation of bpf_helper_defs.h

On Wed, Nov 27, 2019 at 5:17 PM Arnaldo Carvalho de Melo
<arnaldo.melo@...il.com> wrote:
>
> On November 27, 2019 9:59:15 PM GMT-03:00, Alexei Starovoitov <alexei.starovoitov@...il.com> wrote:
> >On Wed, Nov 27, 2019 at 4:50 PM Arnaldo Carvalho de Melo
> ><arnaldo.melo@...il.com> wrote:
> >>
> >> Take it as one, I think it's what should have been in the cset it is
> >fixing, that way no breakage would have happened.
> >
> >Ok. I trimmed commit log and applied here:
> >https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git/commit/?id=1fd450f99272791df8ea8e1b0f5657678e118e90
> >
> >What about your other fix and my suggestion there?
> >(__u64) cast instead of PRI ?
> >We do this already in two places:
> >libbpf.c:                shdr_idx, (__u64)sym->st_value);
> >libbpf.c:             (__u64)sym.st_value, GELF_ST_TYPE(sym.st_info),
>
>
> I'm using the smartphone now, but I thought you first suggested using a cast to long, if you mean using %llu + cast to __u64, then should be was ugly as using PRI, IOW, should work on both 64 bit and 32 bit. :-)

Yes. I suggested (long) first, but then found two cases in libbpf that
solve this with (__u64),
so better to stick to that for consistency.