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

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Message-ID: <D93F5A0F-7675-4A66-B90A-C6091F995BE5@kernel.org>
Date:   Wed, 27 Nov 2019 22:27:31 -0300
From:   Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>,
        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 November 27, 2019 10:20:17 PM GMT-03:00, Alexei Starovoitov <alexei.starovoitov@...il.com> wrote:
>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.

If it's already being used elsewhere in lubbpf, it was tested already with the build containers and since nobody complained, go with it :-)

- Arnaldo