netdev - Re: [PATCH bpf-next v5 00/10] BTF: BPF Type Format

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Date:   Thu, 7 Jun 2018 17:25:24 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Martin KaFai Lau <kafai@...com>
Cc:     netdev@...r.kernel.org, Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>, kernel-team@...com,
        Wang Nan <wangnan0@...wei.com>, Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH bpf-next v5 00/10] BTF: BPF Type Format

Em Thu, Jun 07, 2018 at 01:07:01PM -0700, Martin KaFai Lau escreveu:
> On Thu, Jun 07, 2018 at 04:30:29PM -0300, Arnaldo Carvalho de Melo wrote:
> > So this must be available in a newer llvm version? Which one?

> I should have put in the details in my last email or
> in the commit message, my bad.
 
> 1. The tools/testing/selftests/bpf/Makefile has the CLANG_FLAGS and
>    LLC_FLAGS needed to compile the bpf prog.  It requires a new
>    "-mattr=dwarf" llc option which was added to the future
>    llvm 7.0.
 
>    Hence, I have been using the llvm's master in github which
>    also has the llvm-objcopy.
 
> 2. The kernel's btf part only focus on the BPF map.
>    Hence, the testing bpf program should have the map's key
>    and map's value.  e.g. tools/testing/selftests/bpf/test_btf_haskv.c

Thanks for the version required to test this, but where is this
test_btf_haskv.c file? Which tree? net-next?

Ok, just pulled torvalds/master and there it is. Gotcha.

struct bpf_map_def SEC("maps") __bpf_stdout__ = {
       .type = BPF_MAP_TYPE_PERF_EVENT_ARRAY,
       .key_size = sizeof(int),
       .value_size = sizeof(u32),
       .max_entries = __NR_CPUS__,
};

This map is in the above hello.c example, but I guess its way too simple
:-)

Ok, I'll test this at home in another machine where I have the llvm's
git repo.

- Arnaldo