netdev - Re: Strange samples/bpf loading error for maps on net-next?

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Message-ID: <20170428054950.teh53ssg6ei4xkvx@ast-mbp>
Date:   Thu, 27 Apr 2017 22:49:51 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Jesper Dangaard Brouer <brouer@...hat.com>
Cc:     Daniel Borkmann <borkmann@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>, eric@...it.org
Subject: Re: Strange samples/bpf loading error for maps on net-next?

On Thu, Apr 27, 2017 at 01:15:42PM +0200, Jesper Dangaard Brouer wrote:
> 
> To provoke this bug, remember that you MUST call:
> 
>  make headers_install
> 
> In the kernels root directory, else you will be compiling samples/bpf/
> against the older headers previously installed.
> 
> The error looks like:
> 
>  $ sudo ./sockex1
>  bpf_load_program() err=22
>  fd 0 is not pointing to valid bpf_map
>  sockex1: [...]/samples/bpf/sockex1_user.c:26: main: Assertion `setsockopt(sock, SOL_SOCKET, SO_ATTACH_BPF, prog_fd, sizeof(prog_fd[0])) == 0' failed.
>  Aborted
> 
> I've found that the bug were introduced in
>  commit: fb30d4b71214 ("bpf: Add tests for map-in-map")

Great debugging!
Indeed that change made samples/bpf/bpf_load.c to be incompatible with .o
generated earlier. We should really get rid of that loader and
switch to tools/lib/bpf/. I believe Eric Leblond already made it
resilient to 'struct bpf_map_def' changes.