netdev - Re: [PATCH bpf 1/2] samples: bpf: fix xdp_sample

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Date:   Sat, 4 Dec 2021 06:17:21 +0530
From:   Kumar Kartikeya Dwivedi <memxor@...il.com>
To:     Alexander Lobakin <alexandr.lobakin@...el.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        John Fastabend <john.fastabend@...il.com>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        netdev@...r.kernel.org, bpf@...r.kernel.org,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [PATCH bpf 1/2] samples: bpf: fix xdp_sample_user.o linking with
 Clang

On Sat, Dec 04, 2021 at 01:20:03AM IST, Alexander Lobakin wrote:
> Clang (13) doesn't get the jokes about specifying libraries to link in
> cclags of individual .o objects:
>
> clang-13: warning: -lm: 'linker' input unused [-Wunused-command-line-argument]
> [ ... ]
>   LD  samples/bpf/xdp_redirect_cpu
>   LD  samples/bpf/xdp_redirect_map_multi
>   LD  samples/bpf/xdp_redirect_map
>   LD  samples/bpf/xdp_redirect
>   LD  samples/bpf/xdp_monitor
> /usr/bin/ld: samples/bpf/xdp_sample_user.o: in function `sample_summary_print':
> xdp_sample_user.c:(.text+0x84c): undefined reference to `floor'
> /usr/bin/ld: xdp_sample_user.c:(.text+0x870): undefined reference to `ceil'
> /usr/bin/ld: xdp_sample_user.c:(.text+0x8cf): undefined reference to `floor'
> /usr/bin/ld: xdp_sample_user.c:(.text+0x8f3): undefined reference to `ceil'
> [ more ]
>
> Specify '-lm' as ldflags for all xdp_sample_user.o users in the main
> Makefile and remove it from ccflags of ^ in Makefile.target -- just
> like it's done for all other samples. This works with all compilers.
>
> Fixes: 6e1051a54e31 ("samples: bpf: Convert xdp_monitor to XDP samples helper")
> Fixes: b926c55d856c ("samples: bpf: Convert xdp_redirect to XDP samples helper")
> Fixes: e531a220cc59 ("samples: bpf: Convert xdp_redirect_cpu to XDP samples helper")
> Fixes: bbe65865aa05 ("samples: bpf: Convert xdp_redirect_map to XDP samples helper")
> Fixes: 594a116b2aa1 ("samples: bpf: Convert xdp_redirect_map_multi to XDP samples helper")
> Signed-off-by: Alexander Lobakin <alexandr.lobakin@...el.com>
> ---

Thanks, something to remember to test for next time.

Acked-by: Kumar Kartikeya Dwivedi <memxor@...il.com>

--
Kartikeya