linux-kernel - Re: [PATCH v2] perf build: Warn for BPF skeletons if endian mismatches

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Date:   Mon, 10 Apr 2023 19:23:54 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Ian Rogers <irogers@...gle.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        Andrii Nakryiko <andrii@...nel.org>
Subject: Re: [PATCH v2] perf build: Warn for BPF skeletons if endian
 mismatches

Em Mon, Apr 10, 2023 at 09:09:05AM -0700, Ian Rogers escreveu:
> Done as a warning as I'm not fully confident of the test's robustness
> of comparing the macro definition of __BYTE_ORDER__.
> 
> Signed-off-by: Ian Rogers <irogers@...gle.com>
> 
> v2. Is a rebase following patch 1 being merged.

Thanks, applied.

- Arnaldo

> ---
>  tools/perf/Makefile.config | 17 ++++++++++-------
>  1 file changed, 10 insertions(+), 7 deletions(-)
> 
> diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
> index 16bea51f0bcd..71442c54c25f 100644
> --- a/tools/perf/Makefile.config
> +++ b/tools/perf/Makefile.config
> @@ -663,14 +663,17 @@ ifndef NO_BPF_SKEL
>    $(call feature_check,clang-bpf-co-re)
>    ifeq ($(feature-clang-bpf-co-re), 0)
>      dummy := $(error: ERROR: BPF skeletons unsupported. clang too old/not installed or build with NO_BPF_SKEL=1.)
> -  else
> -    ifeq ($(filter -DHAVE_LIBBPF_SUPPORT, $(CFLAGS)),)
> -      dummy := $(error: ERROR: BPF skeletons unsupported. BPF skeleton support requires libbpf or build with NO_BPF_SKEL=1.)
> -    else
> -      $(call detected,CONFIG_PERF_BPF_SKEL)
> -      CFLAGS += -DHAVE_BPF_SKEL
> -    endif
>    endif
> +  ifeq ($(filter -DHAVE_LIBBPF_SUPPORT, $(CFLAGS)),)
> +    dummy := $(error: ERROR: BPF skeletons unsupported. BPF skeleton support requires libbpf or build with NO_BPF_SKEL=1.)
> +  endif
> +  host_byte_order=$(echo ""|$(HOSTCC) -dM -E -|grep __BYTE_ORDER__)
> +  target_byte_order=$(echo ""|$(CC) -dM -E -|grep __BYTE_ORDER__)
> +  ifneq ($(host_byte_order), $(target_byte_order))
> +    $(warning Possibly mismatched host and target endianness may break BPF skeletons)
> +  endif
> +  $(call detected,CONFIG_PERF_BPF_SKEL)
> +  CFLAGS += -DHAVE_BPF_SKEL
>  endif
>  
>  dwarf-post-unwind := 1
> -- 
> 2.40.0.577.gac1e443424-goog
> 

-- 

- Arnaldo