Re: Building perf with BUILD_BPF_SKEL=1 by default

[Arnaldo Carvalho de Melo <acme@kernel.org>]

Em Fri, Dec 03, 2021 at 07:32:34PM +0000, Song Liu escreveu:
> 
> 
> > On Dec 3, 2021, at 5:10 AM, Arnaldo Carvalho de Melo <acme@kernel.org> wrote:
> > 
> > Hi Song,
> > 
> > 	So I'm changing all my containers to build with BUILD_BPF_SKEL=1
> > to then make this the default, so far older containers fail either
> > because the clang available is too old, so I've added a NO_BUILD_BPF_SKEL=1
> > env var to disable that in those containers and then there is this other
> > case where clang is recent enough but:
> > 
> >    util/bpf_skel/bperf_leader.bpf.c:13:20: error: use of undeclared identifier 'BPF_F_PRESERVE_ELEMS'
> >            __uint(map_flags, BPF_F_PRESERVE_ELEMS);
> > 
> > Because the system's /usr/include/linux/bpf.h doesn't have that
> > BPF_F_PRESERVE_ELEMS enum entry.
> > 
> > These are enums to make them available via BTF, but then I can't use
> > the:
> > 
> > #ifdef BPF_F_PRESERVE_ELEMS
> > #define BPF_F_PRESERVE_ELEMS (1U << 11)
> > #endif
> > 
> > approach.
> > 
> > But then we _have_ it in the tools/include/uapi/linux/bpf.h we ship:
> > 
> > $ grep BPF_F_PRESERVE_ELEMS tools/include/uapi/linux/bpf.h
> > 	BPF_F_PRESERVE_ELEMS	= (1U << 11),
> > $
> > 
> > so we need to switch to using it somehow, this way we can build in more
> > systems and make bperf and other BPF enabled features.
> > 
> > From a quick look I couldn't find where to add
> > $(sourcedir)/tools/include/uapi/ to the include path used to build
> > util/bpf_skel/bperf_leader.bpf.c, should be easy, can you take a look?
> > 
> > Thanks,
> > 
> > - Arnaldo
> 
> I think the following should fix it

I'm trying this now and tentatively sticking a Signed-off-by: you to it,
ok?

- Arnaldo
 
> Thanks,
> Song
> 
> 
> diff --git i/tools/perf/util/bpf_skel/bperf_follower.bpf.c w/tools/perf/util/bpf_skel/bperf_follower.bpf.c
> index b8fa3cb2da230..4a6acfde14937 100644
> --- i/tools/perf/util/bpf_skel/bperf_follower.bpf.c
> +++ w/tools/perf/util/bpf_skel/bperf_follower.bpf.c
> @@ -1,7 +1,6 @@
>  // SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>  // Copyright (c) 2021 Facebook
> -#include <linux/bpf.h>
> -#include <linux/perf_event.h>
> +#include "vmlinux.h"
>  #include <bpf/bpf_helpers.h>
>  #include <bpf/bpf_tracing.h>
>  #include "bperf.h"
> diff --git i/tools/perf/util/bpf_skel/bperf_leader.bpf.c w/tools/perf/util/bpf_skel/bperf_leader.bpf.c
> index 4f70d1459e86c..40d962b058634 100644
> --- i/tools/perf/util/bpf_skel/bperf_leader.bpf.c
> +++ w/tools/perf/util/bpf_skel/bperf_leader.bpf.c
> @@ -1,7 +1,6 @@
>  // SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>  // Copyright (c) 2021 Facebook
> -#include <linux/bpf.h>
> -#include <linux/perf_event.h>
> +#include "vmlinux.h"
>  #include <bpf/bpf_helpers.h>
>  #include <bpf/bpf_tracing.h>
>  #include "bperf.h"
> diff --git i/tools/perf/util/bpf_skel/bpf_prog_profiler.bpf.c w/tools/perf/util/bpf_skel/bpf_prog_profiler.bpf.c
> index ab12b4c4ece21..97037d3b3d9fa 100644
> --- i/tools/perf/util/bpf_skel/bpf_prog_profiler.bpf.c
> +++ w/tools/perf/util/bpf_skel/bpf_prog_profiler.bpf.c
> @@ -1,6 +1,6 @@
>  // SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>  // Copyright (c) 2020 Facebook
> -#include <linux/bpf.h>
> +#include "vmlinux.h"
>  #include <bpf/bpf_helpers.h>
>  #include <bpf/bpf_tracing.h>
> 

-- 

- Arnaldo