Re: Building perf with BUILD_BPF_SKEL=1 by default

[Athira Rajeev <atrajeev@linux.vnet.ibm.com>]

> On 04-Dec-2021, at 1:02 AM, Song Liu <songliubraving@fb.com> wrote:
> 
> 
> 
>> 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
> 
> Thanks,
> Song
> 

Hi,

Encountered this error while building perf with BUILD_BPF_SKEL.

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);

And verified this patch fixes this issue.

Tested-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>

Thanks
Athira 
> 
> 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>
> 
>