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Date:   Thu, 4 Nov 2021 18:15:57 +0000
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Subject: Re: perf build broken looking for bpf/{libbpf,bpf}.h after merge with
 upstream
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To:     Arnaldo Carvalho de Melo <acme@kernel.org>,
        Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc:     Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>,
        Song Liu <songliubraving@fb.com>, Jiri Olsa <jolsa@kernel.org>,
        Namhyung Kim <namhyung@kernel.org>, bpf <bpf@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
References: <YYQadWbtdZ9Ff9N4@kernel.org>
 <CAEf4Bzaj4_hXDxk18aJvk2bxJ-rPb++DpPVEeUw0pN-tJuiy0Q@mail.gmail.com>
 <YYQhzbh1tL5MPgaI@kernel.org>
From:   Quentin Monnet <quentin@isovalent.com>
In-Reply-To: <YYQhzbh1tL5MPgaI@kernel.org>
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2021-11-04 15:09 UTC-0300 ~ Arnaldo Carvalho de Melo <acme@kernel.org>
> Em Thu, Nov 04, 2021 at 10:47:12AM -0700, Andrii Nakryiko escreveu:
>> On Thu, Nov 4, 2021 at 10:38 AM Arnaldo Carvalho de Melo
>> <arnaldo.melo@gmail.com> wrote:
>>>
>>>
>>> Hi Song,
>>>
>>
>> cc Quentin as well, might be related to recent Makefiles revamp for
>> users of libbpf. But in bpf-next perf builds perfectly fine, so not
>> sure.
> 
> This did the trick:
> 
> ⬢[acme@toolbox perf]$ git show
> commit 504afe6757ec646539ca3b4aa0431820e8c92b45 (HEAD -> perf/core)
> Author: Arnaldo Carvalho de Melo <acme@redhat.com>
> Date:   Thu Nov 4 14:58:56 2021 -0300
> 
>     Revert "bpftool: Remove Makefile dep. on $(LIBBPF) for $(LIBBPF_INTERNAL_HDRS)"
> 
>     This reverts commit 8b6c46241c774c83998092a4eafe40f054568881.
> 
>     Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
> 
> diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
> index c0c30e56988f2cbe..c5ad996ee95d4e87 100644
> --- a/tools/bpf/bpftool/Makefile
> +++ b/tools/bpf/bpftool/Makefile
> @@ -39,14 +39,14 @@ ifeq ($(BPFTOOL_VERSION),)
>  BPFTOOL_VERSION := $(shell make -rR --no-print-directory -sC ../../.. kernelversion)
>  endif
> 
> -$(LIBBPF_OUTPUT) $(BOOTSTRAP_OUTPUT) $(LIBBPF_BOOTSTRAP_OUTPUT) $(LIBBPF_HDRS_DIR):
> +$(LIBBPF_OUTPUT) $(BOOTSTRAP_OUTPUT) $(LIBBPF_BOOTSTRAP_OUTPUT):
>         $(QUIET_MKDIR)mkdir -p $@
> 
>  $(LIBBPF): $(wildcard $(BPF_DIR)/*.[ch] $(BPF_DIR)/Makefile) | $(LIBBPF_OUTPUT)
>         $(Q)$(MAKE) -C $(BPF_DIR) OUTPUT=$(LIBBPF_OUTPUT) \
>                 DESTDIR=$(LIBBPF_DESTDIR) prefix= $(LIBBPF) install_headers
> 
> -$(LIBBPF_INTERNAL_HDRS): $(LIBBPF_HDRS_DIR)/%.h: $(BPF_DIR)/%.h | $(LIBBPF_HDRS_DIR)
> +$(LIBBPF_INTERNAL_HDRS): $(LIBBPF_HDRS_DIR)/%.h: $(BPF_DIR)/%.h $(LIBBPF)
>         $(call QUIET_INSTALL, $@)
>         $(Q)install -m 644 -t $(LIBBPF_HDRS_DIR) $<


Interesting. I needed that patch because otherwise I'd get errors when
compiling bpftool after the switch to libbpf's hashmap implementation.
For the current breakage, it could be a matter of how we pass variables
when descending into bpftool/ from perf's Makefile.perf. I'll try to
look at this in details, and to experiment tonight, if I can. (Thanks
Andrii for the CC!)

Thanks,
Quentin