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Date: Tue, 15 Dec 2015 16:49:33 +0800
From: "Wangnan (F)" <wangnan0@huawei.com>
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 Bhattiprolu" <sukadev@linux.vnet.ibm.com>
Subject: Re: [PATCH v3 3/3] perf: bpf: Fix build breakage due to libbpf
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This patch contains a problem.

On 2015/12/15 11:35, Wang Nan wrote:
> From: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
>
> perf build is currently (v4.4-rc5) broken on powerpc:
>
> bpf.c:28:4: error: #error __NR_bpf not defined. libbpf does not support
> your arch.
>   #  error __NR_bpf not defined. libbpf does not support your arch.
>      ^
>
> Fix this by including tools/perf/config/Makefile.arch for the proper
> $ARCH macro. While at it, remove redundant LP64 macro definition.
>
> Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
> Signed-off-by: Wang Nan <wangnan0@huawei.com>
> Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
> Cc: Jiri Olsa <jolsa@redhat.com>
> Cc: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
> ---
>   tools/lib/bpf/Makefile | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/tools/lib/bpf/Makefile b/tools/lib/bpf/Makefile
> index 636e3dd..3d34a8c 100644
> --- a/tools/lib/bpf/Makefile
> +++ b/tools/lib/bpf/Makefile
> @@ -31,7 +31,8 @@ INSTALL = install
>   DESTDIR ?=
>   DESTDIR_SQ = '$(subst ','\'',$(DESTDIR))'
>   
> -LP64 := $(shell echo __LP64__ | ${CC} ${CFLAGS} -E -x c - | tail -n 1)
> +include $(srctree)/tools/scripts/Makefile.arch
> +

Here we depend on $(srctree), but libbpf's Makefile doesn't automatically
detect it. Directly 'make' in libbpf directory causes an error.

Will post a v4 for it.

Thank you.