linux-kernel - Re: [PATCH bpf-next 2/8] samples: bpf: Makefile: remove target for native build

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Date:   Sat, 7 Sep 2019 03:19:10 +0300
From:   Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Yonghong Song <yhs@...com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Network Development <netdev@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>,
        Clang-Built-Linux ML <clang-built-linux@...glegroups.com>
Subject: Re: [PATCH bpf-next 2/8] samples: bpf: Makefile: remove target for
 native build

On Fri, Sep 06, 2019 at 05:04:08PM -0700, Alexei Starovoitov wrote:
>On Fri, Sep 6, 2019 at 4:52 PM Ivan Khoronzhuk
><ivan.khoronzhuk@...aro.org> wrote:
>>
>> On Fri, Sep 06, 2019 at 04:31:39PM -0700, Alexei Starovoitov wrote:
>> >On Thu, Sep 05, 2019 at 12:22:06AM +0300, Ivan Khoronzhuk wrote:
>> >> No need to set --target for native build, at least for arm, the
>> >> default target will be used anyway. In case of arm, for at least
>> >> clang 5 - 10 it causes error like:
>> >>
>> >> clang: warning: unknown platform, assuming -mfloat-abi=soft
>> >> LLVM ERROR: Unsupported calling convention
>> >> make[2]: *** [/home/root/snapshot/samples/bpf/Makefile:299:
>> >> /home/root/snapshot/samples/bpf/sockex1_kern.o] Error 1
>> >>
>> >> Only set to real triple helps: --target=arm-linux-gnueabihf
>> >> or just drop the target key to use default one. Decision to just
>> >> drop it and thus default target will be used (wich is native),
>> >> looks better.
>> >>
>> >> Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>
>> >> ---
>> >>  samples/bpf/Makefile | 2 --
>> >>  1 file changed, 2 deletions(-)
>> >>
>> >> diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
>> >> index 61b7394b811e..a2953357927e 100644
>> >> --- a/samples/bpf/Makefile
>> >> +++ b/samples/bpf/Makefile
>> >> @@ -197,8 +197,6 @@ BTF_PAHOLE ?= pahole
>> >>  ifdef CROSS_COMPILE
>> >>  HOSTCC = $(CROSS_COMPILE)gcc
>> >>  CLANG_ARCH_ARGS = --target=$(notdir $(CROSS_COMPILE:%-=%))
>> >> -else
>> >> -CLANG_ARCH_ARGS = -target $(ARCH)
>> >>  endif
>> >
>> >I don't follow here.
>> >Didn't you introduce this bug in patch 1 and now fixing it in patch 2?
>> >
>>
>> It looks like but that's not true.
>> Previous patch adds target only for cross compiling,
>> before the patch the target was used for both, cross compiling and w/o cc.
>>
>> This patch removes target only for native build (it's not cross compiling).
>>
>> By fact, it's two separate significant changes.
>
>How so?
>before first patch CLANG_ARCH_ARGS is only used under CROSS_COMPILE.
>After the first patch CLANG_ARCH_ARGS is now suddenly defined w/o CROSS_COMPILE
>and second patch brings it to the state before first patch.

Oh sorry ), messed with my local exp with target bpf, after rebase, even forgot
that's mine. Will drop it, with removing "else" for previous patch.

-- 
Regards,
Ivan Khoronzhuk