linux-kernel - Re: [PATCH v3 bpf-next 08/14] samples: bpf: makefile: base target programs rules on Makefile.target

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Date:   Wed, 18 Sep 2019 13:23:03 +0300
From:   Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>
To:     Andrii Nakryiko <andrii.nakryiko@...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>,
        open list <linux-kernel@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        clang-built-linux@...glegroups.com,
        sergei.shtylyov@...entembedded.com
Subject: Re: [PATCH v3 bpf-next 08/14] samples: bpf: makefile: base target
 programs rules on Makefile.target

On Tue, Sep 17, 2019 at 04:28:01PM -0700, Andrii Nakryiko wrote:
>On Mon, Sep 16, 2019 at 3:58 AM Ivan Khoronzhuk
><ivan.khoronzhuk@...aro.org> wrote:
>>
>
>Please don't prepend "samples: bpf: makefile:" to patches,
>"samples/bpf: " is a typical we've used for BPF samples changes.
Ok.

>
>
>> The main reason for that - HOSTCC and CC have different aims.
>> HOSTCC is used to build programs running on host, that can
>> cross-comple target programs with CC. It was tested for arm and arm64
>> cross compilation, based on linaro toolchain, but should work for
>> others.
>>
>> So, in order to split cross compilation (CC) with host build (HOSTCC),
>> lets base samples on Makefile.target. It allows to cross-compile
>> samples/bpf programs with CC while auxialry tools running on host
>> built with HOSTCC.
>>
>> Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>
>> ---
>>  samples/bpf/Makefile | 135 ++++++++++++++++++++++---------------------
>>  1 file changed, 69 insertions(+), 66 deletions(-)
>>
>> diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
>> index 9d923546e087..1579cc16a1c2 100644
>> --- a/samples/bpf/Makefile
>> +++ b/samples/bpf/Makefile
>> @@ -4,55 +4,53 @@ BPF_SAMPLES_PATH ?= $(abspath $(srctree)/$(src))
>>  TOOLS_PATH := $(BPF_SAMPLES_PATH)/../../tools
>>
>>  # List of programs to build
>> -hostprogs-y := test_lru_dist
[...]
>> -KBUILD_HOSTCFLAGS := $(ARM_ARCH_SELECTOR)
>> +TPROGS_CFLAGS += $(ARM_ARCH_SELECTOR)
>>  endif
>>
>> +TPROGS_LDLIBS := $(KBUILD_HOSTLDLIBS)
>
>Please group TPROGS_LDLIBS definition together with the one below,
>there doesn't seem to be a reason to split them this way.
No. It's used in Makefile.target and should be here, following hostprog logic.

>
>But also, it's kind of weird to use host libraries as cross-compiled
>libraries as well. Is that intentional?
No cross-compile split yet. This patch replace only KBUILD on TPROGS.
It's done in following patches.

>
>> +TPROGS_CFLAGS += $(KBUILD_HOSTCFLAGS) $(HOST_EXTRACFLAGS)
>
>Same here, is it right to use HOSTCFLAGS and HOST_EXTRACFLAGS as a
>base for cross-compiled cflags?
same

[...]

-- 
Regards,
Ivan Khoronzhuk