netdev - Re: [PATCH bpf] tools/bpf: fix bpftool build with OUTPUT set

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Date:   Tue, 23 Jul 2019 13:59:01 +0100
From:   Lorenz Bauer <lmb@...udflare.com>
To:     Ilya Leoshkevich <iii@...ux.ibm.com>
Cc:     bpf <bpf@...r.kernel.org>, Networking <netdev@...r.kernel.org>,
        gor@...ux.ibm.com, heiko.carstens@...ibm.com
Subject: Re: [PATCH bpf] tools/bpf: fix bpftool build with OUTPUT set

Hi Ilya,

Thanks for your patch! I tried it but had problems with
cross-compilation. Not sure if this is related to the patch or not
though, I haven't had the time to follow up.

Best
Lorenz

On Thu, 18 Jul 2019 at 15:20, Ilya Leoshkevich <iii@...ux.ibm.com> wrote:
>
> Hi Lorenz,
>
> I've been using the following patch for quite some time now.
> Please let me know if it works for you.
>
> Best regards,
> Ilya
>
> ---
>
> When OUTPUT is set, bpftool and libbpf put their objects into the same
> directory, and since some of them have the same names, the collision
> happens.
>
> Fix by invoking libbpf build in a manner similar to $(call descend) -
> descend itself cannot be used, since libbpf is a sibling, and not a
> child, of bpftool.
>
> Also, don't link bpftool with libbpf.a twice.
>
> Signed-off-by: Ilya Leoshkevich <iii@...ux.ibm.com>
> ---
>  tools/bpf/bpftool/Makefile | 17 ++++++-----------
>  1 file changed, 6 insertions(+), 11 deletions(-)
>
> diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
> index a7afea4dec47..2cbc3c166f44 100644
> --- a/tools/bpf/bpftool/Makefile
> +++ b/tools/bpf/bpftool/Makefile
> @@ -15,23 +15,18 @@ else
>  endif
>
>  BPF_DIR = $(srctree)/tools/lib/bpf/
> -
> -ifneq ($(OUTPUT),)
> -  BPF_PATH = $(OUTPUT)
> -else
> -  BPF_PATH = $(BPF_DIR)
> -endif
> -
> -LIBBPF = $(BPF_PATH)libbpf.a
> +BPF_PATH = $(objtree)/tools/lib/bpf
> +LIBBPF = $(BPF_PATH)/libbpf.a
>
>  BPFTOOL_VERSION := $(shell make --no-print-directory -sC ../../.. kernelversion)
>
>  $(LIBBPF): FORCE
> -       $(Q)$(MAKE) -C $(BPF_DIR) OUTPUT=$(OUTPUT) $(OUTPUT)libbpf.a
> +       $(Q)mkdir -p $(BPF_PATH)
> +       $(Q)$(MAKE) $(COMMAND_O) subdir=tools/lib/bpf -C $(BPF_DIR) $(LIBBPF)
>
>  $(LIBBPF)-clean:
>         $(call QUIET_CLEAN, libbpf)
> -       $(Q)$(MAKE) -C $(BPF_DIR) OUTPUT=$(OUTPUT) clean >/dev/null
> +       $(Q)$(MAKE) $(COMMAND_O) subdir=tools/lib/bpf -C $(BPF_DIR) clean >/dev/null
>
>  prefix ?= /usr/local
>  bash_compdir ?= /usr/share/bash-completion/completions
> @@ -112,7 +107,7 @@ $(OUTPUT)disasm.o: $(srctree)/kernel/bpf/disasm.c
>         $(QUIET_CC)$(COMPILE.c) -MMD -o $@ $<
>
>  $(OUTPUT)bpftool: $(OBJS) $(LIBBPF)
> -       $(QUIET_LINK)$(CC) $(CFLAGS) $(LDFLAGS) -o $@ $^ $(LIBS)
> +       $(QUIET_LINK)$(CC) $(CFLAGS) $(LDFLAGS) -o $@ $(OBJS) $(LIBS)
>
>  $(OUTPUT)%.o: %.c
>         $(QUIET_CC)$(COMPILE.c) -MMD -o $@ $<
> --
> 2.21.0
>


-- 
Lorenz Bauer  |  Systems Engineer
6th Floor, County Hall/The Riverside Building, SE1 7PB, UK

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