netdev - Re: [PATCH bpf] tools/bpf: properly account for libbfd variations

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Message-ID: <20190115133800.658999bd@cakuba.netronome.com>
Date:   Tue, 15 Jan 2019 13:38:00 -0800
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Stanislav Fomichev <sdf@...gle.com>
Cc:     netdev@...r.kernel.org, davem@...emloft.net, ast@...nel.org,
        daniel@...earbox.net, quentin.monnet@...ronome.com
Subject: Re: [PATCH bpf] tools/bpf: properly account for libbfd variations

On Tue, 15 Jan 2019 11:59:53 -0800, Stanislav Fomichev wrote:
> On some platforms, in order to link against libbfd, we need to
> link against liberty and even possibly libz. Account for that
> in the bpftool Makefile. We now have proper feature detection
> for each case, so handle each one separately.
> 
> See recent commit 14541b1e7e72 ("perf build: Don't unconditionally link the
> libbfd feature test to -liberty and -lz") where I fixed feature
> detection.
> 
> Fixes: 29a9c10e4110 ("bpftool: make libbfd optional")
> Signed-off-by: Stanislav Fomichev <sdf@...gle.com>

Minor nits below, in any case:

Acked-by: Jakub Kicinski <jakub.kicinski@...ronome.com>

Thanks for making bpftool build! :)

> diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
> index 492f0f24e2d3..af9a25bf480d 100644
> --- a/tools/bpf/bpftool/Makefile
> +++ b/tools/bpf/bpftool/Makefile
> @@ -92,10 +92,21 @@ BFD_SRCS = jit_disasm.c
>  
>  SRCS = $(filter-out $(BFD_SRCS),$(wildcard *.c))
>  
> -ifeq ($(feature-libbfd),1)
> +ifeq ($(feature-libbfd), 1)

nit: no space there is more common

$ git grep 'ifeq' | grep ',[^ ]' | wc -l
482
$ git grep 'ifeq' | grep ', ' | wc -l
136


> +LIBS += -lbfd -ldl -lopcodes

nit: should this be indented?

> +else
> +  ifeq ($(feature-libbfd-liberty), 1)
> +    LIBS += -lbfd -ldl -lopcodes -liberty
> +  else
> +    ifeq ($(feature-libbfd-liberty-z), 1)
> +      LIBS += -lbfd -ldl -lopcodes -liberty -lz
> +    endif

Would this syntax:

ifeq ($(feature-libbfd),1)
  LIBS += ..
else ifeq ($(feature-libbfd-liberty),1)
  LIBS += ..
else ifeq ($(feature-libbfd-liberty-z),1)
  LIBS += ..
endif

Not work?

https://www.gnu.org/software/make/manual/html_node/Conditional-Syntax.html

I don't think I've ever tried, but looks more concise.. 

> +  endif
> +endif
> +
> +ifneq ($(filter -lbfd,$(EXTLIBS)),)
>  CFLAGS += -DHAVE_LIBBFD_SUPPORT
>  SRCS += $(BFD_SRCS)
> -LIBS += -lbfd -lopcodes
>  endif
>  
>  OBJS = $(patsubst %.c,$(OUTPUT)%.o,$(SRCS)) $(OUTPUT)disasm.o