netdev - Re: [PATCH bpf] libbpf: fix version identification on busybox

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Date:   Fri, 20 Sep 2019 09:41:54 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin Lau <kafai@...com>, Andrii Nakryiko <andriin@...com>,
        Yonghong Song <yhs@...com>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf] libbpf: fix version identification on busybox

On Fri, Sep 20, 2019 at 1:22 AM Ivan Khoronzhuk
<ivan.khoronzhuk@...aro.org> wrote:
>
> On Thu, Sep 19, 2019 at 01:02:40PM -0700, Andrii Nakryiko wrote:
> >On Thu, Sep 19, 2019 at 11:22 AM Ivan Khoronzhuk
> ><ivan.khoronzhuk@...aro.org> wrote:
> >>
> >> It's very often for embedded to have stripped version of sort in
> >> busybox, when no -V option present. It breaks build natively on target
> >> board causing recursive loop.
> >>
> >> BusyBox v1.24.1 (2019-04-06 04:09:16 UTC) multi-call binary. \
> >> Usage: sort [-nrugMcszbdfimSTokt] [-o FILE] [-k \
> >> start[.offset][opts][,end[.offset][opts]] [-t CHAR] [FILE]...
> >>
> >> Lets modify command a little to avoid -V option.
> >>
> >> Fixes: dadb81d0afe732 ("libbpf: make libbpf.map source of truth for libbpf version")
> >>
> >> Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>
> >> ---
> >>
> >> Based on bpf/master
> >>
> >>  tools/lib/bpf/Makefile | 2 +-
> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/tools/lib/bpf/Makefile b/tools/lib/bpf/Makefile
> >> index c6f94cffe06e..a12490ad6215 100644
> >> --- a/tools/lib/bpf/Makefile
> >> +++ b/tools/lib/bpf/Makefile
> >> @@ -3,7 +3,7 @@
> >>
> >>  LIBBPF_VERSION := $(shell \
> >>         grep -oE '^LIBBPF_([0-9.]+)' libbpf.map | \
> >> -       sort -rV | head -n1 | cut -d'_' -f2)
> >> +       cut -d'_' -f2 | sort -r | head -n1)
> >
> >You can't just sort alphabetically, because:
> >
> >1.2
> >1.11
> >
> >should be in that order. See discussion on mailing thread for original commit.
>
> if X1.X2.X3, where X = {0,1,....99999}
> Then it can be:
>
> -LIBBPF_VERSION := $(shell \
> -       grep -oE '^LIBBPF_([0-9.]+)' libbpf.map | \
> -       sort -rV | head -n1 | cut -d'_' -f2)
> +_LBPFLIST := $(patsubst %;,%,$(patsubst LIBBPF_%,%,$(filter LIBBPF_%, \
> +           $(shell cat libbpf.map))))
> +_LBPFLIST2 := $(foreach v,$(_LBPFLIST), \
> +               $(subst $() $(),,$(foreach n,$(subst .,$() $(),$(v)), \
> +                       $(shell printf "%05d" $(n)))))
> +_LBPF_VER := $(word $(words $(sort $(_LBPFLIST2))), $(sort $(_LBPFLIST2)))
> +LIBBPF_VERSION := $(patsubst %_$(_LBPF_VER),%,$(filter %_$(_LBPF_VER), \
> +        $(join $(addsuffix _, $(_LBPFLIST)),$(_LBPFLIST2))))
>
> It's bigger but avoids invocations of grep/sort/cut/head, only cat/printf
> , thus -V option also.
>

No way, this is way too ugly (and still unreliable, if we ever have
X.Y.Z.W or something). I'd rather go with my original approach of
fetching the last version in libbpf.map file. See
https://www.spinics.net/lists/netdev/msg592703.html.

> >
> >>  LIBBPF_MAJOR_VERSION := $(firstword $(subst ., ,$(LIBBPF_VERSION)))
> >>
> >>  MAKEFLAGS += --no-print-directory
> >> --
> >> 2.17.1
> >>
>
> --
> Regards,
> Ivan Khoronzhuk