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

From: Ivan Khoronzhuk <[email-masked]>
Date: Fri, 20 Sep 2019 21:34:51 +0300

On Fri, Sep 20, 2019 at 09:41:54AM -0700, Andrii Nakryiko wrote:
>On Fri, Sep 20, 2019 at 1:22 AM Ivan Khoronzhuk
><[email-masked]> 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
>> ><[email-masked]> 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 <[email-masked]>
>> >> ---
>> >>
>> >> 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
Yes, forgot to add
X1,X2,X3,...XN, where X = {0,1,....99999} and N = const for all versions.
But frankly, 1.0.0 looks too far.

>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

-- 
Regards,
Ivan Khoronzhuk