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

From: Ivan Khoronzhuk <[email-masked]>
Date: Fri, 20 Sep 2019 22:19:43 +0300

On Fri, Sep 20, 2019 at 09:34:51PM +0300, Ivan Khoronzhuk wrote:
>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.

It actually works for any numbs of X1.X2...X100
but not when you have couple kindof:
X1.X2.X3
and
X1.X2.X3.X4

But, no absolutely any problem to extend this solution to handle all cases,
by just adding leading 0 to every "transformed version", say limit it to 10
possible 'dots' (%5*10d) and it will work as clocks. Advantage - mostly make
functions.

Here can be couple more solutions with sed, not sure it can look less maniac.

>
>>fetching the last version in libbpf.map file. See
>>https://www.spinics.net/lists/netdev/msg592703.html.

Yes it's nice but, no sort, no X1.X2.X3....XN

Main is to solve it for a long time.

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

-- 
Regards,
Ivan Khoronzhuk