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

From: Ivan Khoronzhuk <[email-masked]>
Date: Fri, 20 Sep 2019 11:22:06 +0300

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.

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

-- 
Regards,
Ivan Khoronzhuk