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

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Message-ID: <CAEf4BzZGeY-WD17mq6FTd7Rae_f26j4kBAWCmuppeu4VjZxvUg@mail.gmail.com>
Date:   Fri, 20 Sep 2019 14:51:14 -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 12:19 PM Ivan Khoronzhuk
<ivan.khoronzhuk@...aro.org> wrote:
>
> 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
> >><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
> >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.

Thinking a bit more about this, I'm even more convinced that we should
just go with my original approach: find last section in libbpf.map and
extract LIBBPF version from that. That will handle whatever crazy
version format we might decide to use (e.g., 1.2.3-experimental).
We'll just need to make sure that latest version is the last in
libbpf.map, which will just happen naturally. So instead of this
Makefile complexity, please can you port back my original approach?
Thanks!

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