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From:   Fangrui Song <maskray@google.com>
Date:   Sun, 18 Dec 2022 10:31:39 -0800
Message-ID: <CAFP8O3KZTkSbxXJ2yWt4w-F3xWHY_owCs03wN3Bhss57O-E_JQ@mail.gmail.com>
Subject: Re: [PATCH] vdso: Improve cmd_vdso_check to check all dynamic relocations
To:     Christophe Leroy <christophe.leroy@csgroup.eu>,
        Andy Lutomirski <luto@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Vincenzo Frascino <vincenzo.frascino@arm.com>
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On Sun, Dec 4, 2022 at 8:58 AM Christophe Leroy
<christophe.leroy@csgroup.eu> wrote:
>
>
>
> Le 04/12/2022 =C3=A0 05:50, Fangrui Song a =C3=A9crit :
> > On Mon, Nov 14, 2022 at 4:46 PM Fangrui Song <maskray@google.com> wrote=
:
> >>
> >> On 2022-11-14, Christophe Leroy wrote:
> >>>
> >>>
> >>> Le 28/09/2022 =C3=A0 07:25, Fangrui Song a =C3=A9crit :
> >>>> On Sat, Sep 10, 2022 at 12:53 AM Fangrui Song <maskray@google.com> w=
rote:
> >>>>>
> >>>>> On 2022-08-30, Fangrui Song wrote:
> >>>>>> The actual intention is that no dynamic relocation exists. However=
, some
> >>>>>> GNU ld ports produce unneeded R_*_NONE. (If a port is not care eno=
ugh to
> >>>>>> determine the exact .rel[a].dyn size, the trailing zeros become R_=
*_NONE
> >>>>>> relocations. E.g. powerpc64le ld as of 2.38 has the issue with
> >>>>>> defconfig.) R_*_NONE are generally no-op in the dynamic loaders. S=
o just
> >>>>>> ignore them.
> >>>>>>
> >>>>>> With the change, we can remove ARCH_REL_TYPE_ABS. ARCH_REL_TYPE_AB=
S is a
> >>>>>> bit misnomer as ports may check RELAVETIVE/GLOB_DAT/JUMP_SLOT whic=
h are
> >>>>>> not called "absolute relocations". (The patch is motivated by the =
arm64
> >>>>>> port missing R_AARCH64_RELATIVE.)
> >>>>>>
> >>>>>> While here, replace "egrep" with "grep" as "egrep" is deprecated i=
n GNU
> >>>>>> grep 3.7.
> >>>>>>
> >>>>>> Signed-off-by: Fangrui Song <maskray@google.com>
> >>>>>> ---
> >>>>>> [...]
> >>>>>>
> >>>>>
> >>>>> Ping.
> >>>>
> >>>> Ping^2 :)
> >>>
> >>> Can you explain which ARCH_REL_TYPE_ABS can be removed with this chan=
ge ?
> >>> How is the verification done if ARCH_REL_TYPE_ABS is removed ?
> >>
> >> All ARCH_REL_TYPE_ABS relocation types can be removed. As explained, t=
he
> >> real intention is to check no dynamic relocation, and this is done by
> >> the new
>
> Well, there was a typo in my question, I wanted to ask 'why', not 'which'=
.
>
> >>
> >>     cmd_vdso_check =3D if $(READELF) -rW $@ | grep -v _NONE | grep -q =
"R_\w*_"; \
> >>
> >> in this patch.
> >>
> >> grep -v _NONE is to work around some GNU ld ports (and likely older re=
leases
> >> of some ports even if their latest versions are fixed) which produce
> >> unneeded R_*_NONE dynamic relocations.
> >
> > Ping :)
>
> Ok, that seems to work on powerpc.
>
> Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>

Thanks. Can a maintainer pick up this commit?