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In-Reply-To: <CTM7K580U3T2.261RJKV58M653@wheely>
From:   Masahiro Yamada <masahiroy@kernel.org>
Date:   Mon, 26 Jun 2023 12:11:27 +0900
Message-ID: <CAK7LNARx4exTpkCeR47T+XdF5-a7nLZ19p0R4tvnqyOT5y92XQ@mail.gmail.com>
Subject: Re: [PATCH] powerpc: remove checks for binutils older than 2.25
To:     Nicholas Piggin <npiggin@gmail.com>
Cc:     Joel Stanley <joel@jms.id.au>,
        Michael Ellerman <mpe@ellerman.id.au>,
        linuxppc-dev@lists.ozlabs.org, linux-kbuild@vger.kernel.org,
        Christophe Leroy <christophe.leroy@csgroup.eu>,
        Nathan Chancellor <nathan@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        linux-kernel@vger.kernel.org, Nicolas Schier <nicolas@fjasle.eu>
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On Mon, Jun 26, 2023 at 10:58=E2=80=AFAM Nicholas Piggin <npiggin@gmail.com=
> wrote:
>
> On Sun Jun 25, 2023 at 6:02 PM AEST, Masahiro Yamada wrote:
> > On Thu, Jan 19, 2023 at 9:37=E2=80=AFPM Masahiro Yamada <masahiroy@kern=
el.org> wrote:
> > >
> > > On Thu, Jan 19, 2023 at 9:12 PM Joel Stanley <joel@jms.id.au> wrote:
> > > >
> > > > On Thu, 19 Jan 2023 at 08:24, Masahiro Yamada <masahiroy@kernel.org=
> wrote:
> > > > >
> > > > > Commit e4412739472b ("Documentation: raise minimum supported vers=
ion of
> > > > > binutils to 2.25") allows us to remove the checks for old binutil=
s.
> > > > >
> > > > > There is no more user for ld-ifversion. Remove it as well.
> > > >
> > > > ppc kernels fail to link with 2.27 under some configurations:
> > > >
> > > >  https://github.com/linuxppc/issues/issues/388
> > > >
> > > > We may want to use ld-ifversion to exclude that version.
> > >
> > >
> >
> >
> > Ping?
> >
> >
> >
> >
> > >
> > > For LLD, CONFIG option is directly checked.
>
> Yeah, doesn't seem too difficult to add new linker version tests if neede=
d.
>
> > >
> > >
> > > masahiro@zoe:~/ref/linux(master)$ git grep  CONFIG_LLD_VERSION
> > > Makefile:ifeq ($(call test-lt, $(CONFIG_LLD_VERSION), 130000),y)
> > > arch/riscv/Makefile:ifeq ($(call test-lt, $(CONFIG_LLD_VERSION), 1500=
00),y)
> > > arch/x86/Makefile:ifeq ($(call test-lt, $(CONFIG_LLD_VERSION), 130000=
),y)
> > > scripts/Kbuild.include:# Usage: $(call test-lt, $(CONFIG_LLD_VERSION)=
, 150000)
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > > >
> > > > > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> > > > > ---
> > > > >
> > > > >  arch/powerpc/Makefile     | 22 +---------------------
> > > > >  arch/powerpc/lib/Makefile |  2 +-
> > > > >  scripts/Makefile.compiler |  4 ----
> > > > >  3 files changed, 2 insertions(+), 26 deletions(-)
> > > > >
> > > > > diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
> > > > > index dc4cbf0a5ca9..3d265b16c0ae 100644
> > > > > --- a/arch/powerpc/Makefile
> > > > > +++ b/arch/powerpc/Makefile
> > > > > @@ -42,18 +42,13 @@ machine-$(CONFIG_PPC64) +=3D 64
> > > > >  machine-$(CONFIG_CPU_LITTLE_ENDIAN) +=3D le
> > > > >  UTS_MACHINE :=3D $(subst $(space),,$(machine-y))
> > > > >
> > > > > -# XXX This needs to be before we override LD below
> > > > > -ifdef CONFIG_PPC32
> > > > > -KBUILD_LDFLAGS_MODULE +=3D arch/powerpc/lib/crtsavres.o
> > > > > -else
> > > > > -ifeq ($(call ld-ifversion, -ge, 22500, y),y)
> > > > > +ifeq ($(CONFIG_PPC64)$(CONFIG_LD_IS_BFD),yy)
> > > > >  # Have the linker provide sfpr if possible.
> > > > >  # There is a corresponding test in arch/powerpc/lib/Makefile
> > > > >  KBUILD_LDFLAGS_MODULE +=3D --save-restore-funcs
> > > > >  else
> > > > >  KBUILD_LDFLAGS_MODULE +=3D arch/powerpc/lib/crtsavres.o
> > > > >  endif
> > > > > -endif
> > > > >
> > > > >  ifdef CONFIG_CPU_LITTLE_ENDIAN
> > > > >  KBUILD_CFLAGS  +=3D -mlittle-endian
> > > > > @@ -389,8 +384,6 @@ vdso_prepare: prepare0
> > > > >                 $(build)=3Darch/powerpc/kernel/vdso include/gener=
ated/vdso64-offsets.h)
> > > > >  endif
> > > > >
> > > > > -archprepare: checkbin
> > > > > -
> > > > >  archheaders:
> > > > >         $(Q)$(MAKE) $(build)=3Darch/powerpc/kernel/syscalls all
> > > > >
> > > > > @@ -405,16 +398,3 @@ else
> > > > >         $(eval KBUILD_CFLAGS +=3D -mstack-protector-guard-offset=
=3D$(shell awk '{if ($$2 =3D=3D "TASK_CANARY") print $$3;}' include/generat=
ed/asm-offsets.h))
> > > > >  endif
> > > > >  endif
> > > > > -
> > > > > -PHONY +=3D checkbin
> > > > > -# Check toolchain versions:
> > > > > -# - gcc-4.6 is the minimum kernel-wide version so nothing requir=
ed.
> > > > > -checkbin:
> > > > > -       @if test "x${CONFIG_LD_IS_LLD}" !=3D "xy" -a \
> > > > > -               "x$(call ld-ifversion, -le, 22400, y)" =3D "xy" ;=
 then \
> > > > > -               echo -n '*** binutils 2.24 miscompiles weak symbo=
ls ' ; \
> > > > > -               echo 'in some circumstances.' ; \
> > > > > -               echo    '*** binutils 2.23 do not define the TOC =
symbol ' ; \
> > > > > -               echo -n '*** Please use a different binutils vers=
ion.' ; \
> > > > > -               false ; \
> > > > > -       fi
> > > > > diff --git a/arch/powerpc/lib/Makefile b/arch/powerpc/lib/Makefil=
e
> > > > > index 4de71cbf6e8e..c53618c34b70 100644
> > > > > --- a/arch/powerpc/lib/Makefile
> > > > > +++ b/arch/powerpc/lib/Makefile
> > > > > @@ -42,7 +42,7 @@ obj-$(CONFIG_FUNCTION_ERROR_INJECTION)        +=
=3D error-inject.o
> > > > >  # 64-bit linker creates .sfpr on demand for final link (vmlinux)=
,
> > > > >  # so it is only needed for modules, and only for older linkers w=
hich
> > > > >  # do not support --save-restore-funcs
> > > > > -ifeq ($(call ld-ifversion, -lt, 22500, y),y)
> > > > > +ifndef CONFIG_LD_IS_BFD
> > > > >  extra-$(CONFIG_PPC64)  +=3D crtsavres.o
> > > > >  endif
>
> This test got inverted for LLD now AFAIKS?


In my understanding,
For a BFD linker, use --save-restore-funcs.
Otherwise (i.e. CONFIG_LD_IS_BFD is unset), link crtsavres.o to modules.

I hope I did not change the logic.


>
> Does LLVM support --save-restore-funcs and supply .sfpr already I
> wonder? We could remove this stuff entirely.

I don't know.

If LLVM 11.0.0  (the minimum supported LLVM version) supports
--save-restore-funcs, you can remove this check entirely.
Even so, it should be done in a follow-up patch.


This patch is just dropping dead code for BFD linker < 2.25,
which is now unsupported. Nothing else has changed (I believe).


--=20
Best Regards
Masahiro Yamada