linux-kernel - Re: [PATCH 2/2] powerpc: remove old code for binutils

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Date:   Tue, 30 Aug 2022 15:01:12 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Nathan Chancellor <nathan@...nel.org>
Cc:     Masahiro Yamada <masahiroy@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        Fangrui Song <maskray@...gle.com>, nemanja.i.ibm@...il.com
Subject: Re: [PATCH 2/2] powerpc: remove old code for binutils < 2.25

On Tue, Aug 30, 2022 at 2:44 PM Nathan Chancellor <nathan@...nel.org> wrote:
>
> On Tue, Aug 30, 2022 at 02:13:20PM -0700, Nick Desaulniers wrote:
> > On Tue, Aug 30, 2022 at 12:10 PM Masahiro Yamada <masahiroy@...nel.org> wrote:
> > >
> > > The minimum supported version of binutils has been raised to 2.25.1.
> > > Drop the old code.
> > >
> > > PPC is the last user of ld-ifversion. With all the callers removed,
> > > the macro definition in scripts/Makefile.compiler can go away.
> > >
> > > Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> > > ---
> > >
> > >  arch/powerpc/Makefile     | 21 ---------------------
> > >  arch/powerpc/lib/Makefile |  8 --------
> > >  scripts/Makefile.compiler |  4 ----
> > >  3 files changed, 33 deletions(-)
> > >
> > > diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
> > > index 02742facf895..fb607758eeca 100644
> > > --- a/arch/powerpc/Makefile
> > > +++ b/arch/powerpc/Makefile
> > > @@ -46,13 +46,7 @@ UTS_MACHINE := $(subst $(space),,$(machine-y))
> > >  ifdef CONFIG_PPC32
> > >  KBUILD_LDFLAGS_MODULE += arch/powerpc/lib/crtsavres.o
> > >  else
> > > -ifeq ($(call ld-ifversion, -ge, 22500, y),y)
> > > -# Have the linker provide sfpr if possible.
> >
> > ^ Perhaps this comment is still relevant and should not yet be
> > discarded? Or updated, dropping " if possible".
> >
> > Either way:
> > Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>
>
> I think we still want this block for ld.lld. Prior to this change,
> ld.lld would fail the ld-ifversion check and use crtsavres.o. Now, it
> will try to use '--save-restore-funcs', which it doesn't have support
> for, breaking the build for at least powernv_defconfig:
>
> ld.lld: error: unknown argument '--save-restore-funcs'

Good catch, this should probably be rewritten to use ld-option then.

I wonder what LLD's default behavior is, and if we need a feature request filed?

>
> > > -# There is a corresponding test in arch/powerpc/lib/Makefile
> > >  KBUILD_LDFLAGS_MODULE += --save-restore-funcs
> > > -else
> > > -KBUILD_LDFLAGS_MODULE += arch/powerpc/lib/crtsavres.o
> > > -endif
> > >  endif
> > >
> > >  ifdef CONFIG_CPU_LITTLE_ENDIAN
> > > @@ -395,8 +389,6 @@ vdso_prepare: prepare0
> > >                 $(build)=arch/powerpc/kernel/vdso include/generated/vdso64-offsets.h)
> > >  endif
> > >
> > > -archprepare: checkbin
> > > -
> > >  archheaders:
> > >         $(Q)$(MAKE) $(build)=arch/powerpc/kernel/syscalls all
> > >
> > > @@ -411,16 +403,3 @@ else
> > >         $(eval KBUILD_CFLAGS += -mstack-protector-guard-offset=$(shell awk '{if ($$2 == "TASK_CANARY") print $$3;}' include/generated/asm-offsets.h))
> > >  endif
> > >  endif
> > > -
> > > -PHONY += checkbin
> > > -# Check toolchain versions:
> > > -# - gcc-4.6 is the minimum kernel-wide version so nothing required.
> > > -checkbin:
> > > -       @if test "x${CONFIG_LD_IS_LLD}" != "xy" -a \
> > > -               "x$(call ld-ifversion, -le, 22400, y)" = "xy" ; then \
> > > -               echo -n '*** binutils 2.24 miscompiles weak symbols ' ; \
> > > -               echo 'in some circumstances.' ; \
> > > -               echo    '*** binutils 2.23 do not define the TOC symbol ' ; \
> > > -               echo -n '*** Please use a different binutils version.' ; \
> > > -               false ; \
> > > -       fi
> > > diff --git a/arch/powerpc/lib/Makefile b/arch/powerpc/lib/Makefile
> > > index 8560c912186d..5eb3971ccb9c 100644
> > > --- a/arch/powerpc/lib/Makefile
> > > +++ b/arch/powerpc/lib/Makefile
> > > @@ -38,14 +38,6 @@ obj-$(CONFIG_PPC32)  += div64.o copy_32.o crtsavres.o
> > >
> > >  obj-$(CONFIG_FUNCTION_ERROR_INJECTION) += error-inject.o
> > >
> > > -# See corresponding test in arch/powerpc/Makefile
> > > -# 64-bit linker creates .sfpr on demand for final link (vmlinux),
> > > -# so it is only needed for modules, and only for older linkers which
> > > -# do not support --save-restore-funcs
> > > -ifeq ($(call ld-ifversion, -lt, 22500, y),y)
> > > -extra-$(CONFIG_PPC64)  += crtsavres.o
> > > -endif
> > > -
> > >  obj-$(CONFIG_PPC_BOOK3S_64) += copyuser_power7.o copypage_power7.o \
> > >                                memcpy_power7.o restart_table.o
> > >
> > > diff --git a/scripts/Makefile.compiler b/scripts/Makefile.compiler
> > > index 94d0d40cddb3..63e7d79dd877 100644
> > > --- a/scripts/Makefile.compiler
> > > +++ b/scripts/Makefile.compiler
> > > @@ -68,7 +68,3 @@ cc-ifversion = $(shell [ $(CONFIG_GCC_VERSION)0 $(1) $(2)000 ] && echo $(3) || e
> > >  # ld-option
> > >  # Usage: KBUILD_LDFLAGS += $(call ld-option, -X, -Y)
> > >  ld-option = $(call try-run, $(LD) $(KBUILD_LDFLAGS) $(1) -v,$(1),$(2),$(3))
> > > -
> > > -# ld-ifversion
> > > -# Usage:  $(call ld-ifversion, -ge, 22252, y)
> > > -ld-ifversion = $(shell [ $(CONFIG_LD_VERSION)0 $(1) $(2)0 ] && echo $(3) || echo $(4))
> > > --
> > > 2.34.1
> > >
> >
> >
> > --
> > Thanks,
> > ~Nick Desaulniers



-- 
Thanks,
~Nick Desaulniers