RE: [PATCH] ARM: fix linker call for ARM_MODULE_PLTS - Wiebe, Wladislav (Nokia

From: "Wiebe, Wladislav (Nokia - DE/Ulm)" <wladislav.wiebe@nokia.com>
To: Russell King - ARM Linux <linux@armlinux.org.uk>
Cc: "linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH] ARM: fix linker call for ARM_MODULE_PLTS
Date: Fri, 2 Sep 2016 12:02:43 +0000	[thread overview]
Message-ID: <HE1PR07MB1483372BB908734FF6459DD2FAE50@HE1PR07MB1483.eurprd07.prod.outlook.com> (raw)
In-Reply-To: <20160902092450.GB1041@n2100.armlinux.org.uk>

> From: Russell King - ARM Linux [mailto:linux@armlinux.org.uk]
> Sent: Friday, September 02, 2016 11:25 AM
> 
> On Fri, Sep 02, 2016 at 09:17:58AM +0000, Wiebe, Wladislav (Nokia - DE/Ulm)
> wrote:
> > module.lds script doesn't get called when
> > CONFIG_ARM_MODULE_PLTS is enabled.
> > Use KBUILD_LDFLAGS_MODULE to fix it.
> 
> For those of us who haven't encountered this problem, could you include
> some commentry in the commit message describing the failure mechanism
> and why you think this is the correct solution?
> 
> The final link for modules is:
> 
> quiet_cmd_ld_ko_o = LD [M]  $@
>       cmd_ld_ko_o = $(LD) -r $(LDFLAGS)                                 \
>                              $(KBUILD_LDFLAGS_MODULE) $(LDFLAGS_MODULE) \
>                              -o $@ $(filter-out FORCE,$^)
> 
> which seems to always include both flags.  Why is it ignored when it's
> in LDFLAGS_MODULE?  What about the other flags we pass in
> LDFLAGS_MODULE?

aah -- just found an issue in my environment where LDFLAGS_MODULE gets overwritten
due to a none upstream patch on scripts/Makefile.modpost.

It worked only for me when using the KBUILD_LDFLAGS_MODULE
and I did not get deep inside after I saw in 
https://www.kernel.org/doc/Documentation/kbuild/makefiles.txt
+++++
    KBUILD_LDFLAGS_MODULE   Options for $(LD) when linking modules

	$(KBUILD_LDFLAGS_MODULE) is used to add arch-specific options
	used when linking modules. This is often a linker script.
	From commandline LDFLAGS_MODULE shall be used (see kbuild.txt).
+++++

and found that all other architectures are also users of KBUILD_LDFLAGS_MODULE for that purpose
$ git grep LDFLAGS_MODULE arch/
arch/arm/Makefile:LDFLAGS_MODULE        += --be8
arch/arm/Makefile:LDFLAGS_MODULE        += -T $(srctree)/arch/arm/kernel/module.lds
arch/arm64/Makefile:KBUILD_LDFLAGS_MODULE       += -T $(srctree)/arch/arm64/kernel/module.lds
arch/hexagon/Makefile:# LDFLAGS_MODULE += -shared
arch/ia64/Makefile:KBUILD_LDFLAGS_MODULE += -T $(srctree)/arch/ia64/module.lds
arch/m68k/Makefile:KBUILD_LDFLAGS_MODULE += -T $(srctree)/arch/m68k/kernel/module.lds
arch/powerpc/Makefile:KBUILD_LDFLAGS_MODULE += arch/powerpc/lib/crtsavres.o
arch/powerpc/Makefile:  KBUILD_LDFLAGS_MODULE += --ppc476-workaround \

Anyway, feel free to ignore this patch and thanks a lot for the fast feedback.

> 
> Thanks.
> 
> >
> > Signed-off-by: Wladislav Wiebe <wladislav.wiebe@nokia.com>
> > ---
> >  arch/arm/Makefile | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/arm/Makefile b/arch/arm/Makefile
> > index 61f6ccc..01c6025 100644
> > --- a/arch/arm/Makefile
> > +++ b/arch/arm/Makefile
> > @@ -20,7 +20,7 @@ LDFLAGS_MODULE	+= --be8
> >  endif
> >
> >  ifeq ($(CONFIG_ARM_MODULE_PLTS),y)
> > -LDFLAGS_MODULE	+= -T $(srctree)/arch/arm/kernel/module.lds
> > +KBUILD_LDFLAGS_MODULE	+= -T $(srctree)/arch/arm/kernel/module.lds
> >  endif
> >
> >  OBJCOPYFLAGS	:=-O binary -R .comment -S
> > --
> > 1.7.12.4
> 
> --
> RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
> FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
> according to speedtest.net.