[V2] LoongArch: Fix module relocation error with binutils 2.41

  Binutils 2.41 enables linker relaxation by default, but the kernel
module loader doesn't support that, so just disable it. Otherwise we
get such an error when loading modules:

"Unknown relocation type 102"

As an alternative, we could add linker relaxation support in the kernel
module loader. But it is relatively large complexity that may or may not
bring a similar gain, and we don't really want to include this linker
pass in the kernel.

Reviewed-by: WANG Xuerui <git@xen0n.name>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
---
 arch/loongarch/Makefile | 2 ++
 1 file changed, 2 insertions(+)
  

Can we backport this patch into stable?  It fixes a build error with
binutils >= 2.41.

On Mon, 2023-07-10 at 13:00 +0800, Huacai Chen wrote:
> Binutils 2.41 enables linker relaxation by default, but the kernel
> module loader doesn't support that, so just disable it. Otherwise we
> get such an error when loading modules:
> 
> "Unknown relocation type 102"
> 
> As an alternative, we could add linker relaxation support in the kernel
> module loader. But it is relatively large complexity that may or may not
> bring a similar gain, and we don't really want to include this linker
> pass in the kernel.
> 
> Reviewed-by: WANG Xuerui <git@xen0n.name>
> Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
> ---
>  arch/loongarch/Makefile | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/loongarch/Makefile b/arch/loongarch/Makefile
> index 09ba338a64de..7466d3b15db8 100644
> --- a/arch/loongarch/Makefile
> +++ b/arch/loongarch/Makefile
> @@ -68,6 +68,8 @@ LDFLAGS_vmlinux                       += -static -n -nostdlib
>  ifdef CONFIG_AS_HAS_EXPLICIT_RELOCS
>  cflags-y                       += $(call cc-option,-mexplicit-relocs)
>  KBUILD_CFLAGS_KERNEL           += $(call cc-option,-mdirect-extern-access)
> +KBUILD_AFLAGS_MODULE           += $(call cc-option,-mno-relax) $(call cc-option,-Wa$(comma)-mno-relax)
> +KBUILD_CFLAGS_MODULE           += $(call cc-option,-mno-relax) $(call cc-option,-Wa$(comma)-mno-relax)
>  else
>  cflags-y                       += $(call cc-option,-mno-explicit-relocs)
>  KBUILD_AFLAGS_KERNEL           += -Wa,-mla-global-with-pcrel
  

On Thu, 2023-08-10 at 11:20 +0800, Xi Ruoyao wrote:
> Can we backport this patch into stable?  It fixes a build error with
> binutils >= 2.41.

Correction: not a build error, but all modules won't load if built with
binutils >= 2.41 without the patch.

> On Mon, 2023-07-10 at 13:00 +0800, Huacai Chen wrote:
> > Binutils 2.41 enables linker relaxation by default, but the kernel
> > module loader doesn't support that, so just disable it. Otherwise we
> > get such an error when loading modules:
> > 
> > "Unknown relocation type 102"
> > 
> > As an alternative, we could add linker relaxation support in the kernel
> > module loader. But it is relatively large complexity that may or may not
> > bring a similar gain, and we don't really want to include this linker
> > pass in the kernel.
> > 
> > Reviewed-by: WANG Xuerui <git@xen0n.name>
> > Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
> > ---
> >  arch/loongarch/Makefile | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/arch/loongarch/Makefile b/arch/loongarch/Makefile
> > index 09ba338a64de..7466d3b15db8 100644
> > --- a/arch/loongarch/Makefile
> > +++ b/arch/loongarch/Makefile
> > @@ -68,6 +68,8 @@ LDFLAGS_vmlinux                       += -static -n -nostdlib
> >  ifdef CONFIG_AS_HAS_EXPLICIT_RELOCS
> >  cflags-y                       += $(call cc-option,-mexplicit-relocs)
> >  KBUILD_CFLAGS_KERNEL           += $(call cc-option,-mdirect-extern-access)
> > +KBUILD_AFLAGS_MODULE           += $(call cc-option,-mno-relax) $(call cc-option,-Wa$(comma)-mno-relax)
> > +KBUILD_CFLAGS_MODULE           += $(call cc-option,-mno-relax) $(call cc-option,-Wa$(comma)-mno-relax)
> >  else
> >  cflags-y                       += $(call cc-option,-mno-explicit-relocs)
> >  KBUILD_AFLAGS_KERNEL           += -Wa,-mla-global-with-pcrel
>
  

Hi, Ruoyao,

On Thu, Aug 10, 2023 at 11:21 AM Xi Ruoyao <xry111@xry111.site> wrote:
>
> On Thu, 2023-08-10 at 11:20 +0800, Xi Ruoyao wrote:
> > Can we backport this patch into stable?  It fixes a build error with
> > binutils >= 2.41.
>
> Correction: not a build error, but all modules won't load if built with
> binutils >= 2.41 without the patch.
Generally we can backport, but I don't think there are users who use
the old kernels. :)

Huacai
>
> > On Mon, 2023-07-10 at 13:00 +0800, Huacai Chen wrote:
> > > Binutils 2.41 enables linker relaxation by default, but the kernel
> > > module loader doesn't support that, so just disable it. Otherwise we
> > > get such an error when loading modules:
> > >
> > > "Unknown relocation type 102"
> > >
> > > As an alternative, we could add linker relaxation support in the kernel
> > > module loader. But it is relatively large complexity that may or may not
> > > bring a similar gain, and we don't really want to include this linker
> > > pass in the kernel.
> > >
> > > Reviewed-by: WANG Xuerui <git@xen0n.name>
> > > Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
> > > ---
> > >  arch/loongarch/Makefile | 2 ++
> > >  1 file changed, 2 insertions(+)
> > >
> > > diff --git a/arch/loongarch/Makefile b/arch/loongarch/Makefile
> > > index 09ba338a64de..7466d3b15db8 100644
> > > --- a/arch/loongarch/Makefile
> > > +++ b/arch/loongarch/Makefile
> > > @@ -68,6 +68,8 @@ LDFLAGS_vmlinux                       += -static -n -nostdlib
> > >  ifdef CONFIG_AS_HAS_EXPLICIT_RELOCS
> > >  cflags-y                       += $(call cc-option,-mexplicit-relocs)
> > >  KBUILD_CFLAGS_KERNEL           += $(call cc-option,-mdirect-extern-access)
> > > +KBUILD_AFLAGS_MODULE           += $(call cc-option,-mno-relax) $(call cc-option,-Wa$(comma)-mno-relax)
> > > +KBUILD_CFLAGS_MODULE           += $(call cc-option,-mno-relax) $(call cc-option,-Wa$(comma)-mno-relax)
> > >  else
> > >  cflags-y                       += $(call cc-option,-mno-explicit-relocs)
> > >  KBUILD_AFLAGS_KERNEL           += -Wa,-mla-global-with-pcrel
> >
>
> --
> Xi Ruoyao <xry111@xry111.site>
> School of Aerospace Science and Technology, Xidian University
  

On Thu, 2023-08-10 at 11:34 +0800, Huacai Chen wrote:
> On Thu, Aug 10, 2023 at 11:21 AM Xi Ruoyao <xry111@xry111.site> wrote:
> > 
> > On Thu, 2023-08-10 at 11:20 +0800, Xi Ruoyao wrote:
> > > Can we backport this patch into stable?  It fixes a build error with
> > > binutils >= 2.41.
> > 
> > Correction: not a build error, but all modules won't load if built with
> > binutils >= 2.41 without the patch.
> Generally we can backport, but I don't think there are users who use
> the old kernels. :)

The problem is 6.4.x is not "so old": 6.4.9 is actually the latest
kernel release.  6.5.0 is not released yet.