linux-kernel - Re: [PATCH] powerpc: vdso: fix building with wrong-endian toolchain

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Date: Fri, 07 Jun 2024 22:42:44 +1000
From: Michael Ellerman <mpe@...erman.id.au>
To: Arnd Bergmann <arnd@...nel.org>
Cc: Masahiro Yamada <masahiroy@...nel.org>, Nathan Chancellor
 <nathan@...nel.org>, Nicolas Schier <nicolas@...sle.eu>,
 linux-kbuild@...r.kernel.org, Arnd Bergmann <arnd@...db.de>, Nicholas
 Piggin <npiggin@...il.com>, Christophe Leroy
 <christophe.leroy@...roup.eu>, "Naveen N. Rao"
 <naveen.n.rao@...ux.ibm.com>, linuxppc-dev@...ts.ozlabs.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] powerpc: vdso: fix building with wrong-endian toolchain

Arnd Bergmann <arnd@...nel.org> writes:
> From: Arnd Bergmann <arnd@...db.de>
>
> Building powerpc64le kernels with the kernel.org crosstool toolchains
> no longer works as the linker attempts to build a big-endian vdso:
>
> powerpc-linux/lib/gcc/powerpc-linux/12.3.0/../../../../powerpc-linux/bin/ld: arch/powerpc/kernel/vdso/sigtramp32-32.o: compiled for a little endian system and target is big endian
> powerpc-linux/lib/gcc/powerpc-linux/12.3.0/../../../../powerpc-linux/bin/ld: failed to merge target specific data of file arch/powerpc/kernel/vdso/sigtramp32-32.o
>
> Apparently creating the vdso.lds files from the lds.S files fails to
> pass the -mlittle-endian argument here, so the output format gets set
> wrong. Changing the conditional to check for CONFIG_CPU_LITTLE_ENDIAN
> instead still works, as the kernel configuration definitions are visible.
>
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
> I'm fairly sure this worked in the past, but I did not try to bisect the
> issue.

It still works for me.

I use the korg toolchains every day, and kisskb uses them too.

What commit / defconfig are you seeing the errors with?

Is it just the 12.3.0 toolchain or all of them? I just tested 12.3.0
here and it built OK.

I guess you're building on x86 or arm64? I build on ppc64le, I wonder if
that makes a difference.

The patch is probably OK regardless, but I'd rather understand what the
actual problem is.

cheers

> diff --git a/arch/powerpc/kernel/vdso/vdso32.lds.S b/arch/powerpc/kernel/vdso/vdso32.lds.S
> index 426e1ccc6971..5845ea2d1cba 100644
> --- a/arch/powerpc/kernel/vdso/vdso32.lds.S
> +++ b/arch/powerpc/kernel/vdso/vdso32.lds.S
> @@ -7,7 +7,7 @@
>  #include <asm/page.h>
>  #include <asm-generic/vmlinux.lds.h>
>  
> -#ifdef __LITTLE_ENDIAN__
> +#ifdef CONFIG_CPU_LITTLE_ENDIAN
>  OUTPUT_FORMAT("elf32-powerpcle", "elf32-powerpcle", "elf32-powerpcle")
>  #else
>  OUTPUT_FORMAT("elf32-powerpc", "elf32-powerpc", "elf32-powerpc")
> diff --git a/arch/powerpc/kernel/vdso/vdso64.lds.S b/arch/powerpc/kernel/vdso/vdso64.lds.S
> index bda6c8cdd459..82c418b18cce 100644
> --- a/arch/powerpc/kernel/vdso/vdso64.lds.S
> +++ b/arch/powerpc/kernel/vdso/vdso64.lds.S
> @@ -7,7 +7,7 @@
>  #include <asm/page.h>
>  #include <asm-generic/vmlinux.lds.h>
>  
> -#ifdef __LITTLE_ENDIAN__
> +#ifdef CONFIG_CPU_LITTLE_ENDIAN
>  OUTPUT_FORMAT("elf64-powerpcle", "elf64-powerpcle", "elf64-powerpcle")
>  #else
>  OUTPUT_FORMAT("elf64-powerpc", "elf64-powerpc", "elf64-powerpc")
> -- 
> 2.39.2