linux-kernel - Re: [PATCH] mips: Use generic endianness macros instead of MIPS-specific ones

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Message-ID: <20251109233720.GB2977577@ax162>
Date: Sun, 9 Nov 2025 16:37:20 -0700
From: Nathan Chancellor <nathan@...nel.org>
To: Jens Reidel <adrian@...nlining.org>
Cc: Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
	Nick Desaulniers <nick.desaulniers+lkml@...il.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>, linux-mips@...r.kernel.org,
	linux-kernel@...r.kernel.org, bpf@...r.kernel.org,
	llvm@...ts.linux.dev
Subject: Re: [PATCH] mips: Use generic endianness macros instead of
 MIPS-specific ones

On Sat, Nov 08, 2025 at 11:05:55PM +0100, Jens Reidel wrote:
> Compiling bpf_skel for mips currently fails because clang --target=bpf
> is invoked and the source files include byteorder.h, which uses the
> MIPS-specific macros to determine the endianness, rather than the generic
> __LITTLE_ENDIAN__ / __BIG_ENDIAN__. Fix this by using the generic
> macros, which are also defined when targeting bpf. This is already done
> similarly for powerpc.
> 
> Signed-off-by: Jens Reidel <adrian@...nlining.org>

As far as I can tell, this should be fine since clang defines these
macros in the generic case since [1] and I assume GCC does as well but
if there is a risk of this being a problem for userspace, these could be
added in addition to __MIPSEB__ / __MIPSEL__.

Reviewed-by: Nathan Chancellor <nathan@...nel.org>

[1]: https://github.com/llvm/llvm-project/commit/2c942c64fb521357ed98c380823e79833a121d18

> ---
>  arch/mips/include/uapi/asm/byteorder.h | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/mips/include/uapi/asm/byteorder.h b/arch/mips/include/uapi/asm/byteorder.h
> index b4edc85f9c30c09aafbc189ec820e6e2f7cbe0d8..5e3c3baa24994a9f3637bf2b63ea7c3577cae541 100644
> --- a/arch/mips/include/uapi/asm/byteorder.h
> +++ b/arch/mips/include/uapi/asm/byteorder.h
> @@ -9,12 +9,10 @@
>  #ifndef _ASM_BYTEORDER_H
>  #define _ASM_BYTEORDER_H
>  
> -#if defined(__MIPSEB__)
> -#include <linux/byteorder/big_endian.h>
> -#elif defined(__MIPSEL__)
> +#ifdef __LITTLE_ENDIAN__
>  #include <linux/byteorder/little_endian.h>
>  #else
> -# error "MIPS, but neither __MIPSEB__, nor __MIPSEL__???"
> +#include <linux/byteorder/big_endian.h>
>  #endif
>  
>  #endif /* _ASM_BYTEORDER_H */
> 
> ---
> base-commit: 9c0826a5d9aa4d52206dd89976858457a2a8a7ed
> change-id: 20251108-mips-bpf-fix-8d1f14bc4903
> 
> Best regards,
> -- 
> Jens Reidel <adrian@...nlining.org>