linux-kernel - Re: [PATCH 1/5] ARC: uapi: Stop leaking CONFIG_ARC_HAS

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Message-ID: <20260102103913-0420048c-d2f3-431b-8bbb-5962a1553aab@linutronix.de>
Date: Fri, 2 Jan 2026 10:40:46 +0100
From: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
To: Arnd Bergmann <arnd@...db.de>
Cc: Vineet Gupta <vgupta@...nel.org>, Russell King <linux@...linux.org.uk>, 
	Dinh Nguyen <dinguyen@...nel.org>, Thomas Gleixner <tglx@...utronix.de>, 
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>, 
	linux-snps-arc@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/5] ARC: uapi: Stop leaking CONFIG_ARC_HAS_SWAPE
 reference to userspace

On Fri, Jan 02, 2026 at 08:55:10AM +0100, Thomas Weißschuh wrote:
> On Tue, Dec 30, 2025 at 10:23:08PM +0100, Arnd Bergmann wrote:
> > On Tue, Dec 30, 2025, at 08:10, Thomas Weißschuh wrote:
> > > UAPI headers are not supposed to leak references to kconfig symbols.
> > > These won't be set when building userspace. Hide the kconfig reference
> > > behind 'if defined(__KERNEL__)', so it will be stripped by
> > > headers_install.sh. The result for userspace will be the same, but the
> > > exception in headers_install.sh can also be removed.
> > >
> > > Signed-off-by: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
> > 
> > Acked-by: Arnd Bergmann <arnd@...db.de>
> > 
> > Same as for the nios2 version, I think the nicer solution would
> > be to use the asm-generic header for uapi and move this one
> > to arch/arc/include/asm/swab.h for kernel-internal use.
> 
> Ack. (...)

This doesn't seem to be true. ARC does have a custom C implementation which
according to its comment is supposed to be more efficient than the generic one.
So I'd like to keep this as-is.

(...)

Thomas