linux-kernel - Re: [PATCH 4/4] asm-generic/bitsperlong.h: Add sanity checks for __BITS_PER

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Message-ID: <20260119143735-ca5b7901-b501-4cb8-8e5d-10f4e2f8b650@linutronix.de>
Date: Mon, 19 Jan 2026 14:41:09 +0100
From: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
To: Arnd Bergmann <arnd@...db.de>
Cc: David Laight <david.laight.linux@...il.com>, 
	"David S . Miller" <davem@...emloft.net>, Andreas Larsson <andreas@...sler.com>, 
	Andy Lutomirski <luto@...nel.org>, Thomas Gleixner <tglx@...nel.org>, 
	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>, 
	Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>, 
	Alexander Gordeev <agordeev@...ux.ibm.com>, Christian Borntraeger <borntraeger@...ux.ibm.com>, 
	Sven Schnelle <svens@...ux.ibm.com>, sparclinux@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Linux-Arch <linux-arch@...r.kernel.org>, linux-s390@...r.kernel.org
Subject: Re: [PATCH 4/4] asm-generic/bitsperlong.h: Add sanity checks for
 __BITS_PER_LONG

On Mon, Jan 19, 2026 at 01:45:04PM +0100, Arnd Bergmann wrote:
> On Mon, Jan 19, 2026, at 11:56, Thomas Weißschuh wrote:
> > On Mon, Jan 19, 2026 at 10:37:58AM +0000, David Laight wrote:
> >> 
> >> Don't you need a check that it isn't wrong on a user system?
> >> Which is what I thought it was doing.
> >
> > Not really. The overrides defined by arch/*/include/uapi/asm/bitsperlong.h are
> > being tested here. If they work in the kernel build I assume they also work
> > in userspace.
> 
> I think You could just move check into include/asm-generic/bitsperlong.h
> to make this more obvious with the #ifdef __KERNEL__, and remove the
> disabled check from my original version there.

Ok. I'd like to keep your existing test though, as it tests something different
and it would be nice to have that too at some point.


Thomas