linux-kernel - Re: [PATCH] uapi: bitops: use UAPI-safe variant of BITS_PER

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Message-ID: <aG0veDJWGHVIO6Cc@yury>
Date: Tue, 8 Jul 2025 10:47:20 -0400
From: Yury Norov <yury.norov@...il.com>
To: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>,
	Vincent Mailhol <mailhol.vincent@...adoo.fr>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] uapi: bitops: use UAPI-safe variant of BITS_PER_LONG
 again (2)

On Tue, Jul 08, 2025 at 08:26:49AM +0200, Thomas Weißschuh wrote:
> On Tue, Jul 01, 2025 at 05:37:40PM -0400, Yury Norov wrote:
> > On Mon, Jun 30, 2025 at 10:52:54AM -0400, Yury Norov wrote:
> > > On Mon, Jun 30, 2025 at 03:02:18PM +0200, Thomas Weißschuh wrote:
> > > > BITS_PER_LONG does not exist in UAPI headers, so can't be used by the UAPI
> > > > __GENMASK(). Instead __BITS_PER_LONG needs to be used.
> > > > 
> > > > When __GENMASK() was introduced in commit 3c7a8e190bc5 ("uapi: introduce uapi-friendly macros for GENMASK"),
> > > > the code was fine. A broken revert in 1e7933a575ed ("uapi: Revert "bitops: avoid integer overflow in GENMASK(_ULL)"")
> > > > introduced the incorrect usage of BITS_PER_LONG.
> > > > That was fixed in commit 11fcf368506d ("uapi: bitops: use UAPI-safe variant of BITS_PER_LONG again").
> > > > But a broken sync of the kernel headers with the tools/ headers in
> > > > commit fc92099902fb ("tools headers: Synchronize linux/bits.h with the kernel sources")
> > > > undid the fix.
> > > > 
> > > > Reapply the fix and while at it also fix the tools header.
> > > > 
> > > > Fixes: fc92099902fb ("tools headers: Synchronize linux/bits.h with the kernel sources")
> > > > Signed-off-by: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
> > > 
> > > Acked-by: Yury Norov (NVIDIA) <yury.norov@...il.com>
> > > 
> > > Arnaldo, do you want to move it yourself or with my branch?
> > 
> > OK, added this in bitmap-for-next together with the MAINTAINERS patch.
> 
> Thanks!
> 
> Any chance to get the fix into v6.16 again?

Yes, just sent a pull request.

> This currently triggers warnings in my code in -next [0], which is intended
> to go into v6.17.
> 
> [0] https://lore.kernel.org/all/20250708160830.36ddf20f@canb.auug.org.au/
> 
> 
> Thomas