linux-kernel - Re: linux-next: build warning after merge of the tip tree

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Message-ID: <20250708082658-851e75f2-6899-49b2-9923-a33df9e2029f@linutronix.de>
Date: Tue, 8 Jul 2025 08:32:27 +0200
From: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
To: Stephen Rothwell <sfr@...b.auug.org.au>
Cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...nel.org>, 
	"H. Peter Anvin" <hpa@...or.com>, Peter Zijlstra <peterz@...radead.org>, 
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Linux Next Mailing List <linux-next@...r.kernel.org>
Subject: Re: linux-next: build warning after merge of the tip tree

Hi Stephen,

On Tue, Jul 08, 2025 at 04:08:30PM +1000, Stephen Rothwell wrote:
> After merging the tip tree, today's linux-next build (powerpc
> ppc64_allmodconfig) produced this warning:
> 
> In file included from include/vdso/datapage.h:8,
>                  from lib/vdso/gettimeofday.c:6,
>                  from <command-line>:
> lib/vdso/gettimeofday.c: In function '__cvdso_clock_gettime_common':
> include/uapi/linux/bits.h:7:56: warning: right shift count >= width of type [-Wshift-count-overflow]
>     7 | #define __GENMASK(h, l) (((~_UL(0)) << (l)) & (~_UL(0) >> (BITS_PER_LONG - 1 - (h))))
>       |                                                        ^~
> include/vdso/datapage.h:50:25: note: in expansion of macro '__GENMASK'
>    50 | #define VDSO_AUX        __GENMASK(CLOCK_AUX_LAST, CLOCK_AUX)
>       |                         ^~~~~~~~~
> lib/vdso/gettimeofday.c:335:24: note: in expansion of macro 'VDSO_AUX'
>   335 |         else if (msk & VDSO_AUX)
>       |                        ^~~~~~~~
> lib/vdso/gettimeofday.c: In function '__cvdso_clock_getres_common':
> include/uapi/linux/bits.h:7:56: warning: right shift count >= width of type [-Wshift-count-overflow]
>     7 | #define __GENMASK(h, l) (((~_UL(0)) << (l)) & (~_UL(0) >> (BITS_PER_LONG - 1 - (h))))
>       |                                                        ^~
> include/vdso/datapage.h:50:25: note: in expansion of macro '__GENMASK'
>    50 | #define VDSO_AUX        __GENMASK(CLOCK_AUX_LAST, CLOCK_AUX)
>       |                         ^~~~~~~~~
> lib/vdso/gettimeofday.c:481:26: note: in expansion of macro 'VDSO_AUX'
>   481 |         } else if (msk & VDSO_AUX) {
>       |                          ^~~~~~~~
> 
> Introduced by commit
> 
>   7893ea1006fc ("vdso/gettimeofday: Add support for auxiliary clocks")

thanks for the report. I am aware of this issue and working on resolving it.
Is this warning a blocking issue for -next at the moment?

Background, from [0]:

This [commit] depends on v6.16-rc2 *exactly*.
The specific dependency is commit 11fcf368506d ("uapi: bitops: use UAPI-safe variant of BITS_PER_LONG again"),
which is available in v6.16-rc2.
Unfortunately that got broken again in v6.16-rc3 by
commit  fc92099902fb ("tools headers: Synchronize linux/bits.h with the kernel sources").
Another fix for this is pending [1] and should make it into v6.16.

[0] https://lore.kernel.org/lkml/20250701-vdso-auxclock-v1-0-df7d9f87b9b8@linutronix.de/
[1] https://lore.kernel.org/lkml/20250630-uapi-genmask-v1-1-eb0ad956a83e@linutronix.de/


Thomas