linux-kernel - Re: [PATCH 1/3] arm64: uapi: Provide correct __BITS_PER

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Message-ID: <CANDhNCqbZbhSLgvFYnzK0Fmu2qndQ-7qHwHmGtRcFwirgZvcEg@mail.gmail.com>
Date: Thu, 21 Aug 2025 10:09:47 -0700
From: John Stultz <jstultz@...gle.com>
To: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
Cc: Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>, 
	Thomas Gleixner <tglx@...utronix.de>, Arnd Bergmann <arnd@...db.de>, Andy Lutomirski <luto@...nel.org>, 
	Vincenzo Frascino <vincenzo.frascino@....com>, linux-arm-kernel@...ts.infradead.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] arm64: uapi: Provide correct __BITS_PER_LONG for the
 compat vDSO

On Thu, Aug 21, 2025 at 12:56 AM Thomas Weißschuh
<thomas.weissschuh@...utronix.de> wrote:
>
> The generic vDSO library uses the UAPI headers. On arm64 __BITS_PER_LONG is
> always '64' even when used from the compat vDSO. In that case __GENMASK()
> does an illegal bitshift, invoking undefined behaviour.
>
> Change __BITS_PER_LONG to also work when used from the comapt vDSO.
> To not confuse real userspace, only do this when building the kernel.
>
> Reported-by: John Stultz <jstultz@...gle.com>
> Closes: https://lore.kernel.org/lkml/CANDhNCqvKOc9JgphQwr0eDyJiyG4oLFS9R8rSFvU0fpurrJFDg@mail.gmail.com/
> Fixes: cd3557a7618b ("vdso/gettimeofday: Add support for auxiliary clocks")
> Signed-off-by: Thomas Weißschuh <thomas.weissschuh@...utronix.de>

Tested-by: John Stultz <jstultz@...gle.com>

Thank you so much for the quick fix!
-john