From: Peter Zijlstra <peterz@infradead•org>
To: Kees Cook <kees@kernel•org>
Cc: linux-arch@vger•kernel.org, linux-kernel@vger•kernel.org,
x86@kernel•org, linux-alpha@vger•kernel.org,
linux-csky@vger•kernel.org, linux-hexagon@vger•kernel.org,
linux-m68k@lists•linux-m68k.org, linux-mips@vger•kernel.org,
linux-openrisc@vger•kernel.org, linux-parisc@vger•kernel.org,
linuxppc-dev@lists•ozlabs.org, linux-riscv@lists•infradead.org,
linux-s390@vger•kernel.org, linux-sh@vger•kernel.org,
sparclinux@vger•kernel.org, llvm@lists•linux.dev,
linux-hardening@vger•kernel.org
Subject: Re: [PATCH 00/17] Add __attribute_const__ to ffs()-family implementations
Date: Fri, 15 Aug 2025 16:16:04 +0200 [thread overview]
Message-ID: <20250815141604.GD3289052@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <20250804163910.work.929-kees@kernel.org>
On Mon, Aug 04, 2025 at 09:43:56AM -0700, Kees Cook wrote:
> Hi,
>
> While tracking down a problem where constant expressions used by
> BUILD_BUG_ON() suddenly stopped working[1], we found that an added static
> initializer was convincing the compiler that it couldn't track the state
> of the prior statically initialized value. Tracing this down found that
> ffs() was used in the initializer macro, but since it wasn't marked with
> __attribute_const__, the compiler had to assume the function might
> change variable states as a side-effect (which is not true for ffs(),
> which provides deterministic math results).
>
> Add KUnit tests for the family of functions and then add __attribute_const__
> to all architecture implementations and wrappers.
>
> -Kees
>
> [1] https://github.com/KSPP/linux/issues/364
>
> Kees Cook (17):
> KUnit: Introduce ffs()-family tests
> bitops: Add __attribute_const__ to generic ffs()-family
> implementations
> csky: Add __attribute_const__ to ffs()-family implementations
> x86: Add __attribute_const__ to ffs()-family implementations
> powerpc: Add __attribute_const__ to ffs()-family implementations
> sh: Add __attribute_const__ to ffs()-family implementations
> alpha: Add __attribute_const__ to ffs()-family implementations
> hexagon: Add __attribute_const__ to ffs()-family implementations
> riscv: Add __attribute_const__ to ffs()-family implementations
> openrisc: Add __attribute_const__ to ffs()-family implementations
> m68k: Add __attribute_const__ to ffs()-family implementations
> mips: Add __attribute_const__ to ffs()-family implementations
> parisc: Add __attribute_const__ to ffs()-family implementations
> s390: Add __attribute_const__ to ffs()-family implementations
> xtensa: Add __attribute_const__ to ffs()-family implementations
> sparc: Add __attribute_const__ to ffs()-family implementations
> KUnit: ffs: Validate all the __attribute_const__ annotations
Acked-by: Peter Zijlstra (Intel) <peterz@infradead•org>
next prev parent reply other threads:[~2025-08-15 14:16 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-08-04 16:43 [PATCH 00/17] Add __attribute_const__ to ffs()-family implementations Kees Cook
2025-08-04 16:43 ` [PATCH 01/17] KUnit: Introduce ffs()-family tests Kees Cook
2025-08-04 16:43 ` [PATCH 02/17] bitops: Add __attribute_const__ to generic ffs()-family implementations Kees Cook
2025-08-04 16:43 ` [PATCH 03/17] csky: Add __attribute_const__ to " Kees Cook
2025-10-19 6:50 ` Guo Ren
2025-08-04 16:44 ` [PATCH 04/17] x86: " Kees Cook
2025-08-04 16:44 ` [PATCH 05/17] powerpc: " Kees Cook
2025-08-07 9:46 ` Madhavan Srinivasan
2025-08-15 16:34 ` Segher Boessenkool
2025-08-15 16:41 ` Segher Boessenkool
2025-08-04 16:44 ` [PATCH 06/17] sh: " Kees Cook
2025-08-04 16:44 ` [PATCH 07/17] alpha: " Kees Cook
2025-08-04 16:44 ` [PATCH 08/17] hexagon: " Kees Cook
2025-08-04 16:44 ` [PATCH 09/17] riscv: " Kees Cook
2025-08-07 14:43 ` Alexandre Ghiti
2025-08-04 16:44 ` [PATCH 10/17] openrisc: " Kees Cook
2025-08-04 17:15 ` Stafford Horne
2025-08-04 16:44 ` [PATCH 11/17] m68k: " Kees Cook
2025-08-05 8:12 ` Geert Uytterhoeven
2025-08-04 16:44 ` [PATCH 12/17] mips: " Kees Cook
2025-08-04 16:44 ` [PATCH 13/17] parisc: " Kees Cook
2025-08-04 16:44 ` [PATCH 14/17] s390: " Kees Cook
2025-08-06 10:33 ` Heiko Carstens
2025-08-04 16:44 ` [PATCH 15/17] xtensa: " Kees Cook
2025-08-04 16:44 ` [PATCH 16/17] sparc: " Kees Cook
2025-08-04 16:44 ` [PATCH 17/17] KUnit: ffs: Validate all the __attribute_const__ annotations Kees Cook
2025-08-15 14:16 ` Peter Zijlstra [this message]
2025-10-09 1:07 ` [PATCH 00/17] Add __attribute_const__ to ffs()-family implementations patchwork-bot+linux-riscv
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