linux-kernel - Re: [PATCH 00/17] Add __attribute_const_

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250815141604.GD3289052@noisy.programming.kicks-ass.net>
Date: Fri, 15 Aug 2025 16:16:04 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Kees Cook <kees@...nel.org>
Cc: linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
	x86@...nel.org, linux-alpha@...r.kernel.org,
	linux-csky@...r.kernel.org, linux-hexagon@...r.kernel.org,
	linux-m68k@...ts.linux-m68k.org, linux-mips@...r.kernel.org,
	linux-openrisc@...r.kernel.org, linux-parisc@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org, linux-riscv@...ts.infradead.org,
	linux-s390@...r.kernel.org, linux-sh@...r.kernel.org,
	sparclinux@...r.kernel.org, llvm@...ts.linux.dev,
	linux-hardening@...r.kernel.org
Subject: Re: [PATCH 00/17] Add __attribute_const__ to ffs()-family
 implementations

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@...radead.org>