linux-kernel - Re: [PATCH next 08/14] bits: simplify GENMASK

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: <aYf2yUazqVJBeWZb@yury>
Date: Sat, 7 Feb 2026 21:36:57 -0500
From: Yury Norov <ynorov@...dia.com>
To: david.laight.linux@...il.com
Cc: Nathan Chancellor <nathan@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Arnd Bergmann <arnd@...db.de>, linux-arch@...r.kernel.org,
	linux-kernel@...r.kernel.org, Yury Norov <yury.norov@...il.com>,
	Lucas De Marchi <lucas.demarchi@...el.com>,
	Jani Nikula <jani.nikula@...el.com>,
	Vincent Mailhol <mailhol.vincent@...adoo.fr>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Kees Cook <keescook@...omium.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH next 08/14] bits: simplify GENMASK_TYPE()

On Wed, Jan 21, 2026 at 02:57:25PM +0000, david.laight.linux@...il.com wrote:
> From: David Laight <david.laight.linux@...il.com>
> 
> Since the type is always unsigned (T)-1 is always the correct value
> so there is no need to use type_max().
> 
> Signed-off-by: David Laight <david.laight.linux@...il.com>

Here you implicitly add a new restriction that all types passed in
GENMASK_TYPE() must be unsigned. Can you enforce it with
is_signed_type(), or at lease with a corresponding comment?

> ---
>  include/linux/bits.h | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/include/linux/bits.h b/include/linux/bits.h
> index a40cc861b3a7..697318f2a47d 100644
> --- a/include/linux/bits.h
> +++ b/include/linux/bits.h
> @@ -45,8 +45,7 @@
>   */
>  #define GENMASK_TYPE(t, h, l)					\
>  	((t)(GENMASK_INPUT_CHECK(h, l) +			\
> -	     (type_max(t) << (l) &				\
> -	      type_max(t) >> (BITS_PER_TYPE(t) - 1 - (h)))))
> +	     ((t)-1 << (l) & (t)-1 >> (BITS_PER_TYPE(t) - 1 - (h)))))
>  
>  #define GENMASK(h, l)		GENMASK_TYPE(unsigned long, h, l)
>  #define GENMASK_ULL(h, l)	GENMASK_TYPE(unsigned long long, h, l)
> -- 
> 2.39.5