linux-kernel - Re: [PATCH v3 1/3] overflow.h: Add arithmetic shift helper

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Message-ID: <0568f73f-c1ff-1e9d-8ef9-04c46eb13d6e@infradead.org>
Date:   Wed, 1 Aug 2018 09:28:25 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Kees Cook <keescook@...omium.org>,
        Rasmus Villemoes <linux@...musvillemoes.dk>
Cc:     Jason Gunthorpe <jgg@...lanox.com>,
        Leon Romanovsky <leonro@...lanox.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Leon Romanovsky <leon@...nel.org>,
        Bart Van Assche <Bart.VanAssche@....com>,
        Doug Ledford <dledford@...hat.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/3] overflow.h: Add arithmetic shift helper

On 07/31/2018 11:09 PM, Kees Cook wrote:
> From: Jason Gunthorpe <jgg@...lanox.com>
> 
> Add shift_overflow() helper to assist driver authors in ensuring that
> shift operations don't cause overflows or other odd conditions.
> 
> Signed-off-by: Jason Gunthorpe <jgg@...lanox.com>
> Signed-off-by: Leon Romanovsky <leonro@...lanox.com>
> [kees: tweaked comments and commit log, dropped unneeded assignment]
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
>  include/linux/overflow.h | 31 +++++++++++++++++++++++++++++++
>  1 file changed, 31 insertions(+)
> 
> diff --git a/include/linux/overflow.h b/include/linux/overflow.h
> index 8712ff70995f..69fc366ce865 100644
> --- a/include/linux/overflow.h
> +++ b/include/linux/overflow.h
> @@ -202,6 +202,37 @@
>  
>  #endif /* COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW */
>  
> +/** check_shift_overflow() - Calculate a left-shifted value and check overflow
> + *
> + * @a: Value to be shifted
> + * @b: How many bits left to shift
> + * @d: Pointer to where to store the result
> + *
> + * Computes *@d = (@a << @s)
> + *

missed                     @b [again]


-- 
~Randy