linux-kernel - Re: [PATCH] kernel.h: add IS_PTR

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Message-ID: <bed3e1c2-7d2f-1883-edc6-263f21365340@zytor.com>
Date:   Wed, 29 Mar 2017 14:24:47 -0700
From:   "H. Peter Anvin" <hpa@...or.com>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Niklas Söderlund 
        <niklas.soderlund+renesas@...natech.se>,
        Jessica Yu <jeyu@...hat.com>,
        Johannes Berg <johannes.berg@...el.com>,
        Petr Mladek <pmladek@...e.com>,
        Larry Finger <Larry.Finger@...inger.net>,
        linux-kernel@...r.kernel.org,
        Gustavo Padovan <gustavo.padovan@...labora.co.uk>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Peter Zijlstra <peterz@...radead.org>,
        Luis de Bethencourt <luisbg@....samsung.com>,
        Josh Triplett <josh@...htriplett.org>
Subject: Re: [PATCH] kernel.h: add IS_PTR_ALIGNED() macro

On 03/29/17 03:22, Masahiro Yamada wrote:
> We often check if a pointer has a specific alignment.  Because the
> '&' (bitwise AND) operator cannot take a pointer for the operand,
> so we need a cast like, IS_ALIGNED((unsigned long)p, a).
> 
> IS_PTR_ALIGNED will be useful as a shorthand.
> 
> Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
> ---
> 
>  include/linux/kernel.h | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/include/linux/kernel.h b/include/linux/kernel.h
> index e5edd55..a810e4b 100644
> --- a/include/linux/kernel.h
> +++ b/include/linux/kernel.h
> @@ -50,6 +50,7 @@
>  #define __ALIGN_MASK(x, mask)	__ALIGN_KERNEL_MASK((x), (mask))
>  #define PTR_ALIGN(p, a)		((typeof(p))ALIGN((unsigned long)(p), (a)))
>  #define IS_ALIGNED(x, a)		(((x) & ((typeof(x))(a) - 1)) == 0)
> +#define IS_PTR_ALIGNED(p, a)		(IS_ALIGNED((unsigned long)p, a))
>  

No need for two macros; make one work for both.

You could move the __inttype() macro from arch/x86/include/asm/uaccess.h
into this file and replace typeof(x) with __inttype(x) in the above macro.

Attached is a set of slightly improved (safer and a bit more
generalized) versions of the same macro that might be more appropriate
to include in <linux/kernel.h>.

	-hpa

View attachment "uinttype.c" of type "text/plain" (1602 bytes)