linux-kernel - Re: [PATCH 5/6] zsmalloc: remove unnecessary type casting

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 for Android: free password hash cracker in your pocket

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

Message-ID: <4F98ABDF.1000702@kernel.org>
Date:	Thu, 26 Apr 2012 10:58:55 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	Nitin Gupta <ngupta@...are.org>
CC:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Seth Jennings <sjenning@...ux.vnet.ibm.com>,
	Dan Magenheimer <dan.magenheimer@...cle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 5/6] zsmalloc: remove unnecessary type casting

On 04/25/2012 10:35 PM, Nitin Gupta wrote:

> On 04/25/2012 02:23 AM, Minchan Kim wrote:
> 
>> Let's remove unnecessary type casting of (void *).
>>
>> Signed-off-by: Minchan Kim <minchan@...nel.org>
>> ---
>>  drivers/staging/zsmalloc/zsmalloc-main.c |    3 +--
>>  1 file changed, 1 insertion(+), 2 deletions(-)
>>
>> diff --git a/drivers/staging/zsmalloc/zsmalloc-main.c b/drivers/staging/zsmalloc/zsmalloc-main.c
>> index b7d31cc..ff089f8 100644
>> --- a/drivers/staging/zsmalloc/zsmalloc-main.c
>> +++ b/drivers/staging/zsmalloc/zsmalloc-main.c
>> @@ -644,8 +644,7 @@ void zs_free(struct zs_pool *pool, void *obj)
>>  	spin_lock(&class->lock);
>>  
>>  	/* Insert this object in containing zspage's freelist */
>> -	link = (struct link_free *)((unsigned char *)kmap_atomic(f_page)
>> -							+ f_offset);
>> +	link = (struct link_free *)(kmap_atomic(f_page)	+ f_offset);
>>  	link->next = first_page->freelist;
>>  	kunmap_atomic(link);
>>  	first_page->freelist = obj;
> 
> 
> 
> Incrementing a void pointer looks weired and should not be allowed by C
> compilers though gcc and clang seem to allow this without any warnings.
> (fortunately C++ forbids incrementing void pointers)


It's a gcc extension and we have been already used lots of place so I think it's no problem
although it's non-standard.
If we compile kernel with -Wpointer-arith, we would find a ton of warning in here and there.

> 
> So, we should keep this cast to unsigned char pointer to avoid relying
> on a non-standard, compiler specific behavior.



Okay. It's a just trivial and I have no justification to do it at the cost of breaking standard.

> 
> Thanks,
> Nitin
> 
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majordomo@...ck.org.  For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
> Don't email: <a href=mailto:"dont@...ck.org"> email@...ck.org </a>
> 



-- 
Kind regards,
Minchan Kim
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/