linux-kernel - Re: [PATCH] NOMMU: use copy_*_user_page() in access_process

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Date:	Wed, 2 Dec 2009 23:00:23 +0800
From:	Jie Zhang <jie.zhang@...log.com>
To:	David Howells <dhowells@...hat.com>
CC:	Mike Frysinger <vapier@...too.org>, uclinux-dev@...inux.org,
	David McCullough <davidm@...pgear.com>,
	Greg Ungerer <gerg@...inux.org>,
	Paul Mundt <lethal@...ux-sh.org>, linux-kernel@...r.kernel.org,
	uclinux-dist-devel@...ckfin.uclinux.org
Subject: Re: [PATCH] NOMMU: use copy_*_user_page() in access_process_vm()

On 12/02/2009 10:36 PM, David Howells wrote:
> Mike Frysinger<vapier@...too.org>  wrote:
>
>> -			len -= copy_to_user((void *) addr, buf, len);
>> +			copy_to_user_page(vma, NULL, NULL,
>> +					  (void *) addr, buf, len);
>>   		else if (!write&&  vma->vm_flags&  VM_MAYREAD)
>> -			len -= copy_from_user(buf, (void *) addr, len);
>> +			copy_from_user_page(vma, NULL, NULL,
>> +					    buf, (void *) addr, len);
>
> Hmmm...  With this, len isn't updated anymore, and so it alters the return
> value of access_process_vm(), and means ptrace_readdata() won't now return
> -EIO under some circumstances where it used to.  I'm not sure that matters,
> though.
>
This keeps access_process_vm() in nommu.c align with the one in 
memory.c. If this does really matter, someone or me can write another 
patch to take care of it for both MMU and !MMU later.


Jie
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