linux-kernel - Re: [PATCH 12/27] asm-generic: add a NOMMU uaccess.h

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Date:	Fri, 01 May 2009 14:38:12 +0200
From:	Michal Simek <monstr@...str.eu>
To:	Arnd Bergmann <arnd@...db.de>
CC:	linux-arch@...r.kernel.org,
	Remis Lima Baima <remis.developer@...glemail.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 12/27] asm-generic: add a NOMMU uaccess.h

Arnd Bergmann wrote:
> On Friday 01 May 2009, Michal Simek wrote:
>>> +#ifndef __put_user
>>> +#define __put_user(x, ptr)                             \
>>> +({                                                     \
>>> +       int __pu_err = 0;                               \
>>> +       typeof(*(ptr)) __pu_val = (x);                  \
>>> +       switch (sizeof (*(ptr))) {                      \
>>> +       case 1:                                         \
>>> +       case 2:                                         \
>>> +       case 4:                                         \
>>> +               *(ptr) = (__pu_val);                    \
>>> +               break;                                  \
>>> +       case 8:                                         \
>>> +               memcpy(ptr, &__pu_val, sizeof (*(ptr)));\
>>
>> potential cast problem
> 
> Yes, I'm looking into this already, probably will do something
> based on the s390 code, which seems to do this correctly.
> 
>>> +#define put_user(x, ptr) (                             \
>>> +       access_ok(VERIFY_WRITE, ptr, sizeof (*ptr)) ?   \
>>> +               __put_user(x, ptr) :                    \
>>> +               -EFAULT)
>>
>> IMHO write it as inline function with type checking.
> 
> Unfortunately, this doesn't work because of the callin
> conventions: __put_user needs to know the type of ptr,
> so it has to be a macro.

yes, I am looking on it too.

Michal

> 
> 	Arnd <><


-- 
Michal Simek, Ing. (M.Eng)
w: www.monstr.eu p: +42-0-721842854
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