linux-kernel - Re: [PATCH V3] asm-generic: add a generic uaccess.h

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Date:	Fri, 01 May 2009 16:11:27 +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,
	Russell King <rmk+lkml@....linux.org.uk>
Subject: Re: [PATCH V3] asm-generic: add a generic uaccess.h

Arnd Bergmann wrote:
> On Friday 01 May 2009, Michal Simek wrote:
>> Arnd Bergmann wrote:
>>> +
>>> +#include <asm/segment.h>
>>> +
>>> +#ifndef get_fs
>>> +#define MAKE_MM_SEG(s)	((mm_segment_t) { (s) })
>> one line above -> get_fs could be defined in different space
>> and this arch could use MAKE_MM_SEG too -> for example powerpc.
> 
> I don't think I understand what you are trying to tell me.
> How do you think this should look?

I meant move MAKE_MM_SEG macro to this position because this macro could be use
with arch which define different get_fs.

#define MAKE_MM_SEG(s)	((mm_segment_t) { (s) })
#ifndef get_fs
...


> 
>>> +
>>> +#define VERIFY_READ	0
>>> +#define VERIFY_WRITE	1
>>> +
>>
>> Not sure if any arch do READ/WRITE check but if yes.
> 
> I could not find any architecture using it either, but the
> API is defined this way.
> 
>> #ifndef access_ok
>>
>>> +#define access_ok(type, addr, size) __access_ok((unsigned long)(addr),(size))
>> #endif
> 
> right, will change.
> 
>>> +
>>> +/*
>>> + * The architecture should really override this if possible, at least
>>> + * doing a check on the get_fs()
>>> + */
>> If they should really override it but why write it here.
> 
> Mostly for documentation purposes, so that an architecture maintainer
> can copy the prototype. I see the asm-generic headers as both fallbacks
> for architectures and as templates of what should be implemented.
> 
>>> +#define get_user(x, ptr)					\
>>> +({								\
>>> +	might_sleep();						\
>>> +	__access_ok(ptr, sizeof (*ptr)) ?			\
>>> +		__get_user(x, ptr) :				\
>>> +		-EFAULT;					\
>>> +})
>> I am getting here (for put_user macro too) any error on noMMU. :-(
> 
> What kind of error do you see?

System is getting crazy with -> I am debugging it.


>  
>>> +static inline long
>>> +strncpy_from_user(char *dst, const char __user *src, long count)
>>> +{
>>> +	if (!__access_ok(src, 1))
>>> +		return -EFAULT;
>>> +	return __strncpy_from_user(dst, src, count);
>>> +}
>> Is it a good place to add might_sleep() and unlikely(+ some other cases) too?
>> We have almost the same code.
> 
> Yes, I think so. The unlikely() can probably go into __access_ok() though,
> so we don't have to write it every time.

ok

Michal


> 
> 	Arnd <><


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