linux-kernel - Re: 回复： [PATCH] arch:unicore32:mm: add devmem_is_allowed() to support STRICT

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Message-ID: <534C79EE.3030505@gmail.com>
Date:	Tue, 15 Apr 2014 08:14:38 +0800
From:	Chen Gang <gang.chen.5i5j@...il.com>
To:	管雪涛 <gxt@....edu.cn>
CC:	Guan Xuetao <gxt@...c.pku.edu.cn>, akpm@...ux-foundation.org,
	liuj97@...il.com, rientjes@...gle.com, dhowells@...hat.com,
	mhocko@...e.cz, mgorman@...e.de, linux-kernel@...r.kernel.org
Subject: Re: 回复： [PATCH] arch:unicore32:mm: add devmem_is_allowed() to support STRICT_DEVMEM


We got no-reply almost a week, so we can assume "can put the code into
"asm/io.h" as static inline function".

I will/should send patch v2 for it.

Thanks.

On 04/08/2014 12:54 PM, Chen Gang wrote:
> 
> On 04/08/2014 11:20 AM, 管雪涛 wrote:
>> I'd like to put the code into asm/io.h, and make it static.
>>
> 
> It sounds OK to me, but I don't know why the other architectures (e.g.
> arm, powerpc, x86) put them into ".c".
> 
> iomem_is_exclusive() and page_is_ram() are all extern functions, so for
> me, devmem_is_allowed() is shot enough to be as inline function.
> 
>>> +#ifdef CONFIG_STRICT_DEVMEM
>>> +/*
>>> + * devmem_is_allowed() checks to see if /dev/mem access to a certain
>>> + * address is valid. The argument is a physical page number.
>>> + * We mimic x86 here by disallowing access to system RAM as well as
>>> + * device-exclusive MMIO regions. This effectively disable read()/write()
>>> + * on /dev/mem.
>>> + */
>>> +static int devmem_is_allowed(unsigned long pfn)
> 
> How about "static inline int devmem_is_allowed(unsigned long pfn)"?
> 
>>> +{
>>> +	if (iomem_is_exclusive(pfn << PAGE_SHIFT))
>>> +		return 0;
>>> +	if (!page_is_ram(pfn))
>>> +		return 1;
>>> +	return 0;
>>> +}
>>> +#endif /* CONFIG_STRICT_DEVMEM */
>>
>> Thanks,
>>
>> Acked-by: Xuetao Guan <gxt@...c.pku.edu.cn>
>>
> 
> [...]
> 
> Thanks.
> 

-- 
Chen Gang

Open, share, and attitude like air, water, and life which God blessed
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