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

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Message-ID: <534380F6.7090703@gmail.com>
Date:	Tue, 08 Apr 2014 12:54:14 +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


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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