linux-kernel - Re: 回复： [PATCH v3] arch:unicore32:mm: add devmem_is_allowed() to support STRICT

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Message-ID: <534E187E.6050908@gmail.com>
Date:	Wed, 16 Apr 2014 13:43:26 +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 v3] arch:unicore32:mm: add devmem_is_allowed() to support STRICT_DEVMEM

On 04/16/2014 01:15 PM, 管雪涛 wrote:
> Acked-by: Xuetao Guan <gxt@...c.pku.edu.cn>
> 

OK, thanks.

> ----- Chen Gang <gang.chen.5i5j@...il.com> 写道：
>> unicore32 supports STRICT_DEVMEM, so it needs devmem_is_allowed(), like
>> some of other architectures have done (e.g. arm, powerpc, x86 ...).
>>
>> The related error with allmodconfig:
>>
>>     CC      drivers/char/mem.o
>>   drivers/char/mem.c: In function ‘range_is_allowed’:
>>   drivers/char/mem.c:69: error: implicit declaration of function ‘devmem_is_allowed’
>>   make[2]: *** [drivers/char/mem.o] Error 1
>>   make[1]: *** [drivers/char] Error 2
>>   make: *** [drivers] Error 2
>>
>>
>> Signed-off-by: Chen Gang <gang.chen.5i5j@...il.com>
>> ---
>>  arch/unicore32/include/asm/io.h |   23 +++++++++++++++++++++++
>>  1 file changed, 23 insertions(+)
>>
>> diff --git a/arch/unicore32/include/asm/io.h b/arch/unicore32/include/asm/io.h
>> index 39decb6..ae327e4 100644
>> --- a/arch/unicore32/include/asm/io.h
>> +++ b/arch/unicore32/include/asm/io.h
>> @@ -44,5 +44,28 @@ extern void __uc32_iounmap(volatile void __iomem *addr);
>>  #define PIO_MASK		(unsigned int)(IO_SPACE_LIMIT)
>>  #define PIO_RESERVED		(PIO_OFFSET + PIO_MASK + 1)
>>  
>> +#ifdef CONFIG_STRICT_DEVMEM
>> +
>> +#include <linux/ioport.h>
>> +#include <linux/mm.h>
>> +
>> +/*
>> + * 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 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 */
>> +
>>  #endif	/* __KERNEL__ */
>>  #endif	/* __UNICORE_IO_H__ */
>> -- 
>> 1.7.9.5
>>
> 

-- 
Chen Gang

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