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

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Date:	Wed, 16 Apr 2014 13:15:29 +0800 (CST)
From:	管雪涛 <gxt@....edu.cn>
To:	Chen Gang <gang.chen.5i5j@...il.com>
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: 回复： [PATCH v3] arch:unicore32:mm: add devmem_is_allowed() to support STRICT_DEVMEM

Acked-by: Xuetao Guan <gxt@...c.pku.edu.cn>

----- 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
> 

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