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

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Date:	Tue, 8 Apr 2014 11:20:16 +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] arch:unicore32:mm: add devmem_is_allowed() to support STRICT_DEVMEM

I'd like to put the code into asm/io.h, and make it static.

> +#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)
> +{
> +	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>


----- 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/page.h |    4 ++++
>  arch/unicore32/mm/init.c          |   18 ++++++++++++++++++
>  2 files changed, 22 insertions(+)
> 
> diff --git a/arch/unicore32/include/asm/page.h b/arch/unicore32/include/asm/page.h
> index 594b322..231cb89 100644
> --- a/arch/unicore32/include/asm/page.h
> +++ b/arch/unicore32/include/asm/page.h
> @@ -68,6 +68,10 @@ typedef struct page *pgtable_t;
>  
>  extern int pfn_valid(unsigned long);
>  
> +#ifdef CONFIG_STRICT_DEVMEM
> +extern int devmem_is_allowed(unsigned long pfn);
> +#endif /* CONFIG_STRICT_DEVMEM */
> +
>  #include <asm/memory.h>
>  
>  #endif /* !__ASSEMBLY__ */
> diff --git a/arch/unicore32/mm/init.c b/arch/unicore32/mm/init.c
> index be2bde9..3bc3a59 100644
> --- a/arch/unicore32/mm/init.c
> +++ b/arch/unicore32/mm/init.c
> @@ -449,3 +449,21 @@ static int __init keepinitrd_setup(char *__unused)
>  
>  __setup("keepinitrd", keepinitrd_setup);
>  #endif
> +
> +#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.
> + */
> +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 */
> -- 
> 1.7.9.5
--
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