linux-kernel - Re: [PATCH] arm64: export __cpu_{clear,copy}_user

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Date:	Wed, 18 Jun 2014 11:39:54 +0100
From:	Catalin Marinas <catalin.marinas@....com>
To:	Mark Salter <msalter@...hat.com>
Cc:	Will Deacon <Will.Deacon@....com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] arm64: export __cpu_{clear,copy}_user_page functions

On Tue, Jun 17, 2014 at 06:14:26PM +0100, Mark Salter wrote:
> The __cpu_clear_user_page() and __cpu_copy_user_page() functions
> are not currently exported. This prevents modules from using
> clear_user_page() and opy_user_page().
> 
> Signed-off-by: Mark Salter <msalter@...hat.com>
> ---
>  arch/arm64/mm/copypage.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/arm64/mm/copypage.c b/arch/arm64/mm/copypage.c
> index 9aecbac..13bbc3be 100644
> --- a/arch/arm64/mm/copypage.c
> +++ b/arch/arm64/mm/copypage.c
> @@ -27,8 +27,10 @@ void __cpu_copy_user_page(void *kto, const void *kfrom, unsigned long vaddr)
>  	copy_page(kto, kfrom);
>  	__flush_dcache_area(kto, PAGE_SIZE);
>  }
> +EXPORT_SYMBOL_GPL(__cpu_copy_user_page);
>  
>  void __cpu_clear_user_page(void *kaddr, unsigned long vaddr)
>  {
>  	clear_page(kaddr);
>  }
> +EXPORT_SYMBOL_GPL(__cpu_clear_user_page);

I wonder why we still have these functions. I don't think we need any
D-cache flushing for copy_user_page(), so we could simply remove this
code and define copy_user_page() as copy_page() (similarly for
clear_user_page). I'll post a patch separately removing the copy_page,
copy_user_page etc. functions (now that we also have optimised memcpy
and memset).

-- 
Catalin
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