linux-kernel - Re: virt_to_page for userspace pointers

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Message-ID: <4D4DC2D6.8030905@ens-lyon.org>
Date:	Sat, 05 Feb 2011 22:36:22 +0100
From:	Brice Goglin <Brice.Goglin@...-lyon.org>
To:	Nikolaus Rath <Nikolaus@...h.org>
CC:	LKML <linux-kernel@...r.kernel.org>
Subject: Re: virt_to_page for userspace pointers

Le 05/02/2011 22:04, Nikolaus Rath a écrit :
> Nikolaus Rath <Nikolaus@...h.org> writes:
>   
>> Is there a way that my own kernel module can "reverse" this mmap call?
>> I.e. given the userspace pointer, how do I get access to the physical
>> location of the memory that has been mapped?
>>     
> Ok, after some studying I think I can ask the question in a better way:
>
> Is there an equivalent function to virt_to_page (and virt_to_phys) that
> works with userspace pointers? Or do I have to manually walk through the
> page tables? In the later case, are there any examples of this kind of
> search that I could use as a basis?
>   

You probably want get_user_pages() (or get_user_pages_fast()).

Brice

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