linux-kernel - Re: Copy large memory regions from & to userspace

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Date:	Fri, 31 Aug 2007 15:45:28 +0200
From:	Clemens Kolbitsch <clemens.kol@....at>
To:	"Chris Smith" <smitty1elkml@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>
Subject: Re: Copy large memory regions from & to userspace

On Friday 31 August 2007 15:25:40 you wrote:
> On 8/30/07, Clemens Kolbitsch <clemens.kol@....at> wrote:
> > Hi!
> > Just a short question: What is the correct method of copying large areas
> > of memory from userspace into userspace when running in kernel-mode?
>
> relayfs?

no... I'm copying user-memory to user-memory, not kernel-to-user, however 
running the code in kernel-mode.

what i wanted to know is how to check the access-rights...
i didn't get any other answers, so for now i'm just using 

if (access_ok(VERIFY_READ, from, PAGE_SIZE) &&
    access_ok(VERIFY_WRITE, to, PAGE_SIZE))
{
    memcpy(to, from, PAGE_SIZE);
}

and hope that this is the *correct* way to do it...

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