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Message-ID: <3D78CD5D.9060002@colorfullife.com>
Date: Fri, 06 Sep 2002 17:44:29 +0200
From: Manfred Spraul <manfred@colorfullife.com>
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To: "Imran Badr" <imran.badr@cavium.com>
CC: linux-kernel@vger.kernel.org
Subject: Re: Calculating kernel logical address ..
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> adr = user_address;
> pgd_offset(current->mm, adr);
> 
> if (!pgd_none(*pgd)) {
> 	pmd = pmd_offset(pgd, adr);
> 	if (!pmd_none(*pmd)) {
> 		ptep = pte_offset(pmd, adr);
> 		pte = *ptep;
> 		if(pte_present(pte)) {
> 			kaddr  = (unsigned long) page_address(pte_page(pte));
> 			kaddr |= (adr & (PAGE_SIZE - 1));
> 		}
> 	}
> }
> 
> Will this code always give me correct kernel logical address?
> 
What about

	kmalloc_buffer+(user_address-vma->vm_start)

?
A driver should avoid accessing the page tables.

--
	Manfred

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