linux-kernel - Re: [PATCH 1 of 4] mm: add a ptep_modify

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Date:	Wed, 18 Jun 2008 17:15:36 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	benh@...nel.crashing.org
CC:	xen-devel <xen-devel@...ts.xensource.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	kvm-devel <kvm-devel@...ts.sourceforge.net>, x86@...nel.org,
	LKML <linux-kernel@...r.kernel.org>,
	Virtualization Mailing List <virtualization@...ts.osdl.org>,
	Hugh Dickins <hugh@...itas.com>, Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 1 of 4] mm: add a ptep_modify_prot transaction	abstraction

Jeremy Fitzhardinge wrote:
> Benjamin Herrenschmidt wrote:
>   
>> On Mon, 2008-06-16 at 04:30 -0700, Jeremy Fitzhardinge wrote:
>>   
>>     
>>> The only current user of this interface is mprotect
>>>     
>>>       
>> Do you plan to use it with fork ultimately ?
>>   
>>     
>
> Good point, I'd overlooked that.  I guess that means using it in 
> ptep_set_wrprotect().
Along the lines of:

--- a/include/asm-x86/pgtable.h	Wed Jun 18 13:54:49 2008 -0700
+++ b/include/asm-x86/pgtable.h	Wed Jun 18 17:03:39 2008 -0700
@@ -491,7 +491,11 @@
 static inline void ptep_set_wrprotect(struct mm_struct *mm,
 				      unsigned long addr, pte_t *ptep)
 {
-	clear_bit(_PAGE_BIT_RW, (unsigned long *)&ptep->pte);
+	pte_t pte = ptep_modify_prot_start(mm, addr, ptep);
+	
+	pte = pte_wrprotect(pte);
+
+	ptep_modify_prot_commit(mm, addr, ptep, pte);
 	pte_update(mm, addr, ptep);
 }
 

	J

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