linux-kernel - Re: [PATCHv11 2.6.36-rc2-tip 3/15] 3: uprobes: Slot allocation for Execution out of line(XOL)

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Date:	Fri, 03 Sep 2010 19:25:18 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Steven Rostedt <rostedt@...dmis.org>,
	Randy Dunlap <rdunlap@...otime.net>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Christoph Hellwig <hch@...radead.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Mark Wielaard <mjw@...hat.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Naren A Devaiah <naren.devaiah@...ibm.com>,
	Jim Keniston <jkenisto@...ux.vnet.ibm.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	"Frank Ch. Eigler" <fche@...hat.com>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: Re: [PATCHv11 2.6.36-rc2-tip 3/15]  3: uprobes: Slot allocation
 for Execution out of line(XOL)

On Fri, 2010-09-03 at 22:10 +0530, Srikar Dronamraju wrote:
> > > +   vma = find_vma(mm, addr);
> > > +
> > > +   /* Don't expand vma on mremap(). */
> > > +   vma->vm_flags |= VM_DONTEXPAND | VM_DONTCOPY;
> > > +   area->vaddr = vma->vm_start;
> > 
> > Seems interesting,.. why not use install_special_mapping(), that's what
> > the VDSO uses.
> 
> Okay, I hadnt looked at install_special_mapping earlier so I will take a
> look and incorporate it. However I am not clear at this point what
> install_special_mapping is giving us here.  Also install_special_mapping
> is already defining its own vm_ops esp a close method thats doesnt seem
> to be doing anything. So at this point I am not clear how we are link
> the vm_ops, the close method and install_special_mapping.

What you're doing might well be the right thing, I was just wondering.

I think that, after thinking about it more, that the shmem file thing
you're doing has the added benefit that the things gets auto-magic
paging, which is a good thing.


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