linux-kernel - Re: [PATCH 4/7] uretprobes: return probe entry, prepare

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Date:	Tue, 26 Mar 2013 13:26:01 +0100
From:	Anton Arapov <anton@...hat.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Josh Stone <jistone@...hat.com>,
	Frank Eigler <fche@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...e.hu>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	adrian.m.negreanu@...el.com, Torsten.Polle@....de
Subject: Re: [PATCH 4/7] uretprobes: return probe entry, prepare_uretprobe()

On Fri, Mar 22, 2013 at 04:02:52PM +0100, Oleg Nesterov wrote:
> I'll try to read this series later. Just one note...
> 
> On 03/22, Anton Arapov wrote:
> >
> >    IOW, we must ensure that uprobe_pre_sstep_notifier() can't return 0.
> 
> Yes, but I do not see this change?
> 
> > +static void prepare_uretprobe(struct uprobe *uprobe, struct pt_regs *regs)
> > +{
> > +	struct return_instance *ri;
> > +	struct uprobe_task *utask;
> > +	struct xol_area *area;
> > +	unsigned long trampoline_vaddr;
> > +	unsigned long prev_ret_vaddr, ret_vaddr;
> > +
> > +	area = get_xol_area();
> > +	if (!area)
> > +		return;
> > +
> > +	utask = get_utask();
> > +	if (!utask)
> > +		return;
> > +
> > +	prev_ret_vaddr = -1;
> > +	if (utask->return_instances)
> > +		prev_ret_vaddr = utask->return_instances->orig_ret_vaddr;
> > +
> > +	ri = kzalloc(sizeof(struct return_instance), GFP_KERNEL);
> > +	if (!ri)
> > +		return;
> > +
> > +	ri->dirty = false;
> > +	trampoline_vaddr = get_trampoline_vaddr(area);
> > +	ret_vaddr = arch_uretprobe_hijack_return_addr(trampoline_vaddr, regs);
> 
> OK, but you need to ensure that this code can be compiled on poweprc.

It does compile, unlike the obvious arch_uretprobe_hijack_return_addr() where
I'll look for the Ananth's help, perhaps. 

Anton. 
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