linux-kernel - Re: [RFC PATCH 5/6] uprobes: add bp_vaddr argument to consumer handler

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Date:	Tue, 8 Jan 2013 15:27:15 +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>
Subject: Re: [RFC PATCH 5/6] uprobes: add bp_vaddr argument to consumer
 handler

On Sun, Dec 23, 2012 at 04:49:10PM +0100, Oleg Nesterov wrote:
> On 12/22, Oleg Nesterov wrote:
> >
> > Forgot to ask...
> >
> > On 12/22, Oleg Nesterov wrote:
> > >
> > > On 12/21, Anton Arapov wrote:
> > > >
> > > >  struct uprobe_consumer {
> > > > -	int (*handler)(struct uprobe_consumer *self, struct pt_regs *regs);
> > > > +	int (*handler)(struct uprobe_consumer *self, unsigned long bp_vaddr, struct pt_regs *regs);
> > >
> > > It seems that we can do better...
> > >
> > > Just change regs->ip before calling ->handler().
> >
> > Josh, Frank, will it work for you?
> 
> Wait, probably I was confused by this patch and 4/6...
> 
> To simplify, lets ignore the normal uprobes. Yes I still think that it
> would be better to set "regs->ip = orig_return_vaddr" before calling
> ->handler() and not pass it as an argument.
> 
> But, probably uprobe_consumer also needs to know bp_vaddr? IOW, the
> address of the function which we are going to return from? In this case,
> yes, we also need another argument. And prepare_uretprobe/etc should
> be changed to record bp_vaddr passed from handle_swbp(). And
> uretprobe_run_handlers() should pass this bp_vaddr, not orig_return_vaddr.
> 
> Or I am confused.
> 
> Anton?

  Oleg, you are absolutely right and change the ip before calling the
->handle is much better then what I 'invented'.
 
  I'm working on v2 to address this and other issues, will post it soon.

Anton.
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