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

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Date:	Sun, 23 Dec 2012 16:49:10 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Anton Arapov <anton@...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 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.

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