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

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Date:	Wed, 16 Jan 2013 17:20:22 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Josh Stone <jistone@...hat.com>
Cc:	Anton Arapov <anton@...hat.com>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Frank Eigler <fche@...hat.com>
Subject: Re: [RFC PATCH 5/6] uprobes: add bp_vaddr argument to consumer
	handler

On 01/15, Josh Stone wrote:
>
> On 01/12/2013 09:06 AM, Oleg Nesterov wrote:
> > On 01/10, Josh Stone wrote:
> >> and for uretprobes we want the original return address.
> >
> > Yes, Anton's v2 does this.
> >
> > But. Don't you also need to know the address of function we are going
> > to return from?
> >
> > Probably you do not, uprobe_consumer should know which function (but
> > not vaddr) it probes, but please confirm.
>
> Right, this is fine.

OK, thanks.

> Setting regs->ip to the entry address of the function we just returned
> from would actually be harmful,

Yes, yes, I understand. I meant, ->ret_hander() could have the additional
argument to tell the address of the function.

> Maybe it would be useful if regs->ip reflected the address of the RET
> instruction we just executed, but only if e.g. regs->sp also got rewound
> accordingly.  Since I don't think this is possible, just setting
> regs->ip to the return target is good enough.

Yes, I guess this is not possible.

Oleg.

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