linux-kernel - Re: [RFC PATCH v2 0/4] uprobes: return probe implementation

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Date:	Wed, 9 Jan 2013 17:12:22 +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>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...e.hu>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>
Subject: Re: [RFC PATCH v2 0/4] uprobes: return probe implementation

On 01/09, Anton Arapov wrote:
>
> There are RFC uretprobes implementation. I'd be grateful for review.
>
>   RFCv1: https://lkml.org/lkml/2012/12/21/133
>
> I've intentionally removed the retprobe bypass logic, it requires
> a bit more work.

Yes, this is not trivial, lets do this separately.

> not fixed since last prior RFC review:
>   unify xol_get_trampoline_slot() and xol_take_insn_slot()

This was of the reasons for "Do not play with utask in xol_get_insn_slot()"
I sent. After this patch you only need the trivial change

	- static unsigned long xol_get_insn_slot(struct uprobe *uprobe)
	+ static unsigned long xol_get_insn_slot(unsigned char *insn)

and now you do not need xol_get_trampoline_slot().

However. Why do you need it at all? Let me quote myself:

	Or. Perhaps even better, do not add this helper at all. xol_alloc_area()
	could reserve the first slot/bit for trampoline. And note that in this
	case we do not need xol_area->rp_trampoline_vaddr, it is always equal
	to xol_area->vaddr.

?

>   protect uprobe in prepare_uretprobe()

This should be fixed ;)

Oleg.

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