linux-kernel - Re: [PATCH 2/2] ppc64le live patch: get rid of mini stack frame

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Message-ID: <20160310125116.GS10940@pathway.suse.cz>
Date:	Thu, 10 Mar 2016 13:51:16 +0100
From:	Petr Mladek <pmladek@...e.com>
To:	Torsten Duwe <duwe@....de>
Cc:	jeyu@...hat.com, jkosina@...e.cz, jikos@...nel.org,
	linux-kernel@...r.kernel.org, rostedt@...dmis.org,
	kamalesh@...ux.vnet.ibm.com, linuxppc-dev@...abs.org,
	live-patching@...r.kernel.org, mbenes@...e.cz
Subject: Re: [PATCH 2/2] ppc64le live patch: get rid of mini stack frame

On Thu 2016-03-10 13:25:08, Petr Mladek wrote:
> On Wed 2016-03-09 18:30:17, Torsten Duwe wrote:
> > After the mini stack frame is no longer required for TOC storage, it can
> > be eliminated iff the functionality of klp_return_helper, which required
> > a stack frame for the extra return address previously, is carried out
> > by the replacement function now. This requires _every_ live patch replacement
> > function to execute the following (or similar) sequence of machine instructions
> > just before every return to the original caller:
> 
> I have thought about it and it is a nono from my point of view.
> It is too error prone, especially that there are functions that
> call return on several locations.

BTW: How is this solved in kretprobes? Or is it easier there?

Best Regards,
Petr