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

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Message-ID: <20160310122508.GR10940@pathway.suse.cz>
Date:	Thu, 10 Mar 2016 13:25:08 +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 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.

Best Regards,
Petr