linux-kernel - Re: [PATCH 1/2] ppc64le live patch: clear out storage location(s) in mini stack frame

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Message-ID: <56E23D7A.4040903@gmail.com>
Date:	Fri, 11 Mar 2016 14:37:30 +1100
From:	Balbir Singh <bsingharora@...il.com>
To:	Torsten Duwe <duwe@....de>, Petr Mladek <pmladek@...e.com>
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 1/2] ppc64le live patch: clear out storage location(s) in
 mini stack frame



On 10/03/16 04:28, Torsten Duwe wrote:
> This can be applied on top of Petr Mladek's v4 rework of the ppc64le
> live patching. Inspired by Balbir Singh's v5, information about the
> callee's r2 is stored in a "reserved" 32 bit location in the caller's
> stack frame, instead of 64 bits in the newly created mini frame 24(r1).
>
> It only needs to work for a local call, when caller's TOC == callee's
> TOC, and along with the return address (LR) it's all within a 4GiB
> range (+-31 bits). If the original call already was global, we are
> allowed to restore any nonsense into r2, because the global caller
> will restore its TOC anyway from the ABI compliant location 24(r1)
> right after return.
>
>
Hi, Torsten

Sorry, I've had no time to test this. Caught up with something else for the moment.
Hopefully I'll get a chance over the weekend.

Have you tested this against Petr's sample changes to patch printk?

Balbir Singh.