Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932232AbcCILQ7 (ORCPT ); Wed, 9 Mar 2016 06:16:59 -0500 Received: from verein.lst.de ([213.95.11.211]:47686 "EHLO newverein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753058AbcCILQu (ORCPT ); Wed, 9 Mar 2016 06:16:50 -0500 Date: Wed, 9 Mar 2016 12:16:47 +0100 From: Torsten Duwe To: Jiri Kosina Cc: Petr Mladek , Balbir Singh , linuxppc-dev@ozlabs.org, linux-kernel@vger.kernel.org, rostedt@goodmis.org, kamalesh@linux.vnet.ibm.com, jeyu@redhat.com, live-patching@vger.kernel.org, mbenes@suse.cz Subject: Re: [PATCH][v6][RFC] livepatch/ppc: Enable livepatching on powerpc Message-ID: <20160309111647.GA27913@lst.de> References: <1457506780-19556-1-git-send-email-bsingharora@gmail.com> <20160309091904.GA23039@lst.de> <20160309094423.GH10940@pathway.suse.cz> <20160309100328.GB23039@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1090 Lines: 25 On Wed, Mar 09, 2016 at 11:13:05AM +0100, Jiri Kosina wrote: > On Wed, 9 Mar 2016, Torsten Duwe wrote: > > was my first choice. Arguments on the stack? I thought we'll deal with them > > once we get there (e.g. _really_ need to patch a varargs function or one > > with a silly signature). > > Well, the problem is, once such need arises, it's too late already. No, not if it's documented. > You need to be able to patch the kernels which are already out there, > running on machines potentially for ages once all of a sudden there is a > CVE for >8args / varargs function. Then you'd need a solution like I sent out yesterday, with a pre-prologue caller that pops the extra frame, so the replacement can be more straight- forward. Or you can just deal with the shifted offsets in the replacement. I'll try to demonstrate the alternative. That would then be required for _all_ replacement functions. Or can the live patching framework differentiate and tell ftrace_caller whether to place a stack frame or not? Miroslav? Petr? Can we have 2 sorts of replacement functions? Torsten