From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754641AbdBISSH (ORCPT ); Thu, 9 Feb 2017 13:18:07 -0500 Received: from pandora.armlinux.org.uk ([78.32.30.218]:41006 "EHLO pandora.armlinux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753616AbdBISRx (ORCPT ); Thu, 9 Feb 2017 13:17:53 -0500 Date: Thu, 9 Feb 2017 18:06:44 +0000 From: Russell King - ARM Linux To: Steven Rostedt Cc: Abel Vesa , mingo@redhat.com, viro@zeniv.linux.org.uk, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, jjhiblot@traphandler.com, pmladek@suse.com, robin.murphy@arm.com, zhouchengming1@huawei.com Subject: Re: [PATCHv3] arm: ftrace: Adds support for CONFIG_DYNAMIC_FTRACE_WITH_REGS Message-ID: <20170209180644.GJ27312@n2100.armlinux.org.uk> References: <1486508275-18449-1-git-send-email-abelvesa@linux.com> <20170209162956.GH27312@n2100.armlinux.org.uk> <20170209121322.5229e6cf@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170209121322.5229e6cf@gandalf.local.home> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 09, 2017 at 12:13:22PM -0500, Steven Rostedt wrote: > Then came along live kernel patching, which I believe this series is > trying to support. What is needed by pt_regs is a way to "hijack" the > function being called to instead call the patched function. That is, > ftrace is not being used for tracing, but in reality, being used to > modify the running kernel. It is being used to change what function > gets called. ftrace is just a hook for that mechanism. So, would I be correct to assume that the only parts of pt_regs that would be touched are those which contain arguments to the function, and the register which would contain the return value? -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net.