From mboxrd@z Thu Jan 1 00:00:00 1970 From: Steven Rostedt Subject: Re: [PATCH v2 1/2] arm64: implement FTRACE_WITH_REGS Date: Fri, 8 Jul 2016 11:57:10 -0400 Message-ID: <20160708115710.5c657b5f@gandalf.local.home> References: <20160627151500.2247A68D20@newverein.lst.de> <20160627151717.BD25468D26@newverein.lst.de> <20160708145800.GE3556@pathway.suse.cz> <20160708150709.GA8979@lst.de> <20160708152421.GG3556@pathway.suse.cz> <20160708154824.ikq45dgk2auigqn7@treble> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: Received: from smtprelay0024.hostedemail.com ([216.40.44.24]:56216 "EHLO smtprelay.hostedemail.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754944AbcGHP5P (ORCPT ); Fri, 8 Jul 2016 11:57:15 -0400 In-Reply-To: <20160708154824.ikq45dgk2auigqn7@treble> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Josh Poimboeuf Cc: Petr Mladek , Torsten Duwe , Catalin Marinas , Will Deacon , takahiro.akashi@linaro.org, Jungseok Lee , Arnd Bergmann , Li Bin , Ingo Molnar , Christopher Li , Jiri Kosina , andrew.wafaa@arm.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, live-patching@vger.kernel.org, linux-arch@vger.kernel.org, linux-sparse@vger.kernel.org On Fri, 8 Jul 2016 10:48:24 -0500 Josh Poimboeuf wrote: > My understanding is that other arches don't need this check because they > use -mfentry, so they have to modify the "call fentry" instruction to a > nop on startup. > > Here, with -fprolog-pad, it's already a nop, so no change is needed. > That's what I was thinking. But as I stated in another email (probably in the air when you wrote this), the call to ftrace_modify_code() may be completely circumvented by ftrace_make_nop() if the addr is MCOUNT_ADDR. -- Steve