From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754829AbaCMSIJ (ORCPT ); Thu, 13 Mar 2014 14:08:09 -0400 Received: from cdptpa-outbound-snat.email.rr.com ([107.14.166.225]:59185 "EHLO cdptpa-oedge-vip.email.rr.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754166AbaCMSII (ORCPT ); Thu, 13 Mar 2014 14:08:08 -0400 Message-ID: <1394734070.26600.6.camel@pippen.local.home> Subject: Re: [PATCH v6 6/7] arm64: ftrace: Add CALLER_ADDRx macros From: Steven Rostedt To: Will Deacon Cc: AKASHI Takahiro , "fweisbec@gmail.com" , "mingo@redhat.com" , Catalin Marinas , "tim.bird@sonymobile.com" , "gkulkarni@caviumnetworks.com" , "dsaxena@linaro.org" , "arndb@arndb.de" , "linux-arm-kernel@lists.infradead.org" , "linaro-kernel@lists.linaro.org" , "linux-kernel@vger.kernel.org" Date: Thu, 13 Mar 2014 14:07:50 -0400 In-Reply-To: <20140313155415.GB25472@mudshark.cambridge.arm.com> References: <1393564724-3966-1-git-send-email-takahiro.akashi@linaro.org> <1394705630-12384-1-git-send-email-takahiro.akashi@linaro.org> <1394705630-12384-7-git-send-email-takahiro.akashi@linaro.org> <20140313155415.GB25472@mudshark.cambridge.arm.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.4.4-4+b1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-RR-Connecting-IP: 107.14.168.130:25 X-Cloudmark-Score: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2014-03-13 at 15:54 +0000, Will Deacon wrote: > On Thu, Mar 13, 2014 at 10:13:49AM +0000, AKASHI Takahiro wrote: > > CALLER_ADDRx returns caller's address at specified level in call stacks. > > They are used for several tracers like irqsoff and preemptoff. > > Strange to say, however, they are refered even without FTRACE. > > > > Please note that this implementation assumes that we have frame pointers. > > (which means kernel should be compiled with -fno-omit-frame-pointer.) > > How do you ensure that -fno-omit-frame-pointer is passed? Perhaps -pg does the same thing? > > +#define HAVE_ARCH_CALLER_ADDR > > + > > +#define CALLER_ADDR0 ((unsigned long)__builtin_return_address(0)) > > +#define CALLER_ADDR1 ((unsigned long)return_address(1)) > > +#define CALLER_ADDR2 ((unsigned long)return_address(2)) > > +#define CALLER_ADDR3 ((unsigned long)return_address(3)) > > +#define CALLER_ADDR4 ((unsigned long)return_address(4)) > > +#define CALLER_ADDR5 ((unsigned long)return_address(5)) > > +#define CALLER_ADDR6 ((unsigned long)return_address(6)) > > Could we change the core definitions of these macros (in linux/ftrace.h) to > use return_address, then provide an overridable version of return_address > that defaults to __builtin_return_address, instead of copy-pasting this > sequence? We could add a new macro: /* All archs should have this, but we define it for consistency */ #ifndef ftrace_return_address0 # define ftrace_return_address0 __builtin_return_address(0) #endif /* Archs may use other ways for ADDR1 and beyond */ #ifndef ftrace_return_address # define ftrace_return_address(n) __builtin_return_address(n) #endif And then have: #define CALLER_ADDR0 ((unsigned long)ftrace_return_address0) #define CALLER_ADDR1 ((unsigned long)ftrace_return_address(1)) [...] And then you would only need to redefine ftrace_return_address. -- Steve