From mboxrd@z Thu Jan 1 00:00:00 1970 From: Steven Rostedt Subject: Re: [RFC][PATCH] objtool,x86_64: Replace recordmcount with objtool Date: Wed, 22 Jul 2020 15:09:43 -0400 Message-ID: <20200722150943.53046592@oasis.local.home> References: <20200624203200.78870-1-samitolvanen@google.com> <20200624203200.78870-5-samitolvanen@google.com> <20200624212737.GV4817@hirez.programming.kicks-ass.net> <20200624214530.GA120457@google.com> <20200625074530.GW4817@hirez.programming.kicks-ass.net> <20200625161503.GB173089@google.com> <20200625200235.GQ4781@hirez.programming.kicks-ass.net> <20200625224042.GA169781@google.com> <20200626112931.GF4817@hirez.programming.kicks-ass.net> <20200722135542.41127cc4@oasis.local.home> <20200722184137.GP10769@hirez.programming.kicks-ass.net> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20200722184137.GP10769@hirez.programming.kicks-ass.net> Sender: linux-pci-owner@vger.kernel.org To: Peter Zijlstra Cc: Sami Tolvanen , Masahiro Yamada , Will Deacon , Greg Kroah-Hartman , "Paul E. McKenney" , Kees Cook , Nick Desaulniers , clang-built-linux@googlegroups.com, kernel-hardening@lists.openwall.com, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, x86@kernel.org, Josh Poimboeuf List-Id: linux-arch.vger.kernel.org On Wed, 22 Jul 2020 20:41:37 +0200 Peter Zijlstra wrote: > > That said, Andi Kleen added an option to gcc called -mnop-mcount which > > will have gcc do both create the mcount section and convert the calls > > into nops. When doing so, it defines CC_USING_NOP_MCOUNT which will > > tell ftrace to expect the calls to already be converted. > > That seems like the much easier solution, then we can forget about > recordmcount / objtool entirely for this. Of course that was only for some gcc compilers, and I'm not sure if clang can do this. Or do you just see all compilers doing this in the future, and not worrying about record-mcount at all, and bothering with objtool? -- Steve From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.kernel.org ([198.145.29.99]:53230 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726157AbgGVTJq (ORCPT ); Wed, 22 Jul 2020 15:09:46 -0400 Date: Wed, 22 Jul 2020 15:09:43 -0400 From: Steven Rostedt Subject: Re: [RFC][PATCH] objtool,x86_64: Replace recordmcount with objtool Message-ID: <20200722150943.53046592@oasis.local.home> In-Reply-To: <20200722184137.GP10769@hirez.programming.kicks-ass.net> References: <20200624203200.78870-1-samitolvanen@google.com> <20200624203200.78870-5-samitolvanen@google.com> <20200624212737.GV4817@hirez.programming.kicks-ass.net> <20200624214530.GA120457@google.com> <20200625074530.GW4817@hirez.programming.kicks-ass.net> <20200625161503.GB173089@google.com> <20200625200235.GQ4781@hirez.programming.kicks-ass.net> <20200625224042.GA169781@google.com> <20200626112931.GF4817@hirez.programming.kicks-ass.net> <20200722135542.41127cc4@oasis.local.home> <20200722184137.GP10769@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-arch-owner@vger.kernel.org List-ID: To: Peter Zijlstra Cc: Sami Tolvanen , Masahiro Yamada , Will Deacon , Greg Kroah-Hartman , "Paul E. McKenney" , Kees Cook , Nick Desaulniers , clang-built-linux@googlegroups.com, kernel-hardening@lists.openwall.com, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, x86@kernel.org, Josh Poimboeuf Message-ID: <20200722190943.fK1aGe-YBkp7vcpFQKy3pGb8HBrHmIXfIXCT3WjtsaQ@z> On Wed, 22 Jul 2020 20:41:37 +0200 Peter Zijlstra wrote: > > That said, Andi Kleen added an option to gcc called -mnop-mcount which > > will have gcc do both create the mcount section and convert the calls > > into nops. When doing so, it defines CC_USING_NOP_MCOUNT which will > > tell ftrace to expect the calls to already be converted. > > That seems like the much easier solution, then we can forget about > recordmcount / objtool entirely for this. Of course that was only for some gcc compilers, and I'm not sure if clang can do this. Or do you just see all compilers doing this in the future, and not worrying about record-mcount at all, and bothering with objtool? -- Steve