From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.9 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_NEOMUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 525A5C04AB1 for ; Thu, 9 May 2019 14:00:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2AA1E208C3 for ; Thu, 9 May 2019 14:00:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726652AbfEIOAO (ORCPT ); Thu, 9 May 2019 10:00:14 -0400 Received: from mx1.redhat.com ([209.132.183.28]:47604 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726192AbfEIOAN (ORCPT ); Thu, 9 May 2019 10:00:13 -0400 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 435DB307C643; Thu, 9 May 2019 14:00:13 +0000 (UTC) Received: from treble (ovpn-123-166.rdu2.redhat.com [10.10.123.166]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 76DEB10027C3; Thu, 9 May 2019 14:00:03 +0000 (UTC) Date: Thu, 9 May 2019 09:00:01 -0500 From: Josh Poimboeuf To: Peter Zijlstra Cc: Masami Hiramatsu , linux-kernel@vger.kernel.org, Linus Torvalds , Ingo Molnar , Andrew Morton , Andy Lutomirski , Nicolai Stange , Thomas Gleixner , Borislav Petkov , "H. Peter Anvin" , x86@kernel.org, Jiri Kosina , Miroslav Benes , Petr Mladek , Joe Lawrence , Shuah Khan , Konrad Rzeszutek Wilk , Tim Chen , Sebastian Andrzej Siewior , Mimi Zohar , Juergen Gross , Nick Desaulniers , Nayna Jain , Masahiro Yamada , Joerg Roedel , linux-kselftest@vger.kernel.org Subject: Re: [PATCH 2/4] x86/kprobes: Fix frame pointer annotations Message-ID: <20190509140001.fvwzlnhai6ddqjmt@treble> References: <20190508074901.982470324@infradead.org> <20190508080612.721269814@infradead.org> <20190508115416.nblx7c2kocidpytm@treble> <20190508120416.GL2589@hirez.programming.kicks-ass.net> <20190508124248.u5ukpbhnh4wpiccq@treble> <20190508153907.GM2589@hirez.programming.kicks-ass.net> <20190508184848.qerg3flv3ej3xsev@treble> <20190509102030.dfa62e058f09d0d8cbdd6053@kernel.org> <20190509081431.GO2589@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190509081431.GO2589@hirez.programming.kicks-ass.net> User-Agent: NeoMutt/20180716 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.42]); Thu, 09 May 2019 14:00:13 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 09, 2019 at 10:14:31AM +0200, Peter Zijlstra wrote: > But what I'd love to do is something like the belwo patch, and make all > the trampolines (very much including ftrace) use that. Such that we then > only have 1 copy of this magic (well, 2 because x86_64 also needs an > implementation of this of course). > > Changing ftrace over to this would be a little more work but it can > easily chain things a little to get its original context back: > > ENTRY(ftrace_regs_caller) > GLOBAL(ftrace_regs_func) > push ftrace_stub > push ftrace_regs_handler > jmp call_to_exception_trampoline > END(ftrace_regs_caller) > > typedef void (*ftrace_func_t)(unsigned long, unsigned long, struct ftrace_op *, struct pt_regs *); > > struct ftrace_regs_stack { > ftrace_func_t func; > unsigned long parent_ip; > }; > > void ftrace_regs_handler(struct pr_regs *regs) > { > struct ftrace_regs_stack *st = (void *)regs->sp; > ftrace_func_t func = st->func; > > regs->sp += sizeof(long); /* pop func */ > > func(regs->ip, st->parent_ip, function_trace_op, regs); > } > > Hmm? I didn't look into the function_graph thing, but I imagine it can > be added without too much pain. I like this patch a lot, assuming it can be made to work for the different users. -- Josh