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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 694DFC43331 for ; Wed, 1 Apr 2020 15:38:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 387C420CC7 for ; Wed, 1 Apr 2020 15:38:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="K+Oe4lla" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732949AbgDAPiV (ORCPT ); Wed, 1 Apr 2020 11:38:21 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:40546 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732789AbgDAPiU (ORCPT ); Wed, 1 Apr 2020 11:38:20 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=SZEua1exB+fJhLXEKQKY3fxy8SCkkGqIypKBr5G5eFs=; b=K+Oe4llapIfkNedKpC+wpB1023 jkFGXLrQNgvhUix8rVaz6J9wf4Ef7fSnIKa/FWx1+qIlPcXm1TU0LRLky4chWFzkm+PpoOMcKQ6rE 3mGpiJFbwe2HXCupHAWEFn2iEQ2reEOaW4xRbK+DxFBMbKhfXp/4VrZ6S3oHIhwVUUwiOjfYqL4dF P8U964wDbeFdhnQ0MxWqGeG7AVjvb7N8jpE7zvddjPbBlFobzWSrksIfDuQeRyY4AvR2GN7REEn+j MeZA1UCjE0DAzioqAUoM4c+WbUyDSh1qN8gK4ZdCe9j4F2Pgb9zbyTC41B/aiZHHjoG3zZlE1NxHz pU0eD8VA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jJfRV-0004bR-3F; Wed, 01 Apr 2020 15:38:13 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id ED71C3060FD; Wed, 1 Apr 2020 17:38:10 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id A117C2041897F; Wed, 1 Apr 2020 17:38:10 +0200 (CEST) Date: Wed, 1 Apr 2020 17:38:10 +0200 From: Peter Zijlstra To: Josh Poimboeuf Cc: tglx@linutronix.de, linux-kernel@vger.kernel.org, x86@kernel.org, mhiramat@kernel.org, mbenes@suse.cz, Steven Rostedt Subject: Re: [PATCH v2] objtool,ftrace: Implement UNWIND_HINT_RET_OFFSET Message-ID: <20200401153810.GV20696@hirez.programming.kicks-ass.net> References: <20200330200254.GV20713@hirez.programming.kicks-ass.net> <20200331111652.GH20760@hirez.programming.kicks-ass.net> <20200331202315.zialorhlxmml6ec7@treble> <20200331204047.GF2452@worktop.programming.kicks-ass.net> <20200331211755.pb7f3wa6oxzjnswc@treble> <20200331212040.7lrzmj7tbbx2jgrj@treble> <20200331222703.GH2452@worktop.programming.kicks-ass.net> <20200401141402.m4klvezp5futb7ff@treble> <20200401142226.GU20696@hirez.programming.kicks-ass.net> <20200401143916.h5keq55yabetyv5u@treble> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200401143916.h5keq55yabetyv5u@treble> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 01, 2020 at 09:39:16AM -0500, Josh Poimboeuf wrote: > On Wed, Apr 01, 2020 at 04:22:26PM +0200, Peter Zijlstra wrote: > > > > @@ -366,6 +367,13 @@ create_trampoline(struct ftrace_ops *ops > > > > if (WARN_ON(ret < 0)) > > > > goto fail; > > > > > > > > + if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) { > > > > + ip = ftrace_regs_caller_ret; > > > > + ret = probe_kernel_read(ip, (void *)retq, RET_SIZE); > > > > + if (WARN_ON(ret < 0)) > > > > + goto fail; > > > > + } > > > > + > Right, but 'ip' needs to point to the trampoline's version of > 'ftrace_regs_caller_ret', not the original ftrace_64 version. Duh, ip = trampline + (ftrace_regs_caller_ret - ftrace_regs_caller); it is. Luckily this would've triggerd a splat the first time I'd have actually booted this, because the regular text is RO, while the trampoline is still RW here. Still, good spotting.