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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 1164DC31E4B for ; Fri, 14 Jun 2019 10:50:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E8518208CA for ; Fri, 14 Jun 2019 10:50:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727328AbfFNKu3 convert rfc822-to-8bit (ORCPT ); Fri, 14 Jun 2019 06:50:29 -0400 Received: from eu-smtp-delivery-151.mimecast.com ([207.82.80.151]:60460 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727054AbfFNKu2 (ORCPT ); Fri, 14 Jun 2019 06:50:28 -0400 Received: from AcuMS.aculab.com (156.67.243.126 [156.67.243.126]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-84-SRaRB_jZPHixQ5QjJdckwQ-1; Fri, 14 Jun 2019 11:50:24 +0100 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) by AcuMS.aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) with Microsoft SMTP Server (TLS) id 15.0.1347.2; Fri, 14 Jun 2019 11:50:23 +0100 Received: from AcuMS.Aculab.com ([fe80::43c:695e:880f:8750]) by AcuMS.aculab.com ([fe80::43c:695e:880f:8750%12]) with mapi id 15.00.1347.000; Fri, 14 Jun 2019 11:50:23 +0100 From: David Laight To: 'Alexei Starovoitov' , Josh Poimboeuf CC: "x86@kernel.org" , "linux-kernel@vger.kernel.org" , Alexei Starovoitov , "Daniel Borkmann" , "netdev@vger.kernel.org" , "bpf@vger.kernel.org" , "Peter Zijlstra" , Song Liu , "Kairui Song" Subject: RE: [PATCH 6/9] x86/bpf: Fix JIT frame pointer usage Thread-Topic: [PATCH 6/9] x86/bpf: Fix JIT frame pointer usage Thread-Index: AQHVIjMat8Fq1dO6sUKm4aXwvliIEKaa+Ndg Date: Fri, 14 Jun 2019 10:50:23 +0000 Message-ID: <57f6e69da6b3461a9c39d71aa1b58662@AcuMS.aculab.com> References: <03ddea21a533b7b0e471c1d73ebff19dacdcf7e3.1560431531.git.jpoimboe@redhat.com> <20190613215807.wjcop6eaadirz5xm@ast-mbp.dhcp.thefacebook.com> In-Reply-To: <20190613215807.wjcop6eaadirz5xm@ast-mbp.dhcp.thefacebook.com> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 X-MC-Unique: SRaRB_jZPHixQ5QjJdckwQ-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Thu, Jun 13, 2019 at 08:21:03AM -0500, Josh Poimboeuf wrote: > The BPF JIT code clobbers RBP. This breaks frame pointer convention and > thus prevents the FP unwinder from unwinding through JIT generated code. > > RBP is currently used as the BPF stack frame pointer register. The > actual register used is opaque to the user, as long as it's a > callee-saved register. Change it to use R12 instead. Could you maintain the system %rbp chain through the BPF stack? It might even be possible to put something relevant in the %rip location. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)