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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 2B5A1C433E0 for ; Fri, 3 Jul 2020 19:21:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 167E72084C for ; Fri, 3 Jul 2020 19:21:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726767AbgGCTVK (ORCPT ); Fri, 3 Jul 2020 15:21:10 -0400 Received: from jabberwock.ucw.cz ([46.255.230.98]:51470 "EHLO jabberwock.ucw.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726147AbgGCTVJ (ORCPT ); Fri, 3 Jul 2020 15:21:09 -0400 Received: by jabberwock.ucw.cz (Postfix, from userid 1017) id E91E01C0BD2; Fri, 3 Jul 2020 21:21:06 +0200 (CEST) Date: Fri, 3 Jul 2020 21:21:03 +0200 From: Pavel Machek To: Greg Kroah-Hartman Cc: Pavel Machek , Sasha Levin , linux-kernel@vger.kernel.org, stable@vger.kernel.org, Masami Hiramatsu , Tom Zanussi , Steven Rostedt Subject: Re: [PATCH 4.19 119/131] tracing: Fix event trigger to accept redundant spaces Message-ID: <20200703192102.GA31738@amd> References: <20200629153502.2494656-1-sashal@kernel.org> <20200629153502.2494656-120-sashal@kernel.org> <20200702211728.GD5787@amd> <20200703060439.GB6344@kroah.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="mYCpIKhGyMATD0i+" Content-Disposition: inline In-Reply-To: <20200703060439.GB6344@kroah.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --mYCpIKhGyMATD0i+ Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable > > > commit 6784beada631800f2c5afd567e5628c843362cee upstream. > > >=20 > > > Fix the event trigger to accept redundant spaces in > > > the trigger input. > > >=20 > > > For example, these return -EINVAL > > >=20 > > > echo " traceon" > events/ftrace/print/trigger > > > echo "traceon if common_pid =3D=3D 0" > events/ftrace/print/trigger > > > echo "disable_event:kmem:kmalloc " > events/ftrace/print/trigger > > >=20 > > > But these are hard to find what is wrong. > > >=20 > > > To fix this issue, use skip_spaces() to remove spaces > > > in front of actual tokens, and set NULL if there is no > > > token. > >=20 > > For the record, I'm not fan of this one. It is ABI change, not a > > bugfix. > >=20 > > Yes, it makes kernel interface "easier to use". It also changes > > interface in the middle of stable series, and if people start relying > > on new interface and start putting extra spaces, they'll get nasty > > surprise when they move code to the older kernel. >=20 > If an interface changes anywhere that breaks userspace, it needs to be > not done, stable kernels are not an issue here or not. I'm not saying it is a regression; I'd scream way more if that was the case. I'm saying it is nowhere near a fix. We really don't want userspace doing: > > > echo " traceon" > events/ftrace/print/trigger Because it does not work on older kernels. It will work on 4.19.131 and break on 5.6.19. Best regards, Pavel --=20 DENX Software Engineering GmbH, Managing Director: Wolfgang Denk HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany --mYCpIKhGyMATD0i+ Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iEYEARECAAYFAl7/hR4ACgkQMOfwapXb+vKmYwCghKkPCwuF8Pk0V5QFUxPxyy/5 CWEAnj9xFfErmFoPgeAdx9X9x2gN3LFG =UJ3w -----END PGP SIGNATURE----- --mYCpIKhGyMATD0i+--