From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on archive.lwn.net X-Spam-Level: X-Spam-Status: No, score=-5.8 required=5.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=unavailable autolearn_force=no version=3.4.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by archive.lwn.net (Postfix) with ESMTP id 45ED57D08A for ; Fri, 2 Nov 2018 07:58:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728237AbeKBRE4 (ORCPT ); Fri, 2 Nov 2018 13:04:56 -0400 Received: from mx1.mailbox.org ([80.241.60.212]:11326 "EHLO mx1.mailbox.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727387AbeKBRE4 (ORCPT ); Fri, 2 Nov 2018 13:04:56 -0400 Received: from smtp2.mailbox.org (unknown [IPv6:2001:67c:2050:105:465:1:2:0]) (using TLSv1.2 with cipher ECDHE-RSA-CHACHA20-POLY1305 (256/256 bits)) (No client certificate requested) by mx1.mailbox.org (Postfix) with ESMTPS id 100A543409; Fri, 2 Nov 2018 08:58:37 +0100 (CET) X-Virus-Scanned: amavisd-new at heinlein-support.de Received: from smtp2.mailbox.org ([80.241.60.241]) by gerste.heinlein-support.de (gerste.heinlein-support.de [91.198.250.173]) (amavisd-new, port 10030) with ESMTP id mW1eQMjYusdU; Fri, 2 Nov 2018 08:58:32 +0100 (CET) Date: Fri, 2 Nov 2018 18:58:18 +1100 From: Aleksa Sarai To: Steven Rostedt Cc: "Naveen N. Rao" , Anil S Keshavamurthy , "David S. Miller" , Masami Hiramatsu , Jonathan Corbet , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Shuah Khan , Alexei Starovoitov , Daniel Borkmann , Brendan Gregg , Christian Brauner , Aleksa Sarai , netdev@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, Josh Poimboeuf Subject: Re: [PATCH v3 1/2] kretprobe: produce sane stack traces Message-ID: <20181102075818.fk55mxb3snqj5rjt@yavin> References: <20181101083551.3805-1-cyphar@cyphar.com> <20181101083551.3805-2-cyphar@cyphar.com> <20181101204720.6ed3fe37@vmware.local.home> <20181102050509.tw3dhvj5urudvtjl@yavin> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="ohgwqw7to7laxvft" Content-Disposition: inline In-Reply-To: <20181102050509.tw3dhvj5urudvtjl@yavin> Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org --ohgwqw7to7laxvft Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On 2018-11-02, Aleksa Sarai wrote: > Unfortunately, I'm having a lot of trouble understanding how the current > ftrace hooking works -- ORC has a couple of ftrace hooks that seem > reasonable on the surface but I don't understand (for instance) how > HAVE_FUNCTION_GRAPH_RET_ADDR_PTR *actually* works. Though your comment > appears to indicate that it doesn't work for stack traces? Sorry, I just figured out how it works! (To make sure I actually understand -- retp is a pointer to the place in the stack where the return address is stored, so it uniquely specifies what each trampoline actually points to -- this trick could also be used for kretprobes). --=20 Aleksa Sarai Senior Software Engineer (Containers) SUSE Linux GmbH --ohgwqw7to7laxvft Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAABCAAdFiEEb6Gz4/mhjNy+aiz1Snvnv3Dem58FAlvcA5cACgkQSnvnv3De m5/Fbg//cNaNafzuvOJBuDYI+bTOXGARp3LQ1DyqUSj7Qmak6e5vxtjF6AQgkhs0 HH9bGvIXRfUaWU5bRSCMOkXsRVs3vsuQK7RkDjOx9n3AOtu5+eXay6k/opldFjcG qRXfiiplsB8ijwF6o1shm95v/g9hsr0hRuP7mxFGdqmbH17i7pJ0VEYFjAIS0+b0 130oOQvP119GVM3wRaOWN88N4DqVjCW5WWURfdWVzH31c9VQzSYy6p7Y/t0ZLkiW gOOi3/7JrE9dqj2Qp/+dSRa2MEzgD3mHCrcVTDwalR5NScuoDrJQEXHSkrRnborJ vZ8vDuwuVVNidRys7bH/EE4DSevswoExpNN1OtYKm6f7h3C35DMEyws6MgitHGXI F4yy07AUFoBUkMZKaFI51Y8gCQZEUv2MvLK+i+Pf0gW1nZNnORUOx4/WnVxO4XTZ IXoT/Exq8RMVnmEzOQHn6wWSgVLXQvel/TzwoDfbbZb4EJYbs9EevNx9QYcRhPYq Inte2hnvEW8MWufrxhJKHwE2lbMV90OX6bM4O+4TDZn1F8/Z5BdNI0xQ3K/zi4K/ dWeXvFhkiCPoLsORSzqeby5bUp6c8gjzPNaWQC8BrWwZuSSzX85Dtcs3qIMOrzIj smbXYhS0nE1FdEIqeZ6RWNPHLHGRyDCHAvZ8mz55H+4+ZIxtqv8= =kzT1 -----END PGP SIGNATURE----- --ohgwqw7to7laxvft--