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=-5.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 8779BC4332E for ; Fri, 5 Mar 2021 19:33:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 62B27650B4 for ; Fri, 5 Mar 2021 19:33:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230143AbhCETdM (ORCPT ); Fri, 5 Mar 2021 14:33:12 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:47978 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229730AbhCETc4 (ORCPT ); Fri, 5 Mar 2021 14:32:56 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1614972775; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=lzFUlmEwerGb1otgAwUz4uvPmsIdAWjstYZ2iDVwDbo=; b=UvfIXrBfriXI4YjojfhH7OgeOVmVLS2cCd7bep6x310ohNAdHPeAAOPKCjiNn0E/+bt1rT dU5IHsA0j4MIuiKWh4oxxVxDXGBSIqXHUFUBY5IDSkzArUtZWarmJlipFuF52QY+xdvZc8 1uhVacYDB6ZsMz0g/YjocKVEVjYuXwg= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-302-QUCO94aoNBaBZDyW2FovUA-1; Fri, 05 Mar 2021 14:32:51 -0500 X-MC-Unique: QUCO94aoNBaBZDyW2FovUA-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id E29E28143F0; Fri, 5 Mar 2021 19:32:49 +0000 (UTC) Received: from treble (ovpn-116-51.rdu2.redhat.com [10.10.116.51]) by smtp.corp.redhat.com (Postfix) with ESMTPS id F37E760843; Fri, 5 Mar 2021 19:32:46 +0000 (UTC) Date: Fri, 5 Mar 2021 13:32:44 -0600 From: Josh Poimboeuf To: Daniel Xu Cc: Masami Hiramatsu , rostedt@goodmis.org, kuba@kernel.org, ast@kernel.org, tglx@linutronix.de, mingo@redhat.com, x86@kernel.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, kernel-team@fb.com, yhs@fb.com Subject: Re: [PATCH] x86: kprobes: orc: Fix ORC walks in kretprobes Message-ID: <20210305193244.odtphdj5wm5cslf7@treble> References: <20210305182806.df403dec398875c2c1b2c62d@kernel.org> <20210305195809.a9784ecf0b321c14fd18d247@kernel.org> <20210305192515.6utyhm5kks4zexwn@maharaja.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20210305192515.6utyhm5kks4zexwn@maharaja.localdomain> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Mar 05, 2021 at 11:25:15AM -0800, Daniel Xu wrote: > > BTW, is this a regression? or CONFIG_UNWINDER_ORC has this issue before? > > It seems that the above commit just changed the default unwinder. This means > > OCR stack unwinder has this bug before that commit. > > I see your point -- I suppose it depends on point of view. Viewed from > userspace, a change in kernel defaults means that one kernel worked and > the next one didn't -- all without the user doing anything. Consider it > from the POV of a typical linux user who just takes whatever the distro > gives them and doesn't compile their own kernels. > > From the kernel point of view, you're also right. ORC didn't regress, it > was always broken for this particular use case. But as a primarily > userspace developer, I would consider this a kernel regression. Either way, if the bug has always existed in the ORC unwinder, the Fixes tag needs to reference the original ORC commit: Fixes: ee9f8fce9964 ("x86/unwind: Add the ORC unwinder") That makes it possible for stable kernels to identify the source of the bug and corresponding fix. Many people used the ORC unwinder before it became the default. -- Josh