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 4CF33C433E0 for ; Mon, 25 May 2020 09:18:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 16C3820787 for ; Mon, 25 May 2020 09:18:47 +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="NsVypL1y" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389328AbgEYJSq (ORCPT ); Mon, 25 May 2020 05:18:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53968 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725809AbgEYJSq (ORCPT ); Mon, 25 May 2020 05:18:46 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BC85CC061A0E for ; Mon, 25 May 2020 02:18:45 -0700 (PDT) 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=sb77lX+DMcqY6cREpR0MjEzbsR6ud83Odwt/z0stuhI=; b=NsVypL1ygpElBuT3GTopsIuXUZ aOILjRmDHzsb1vyAEUwW83smtj4KlujTDWHIeyDfcOORYy/+9RJmt3v9n5jBgU9k0iN4XN26ggIrC gh+RHCSbZR0sOjuCyMaP000NwmGZc0BcM8mfRO8tbo2d2ydRAKAwSfOygrfndfMBO1iB7ymkx+CZK tKg3/kku828OUM8ahrGQLCO+6bPyEBAJs25oqdiqUCni8+7agpPgfdb2CsBzDiICojQvDEGS/mkeu Ym7wpoZMQKc9j37w0Bl/9Ww45a3ZAkQyrojkg+2pVGo1c1I+j4eYcwpHEvQnTOsHG9IZD+a1XxHLN rFtUddFg==; 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 1jd9Fi-0008Qe-DQ; Mon, 25 May 2020 09:18:34 +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 28B6C30018B; Mon, 25 May 2020 11:18:32 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 12D81286BFC11; Mon, 25 May 2020 11:18:32 +0200 (CEST) Date: Mon, 25 May 2020 11:18:32 +0200 From: Peter Zijlstra To: daniel.thompson@linaro.org, x86@kernel.org Cc: sumit.garg@linaro.org, jason.wessel@windriver.com, dianders@chromium.org, kgdb-bugreport@lists.sourceforge.net, linux-kernel@vger.kernel.org, pmladek@suse.com, sergey.senozhatsky@gmail.com, will@kernel.org Subject: Re: x86/entry vs kgdb Message-ID: <20200525091832.GE325303@hirez.programming.kicks-ass.net> References: <20200525083605.GB317569@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200525083605.GB317569@hirez.programming.kicks-ass.net> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 25, 2020 at 10:36:05AM +0200, Peter Zijlstra wrote: > Hi! > > Since you seem to care about kgdb, I figured you might want to fix this > before I mark it broken on x86 (we've been considering doing that for a > while). > > AFAICT the whole debugreg usage of kgdb-x86_64 is completely hosed; it > doesn't respsect the normal exclusion zones as per arch_build_bp_info(). > > That is, breakpoints must never be in: > > - in the cpu_entry_area > - in .entry.text > - in .noinstr.text > - in anything else marked NOKPROBE > > by not respecting these constraints it is trivial to completely and > utterly hose the machine. The entry rework that is current underway will > explicitly not deal with #DB triggering in any of those places. This also very much includes single stepping those bits. Which KGDB obviously also does not respects.