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=-2.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, 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 89111C4BA0E for ; Wed, 26 Feb 2020 09:20:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5C6342084E for ; Wed, 26 Feb 2020 09:20:48 +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="V7rKnQLj" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727885AbgBZJUr (ORCPT ); Wed, 26 Feb 2020 04:20:47 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:51350 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726494AbgBZJUq (ORCPT ); Wed, 26 Feb 2020 04:20:46 -0500 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=T5hihDBQQpHndGa1huLjobEba30S9LiISjOQ+UQG2uM=; b=V7rKnQLjdz8MCJZzThtGfkvK1y KhgBfrRPIVqCPgSvV2B+Z44Box+9J0bdO+fE6kzONnPts2ZssJ0VXAapeLHS8iFQqPmcoPMB+ABSp x9d9n/YkmwBIjJxjbJQh79aTEZG+bmph9qNo3YTfVFWfmHPsQFV6kZKt4JdX5ZkzNo4PlSJnH3GBj +1Z7sCty7K5gsdbAIuKYlyfvIOS7CCZMkJ2AkX4aIDPtcMyXs1tgifJcfa+tqV8ftC+78Dwt0NsOD YmDIriKt2j2h9xMZAlWbMSaMfpEbnRMCrnaHbZcV6rW/zYqPTK6jxsUF2nFNu5M59L4GzWnd+obxK dfdM3o9g==; 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 1j6srd-0002md-2J; Wed, 26 Feb 2020 09:20:21 +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 A09C9306060; Wed, 26 Feb 2020 10:18:22 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 1272D2013DAEE; Wed, 26 Feb 2020 10:20:18 +0100 (CET) Date: Wed, 26 Feb 2020 10:20:18 +0100 From: Peter Zijlstra To: Thomas Gleixner Cc: LKML , x86@kernel.org, Steven Rostedt , Brian Gerst , Juergen Gross , Paolo Bonzini , Arnd Bergmann Subject: Re: [patch 13/16] x86/entry: Move irqflags and context tracking to C for simple idtentries Message-ID: <20200226092018.GR18400@hirez.programming.kicks-ass.net> References: <20200225223321.231477305@linutronix.de> <20200225224145.444611199@linutronix.de> <20200226080538.GO18400@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200226080538.GO18400@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 26, 2020 at 09:05:38AM +0100, Peter Zijlstra wrote: > On Tue, Feb 25, 2020 at 11:33:34PM +0100, Thomas Gleixner wrote: > > > --- a/arch/x86/include/asm/idtentry.h > > +++ b/arch/x86/include/asm/idtentry.h > > @@ -7,14 +7,31 @@ > > > > #ifndef __ASSEMBLY__ > > > > +#ifdef CONFIG_CONTEXT_TRACKING > > +static __always_inline void enter_from_user_context(void) > > +{ > > + CT_WARN_ON(ct_state() != CONTEXT_USER); > > + user_exit_irqoff(); > > +} > > +#else > > +static __always_inline void enter_from_user_context(void) { } > > +#endif > > + > > /** > > * idtentry_enter - Handle state tracking on idtentry > > * @regs: Pointer to pt_regs of interrupted context > > * > > - * Place holder for now. > > + * Invokes: > > + * - The hardirq tracer to keep the state consistent as low level ASM > > + * entry disabled interrupts. > > + * > > + * - Context tracking if the exception hit user mode > > */ > > static __always_inline void idtentry_enter(struct pt_regs *regs) > > { > > + trace_hardirqs_off(); > > + if (user_mode(regs)) > > + enter_from_user_context(); > > } > > So: > > asm_exc_int3 > exc_int3 > idtentry_enter() > enter_from_user_context > if (context_tracking_enabled()) > > poke_int3_handler(); > > Is, AFAICT, completely buggered. > > You can't have a static_branch before the poke_int3_handler that deals > with text_poke. Forgot to say that this isn't new with this patch, just noticed it when chasing after tracepoints. After my patch series we can actually fix this by moving the poke_int3_handler() before idtentry_enter().