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=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 018BDC43381 for ; Thu, 14 Feb 2019 19:34:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C576F21B1C for ; Thu, 14 Feb 2019 19:34:45 +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="CjWgBq3A" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2436567AbfBNTeo (ORCPT ); Thu, 14 Feb 2019 14:34:44 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:34896 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388779AbfBNTen (ORCPT ); Thu, 14 Feb 2019 14:34:43 -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:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=wAWlSc8WUsfd6EBHvaF0wPD58l9UhJKsmBtO3VlkGyA=; b=CjWgBq3Ax+WZX3gM7wzLHPdZk V4tNSceGnj1iBL4IkOxIO5BVz16F/kH1xjvHMKhkWgAG8ilpZCzibPnxHfO8p+SbCowqnWPoUPQV+ 1Jj7oI3MDQltSy4Zs35oW8qJbixqCMq1daFnTYanrS9l5pLQWC/lhjPGXnFW8vNNgRw8dnd2Fvibr MICIPPcqoR7DckRH7qwt2XllesnNnXuOdaqPcchON9gY7z0XZXXCWMPwJBH71n/Y+J2FKL7HPNPzz SODfx4L8dw8o0xdHG+dXwrE2nkiqrRQw5Ft1R0jdJTJ+Pwp/hmI1qZgHVZCFIfJHJPKn+Tpsd2R42 jo+cccHBQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1guMmH-0007cB-QL; Thu, 14 Feb 2019 19:34:33 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 45F2E20297D44; Thu, 14 Feb 2019 20:34:32 +0100 (CET) Date: Thu, 14 Feb 2019 20:34:32 +0100 From: Peter Zijlstra To: Brian Gerst Cc: Andy Lutomirski , Julien Thierry , Will Deacon , Ingo Molnar , Linux Kernel Mailing List , linux-arm-kernel@lists.infradead.org, Ingo Molnar , Catalin Marinas , James Morse , "H. Peter Anvin" , valentin.schneider@arm.com, Josh Poimboeuf , Andy Lutomirski , Borislav Petkov , Denys Vlasenko , Linus Torvalds , Thomas Gleixner Subject: Re: [PATCH] sched/x86: Save [ER]FLAGS on context switch Message-ID: <20190214193432.GR32477@hirez.programming.kicks-ass.net> References: <20190213140025.GB6346@brain-police> <20190213142524.GW32494@hirez.programming.kicks-ass.net> <20190213144145.GY32494@hirez.programming.kicks-ass.net> <20190213154532.GQ32534@hirez.programming.kicks-ass.net> <20190213222146.GC32494@hirez.programming.kicks-ass.net> <20190214101429.GD32494@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 Thu, Feb 14, 2019 at 11:18:01AM -0500, Brian Gerst wrote: > > --- a/arch/x86/include/asm/switch_to.h > > +++ b/arch/x86/include/asm/switch_to.h > > @@ -40,6 +40,7 @@ asmlinkage void ret_from_fork(void); > > * order of the fields must match the code in __switch_to_asm(). > > */ > > struct inactive_task_frame { > > + unsigned long flags; > > #ifdef CONFIG_X86_64 > > unsigned long r15; > > unsigned long r14; > > flags should be initialized in copy_thread_tls(). I think the new > stack is zeroed already, but it would be better to explicitly set it. Ah indeed. I somehow misread that code and thought we got initialized with a copy of current. Something like the below, right? --- --- a/arch/x86/kernel/process_32.c +++ b/arch/x86/kernel/process_32.c @@ -127,6 +127,7 @@ int copy_thread_tls(unsigned long clone_ struct task_struct *tsk; int err; + frame->flags = 0; frame->bp = 0; frame->ret_addr = (unsigned long) ret_from_fork; p->thread.sp = (unsigned long) fork_frame; --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -392,6 +392,7 @@ int copy_thread_tls(unsigned long clone_ childregs = task_pt_regs(p); fork_frame = container_of(childregs, struct fork_frame, regs); frame = &fork_frame->frame; + frame->flags = 0; frame->bp = 0; frame->ret_addr = (unsigned long) ret_from_fork; p->thread.sp = (unsigned long) fork_frame;