From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755959AbcCCM2s (ORCPT ); Thu, 3 Mar 2016 07:28:48 -0500 Received: from mail.skyhub.de ([78.46.96.112]:39797 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752921AbcCCM2o (ORCPT ); Thu, 3 Mar 2016 07:28:44 -0500 Date: Thu, 3 Mar 2016 13:28:36 +0100 From: Borislav Petkov To: "H. Peter Anvin" Cc: Brian Gerst , X86 ML , LKML , Tom Lendacky Subject: Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack Message-ID: <20160303122836.GC24621@pd.tnic> References: <20160302181556.GD8362@pd.tnic> <56D73349.3020609@zytor.com> <20160302195053.GG8362@pd.tnic> <56D75C8D.90800@zytor.com> <20160302214654.GK8362@pd.tnic> <56D7612A.4080107@zytor.com> <20160302220954.GL8362@pd.tnic> <56D76527.5020806@zytor.com> <20160302222842.GM8362@pd.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Mar 02, 2016 at 02:32:54PM -0800, H. Peter Anvin wrote: > I'm trying to think of any reason why we couldn't simply have a symbol > at the top of the initial stack? Then a simple leaq would suffice; > this is for the BSP after all. How about something like this: --- From: Borislav Petkov Date: Sun, 28 Feb 2016 21:35:44 +0100 Subject: [PATCH -v2] x86/asm: Make sure verify_cpu() has a good stack MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 04633df0c43d ("x86/cpu: Call verify_cpu() after having entered long mode too") added the call to verify_cpu() for sanitizing CPU configuration. The latter uses the stack minimally and it can happen that we land in startup_64() directly from a 64-bit bootloader. Then we want to use our own, known good stack. Do that. APs don't need this as the trampoline sets up a stack for them. Reported-by: Tom Lendacky Signed-off-by: Borislav Petkov Cc: Brian Gerst Cc: "H. Peter Anvin" Cc: Mika Penttilä --- arch/x86/kernel/head_64.S | 3 +++ include/asm-generic/vmlinux.lds.h | 4 +++- 2 files changed, 6 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S index 22fbf9df61bb..968d6408b887 100644 --- a/arch/x86/kernel/head_64.S +++ b/arch/x86/kernel/head_64.S @@ -64,6 +64,9 @@ startup_64: * tables and then reload them. */ + /* Setup stack for verify_cpu(). */ + leaq (__end_init_task - 8)(%rip), %rsp + /* Sanitize CPU configuration */ call verify_cpu diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index 772c784ba763..cba2a26628fc 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -246,7 +246,9 @@ #define INIT_TASK_DATA(align) \ . = ALIGN(align); \ - *(.data..init_task) + VMLINUX_SYMBOL(__start_init_task) = .; \ + *(.data..init_task) \ + VMLINUX_SYMBOL(__end_init_task) = .; /* * Read only Data -- 2.3.5 -- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply.