From mboxrd@z Thu Jan 1 00:00:00 1970 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754829AbdBEU3r (ORCPT + 2 others); Sun, 5 Feb 2017 15:29:47 -0500 Received: from wtarreau.pck.nerim.net ([62.212.114.60]:27418 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752677AbdBETWj (ORCPT ); Sun, 5 Feb 2017 14:22:39 -0500 From: Willy Tarreau To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, linux@roeck-us.net Cc: Andy Lutomirski , "H . Peter Anvin" , Willy Tarreau Subject: [PATCH 3.10 045/319] x86/traps: Ignore high word of regs->cs in early_idt_handler_common Date: Sun, 5 Feb 2017 20:20:32 +0100 Message-Id: <1486322486-8024-16-git-send-email-w@1wt.eu> X-Mailer: git-send-email 2.8.0.rc2.1.gbe9624a In-Reply-To: <1486322486-8024-1-git-send-email-w@1wt.eu> References: <1486322486-8024-1-git-send-email-w@1wt.eu> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: From: Andy Lutomirski This is a backport of: commit fc0e81b2bea0ebceb71889b61d2240856141c9ee upstream On the 80486 DX, it seems that some exceptions may leave garbage in the high bits of CS. This causes sporadic failures in which early_fixup_exception() refuses to fix up an exception. As far as I can tell, this has been buggy for a long time, but the problem seems to have been exacerbated by commits: 1e02ce4cccdc ("x86: Store a per-cpu shadow copy of CR4") e1bfc11c5a6f ("x86/init: Fix cr4_init_shadow() on CR4-less machines") This appears to have broken for as long as we've had early exception handling. [ This backport should apply to kernels from 3.4 - 4.5. ] Fixes: 4c5023a3fa2e ("x86-32: Handle exception table entries during early boot") Cc: H. Peter Anvin Cc: stable@vger.kernel.org Reported-by: Matthew Whitehead Signed-off-by: Andy Lutomirski Signed-off-by: Willy Tarreau --- arch/x86/kernel/head_32.S | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S index 8060c8b..b7e330c 100644 --- a/arch/x86/kernel/head_32.S +++ b/arch/x86/kernel/head_32.S @@ -586,7 +586,7 @@ early_idt_handler_common: movl %eax,%ds movl %eax,%es - cmpl $(__KERNEL_CS),32(%esp) + cmpw $(__KERNEL_CS),32(%esp) jne 10f leal 28(%esp),%eax # Pointer to %eip -- 2.8.0.rc2.1.gbe9624a