From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S265773AbUG3OFc (ORCPT ); Fri, 30 Jul 2004 10:05:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S267682AbUG3OFc (ORCPT ); Fri, 30 Jul 2004 10:05:32 -0400 Received: from cantor.suse.de ([195.135.220.2]:17635 "EHLO Cantor.suse.de") by vger.kernel.org with ESMTP id S265773AbUG3OFX (ORCPT ); Fri, 30 Jul 2004 10:05:23 -0400 Date: Fri, 30 Jul 2004 15:58:40 +0200 From: Karsten Keil To: Linux Kernel list Subject: Re: [cleanup] do_general_protection doesn't disable irq Message-ID: <20040730135840.GA12152@pingi3.kke.suse.de> Mail-Followup-To: Linux Kernel list References: <20040730025349.GE30369@dualathlon.random> <4109CCED.5020808@quark.didntduck.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4109CCED.5020808@quark.didntduck.org> Organization: SuSE Linux AG X-Operating-System: Linux 2.6.4-52-default i686 User-Agent: Mutt/1.5.6i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 30, 2004 at 12:22:05AM -0400, Brian Gerst wrote: > Andrea Arcangeli wrote: > >A trap gate shouldn't affect the irq status at all. > > > >This should be a valid cleanup that removes a slightly confusing noop: > > > >Index: linux-2.5/arch/i386/kernel/traps.c > >=================================================================== > >RCS file: /home/andrea/crypto/cvs/linux-2.5/arch/i386/kernel/traps.c,v > >retrieving revision 1.77 > >diff -u -p -r1.77 traps.c > >--- linux-2.5/arch/i386/kernel/traps.c 13 Jul 2004 18:02:33 -0000 > >1.77 > >+++ linux-2.5/arch/i386/kernel/traps.c 30 Jul 2004 02:44:23 -0000 > >@@ -431,9 +431,6 @@ DO_ERROR_INFO(17, SIGBUS, "alignment che > > > > asmlinkage void do_general_protection(struct pt_regs * regs, long > > error_code) > > { > >- if (regs->eflags & X86_EFLAGS_IF) > >- local_irq_enable(); > >- > > if (regs->eflags & VM_MASK) > > goto gp_in_vm86; > > > > > >Thanks to Karsten for noticing a trap gate doesn't actually enable irq > >by default either (offtopic issue with the above patch, but while > >reading the 2.6 code I found the above bit which just confused me more > >since it's a noop, either that or you meant to use set_intr_gate, not > >set_trap_gate on the do_general_protection handler, but it seems not > >needed to use a trap gate since a trap gate shouldn't enable irqs by > >default). Please correct me if wrong. > > This is there for vm86 mode. See http://tinyurl.com/3m5nr > It makes also no sense, if the GP comes from VM86 mode, what you need there is the second hunk in the patch which does local_irq_enable(); if it was from VM86. Note: the trap gate do not touch X86_EFLAGS_IF bit, so the saved value in regs->eflags is the same as in the CPU EFLAGS register. -- Karsten Keil SuSE Labs ISDN development