Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932153AbWH0QCJ (ORCPT ); Sun, 27 Aug 2006 12:02:09 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932157AbWH0QCJ (ORCPT ); Sun, 27 Aug 2006 12:02:09 -0400 Received: from ns1.suse.de ([195.135.220.2]:33478 "EHLO mx1.suse.de") by vger.kernel.org with ESMTP id S932153AbWH0QCG (ORCPT ); Sun, 27 Aug 2006 12:02:06 -0400 From: Andi Kleen To: Jeremy Fitzhardinge Subject: Re: [PATCH RFC 3/6] Use %gs as the PDA base-segment in the kernel. Date: Sun, 27 Aug 2006 17:57:18 +0200 User-Agent: KMail/1.9.3 Cc: linux-kernel@vger.kernel.org, Chuck Ebbert <76306.1226@compuserve.com>, Zachary Amsden , Jan Beulich , Andrew Morton References: <20060827084417.918992193@goop.org> <20060827084451.492329798@goop.org> In-Reply-To: <20060827084451.492329798@goop.org> MIME-Version: 1.0 Content-Disposition: inline Message-Id: <200608271757.18621.ak@suse.de> Content-Type: text/plain; charset="iso-8859-15" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1861 Lines: 58 > > - /* Clear %fs and %gs. */ > - asm volatile ("movl %0, %%fs; movl %0, %%gs" : : "r" (0)); > + /* Clear %fs. */ > + asm volatile ("mov %0, %%fs" : : "r" (0)); > + > + /* Set %gs for this CPU's PDA */ > + asm volatile ("mov %0, %%gs" : : "r" (__KERNEL_PDA)); I would add memory clobbers here to make sure the dependency on read/write pda is right. > +1: movw GS(%esp), %gs movl is recommended in 32bit mode > --- a/arch/i386/kernel/signal.c > +++ b/arch/i386/kernel/signal.c > @@ -128,7 +128,7 @@ restore_sigcontext(struct pt_regs *regs, > X86_EFLAGS_TF | X86_EFLAGS_SF | X86_EFLAGS_ZF | \ > X86_EFLAGS_AF | X86_EFLAGS_PF | X86_EFLAGS_CF) > > - GET_SEG(gs); > + COPY_SEG(gs); > GET_SEG(fs); > COPY_SEG(es); > COPY_SEG(ds); > @@ -244,9 +244,7 @@ setup_sigcontext(struct sigcontext __use > { > int tmp, err = 0; > > - tmp = 0; > - savesegment(gs, tmp); > - err |= __put_user(tmp, (unsigned int __user *)&sc->gs); > + err |= __put_user(regs->xgs, (unsigned int __user *)&sc->gs); > savesegment(fs, tmp); > err |= __put_user(tmp, (unsigned int __user *)&sc->fs); Hmm, changing it for the sc looks a bit bogus. If everything is right nothing should change for user space, but this changes something. > @@ -306,7 +306,7 @@ static void do_sys_vm86(struct kernel_vm > tsk->thread.screen_bitmap = info->screen_bitmap; > if (info->flags & VM86_SCREEN_BITMAP) > mark_screen_rdonly(tsk->mm); > - __asm__ __volatile__("xorl %eax,%eax; movl %eax,%fs; movl %eax,%gs\n\t"); > + __asm__ __volatile__("movl %0,%%fs\n\t" : : "r" (0)); This is actually a useful bug fix on its own. -Andi - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/