Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754950AbbFQJ2k (ORCPT ); Wed, 17 Jun 2015 05:28:40 -0400 Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:58401 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752303AbbFQJ2f (ORCPT ); Wed, 17 Jun 2015 05:28:35 -0400 Date: Wed, 17 Jun 2015 11:28:32 +0200 From: Pavel Machek To: Denys Vlasenko Cc: Ingo Molnar , Linus Torvalds , Steven Rostedt , Borislav Petkov , "H. Peter Anvin" , Andy Lutomirski , Oleg Nesterov , Frederic Weisbecker , Alexei Starovoitov , Will Drewry , Kees Cook , x86@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/3] x86, acpi: Eliminate saved_eip Message-ID: <20150617092832.GA17009@amd> References: <1434288190-24993-1-git-send-email-dvlasenk@redhat.com> <20150616100546.GA22928@amd> <55801A9C.9010207@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <55801A9C.9010207@redhat.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1737 Lines: 53 On Tue 2015-06-16 14:46:20, Denys Vlasenko wrote: > On 06/16/2015 12:05 PM, Pavel Machek wrote: > > > >> diff --git a/arch/x86/kernel/acpi/wakeup_32.S b/arch/x86/kernel/acpi/wakeup_32.S > >> index 665c6b7..eef2bd3 100644 > >> --- a/arch/x86/kernel/acpi/wakeup_32.S > >> +++ b/arch/x86/kernel/acpi/wakeup_32.S > >> @@ -31,17 +31,11 @@ wakeup_pmode_return: > >> > >> movl %cs:saved_magic, %eax > >> cmpl $0x12345678, %eax > >> - jne bogus_magic > >> - > >> - # jump to place where we left off > >> - movl saved_eip, %eax > >> - jmp *%eax > >> - > >> + je ret_point > >> bogus_magic: > > > > Longjump is supposed to flush the prefetch, but hopefully nothing > > depends on that detail... ... > > > > no. > > > > https://en.wikibooks.org/wiki/X86_Assembly/Protected_Mode#Entering_Protected_Mode > > > > longjump is supposed to be there. Sorry about that. I guess indirect > > jump is not neccessary, and we should add a comment there. > > What "long jump"? It's not a far (segment:offset) jump, it's a near > jump (one which only changes the offset), indirect one through a register. Yup, you are right, the ljmp is few instructions above that. > And we aren't switching to or from protected mode here. wakeup_pmode_return... that's just after switching to protected mode AFAICT. Anyway, Acked-by: Pavel Machek Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- 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/