From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753580AbcLGQrM convert rfc822-to-8bit (ORCPT ); Wed, 7 Dec 2016 11:47:12 -0500 Received: from mx1.redhat.com ([209.132.183.28]:47334 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752017AbcLGQrK (ORCPT ); Wed, 7 Dec 2016 11:47:10 -0500 Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: <20161207152434.GB5462@codeblueprint.co.uk> References: <20161207152434.GB5462@codeblueprint.co.uk> <21775.1481123477@warthog.procyon.org.uk> To: Matt Fleming Cc: dhowells@redhat.com, linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: Does anything ever enter through startup_64 in head_64.S? MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <24721.1481129227.1@warthog.procyon.org.uk> Content-Transfer-Encoding: 8BIT Date: Wed, 07 Dec 2016 16:47:07 +0000 Message-ID: <24722.1481129227@warthog.procyon.org.uk> X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Wed, 07 Dec 2016 16:47:09 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Matt Fleming wrote: > > Does anything ever enter the kernel through startup_64 in head_64.S?[*] Do > > all 64-bit mode entries always enter through one of the EFI entry points? > > Which head_64.S? There are two ;-) > > Assuming you mean startup_64 in boot/compressed/head_64.S, then the > answer is "yes". 64-bit BIOS boot loaders will jump there. Sorry, yes, that one. > I'm fairly sure it's possible to boot that way on EFI too, you just > lose some of the newer functionality that is dependent on the EFI boot > stub. But I don't remember the last time I tried it. > > In general, we've always tried to maintain backwards compat, but you > don't get the new features without switching to the EFI entry points. > > Whether or not any distros are still using the old 0x200 entry point > for EFI is a good question, though. I think I have to assume that there might be. David