From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Howells Subject: Re: Does anything ever enter through startup_64 in head_64.S? Date: Wed, 07 Dec 2016 16:47:07 +0000 Message-ID: <24722.1481129227@warthog.procyon.org.uk> References: <20161207152434.GB5462@codeblueprint.co.uk> <21775.1481123477@warthog.procyon.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT Return-path: In-Reply-To: <20161207152434.GB5462-mF/unelCI9GS6iBeEJttW/XRex20P6io@public.gmane.org> Content-ID: <24721.1481129227.1-S6HVgzuS8uM4Awkfq6JHfwNdhmdF6hFW@public.gmane.org> Sender: linux-efi-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Matt Fleming Cc: dhowells-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-efi@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