From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50217) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gUWGJ-00042Z-H6 for qemu-devel@nongnu.org; Wed, 05 Dec 2018 07:26:49 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gUWAn-0002ZT-J6 for qemu-devel@nongnu.org; Wed, 05 Dec 2018 07:21:05 -0500 Received: from mx1.redhat.com ([209.132.183.28]:38228) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1gUWAn-0002Yw-AX for qemu-devel@nongnu.org; Wed, 05 Dec 2018 07:21:01 -0500 References: From: Paolo Bonzini Message-ID: Date: Wed, 5 Dec 2018 13:20:51 +0100 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] i386: don't require elf64 for multiboot kernel List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Thomas Huth , Gonzo FWS , "qemu-devel@nongnu.org" Cc: Richard Henderson , Eduardo Habkost , "Michael S. Tsirkin" , Marcel Apfelbaum On 05/12/18 06:35, Thomas Huth wrote: > On 2018-12-04 17:55, Gonzo FWS wrote: >> Right now IncludeOS on x86_64 must use a chainloader for multiboot >> support. The chainloader is an ELF32 kernel that loads the real >> ELF64 kernel and jumps to it. As long as the ELF has the .multiboot >> section and conforms to the spec, meaning _start is be a 32-bit >> entry, it should be fine. >>=20 >> By removing the extra check in multiboot.c, we can also boot ELF64 >> files. As can be seen here:=20 >> https://cloud.fwsnet.net/index.php/s/XrkBkC8zy7MLa9p >>=20 >> Signed-off-by: Alf-Andr=C3=A9 Walla I think a 64-bit multiboot specification doesn't exist, but if it existed, it would require an EM_X86_64 ELF file to be booted already in long mode. I don't think it's a good idea to allow booting into an EM_X86_64 ELF file with the processor in 32-bit mode. Paolo