From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with archive (Exim 4.43) id 1N9I3B-0005Ax-0s for mharc-grub-devel@gnu.org; Sat, 14 Nov 2009 07:48:21 -0500 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1N9I38-0005AY-K1 for grub-devel@gnu.org; Sat, 14 Nov 2009 07:48:18 -0500 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1N9I34-0005A2-Dt for grub-devel@gnu.org; Sat, 14 Nov 2009 07:48:18 -0500 Received: from [199.232.76.173] (port=33902 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1N9I34-00059q-8V for grub-devel@gnu.org; Sat, 14 Nov 2009 07:48:14 -0500 Received: from mail-bw0-f215.google.com ([209.85.218.215]:44934) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1N9I33-0003KS-R5 for grub-devel@gnu.org; Sat, 14 Nov 2009 07:48:14 -0500 Received: by bwz7 with SMTP id 7so4322628bwz.26 for ; Sat, 14 Nov 2009 04:48:12 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:message-id:date:from :user-agent:mime-version:to:subject:references:in-reply-to :x-enigmail-version:content-type; bh=EgoloVZsOdXwWBPwiPlunN8WBJxIyt4fwWJzkLoEWyg=; b=C3/GSExyu5B0Vzsnq08itmesXB23Lxnw3VOCqarwkWIulPghLkXwI//R/NnQsudKXN 8jMlnz89NEaAAGusgwMIWDMzquX11EaiJm0N2e0EVtcdi9ztUHnalL01fUBUEKFvzH/C IoQwTwlY2R80VtxUwWOZ+c+jMUtIL5JBsilxo= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:user-agent:mime-version:to:subject:references :in-reply-to:x-enigmail-version:content-type; b=xeaxDbT5sJqnvegd0LY0G6wCV2g0rsI72+GTZcskz/Bg8WguQkEQpGR/vq9eA2ro0m kClO/+xxJhZldZq4Cb4Ts0ELX7MS+xzcZMpcPC7w3jlZqd1e0Owugrh8j9xyqTh1tcf7 +wYLOGyFb6uWwVyJYWSwxlvxNRPqO0nvksh0E= Received: by 10.216.89.209 with SMTP id c59mr1712870wef.181.1258202892729; Sat, 14 Nov 2009 04:48:12 -0800 (PST) Received: from debian.bg45.phnet (125-69.1-85.cust.bluewin.ch [85.1.69.125]) by mx.google.com with ESMTPS id 5sm1075262eyf.8.2009.11.14.04.48.11 (version=TLSv1/SSLv3 cipher=RC4-MD5); Sat, 14 Nov 2009 04:48:11 -0800 (PST) Message-ID: <4AFEA700.4030204@gmail.com> Date: Sat, 14 Nov 2009 13:48:00 +0100 From: Vladimir 'phcoder' Serbinenko User-Agent: Mozilla-Thunderbird 2.0.0.22 (X11/20091109) MIME-Version: 1.0 To: The development of GNU GRUB References: <20091114105926.GA9262@aybabtu.com> In-Reply-To: <20091114105926.GA9262@aybabtu.com> X-Enigmail-Version: 0.95.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="------------enigE8DEFCD85C13D8308BAB3E5F" X-detected-operating-system: by monty-python.gnu.org: GNU/Linux 2.6 (newer, 2) Subject: Re: gate A20 and i386-qemu port X-BeenThere: grub-devel@gnu.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: The development of GNU GRUB List-Id: The development of GNU GRUB List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 14 Nov 2009 12:48:18 -0000 This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enigE8DEFCD85C13D8308BAB3E5F Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Robert Millan wrote: > I'm wondering how come the i386-qemu port works if none of its > initialization code takes into account gate A20. Does this > mean it's supposed to be already disabled in initial CPU state, > and only enabled by BIOS? > > Or maybe the code only works by chance and would break unexpectedly > in specific situations? > > =20 Without disabling A20 even and odd mibibytes will be squashed together. Following code can check A20: *((volatile grub_uint8_t *) 0x200000) =3D 0; *((volatile grub_uint8_t *) 0x300000) =3D 1; if (*((volatile grub_uint8_t *) 0x200000)) grub_printf ("Expect bugs\n"); else grub_printf ("You're safe\n"); --=20 Regards Vladimir 'phcoder' Serbinenko --------------enigE8DEFCD85C13D8308BAB3E5F Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iF4EAREKAAYFAkr+pwoACgkQNak7dOguQgm7jQD9HnB8V1nc6aIOEoaPUGxrOvIO 1HzmN6tiiGhPf97EHwwA/25UOXvpYllyFhTsnSv0+3h8epdOjMHgqBBLSSzhqwUu =dhwu -----END PGP SIGNATURE----- --------------enigE8DEFCD85C13D8308BAB3E5F--