From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from list by lists.gnu.org with archive (Exim 4.71) id 1Z6JBr-0002AT-92 for mharc-grub-devel@gnu.org; Sat, 20 Jun 2015 09:52:11 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50119) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Z6JBo-00027w-R3 for grub-devel@gnu.org; Sat, 20 Jun 2015 09:52:09 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Z6JBk-0001lP-PV for grub-devel@gnu.org; Sat, 20 Jun 2015 09:52:08 -0400 Received: from mout.gmx.net ([212.227.17.20]:62617) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Z6JBk-0001lL-GA for grub-devel@gnu.org; Sat, 20 Jun 2015 09:52:04 -0400 Received: from scdbackup.webframe.org ([79.192.81.251]) by mail.gmx.com (mrgmx103) with ESMTPSA (Nemesis) id 0McUnM-1ZNq4X3OKW-00HgHf for ; Sat, 20 Jun 2015 15:52:01 +0200 Date: Sat, 20 Jun 2015 15:52:24 +0200 From: "Thomas Schmitt" To: grub-devel@gnu.org Subject: Re: [PATCH] core/partmap: Add El Torito boot catalog parsing Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit References: In-Reply-To: Message-Id: <67785557686121007363@scdbackup.webframe.org> X-Provags-ID: V03:K0:gmZKI6aqNinXCBOmPwnq9tje0WkFRyu7LZmGE/nBHivZOAmKEHV 4sb1qaXKmMCyCAvOyHGFfGnM5CuRrpCa6slAQhka+2pl1LoafZyZFewAHHM8Zr92Cx2tpVo zNPRetHwtn6/yP7bTLNRivX2134A0Xbb6aO3GNTDYtSURGiFFP3+Zg58Pssi80b7JKIsWBW 8JZH23TE/FWXJWcFav2/g== X-UI-Out-Filterresults: notjunk:1; X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x [generic] X-Received-From: 212.227.17.20 X-BeenThere: grub-devel@gnu.org X-Mailman-Version: 2.1.14 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, 20 Jun 2015 13:52:10 -0000 Hi, not that i would want to interfere with GRUB2 development decisions. Nevertheless, i have some comments from the view of the specs. Vladimir Serbinenko wrote: > El torito catalog contains bootable binaries. UEFI 2.4 9.3.6.2 "CD-ROM Media Device Path" "The CD-ROM Media Device Path is used to define a system partition that exists on a CD-ROM. The CD-ROM is assumed to contain an ISO-9660 file system and follow the CD-ROM “El Torito” format. [...] In EFI the bootable entity is an EFI System Partition that is pointed to by the Boot Entry." According to El Torito 1.0 the boot images may be emulated disk-like devices or executable binaries for the given platform: 2.0 "ISO-9660 and the Booting Catalog" "The image may be virtualized into INT 13 drive number 00 or 80 for bootable disk emulation, or [... some BIOS shortcut ...]. The image may also simply be some code which will be loaded at boot time (no emulation)." UEFI pierces a little hole into the theory of running on an emulated disk by prescribing the "no emulation" mark in the boot catalog which for BIOS means: load and execute binary. 12.3.2.1 "ISO-9660 and El Torito" "[...] To boot from a CD-ROM or DVD-ROM in the boot services environment, an EFI System partition is stored in a “no emulation” mode as defined by the “El Torito” specification. [...] EFI differs from “El Torito” “no emulation” mode in that it does not load the “no emulation” image into memory and jump to it. EFI interprets the “no emulation” image as an EFI system partition." ------------------------------------------------------------------ So i think the general role of an El Torito boot image is not a strong reason to reject its view as full flegded EFI system partition. But i see other reasons to restrict its role to an opaque launcher for software in a directory of the ISO: The El Torito catalog format implies size restriction to 32 MB. EFI allows open end by size 0, but that's really not very neat. I assume the higher boot stages of BIOS and EFI can share a lot of GRUB2 software. The GRUB2 software needed for BIOS traditionally resides in ISO 9660 directories. So it is easier and less error prone to re-use it there rather than changing the BIOS boot procedure to finding the ESP and using its software. Have a nice day :) Thomas