Date: Thu, 14 Apr 2016 14:00:14 +0200 (CEST) From: =?ISO-8859-1?Q?Trond_Endrest=F8l?= <Trond.Endrestol@fagskolen.gjovik.no> To: Aleksander Alekseev <afiskon@devzen.ru> Cc: freebsd-hackers@freebsd.org Subject: Re: A few stupid questions regarding MBR and boot0 Message-ID: <alpine.BSF.2.20.1604141353310.14591@mail.fig.ol.no> In-Reply-To: <20160414144849.7a08b1db@fujitsu> References: <20160414144849.7a08b1db@fujitsu>
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On Thu, 14 Apr 2016 14:48+0300, Aleksander Alekseev wrote: > Hello > > I was trying to figure out how FreeBSD boot process works and noticed > something strange. > > 1) If I understand correctly first 512 bytes of /dev/ad0 > and /boot/boot0 file should match, but they don't: > > http://afiskon.ru/s/31/665dc9755c_mbr.txt The MBR consists of two parts, the bootcode and the partition table. Any discrepancies is generally due to the partition table being zero in /boot/boot0 and realistic data stored in block 0. > Could someone please explain why they don't match? > > 2) I tried to compile boot0 from source (r297956) but compilation > failed: > > ``` > $ cd sys/boot/i386/boot0 > $ make > > Warning: Object directory not changed from > original /usr/home/eax/freebsd-src/sys/boot/i386/boot0 > > /usr/local/bin/clang38 -O2 -pipe -O2 -pipe -g -march=native > -DVOLUME_SERIAL -DPXE -DFLAGS=0x8f -DTICKS=0xb6 -DCOMSPEED="7 << 5 + > 3" -march=i386 -ffreestanding -msoft-float -m32 -std=gnu99 > -Qunused-arguments -m32 -c boot0.S -o boot0.o clang -cc1as: fatal > error: error in backend: invalid .org offset '430' (at offset '439') > *** Error code 1 > > Stop. > make: stopped in /usr/home/eax/freebsd-src/sys/boot/i386/boot0 > ``` > > Am I doing something wrong? I have never attempted to build the FreeBSD sources outside /usr/src. The advice below might be plain wrong. Try: cd sys/boot/i386/boot0 make clean make OBJDIR=/usr/home/eax/freebsd-obj obj make OBJDIR=/usr/home/eax/freebsd-obj all If you want it installed, run make OBJDIR=/usr/home/eax/freebsd-obj install -- +-------------------------------+------------------------------------+ | Vennlig hilsen, | Best regards, | | Trond Endrestøl, | Trond Endrestøl, | | IT-ansvarlig, | System administrator, | | Fagskolen Innlandet, | Gjøvik Technical College, Norway, | | tlf. mob. 952 62 567, | Cellular...: +47 952 62 567, | | sentralbord 61 14 54 00. | Switchboard: +47 61 14 54 00. | +-------------------------------+------------------------------------+ From owner-freebsd-hackers@freebsd.org Thu Apr 14 12:05:43 2016 Return-Path: <owner-freebsd-hackers@freebsd.org> Delivered-To: freebsd-hackers@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 69B3EB10EA4 for <freebsd-hackers@mailman.ysv.freebsd.org>; Thu, 14 Apr 2016 12:05:43 +0000 (UTC) (envelope-from trond@fagskolen.gjovik.no) Received: from smtp.fagskolen.gjovik.no (smtp.fagskolen.gjovik.no [IPv6:2001:700:1100:1:200:ff:fe00:b]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "smtp.fagskolen.gjovik.no", Issuer "Fagskolen i Gj??vik" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id 137D91226 for <freebsd-hackers@freebsd.org>; Thu, 14 Apr 2016 12:05:42 +0000 (UTC) (envelope-from trond@fagskolen.gjovik.no) Received: from mail.fig.ol.no (localhost [127.0.0.1]) by mail.fig.ol.no (8.15.2/8.15.2) with ESMTPS id u3EC5SAF070307 (version=TLSv1.2 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Thu, 14 Apr 2016 14:05:29 +0200 (CEST) (envelope-from trond@fagskolen.gjovik.no) Received: from localhost (trond@localhost) by mail.fig.ol.no (8.15.2/8.15.2/Submit) with ESMTP id u3EC5SdD070304; Thu, 14 Apr 2016 14:05:28 +0200 (CEST) (envelope-from trond@fagskolen.gjovik.no) X-Authentication-Warning: mail.fig.ol.no: trond owned process doing -bs Date: Thu, 14 Apr 2016 14:05:28 +0200 (CEST) From: =?ISO-8859-1?Q?Trond_Endrest=F8l?= <Trond.Endrestol@fagskolen.gjovik.no> Sender: Trond.Endrestol@fagskolen.gjovik.no To: Aleksander Alekseev <afiskon@devzen.ru> cc: freebsd-hackers@freebsd.org Subject: Re: A few stupid questions regarding MBR and boot0 In-Reply-To: <alpine.BSF.2.20.1604141353310.14591@mail.fig.ol.no> Message-ID: <alpine.BSF.2.20.1604141404540.14591@mail.fig.ol.no> References: <20160414144849.7a08b1db@fujitsu> <alpine.BSF.2.20.1604141353310.14591@mail.fig.ol.no> User-Agent: Alpine 2.20 (BSF 67 2015-01-07) Organization: Fagskolen Innlandet OpenPGP: url=http://fig.ol.no/~trond/trond.key MIME-Version: 1.0 X-Spam-Status: No, score=-1.0 required=5.0 tests=ALL_TRUSTED, AWL autolearn=ham autolearn_force=no version=3.4.1 X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on mail.fig.ol.no Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT X-Content-Filtered-By: Mailman/MimeDel 2.1.21 X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: Technical Discussions relating to FreeBSD <freebsd-hackers.freebsd.org> List-Unsubscribe: <https://lists.freebsd.org/mailman/options/freebsd-hackers>, <mailto:freebsd-hackers-request@freebsd.org?subject=unsubscribe> List-Archive: <http://lists.freebsd.org/pipermail/freebsd-hackers/>; List-Post: <mailto:freebsd-hackers@freebsd.org> List-Help: <mailto:freebsd-hackers-request@freebsd.org?subject=help> List-Subscribe: <https://lists.freebsd.org/mailman/listinfo/freebsd-hackers>, <mailto:freebsd-hackers-request@freebsd.org?subject=subscribe> X-List-Received-Date: Thu, 14 Apr 2016 12:05:43 -0000 On Thu, 14 Apr 2016 14:00+0200, Trond Endrestøl wrote: > On Thu, 14 Apr 2016 14:48+0300, Aleksander Alekseev wrote: > > > Hello > > > > I was trying to figure out how FreeBSD boot process works and noticed > > something strange. > > > > 1) If I understand correctly first 512 bytes of /dev/ad0 > > and /boot/boot0 file should match, but they don't: > > > > http://afiskon.ru/s/31/665dc9755c_mbr.txt > > The MBR consists of two parts, the bootcode and the partition table. > Any discrepancies is generally due to the partition table being zero > in /boot/boot0 and realistic data stored in block 0. BTW, check out /boot/mbr. > > Could someone please explain why they don't match? > > > > 2) I tried to compile boot0 from source (r297956) but compilation > > failed: > > > > ``` > > $ cd sys/boot/i386/boot0 > > $ make > > > > Warning: Object directory not changed from > > original /usr/home/eax/freebsd-src/sys/boot/i386/boot0 > > > > /usr/local/bin/clang38 -O2 -pipe -O2 -pipe -g -march=native > > -DVOLUME_SERIAL -DPXE -DFLAGS=0x8f -DTICKS=0xb6 -DCOMSPEED="7 << 5 + > > 3" -march=i386 -ffreestanding -msoft-float -m32 -std=gnu99 > > -Qunused-arguments -m32 -c boot0.S -o boot0.o clang -cc1as: fatal > > error: error in backend: invalid .org offset '430' (at offset '439') > > *** Error code 1 > > > > Stop. > > make: stopped in /usr/home/eax/freebsd-src/sys/boot/i386/boot0 > > ``` > > > > Am I doing something wrong? > > I have never attempted to build the FreeBSD sources outside /usr/src. > The advice below might be plain wrong. > > Try: > > cd sys/boot/i386/boot0 > make clean > make OBJDIR=/usr/home/eax/freebsd-obj obj > make OBJDIR=/usr/home/eax/freebsd-obj all > > If you want it installed, run > > make OBJDIR=/usr/home/eax/freebsd-obj install -- +-------------------------------+------------------------------------+ | Vennlig hilsen, | Best regards, | | Trond Endrestøl, | Trond Endrestøl, | | IT-ansvarlig, | System administrator, | | Fagskolen Innlandet, | Gjøvik Technical College, Norway, | | tlf. mob. 952 62 567, | Cellular...: +47 952 62 567, | | sentralbord 61 14 54 00. | Switchboard: +47 61 14 54 00. | +-------------------------------+------------------------------------+ From owner-freebsd-hackers@freebsd.org Thu Apr 14 12:37:18 2016 Return-Path: <owner-freebsd-hackers@freebsd.org> Delivered-To: freebsd-hackers@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 3E33EAECE8D for <freebsd-hackers@mailman.ysv.freebsd.org>; Thu, 14 Apr 2016 12:37:18 +0000 (UTC) (envelope-from afiskon@devzen.ru) Received: from relay11.nicmail.ru (relay11.nicmail.ru [195.208.3.7]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id E901817CF for <freebsd-hackers@freebsd.org>; Thu, 14 Apr 2016 12:37:17 +0000 (UTC) (envelope-from afiskon@devzen.ru) Received: from [109.70.25.187] (port=35887 helo=fujitsu) by f06.mail.nic.ru with esmtp (Exim 5.55) (envelope-from <afiskon@devzen.ru>) id 1aqgWQ-000K7C-2E; Thu, 14 Apr 2016 15:37:22 +0300 Received: from [93.174.131.138] (account afiskon@devzen.ru HELO fujitsu) by proxy08.mail.nic.ru (Exim 5.55) with id 1aqgWA-00044W-HY; Thu, 14 Apr 2016 15:37:06 +0300 Date: Thu, 14 Apr 2016 15:36:27 +0300 From: Aleksander Alekseev <afiskon@devzen.ru> To: Trond =?UTF-8?B?RW5kcmVzdMO4bA==?= <Trond.Endrestol@fagskolen.gjovik.no> Cc: freebsd-hackers@freebsd.org Subject: Re: A few stupid questions regarding MBR and boot0 Message-ID: <20160414153627.7fc50247@fujitsu> In-Reply-To: <alpine.BSF.2.20.1604141353310.14591@mail.fig.ol.no> References: <20160414144849.7a08b1db@fujitsu> <alpine.BSF.2.20.1604141353310.14591@mail.fig.ol.no> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: Technical Discussions relating to FreeBSD <freebsd-hackers.freebsd.org> List-Unsubscribe: <https://lists.freebsd.org/mailman/options/freebsd-hackers>, <mailto:freebsd-hackers-request@freebsd.org?subject=unsubscribe> List-Archive: <http://lists.freebsd.org/pipermail/freebsd-hackers/>; List-Post: <mailto:freebsd-hackers@freebsd.org> List-Help: <mailto:freebsd-hackers-request@freebsd.org?subject=help> List-Subscribe: <https://lists.freebsd.org/mailman/listinfo/freebsd-hackers>, <mailto:freebsd-hackers-request@freebsd.org?subject=subscribe> X-List-Received-Date: Thu, 14 Apr 2016 12:37:18 -0000 Hello, Trond Thanks for your replies. > > 1) If I understand correctly first 512 bytes of /dev/ad0 > > and /boot/boot0 file should match, but they don't: > > > > http://afiskon.ru/s/31/665dc9755c_mbr.txt > > The MBR consists of two parts, the bootcode and the partition table. > Any discrepancies is generally due to the partition table being zero > in /boot/boot0 and realistic data stored in block 0. Yes, but if I'm not mistaken partition table starts only at 0x1be. But in my case data is not just slightly different in last few bytes. Its not the same at all. > BTW, check out /boot/mbr. OK, this looks like something I have on ad0. But this file is not mentioned in corresponding chapters of Handbook [1] or Architecture Handbook [2]. Besides Architecture Handbook clearly states: """ Indeed, boot0 /is/ the MBR. """ If /boot/boot0 is MBR then what is /boot/mbr? Current version of Handbook mentions it twice in 18.3.2 and doesn't exactly explains what this file is for. According to FreeBSD 8.4 Handbook [3]: """ By default, the MBR installed by fdisk(8) is such an MBR and is based on /boot/mbr. """ Do I right understand that current version of Handbook is wrong regarding: """ The MBR installed by the FreeBSD installer is based on /boot/boot0. """ ... and in fact boot0 is only used in dual-boot case? BTW `cd sys/boot/i386/mbr && make` works as expected. > I have never attempted to build the FreeBSD sources outside /usr/src. > The advice below might be plain wrong. > > Try: > > cd sys/boot/i386/boot0 > make clean > make OBJDIR=/usr/home/eax/freebsd-obj obj > make OBJDIR=/usr/home/eax/freebsd-obj all > > If you want it installed, run > > make OBJDIR=/usr/home/eax/freebsd-obj install > Doesn't work: ``` $ make OBJDIR=/usr/home/eax/freebsd-obj obj mkdir: /usr/obj/usr: Permission denied *** Error code 1 Stop. make: stopped in /usr/home/eax/freebsd-src/sys/boot/i386/boot0 ``` I also tried `OBJDIR=... make`. Naturally I could try `sudo make ...` but if I'm not wrong boot0 doesn't have any dependencies, it's a reasonably simple assembly program. [1]https://www.freebsd.org/doc/handbook/boot-introduction.html [2]https://www.freebsd.org/doc/en/books/arch-handbook/boot-boot0.html [3]https://docs.freebsd.org/doc/8.4-RELEASE/share/doc/freebsd/handbook/boot-introduction.html -- Best regards, Aleksander Alekseev http://eax.me/
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