Re: Boot2 loading process
Sat, Oct 14, 2006 at 21:15:55, jerrymc wrote about Re: Boot2 loading process: So my question is: where does the rest of the boot2 binary is located and how is it loaded ? You skipped boot1 from attention. boot2 is loaded by boot1, not boot0. Not according to that piece of architecture documentation that was quoted. www.freebsd.org/doc/en_US.ISO8859-1/books/arch-handbook/book.html#BOOT-BOOT0 It says that boot1 is used only with floppy boots. The doc is incorrect, or at least uses less detailed description. One can see from code that boot0 loads _one_ sector from slice and calls its code. Initial block of the bootable slice is identical to /boot/boot1: $ dd if=/dev/ad0s1a bs=512 count=1 | head -c 446 | md5 -r 42b4daabbfea8c8d3ec45e24b340868a $ head -c 446 /boot/boot1 | md5 -r 42b4daabbfea8c8d3ec45e24b340868a And reading code in /usr/src/sys/boot/i386/boot2/boot1.S is enough to see that it is the routine which loads 8K including boot2. Maybe documentation clause (that boot0 loads boot2 directly) remains from other version of boot0, or is used to simplify the description (because boot1 is silent part and shows something only in case of fatal error). But it's anyway too simplified as to reply to original question in this thread. This difference (boot0 loads boot2 directly or thru boot1) was vital when 4.x and 5.x resides on the same disk. This was case for my home machine a few years ago. Boot1 shall be the same version as boot2. Changes in their interaction caused problem to load FreeBSD from second slice (it was 5.x), that's why I had to use special boot setup. -netch- ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: Boot2 loading process
Sun, Oct 15, 2006 at 11:33:06, netch wrote about Re: Boot2 loading process: Not according to that piece of architecture documentation that was quoted. www.freebsd.org/doc/en_US.ISO8859-1/books/arch-handbook/book.html#BOOT-BOOT0 It says that boot1 is used only with floppy boots. The doc is incorrect, or at least uses less detailed description. One Heh, according to CVS history this is obsoleted at least for 3.1-release. -netch- ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: Boot2 loading process
Sat, Oct 14, 2006 at 09:41:01, jan.pfeifer wrote about Boot2 loading process: I was reading through the architecture handbook (http://www.freebsd.org/doc/en_US.ISO8859-1/books/arch-handbook/book.html) about the boot process, and something strange caught my attention. According to the docs boot0 loads only the first record of the partition, that is 512bytes. But boot2 in my 4.11 freebsd has 7K in size -- what makes sense, considering the amount of things it does and that it links btxld. Name it slice, not partition. So my question is: where does the rest of the boot2 binary is located and how is it loaded ? You skipped boot1 from attention. boot2 is loaded by boot1, not boot0. boot1 resides in first block of FreeBSD slice (or whole disk in dedicated partitioning). It reads MBR, detects first active FreeBSD slice (or first FreeBSD slice if none active), loads first 8K from its (they are boot1 + disklabel + boot2) and passes control to boot2. boot2 is placed in blocks 2-15 of the FreeBSD slice. thanks in advance for any answers! -netch- ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: Boot2 loading process
On Sat, Oct 14, 2006 at 09:30:53PM +0300, Valentin Nechayev wrote: Sat, Oct 14, 2006 at 09:41:01, jan.pfeifer wrote about Boot2 loading process: I was reading through the architecture handbook (http://www.freebsd.org/doc/en_US.ISO8859-1/books/arch-handbook/book.html) about the boot process, and something strange caught my attention. According to the docs boot0 loads only the first record of the partition, that is 512bytes. But boot2 in my 4.11 freebsd has 7K in size -- what makes sense, considering the amount of things it does and that it links btxld. Name it slice, not partition. So my question is: where does the rest of the boot2 binary is located and how is it loaded ? You skipped boot1 from attention. boot2 is loaded by boot1, not boot0. Not according to that piece of architecture documentation that was quoted. www.freebsd.org/doc/en_US.ISO8859-1/books/arch-handbook/book.html#BOOT-BOOT0 It says that boot1 is used only with floppy boots. So, either the question remains or that oiece of doc is incorrect. Cheers, jerry boot1 resides in first block of FreeBSD slice (or whole disk in dedicated partitioning). It reads MBR, detects first active FreeBSD slice (or first FreeBSD slice if none active), loads first 8K from its (they are boot1 + disklabel + boot2) and passes control to boot2. boot2 is placed in blocks 2-15 of the FreeBSD slice. thanks in advance for any answers! -netch- ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to [EMAIL PROTECTED] ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: Boot2 loading process
Thanks for the reference Jerry, you are right, from the docs: boot0: saved into MBR, loads boot2 (the boot1 being the floppy version of it) But still, according to the docs, boot0 loads only 512 bytes of it. So thanks for the note Valentin, I understand then that boot0 loads 15 records, that is 7.5kb. many thanks again, - jan ps.: the docs also mentions that slices are the FreeBSD jargon for partitions, sorry. - Original Message From: Jerry McAllister [EMAIL PROTECTED] To: Valentin Nechayev [EMAIL PROTECTED] Cc: Jan Pfeifer [EMAIL PROTECTED]; freebsd-questions@freebsd.org Sent: Saturday, October 14, 2006 6:15:55 PM Subject: Re: Boot2 loading process On Sat, Oct 14, 2006 at 09:30:53PM +0300, Valentin Nechayev wrote: Sat, Oct 14, 2006 at 09:41:01, jan.pfeifer wrote about Boot2 loading process: I was reading through the architecture handbook (http://www.freebsd.org/doc/en_US.ISO8859-1/books/arch-handbook/book.html) about the boot process, and something strange caught my attention. According to the docs boot0 loads only the first record of the partition, that is 512bytes. But boot2 in my 4.11 freebsd has 7K in size -- what makes sense, considering the amount of things it does and that it links btxld. Name it slice, not partition. So my question is: where does the rest of the boot2 binary is located and how is it loaded ? You skipped boot1 from attention. boot2 is loaded by boot1, not boot0. Not according to that piece of architecture documentation that was quoted. www.freebsd.org/doc/en_US.ISO8859-1/books/arch-handbook/book.html#BOOT-BOOT0 It says that boot1 is used only with floppy boots. So, either the question remains or that oiece of doc is incorrect. Cheers, jerry boot1 resides in first block of FreeBSD slice (or whole disk in dedicated partitioning). It reads MBR, detects first active FreeBSD slice (or first FreeBSD slice if none active), loads first 8K from its (they are boot1 + disklabel + boot2) and passes control to boot2. boot2 is placed in blocks 2-15 of the FreeBSD slice. thanks in advance for any answers! -netch- ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to [EMAIL PROTECTED] ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to [EMAIL PROTECTED]
