Date: Sat, 03 Nov 2001 19:34:07 -0800 (PST) From: John Baldwin <jhb@FreeBSD.org> To: John Baldwin <jhb@FreeBSD.org> Cc: cvs-all@FreeBSD.org, cvs-committers@FreeBSD.org Subject: RE: cvs commit: src/sys/boot/i386/cdboot Makefile cdboot.s Message-ID: <XFMail.011103193407.jhb@FreeBSD.org> In-Reply-To: <200111040324.fA43OGQ42308@freefall.freebsd.org>
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On 04-Nov-01 John Baldwin wrote:
> jhb 2001/11/03 19:24:16 PST
>
> Modified files:
> sys/boot/i386/cdboot Makefile cdboot.s
> Log:
> This is a new CD bootstrap utility designed to replace cdldr. According
> to the El Torito standard for CD booting, a CD may boot in "No emulation"
> mode without using a floppy image. In this mode, the BIOS loads a program
> off of the CD into memory and creates a BIOS device using 2048 byte sectors
> for the CD. According to the standard, this program can be up to 0xFFFF
> virtual (512-byte) sectors long. The old cdldr depended on this by having
> the BIOS load the entire loader and the small cdldr stub as one binary
> similar to pxeboot so that cdldr didn't have to read the CD to find the
> loader. However, the NT no emulation loader just uses 1 disk sector
> (4 virtual sectors), so it seems that at least some BIOS writers just did
> enough to get NT to boot by only loading 1 sector and ignoring the sector
> count. Thus, while cdldr should have worked in theory, it doesn't in
> practice. This replacment fits entirely in 1 sector and includes simple
> ISO 9660 support. It looks for /boot/loader on the CD and loads it up
> using the BIOS. This allows us to not have to depend on the limited size
> of floppy images but use a full GENERIC kernel for CD-ROM installs in the
> future, among other things.
>
> This version of cdboot is a bit bloated as it includes some useful
> debugging routines that people can pull to use in other x86 assembly
> modules. Even with all the debugging cruft, we still have 272 bytes to
> spare.
Unfortunately, the loader bits don't quite work yet. I get a cd0 device, but
it can't read off the CD yet. Still need more work before the loader itself is
useful in this case. Here's some sample output:
CD Loader 1.01
Building the boot loader arguments
Len 01 Addr 0900:0000 LBA 00000010
9000:01 43 44 30 30 31 01 00-46 72 65 65 42 53 44 20 |.CD001..FreeBSD |
Read Volume Descriptor
Looking up /BOOT/LOADER...
Starting find_file
909c:22 00 1d 00 00 00 00 00-00 1d 00 08 00 00 00 00 |"...............|
90ac:08 00 65 0a 1e 12 0c 23-e0 02 00 00 01 00 00 01 |..e....#........|
90bc:01 00 - |.. |
Path = "BOOT/LOADER" Length = 04
Len 01 Addr 0980:0000 LBA 0000001d
<snip>
99be:78 00 26 00 00 00 00 00-00 26 00 80 02 00 00 02 |x.&......&......|
99ce:80 00 65 0b 03 10 14 1e-e0 00 00 00 01 00 00 01 |..e.............|
99de:09 4c 4f 41 44 45 52 2e-3b 31 52 52 05 01 89 4e |.LOADER.;1RR...N|
99ee:4d 0b 01 00 6c 6f 61 64-65 72 50 58 24 01 6d 81 |M...loaderPX$.m.|
99fe:00 00 00 00 81 6d 01 00-00 00 00 00 00 01 00 00 |.....m..........|
9a0e:00 00 00 00 00 00 00 00-00 00 00 00 00 00 54 46 |..............TF|
9a1e:1a 01 0e 65 0b 03 10 14-1e e0 65 0b 03 10 0d 34 |...e......e....4|
9a2e:e0 65 0b 03 10 14 1e e0- |.e...... |
ff: Scanning name: 1;;--
ff: Checking name: LOADER
ff: Length matched
Found
Lookup returned
Len 20 Addr 0900:0000 LBA 00000026
Len 20 Addr 1900:0000 LBA 00000046
Len 10 Addr 2900:0000 LBA 00000066
Relocating the loader and the BTX
Entry point: 00200000
Starting the BTX loader
Console: serial port
BIOS CD is cd0
BIOS drive A: is disk0
BIOS drive C: is disk1
BIOS 639kB/130048kB available memory
FreeBSD/i386 bootstrap loader, Revision 1.0
(john@laptop.baldwin.cx, Sat Nov 3 16:19:24 PST 2001)
/
can't load 'kernel'
Type '?' for a list of commands, 'help' for more detailed help.
ok lsdev
cd devices:
cd0: Device 0x700
disk devices:
disk0: BIOS drive A:
disk1: BIOS drive C:
disk1s1a: FFS
disk1s1b: swap
disk1s1e: FFS
disk1s1f: FFS
pxe devices:
ok ls
open '/' failed: no such file or directory
ok
No, I'm not an insane person copying all that by hand (there's actually a lot
more as it does a hexdump of each directory entry while doing the lookup). The
debug version does dual console to both the screen and COM1 at 9600n81 using
the BIOS. :)
--
John Baldwin <jhb@FreeBSD.org> -- http://www.FreeBSD.org/~jhb/
PGP Key: http://www.baldwin.cx/~john/pgpkey.asc
"Power Users Use the Power to Serve!" - http://www.FreeBSD.org/
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