Re: Question about booting
Sorry for the late reply. Also, the pancutan-devel list is private, so
my messages won't show up there. I'm leaving it in the CC list in case
you reply which would get this content onto the list.
On Wed, Aug 08, 2007 at 06:03:38PM +0100, Martín Ferrari wrote:
> On 8/8/07, Brad Boyer <flar@allandria.com> wrote:
> > > - the /install folder is -hfs-blessed, but don't know what that means,
> > > - there is another chrp descriptor called ofboot.b, but I don't know what it is,
> > > - the yaboot boot loader is present, but I couldn't find what enables it,
>
> > of the path is a special Mac shortcut that says to look for a
> > particular file type (tbxi is a code for a bootloader). Older Mac ROM
> > code was hard-coded to only look in the blessed folder for the System
> > file.
> >
> > Because of this, booting from a blessed folder on a CD could use a
> > boot path as simple as "cd:,\\:tbxi".
>
> Ah, I see, so the mapfile does the magic here:
>
> .b Raw 'UNIX' 'tbxi' "bootstrap"
>
> So, this is neither prep nor chrp, yes?
Yes, this part is Mac specific. This is the file that tells what to
use for creator codes and file types when making an HFS or HFS+ image.
This map can also be used for text conversion.
> > The ofboot.b file is a way to give boot options and configuration
> > to Open Firmware. I haven't used it on a CHRP system, but on a Mac
>
> >From what I've read in the CHRP paper, it looks for a file called
> bootinfo.txt; it said nothing about other files...
That does sound correct. The Mac doesn't have a hard coded default
file name like other systems due to the use of the file type as the
hard coded default. However, that only works on HFS or HFS+.
> > it allows you to set an icon for a drive and load a secondary
> > bootloader. The ofboot.b file is generally given the HFS file
> > type of tbxi to fit in with the default settings Apple sets. Here
> > are the relevant files on a real install:
>
> > The yaboot bootloader can be set directly in the firmware or it
> > can be referenced from the ofboot.b file. My system has the following
> > command set as one of the possibilities in ofboot.b:
> >
> > : bootyaboot " Loading second stage bootstrap..." .printf 100 ms load-base release-load-area " /ht@0,f2000000/pci@7/k2-sata-root@c/k2-sata@0/disk@0:2,\\yaboot" $boot ;
>
> I see. But in the debian-cd's map, yaboot gets a filetype of boot
> (just like in your setup). But you said that the firmware was looking
> for tbxi...
The firmware does look for tbxi, but that isn't yaboot. It finds the
ofboot.b CHRP boot script first, which has the forth script to be
able to load yaboot.
> > This is telling the firmware to create a command bootyaboot that will
> > load and run the file yaboot in the blessed folder on the 2nd partition
> > on the SATA disk. The ofboot.b file also has a menu to choose a boot
> > method which can run this command based on the user input.
>
> Yes, and it has the same format as bootinfo.txt, it confuses me completely :)
Apple is good at doing things almost but not quite the same.
> > With an Open Firmware that can directly load an ELF file, the yaboot
> > file could be specified as the boot-file setting. This would mean
> > that the firmware would always load yaboot as the normal boot process.
>
> i see... So, the boot process you described would be: firmware, if
> used with boot "cd:,\\:tbxi", locates a blessed folder with a tbxi
> file on it: the ofboot.b, which calls yaboot. Right? Do you know
> anything about the remaining bits I've found?
That list of steps is correct for Mac style OF procedure. I'm not sure
how many other questions I can answer, but I think I've answered most
of the ones asked. Feel free to ask more questions and I'll answer the
ones that I can.
Brad Boyer
flar@allandria.com
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