Re: Second round of powerpc subarch investigation : boot-loaders.
On Mon, Oct 20, 2003 at 09:31:46PM +0200, Sven Luther wrote:
> On Mon, Oct 20, 2003 at 11:10:21AM -0700, Tom Rini wrote:
> > On Sun, Oct 19, 2003 at 11:29:38AM +0200, Sven Luther wrote:
> >
> > > Hello,
> > >
> > > In order to continue work on making debian-installer subarch friendly, i
> > > now launch a second round of investigation concerning the way different
> > > subarches boot. The situation as i understand it is :
> > [snip]
> > > prep: no idea. yaboot doesn't work, nor does quik. There is no OF, but i
> > > think some kind of direct booting as well as netbooting is available.
> > > kernel with builtin initrd should work.
> >
> > Boots from the firmware the zImage*.prep from arch/ppc/boot/images in
> > the kernel. To build a ramdisk into this, the ramdisk to be used is
> > placed at arch/ppc/boot/images/ramdisk.image.gz, and 'make
> > zImage.initrd' is issued. This file is used on all PReP systems, and
> > the command to boot varries from Motorola to IBM PReP machines (Motorola
> > has PPCBug, and for disk it's pboot ...., and 'help pboot' should
> > describe the arguments, for netboot, 'help niot' or 'help noit', I
> > forget which and 'nbo' to get and boot the kernel.
>
> Ok, so you only need the zImage.initrd or the zImage (which is renamed
> to /boot/vmlinuz-2.4.22-powerpc on debian).
I haven't looked at the packages in ages, but since CONFIG_ALL_PPC
produces many compressed bootable images, I'll take your word at it
here.
> both these methods (PPCBug ot pboot) are OF tools, not something you
> need to/can take steps to install from the linux side.
Correct.
> > In general, to embed an initrd into an image (.coff, etc) the image must
> > be at arch/ppc/boot/images/ramdisk.image.gz and then 'make
> > zImage.initrd'.
>
> Yep, i know, the problem is that the initrd must contain some kernel
> modules, which are built during the kernel build phase, so it is not
> possible to build the initrd before the kernel, nor it is possible to
> build the kernel before the initrd, so ...
It is, kinda. You just do dep/config/modules, build the ramdisk, make
zImage.initrd.
> > > 2) We develop a separate tool (like sparc's piggyback i was told)
> > > which is able to add a initrd onto an existing kernel.
> >
> > As the images used, prior to additional tools being run on them (such as
> > mkprep) use an ldscript to determine locations, this might be possible.
>
> Mmm, i think it may be possible to create such a tool, altough i have
> the feeling that it must be built from the kernel sources maybe (since
> there is no need to duplicate the code for it already found in the
> kernel) and that it needs to be done differently for prep, chrp and
> pmac. Don't know if chrp-rs6k is different from chrp though.
It shouldn't need to be done differently on pmac, prep and chrp (and
chrp-rs6k is not different here, the difference is in mangling the final
image, more or less). They all make use of the same variables, which
are in the linker script. So if you can keep some intermediate images
around, things should be OK. i.e. ship the 'zImage's in their last
state before they stop being true ELF files, and you can then modify
things (new initrd, etc) and then re-mangle the image (mkprep, etc).
--
Tom Rini
http://gate.crashing.org/~trini/
Reply to: