Re: How to debug boot sequence?

Richard Guenther (zxmpm11@student.uni-tuebingen.de)
Mon, 13 Apr 1998 10:36:57 +0200 (METDST)

> > > I have a problem with a diskless, remote booted machine whose
> > > BIOS supports BOOTP.
> > > With nearly all Kernels, booting gets to the 'Loading Linux........'
> > > stage and then instantly rebooting the System (looping forever).
> > > Exceptions are 2.0.31 and 2.1.93 (the only tested 2.1.x kernel) which
> > > get to 'Uncompressing Linux...' and halting with
> > > 'Invalid compressed format (err=1)'
> > > How can I debug this things further? I looked at lib/inflate.c, where
> > > this message comes from, but no clue what happens. Even
> > > arch/i386/boot/compress/misc.c doesn't tell me much.
> >
> > It seems the kernel image gets corrupted. Try booting the same image
> > from a floppy.
> >
>
> Invalid compressed format sounds like the protected-mode kernel
> doesn't end up where it should, or isn't intact. It is hard without
> knowing more about your software setup (boot loaders, etc; just how
> exactly is the BIOS loading the kernel anyway) what's going on.

Yes, it seems to be more like a BIOS problem. What exactly does
the kernel loader depend on? How could I get a non-compressed version of
the bootimage?
Just for information: zImage gets loaded by BOOTP/TFTP, I don't know
anything special about the BIOS of the machine (apart from its TCP
support), but I think there could be some essential features missing
(which features does the kernel loader depend on?).

As I understand from the code, in the 'Loading Linux...' stage, the
kernel gets loaded (err yes, if from floppy, it gets loaded from
floppy, but if already recieved via TFTP, what does happen at this
stage? Does it get just copied? I think this part is BIOS dependend?
Are those BIOSes just simulating a floppy disk? Could the image
get corrupted in the copying process (i.e. overlapping regions)?
How could I verify this?) - lots of questions, no answers for now :)

Thanx, Richard.

PS: tried 2.1.9[012345], all failed with 'invalid compressed format',
2.0.xx instantly reboot after 'Loading Linux...' (2.0.31 too -
dunno what this 2.0.31 image exactly is that I have lying around...)
PPS: dunno about TFTP, is this a secure transfer? could the image
get corrupted (unnoticed) during the transfer?

--
Richard Guenther <richard.guenther@student.uni-tuebingen.de>
PGP: 2E829319 - 2F 83 FC 93 E9 E4 19 E2 93 7A 32 42 45 37 23 57
WWW: http://www.anatom.uni-tuebingen.de/~richi/




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