Re: Compressed kernels currently won't boot

[James Bottomley <James.Bottomley@HansenPartnership.com>]

On Wed, 2019-07-31 at 19:30 +0200, Sven Schnelle wrote:
> Hi,
> 
> On Wed, Jul 31, 2019 at 09:44:03AM -0700, James Bottomley wrote:
> > I noticed this trying to test out compressed kernel booting.  The
> > problem is that a compressed kernel is divided into two pieces, one
> > of which starts at 0x000e0000 and is the bootstrap code which is
> > uncompressed into 0x00100000 and the rest of which is the real
> > compressed kernel which is loaded above the end of the current
> > decompressed size of the entire kernel.  palo decompresses the head
> > and jumps to it and it then decompresses the rest of the kernel
> > into place.  This means that the first part of the compressed image
> > can't be larger than 0x20000 == 131072 because otherwise it will be
> > loaded into an area that decompression will alter.
> > 
> > The problem is that a change was introduced by 
> > 
> > commit 34c201ae49fe9e0bf3b389da5869d810f201c740
> > Author: Helge Deller <deller@gmx.de>
> > Date:   Mon Oct 15 22:14:01 2018 +0200
> 
> Hmm. This is what i've been facing as well.

Yes, except you're a more extreme case than me ... you actually have
the compressed segment overlapping the end of the decompressed text. 
that does seem to mean we have a lot of no-load debug information which
isn't useful to the compressed image.

>  After reading this commit i'm not sure that the patch i've just sent
> ("parisc: strip debug information when building compressed images")
> is really wanted. However, it is really a pain to always copy huge
> lifimages around when booting parisc machines via LAN. Does someone
> really extract the vmlinux file from a compressed kernel images?
> Should we keep that?

Well, it's a thing.  There's a script in the kernel source tree

scripts/extract-vmlinux

that does it.  It doesn't seem to be packaged by debian, though.

James