[flashboot] Updated patch

Rickard Dahlstrand rd at tilde.se
Mon Sep 4 22:55:43 EST 2006

Massimo Lusetti wrote:
> On Fri, 2006-09-01 at 11:48 +0200, Rickard Dahlstrand wrote:
>> Hi All,
>> On popular request here are some updated diffs with bugfixes and
>> cleanups, the ro/rw-scripts are committed and blink got scraped. Please
>> test and comment.
> ./build-largekernel.sh GENRIC-RD produce a kernel which doesn't boot, it
> stops loading the 'second stage' during the boot phase even before 
> starting to outputting the result of the boot process (dmesg).
> The result is the box continuisly rebooting while uncompressing/loading
> the kernel.
That was what we suspected. What factors that are involved when booting
large kernels are a bit of a mystery to us. The 25 mb WRAP12 kernel
boots fine on my 128 MB WRAP-box. But the generic is a bit larger and
could possibly cause problems.

This is what Damien wrote on the subject:
/A couple of caveats regarding kernel customisation: First, if your
kernel+ramdisk blob is larger than 16Mb, then you will need to increase
NKPTP in the kernel config (just uncomment the entry in the file, it's
good for 32Mb kernels). The symptom of a kernel with a too-small NKPTP
is an immediate crash or reboot after the kernel is loaded. Another
caveat is that kernels larger than about 14Mb in size will use up all
the ISA DMA memory and the kernel will panic at boot unless isadma is
disabled in the config or via UKC. This leads to the final problem: if
isadma is disabled, then things that attempt to use it (e.g. floppy disk
access) will panic the kernel. The best solution is to try to keep your
kernels small./

As far as I can tell both of these are done for all kernels:

And then we have this where Damien had some kind of idea on what could
be done: http://cvsweb.mindrot.org/index.cgi/flashboot/TODO?rev=1.6

I'm afraid that I understand to little on this, we need an expert.

Until we get some facts here people should only use the large-kernel
option if tested properly and on systems with console access and a
backup obsd-kernel.

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