Re: [linuxsh-dev] kernel bootstrapping

[Bryan R. <br...@ix...>]

Stuart Menefy wrote:

> Bryan
> 
> I see similar things when the initrd image is loaded outside the memory
> space the kernel knows about. For example, I normally have 32M RAM from
> 0c00,0000 to 0cff,ffff, and load the initrd image at 0d00,0000.

I assume you mean 32M from 0c000000 to 0dffffff... OK.

> However if I lie, and tell the kernel I only have 16M, then the initrd
> image is outside the memory the kernel knows about, and so as it reserves
> the pages the initrd image occupies, I see the error message:
>   hm, page 01000000 reserved twice.
> for every page in the image (remember the address is an offset from
> CONFIG_MEMORY_START).

Hrm. Should I be specifying the initrd position as an offset from
CONFIG_MEMORY_START, or is it absolute as suggested by the sample
.gdbinits
in the CVS kernel source? And for the size argument, do I specify the
actual
length of the compressed image (~1k), the size of the decompressed image
(~64k), 
or the ramdisk size I'd like (~2MB)?

> If you're not deliberatly loading an initrd image, perhaps the parameters
> the kernel is seeing for where one should be are not being initialised?
> These are poked in by the .dbginit script, at offsets 0x1010 (base addr)
> and 0x1014 (size).

I have set both of these to zero now, and no longer get errors. Right
on.

A question though, how much output should I see when booting a kernel
with no
root device (IE telling it IDE when there is no IDE hardware, or telling
it
a ramdisk with 0 size in 0x1014). All I get now is this the banner:

Linux version 2.4.0-test7 (bryan@mtdew) (gcc version 2.95.2 19991024
(release)) #1 Wed Aug 23 12:00:22 PDT 2000

And then GDB just blocks... if I exit GDB and load up a terminal
program, the sh-ipl stub is back
at the menu system--indicating the kernel has exited! (returned) This is
with early printk and GDB debugging enabled, loading the kernel in with
sh-ipl/GDB. Right now the only kernel command line I
am passing is "mem=15M" (I have 16M physical SDRAM, but need to use a
small chunk of it for the gdb stub; so I load the kernel at 0x08002000
and give it to 08F02000, 15MB).

I know there is no root device, but still, wouldn't you expect more
output? No news is good news, but I want full debugging information in
GDB, if only to show my superiors more than a one line kernel banner.
:-)

Thanks for the reply,

Bryan Rittmeyer
mailto:br...@ix...