[OpenBIOS] Exception 13 ?

[James]

As I understand it, the zImage has a whole lot of junk to boot the kernel
at the start and it is compressd, so you can't just read it and jump to
it.  You first have to uncompress zImage (just gunzip zImage, I
forget if you have to rename zImage zImage.gz).  You then must strip the
kernel's boot code.  I always did this in a script like:
  objcopy -O binary -R .note -R .comment -S vmlinux /tmp/$$-tmp-linux
You then must regunzip the image in a format that your gunzip program can
read:
  gzip -f -3 /tmp/$$-tmp-linux

You must then use some C code (like inflate.c provided with the linux
kernel (which is the same inflate.c from openbios)) to inflate the image.
This is kinda tricky.  I do it by first copying the image in at something
like 0x20000 and then uncompressing that image to 0x100000 and then
jumping to 0x100000.  Oh yeah;  the kernel won't just boot completely, it
will get to somewhere (I think the bogomips test) and die because it is
missing interrupts or something like that.

You may want to start more basically by taking the zImage, uncompressing
it, stripping it, and then copying the big, uncompressed image straight to
0x100000 and jumping there.

	- James


On Sat, 12 Feb 2000, [iso-8859-1] Winter Jörg wrote:

> James: (jvh at uclink4.berkeley.edu): Thanks for the hint on loading a Kernel,
> but:
> 
> Now I have a verified routine that loads the kernel (block by block) from my
> ATA-Disk into memory (at whatever I like. Currently at 0x00010000). I´m
> loading a zImage at 0x00010000, the bootsect at 0x9000, 
> the setupsectors (4) at 0x9200. It´s just like the other loaders do it
> ...he?
> 
> I have the code like: static void (*v)() =(void *)KERNEL_START;
> 
> I start like: v();
> 
> and the machine (the openbios) throws me an exception 13. (general
> Protection Fault errorcode 0).
> 
> I tried nearly any combination of stack-location, entry-adress and
> kerneltype ... all fails ...
> I now read alot about descriptors and segments and so cause I suspect the
> problem is somewhere there ...
> 
> But I just dont get the point. What am I doing wrong now ?? I thought the
> kernel would just set up and start?
> 
> I figured out that already the jump done with the   v();  is the one that
> causes the exception, no matter if there is a kernel or just dummy code
> (like: jmp $).
> 
> There must be something I misunderstood completely !!  Help, I´m lost ...
> 
> greetinx,  J.Winter
> 
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