[U-Boot] Debugging into the kernel from u-boot

[Stefan Roese <sr@denx.de>]

Hi Matthias,

On Friday 30 April 2010 14:55:42 Dunda, Matthias wrote:
> I - more or less - successfully got U-Boot up and running on our custom
> designed board.
> 
> U-Boot leaves its premices in boot_jump_linux and this is the last I see on
> the console:
> 
> ## Booting kernel from Legacy Image at 02000000 ...
>    Image Name:   Linux-2.6.29.6-rt23
>    Image Type:   PowerPC Linux Kernel Image (gzip compressed)
>    Data Size:    1830522 Bytes =  1.7 MB
>    Load Address: 00000000
>    Entry Point:  00000000
>    Verifying Checksum ... OK
> ## Flattened Device Tree blob at 00400000
>    Booting using the fdt blob at 0x400000
>    Uncompressing Kernel Image ... OK
> ## Transferring control to Linux (at address 00000000)...
>    Booting using OF flat tree...
> 
> When I halt the board using the BDI3000 debugger, I find the PC somewhere
> in 0xc000c96c in __delay. Accessing 0xc000.... makes no sense, as we don't
> even have mapped memory there.

This address makes perfect sense. Linux maps physical address 0 to virtual 
address 0xc000000 on PowerPC.
 
> Using HW breakpoints I can see the single instructions from 0x0 on, but I
> get no link to the source.
> 
> Where can I get a meaningful starting point in the kernel?

You have all the equipment you need. Use the BDI3000 to debug the Linux 
kernel.
 
> Why are all the symbols in vmlinux located at 0xc0...

See above.

> and how does the
> relocation take place? I saw some comment in arch/powerpc/kernel/setup_32.c
> but yet I have no clue where to start practically?
> 
> Any help would be appreciated!

I suggest you take a look at this link as well:

http://www.denx.de/wiki/view/DULG/LinuxPostMortemAnalysis

Hope this helps.

Cheers,
Stefan

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