Possibly OT: bdi2000 virtual memory on 2.6 kernel

Possibly OT: bdi2000 virtual memory on 2.6 kernel

[Robin Gilks]

Greetings

Debugging a 2.6.18 kernel on a powerpc target with a bdi2000, I'm 
hitting a problem with not being able to read virtual addresses (i.e. 
those starting 0xc......). I get errors in gdb of the form:
     Cannot access memory at address 0xc023634c
I have CONFIG_BDI_SWITCH set and in the bdi config file I have MMU set 
to XLAT to (I thought) get the effective address.

I can set breakpoints OK and using ddd I get to the correct place in the 
source file but I can't then check and variables or structure due to 
this addressing problem.

I'm sure its something simple, I just can't see it at present!!

-- 
Robin

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Re: Possibly OT: bdi2000 virtual memory on 2.6 kernel

[Dan Malek]

On Nov 13, 2006, at 10:17 PM, Robin Gilks wrote:

> Debugging a 2.6.18 kernel on a powerpc target

Which processor, specifically?
What do your MMU XLAT and PTBASE configuration
lines look like?

Thanks.

	-- Dan

Re: Possibly OT: bdi2000 virtual memory on 2.6 kernel

[Robin Gilks]

Dan Malek wrote:
> 
> On Nov 13, 2006, at 10:17 PM, Robin Gilks wrote:
> 
>> Debugging a 2.6.18 kernel on a powerpc target
> 
> Which processor, specifically?
> What do your MMU XLAT and PTBASE configuration
> lines look like?
> 
> Thanks.
> 
>     -- Dan
> 
Hi Dan

Running a 859T processor with the following bdi2000 config lines
MMU     XLAT
PTBASE  0xf0
WSPR    149     0x0082000F


in .config (for the kernel build) I have
CONFIG_BDI_SWITCH=y

Memory dumping 0xf0 - its pointing to abatron_pteptrs which contains the 
  pointer to swapper_pg_dir as expected so it all looks OK.

What I'm NOT doing is using a hardware breakpoint to get beyond the 
decompress stage and then loading the vmlinux image before proceeding. 
I'm just loading up vmlinux in ddd, allowing uboot to tftp the kernel 
binary in and decompressing it and then just letting it rip. This 
approach seems OK as far as maintaining breakpoints across multiple runs 
goes, so I assume its OK.

-- 
Robin



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