Re: [PATCH] hw/ppc/ppc405_boards: Change kernel load address

[Thomas Huth <thuth@redhat.com>]

On 03/12/2021 13.25, Cédric Le Goater wrote:
> On 12/3/21 11:40, Peter Maydell wrote:
>> On Fri, 3 Dec 2021 at 10:32, Thomas Huth <thuth@redhat.com> wrote:
>>> I guess it's an accidential NULL pointer dereference somewhere in the u-boot
>>> code ... which will be quite hard to track down when the first page of
>>> memory is marked as writable... :-/
>>
>> Attach a target-arch gdb to the QEMU gdbstub and put a watchpoint on
>> address zero ? (Or if you suspect something inside QEMU is doing it
>> then run QEMU under gdb and watchpoint the host memory location
>> corresponding to guest address 0, but that's more painful.) Nothing
>> in the pre-kernel part of the boot process will have set up paging,
>> so the watchpointing should be pretty reliable.
> 
> That's the guy:
> 
>    
> https://gitlab.com/huth/u-boot/-/blob/taihu/arch/powerpc/cpu/ppc4xx/sdram.c#L199 
> 
> 
> There must be an error in how get_ram_size() restores the RAM values :
> 
>    https://gitlab.com/huth/u-boot/-/blob/taihu/common/memsize.c

There is definitely something wrong in that function. Seems like they tried 
to fix it once here:

  https://source.denx.de/u-boot/u-boot/-/commit/b8496cced856ff411f

but that patch got later reverted without a replacement later...

  Thomas