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

[Thomas Huth]

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