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

[Thomas Huth]

On 03/12/2021 11.27, Cédric Le Goater wrote:
> On 12/2/21 20:32, LEROY Christophe wrote:
> > Le 02/12/2021 à 20:19, Cédric Le Goater a écrit :
> > > On 12/2/21 20:17, Thomas Huth wrote:
> > > > On 02/12/2021 20.14, Cédric Le Goater wrote:
> > > > > The default addresses to load the kernel, fdt, initrd of AMCC boards
> > > > > in U-Boot v2015.10 are :
> > > > >
> > > > >      "kernel_addr_r=1000000\0"
> > > > >      "fdt_addr_r=1800000\0"
> > > > >      "ramdisk_addr_r=1900000\0"
> > > > >
> > > > > The taihu is one of these boards, the ref405ep is not but we don't
> > > > > have much information on it and both boards have a very similar
> > > > > address space layout. Change the kernel load address to match U-Boot
> > > > > expectations and fix loading.
> > > >
> > > > You could additionally mention that U-Boot corrupts the kernel if it
> > > > gets loaded to address 0.
> > >
> > > True. The first word is overwritten with zeros. I looked for it
> > > in the code but could not find the reason.
> >
> > Isn't it because U-boot unzips the kernel at address 0 ?
>
> Address 0 is trashed before U-boot loads the kernel.

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... :-/

 Thomas