Re: [PATCH qemu] x86: don't let decompressed kernel image clobber setup_data

[H. Peter Anvin]

On 12/31/22 19:21, H. Peter Anvin wrote:
> > > Alternatively, setup_data could be relocated, the boot param protocol
> > > could be bumped, and then QEMU could conditionalized it's use of
> > > setup_data based on that protocol version. That'd work, but seems a bit
> > > more involved.
> >
> > I think this is at least worth considering because the kernel overwriting
> > setup_data after having been told where that setup_data is located is 
> > not really
> > nice.
> >
> > Well not explicitly at least - it gets the pointer to the first 
> > element and
> > something needs to traverse that list to know which addresses are 
> > live. But
> > still, that info is there so perhaps we need to take setup_data into
> > consideration too before decompressing...

It would probably be a good idea to add a "maximum physical address for 
initrd/setup_data/cmdline" field to struct kernel_info, though. It 
appears right now that those fields are being identity-mapped in the 
decompressor, and that means that if 48-bit addressing is used, physical 
memory may extend past the addressable range.

        -hpa