Re: [PATCH v3 5/6] powerpc/fsl_booke/64: clear the original kernel if randomized

[Jason Yan]

å 2020/3/5 5:53, Scott Wood åé:
> On Thu, 2020-02-06 at 10:58 +0800, Jason Yan wrote:
> > The original kernel still exists in the memory, clear it now.
> >
> > Signed-off-by: Jason Yan <yanaijie@xxxxxxxxxx>
> > Cc: Scott Wood <oss@xxxxxxxxxxxx>
> > Cc: Diana Craciun <diana.craciun@xxxxxxx>
> > Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
> > Cc: Christophe Leroy <christophe.leroy@xxxxxx>
> > Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
> > Cc: Paul Mackerras <paulus@xxxxxxxxx>
> > Cc: Nicholas Piggin <npiggin@xxxxxxxxx>
> > Cc: Kees Cook <keescook@xxxxxxxxxxxx>
> > ---
> >   arch/powerpc/mm/nohash/kaslr_booke.c | 4 +++-
> >   1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/powerpc/mm/nohash/kaslr_booke.c
> > b/arch/powerpc/mm/nohash/kaslr_booke.c
> > index c6f5c1db1394..ed1277059368 100644
> > --- a/arch/powerpc/mm/nohash/kaslr_booke.c
> > +++ b/arch/powerpc/mm/nohash/kaslr_booke.c
> > @@ -378,8 +378,10 @@ notrace void __init kaslr_early_init(void *dt_ptr,
> > phys_addr_t size)
> >   	unsigned int *__kaslr_offset = (unsigned int *)(KERNELBASE + 0x58);
> >   	unsigned int *__run_at_load = (unsigned int *)(KERNELBASE + 0x5c);
> >   
> > -	if (*__run_at_load == 1)
> > +	if (*__run_at_load == 1) {
> > +		kaslr_late_init();
> >   		return;
> > +	}
>
> What if you're here because kexec set __run_at_load (or
> CONFIG_RELOCATABLE_TEST is enabled), not because kaslr happened?

Nothing will happen because kaslr_late_init() only clears memory when
kernstart_virt_addr is not KERNELBASE. When __run_at_load is set then
KASLR will not take effect.

> -Scott
>
>
>
> .