Re: [PATCH v6 06/12] powerpc/fsl_booke/32: implement KASLR infrastructure

[Christophe Leroy]

Le 28/08/2019 Ã 06:54, Scott Wood a ÃcritÂ:
> On Fri, Aug 09, 2019 at 06:07:54PM +0800, Jason Yan wrote:
> > This patch add support to boot kernel from places other than KERNELBASE.
> > Since CONFIG_RELOCATABLE has already supported, what we need to do is
> > map or copy kernel to a proper place and relocate. Freescale Book-E
> > parts expect lowmem to be mapped by fixed TLB entries(TLB1). The TLB1
> > entries are not suitable to map the kernel directly in a randomized
> > region, so we chose to copy the kernel to a proper place and restart to
> > relocate.
> >
> > The offset of the kernel was not randomized yet(a fixed 64M is set). We
> > will randomize it in the next patch.
> >
> > Signed-off-by: Jason Yan <yanaijie@xxxxxxxxxx>
> > 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>
> > Tested-by: Diana Craciun <diana.craciun@xxxxxxx>
> > Reviewed-by: Christophe Leroy <christophe.leroy@xxxxxx>
> > ---
> >   arch/powerpc/Kconfig                          | 11 ++++
> >   arch/powerpc/kernel/Makefile                  |  1 +
> >   arch/powerpc/kernel/early_32.c                |  2 +-
> >   arch/powerpc/kernel/fsl_booke_entry_mapping.S | 17 +++--
> >   arch/powerpc/kernel/head_fsl_booke.S          | 13 +++-
> >   arch/powerpc/kernel/kaslr_booke.c             | 62 +++++++++++++++++++
> >   arch/powerpc/mm/mmu_decl.h                    |  7 +++
> >   arch/powerpc/mm/nohash/fsl_booke.c            |  7 ++-
> >   8 files changed, 105 insertions(+), 15 deletions(-)
> >   create mode 100644 arch/powerpc/kernel/kaslr_booke.c

[...]

> > diff --git a/arch/powerpc/kernel/kaslr_booke.c b/arch/powerpc/kernel/kaslr_booke.c
> > new file mode 100644
> > index 000000000000..f8dc60534ac1
> > --- /dev/null
> > +++ b/arch/powerpc/kernel/kaslr_booke.c
>
> Shouldn't this go under arch/powerpc/mm/nohash?
>
> > +/*
> > + * To see if we need to relocate the kernel to a random offset
> > + * void *dt_ptr - address of the device tree
> > + * phys_addr_t size - size of the first memory block
> > + */
> > +notrace void __init kaslr_early_init(void *dt_ptr, phys_addr_t size)
> > +{
> > +	unsigned long tlb_virt;
> > +	phys_addr_t tlb_phys;
> > +	unsigned long offset;
> > +	unsigned long kernel_sz;
> > +
> > +	kernel_sz = (unsigned long)_end - KERNELBASE;
>
> Why KERNELBASE and not kernstart_addr?
>
> > +
> > +	offset = kaslr_choose_location(dt_ptr, size, kernel_sz);
> > +
> > +	if (offset == 0)
> > +		return;
> > +
> > +	kernstart_virt_addr += offset;
> > +	kernstart_addr += offset;
> > +
> > +	is_second_reloc = 1;
> > +
> > +	if (offset >= SZ_64M) {
> > +		tlb_virt = round_down(kernstart_virt_addr, SZ_64M);
> > +		tlb_phys = round_down(kernstart_addr, SZ_64M);
>
> If kernstart_addr wasn't 64M-aligned before adding offset, then "offset
> > = SZ_64M" is not necessarily going to detect when you've crossed a
> mapping boundary.
>
> > +
> > +		/* Create kernel map to relocate in */
> > +		create_tlb_entry(tlb_phys, tlb_virt, 1);
> > +	}
> > +
> > +	/* Copy the kernel to it's new location and run */
> > +	memcpy((void *)kernstart_virt_addr, (void *)KERNELBASE, kernel_sz);
> > +
> > +	reloc_kernel_entry(dt_ptr, kernstart_virt_addr);
> > +}
>
> After copying, call flush_icache_range() on the destination.

Function copy_and_flush() does the copy and the flush. I think it should 
be used instead of memcpy() + flush_icache_range()

Christophe