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

[Jason Yan]

On 2019/8/28 13:47, Christophe Leroy wrote:
> 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>
> > > ---
> > > Â arch/powerpc/KconfigÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ | 11 ++++
> > > Â arch/powerpc/kernel/MakefileÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ |Â 1 +
> > > Â arch/powerpc/kernel/early_32.cÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ |Â 2 +-
> > > Â arch/powerpc/kernel/fsl_booke_entry_mapping.S | 17 +++--
> > > Â arch/powerpc/kernel/head_fsl_booke.SÂÂÂÂÂÂÂÂÂ | 13 +++-
> > > Â arch/powerpc/kernel/kaslr_booke.cÂÂÂÂÂÂÂÂÂÂÂÂ | 62 +++++++++++++++++++
> > > Â arch/powerpc/mm/mmu_decl.hÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ |Â 7 +++
> > > Â arch/powerpc/mm/nohash/fsl_booke.cÂÂÂÂÂÂÂÂÂÂÂ |Â 7 ++-
> > > Â 8 files changed, 105 insertions(+), 15 deletions(-)
> > > Â 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)
> > > +{
> > > +ÂÂÂ unsigned long tlb_virt;
> > > +ÂÂÂ phys_addr_t tlb_phys;
> > > +ÂÂÂ unsigned long offset;
> > > +ÂÂÂ unsigned long kernel_sz;
> > > +
> > > +ÂÂÂ kernel_sz = (unsigned long)_end - KERNELBASE;
> >
> > Why KERNELBASE and not kernstart_addr?
> >
> > > +
> > > +ÂÂÂ offset = kaslr_choose_location(dt_ptr, size, kernel_sz);
> > > +
> > > +ÂÂÂ if (offset == 0)
> > > +ÂÂÂÂÂÂÂ return;
> > > +
> > > +ÂÂÂ kernstart_virt_addr += offset;
> > > +ÂÂÂ kernstart_addr += offset;
> > > +
> > > +ÂÂÂ is_second_reloc = 1;
> > > +
> > > +ÂÂÂ if (offset >= SZ_64M) {
> > > +ÂÂÂÂÂÂÂ tlb_virt = round_down(kernstart_virt_addr, SZ_64M);
> > > +ÂÂÂÂÂÂÂ 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.
> >
> > > +
> > > +ÂÂÂÂÂÂÂ /* Create kernel map to relocate in */
> > > +ÂÂÂÂÂÂÂ create_tlb_entry(tlb_phys, tlb_virt, 1);
> > > +ÂÂÂ }
> > > +
> > > +ÂÂÂ /* Copy the kernel to it's new location and run */
> > > +ÂÂÂ memcpy((void *)kernstart_virt_addr, (void *)KERNELBASE, kernel_sz);
> > > +
> > > +ÂÂÂ 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()

Hi Christophe,

Thanks for the suggestion. But I think copy_and_flush() is not included 
in fsl booke code, maybe move this function to misc.S?

> Christophe
>
> .