On Mon, Sep 21, 2020 at 4:31 PM Will Deacon <will@xxxxxxxxxx> wrote: > > On Mon, Sep 21, 2020 at 03:26:04PM +0200, Marco Elver wrote: > > Add architecture specific implementation details for KFENCE and enable > > KFENCE for the arm64 architecture. In particular, this implements the > > required interface in <asm/kfence.h>. Currently, the arm64 version does > > not yet use a statically allocated memory pool, at the cost of a pointer > > load for each is_kfence_address(). > > > > Reviewed-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> > > Co-developed-by: Alexander Potapenko <glider@xxxxxxxxxx> > > Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx> > > Signed-off-by: Marco Elver <elver@xxxxxxxxxx> > > --- > > For ARM64, we would like to solicit feedback on what the best option is > > to obtain a constant address for __kfence_pool. One option is to declare > > a memory range in the memory layout to be dedicated to KFENCE (like is > > done for KASAN), however, it is unclear if this is the best available > > option. We would like to avoid touching the memory layout. > > Sorry for the delay on this. NP, thanks for looking! > Given that the pool is relatively small (i.e. when compared with our virtual > address space), dedicating an area of virtual space sounds like it makes > the most sense here. How early do you need it to be available? Yes, having a dedicated address sounds good. We're inserting kfence_init() into start_kernel() after timekeeping_init(). So way after mm_init(), if that matters. > An alternative approach would be to patch in the address at runtime, with > something like a static key to swizzle off the direct __kfence_pool load > once we're up and running. IIUC there's no such thing as address patching in the kernel at the moment, at least static keys work differently? I am not sure how much we need to randomize this address range (we don't on x86 anyway). > Will > > -- > You received this message because you are subscribed to the Google Groups "kasan-dev" group. > To unsubscribe from this group and stop receiving emails from it, send an email to kasan-dev+unsubscribe@xxxxxxxxxxxxxxxx. > To view this discussion on the web visit https://groups.google.com/d/msgid/kasan-dev/20200921143059.GO2139%40willie-the-truck. -- Alexander Potapenko Software Engineer Google Germany GmbH Erika-Mann-Straße, 33 80636 München Geschäftsführer: Paul Manicle, Halimah DeLaine Prado Registergericht und -nummer: Hamburg, HRB 86891 Sitz der Gesellschaft: Hamburg
