On Mon, Sep 21, 2020 at 05:37:10PM +0200, Alexander Potapenko wrote: > On Mon, Sep 21, 2020 at 4:58 PM Alexander Potapenko <glider@xxxxxxxxxx> wrote: > > > > 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. > > The question is though, how big should that dedicated area be? > Right now KFENCE_NUM_OBJECTS can be up to 16383 (which makes the pool > size 64MB), but this number actually comes from the limitation on > static objects, so we might want to increase that number on arm64. What happens on x86 and why would we do something different? Will
