On Wed, 4 Nov 2020 at 14:06, Mark Rutland <mark.rutland@xxxxxxx> wrote: > On Tue, Nov 03, 2020 at 06:58:35PM +0100, 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>. > > > > KFENCE requires that attributes for pages from its memory pool can > > individually be set. Therefore, force the entire linear map to be mapped > > at page granularity. Doing so may result in extra memory allocated for > > page tables in case rodata=full is not set; however, currently > > CONFIG_RODATA_FULL_DEFAULT_ENABLED=y is the default, and the common case > > is therefore not affected by this change. > > > > 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> > > Thanks for dilligently handling all the review feedback. This looks good > to me now, so FWIW: > > Reviewed-by: Mark Rutland <mark.rutland@xxxxxxx> Thank you! > There is one thing that I thing we should improve as a subsequent > cleanup, but I don't think that should block this as-is. > > > +#define KFENCE_SKIP_ARCH_FAULT_HANDLER "el1_sync" > > IIUC, the core kfence code is using this to figure out where to trace > from when there's a fault taken on an access to a protected page. Correct. > It would be better if the arch code passed the exception's pt_regs into > the kfence fault handler, and the kfence began the trace began from > there. That would also allow for dumping the exception registers which > can help with debugging (e.g. figuring out how the address was derived > when it's calculated from multiple source registers). That would also be > a bit more robust to changes in an architectures' exception handling > code. Good idea, thanks. I guess there's no reason to not want to always skip to instruction_pointer(regs)? In which case I can prepare a patch to make this change. If this should go into a v8, please let me know. But it'd be easier as a subsequent patch as you say, given it'll be easier to review and these patches are in -mm now. Thanks, -- Marco
