On Mon, Oct 09, 2017 at 08:46:18PM +0200, 'Dmitry Vyukov' via syzkaller wrote: > On Mon, Oct 9, 2017 at 8:37 PM, Mark Rutland <mark.rutland@xxxxxxx> wrote: > > On Mon, Oct 09, 2017 at 08:15:10PM +0200, 'Dmitry Vyukov' via syzkaller wrote: > >> On Mon, Oct 9, 2017 at 5:46 PM, Mark Rutland <mark.rutland@xxxxxxx> wrote: > >> > On Mon, Oct 09, 2017 at 05:05:19PM +0200, Alexander Potapenko wrote: > > > >> > ... I note that a few places in the kernel use a 128-bit type. Are > >> > 128-bit comparisons not instrumented? > >> > >> Yes, they are not instrumented. > >> How many are there? Can you give some examples? > > > > From a quick scan, it doesn't looks like there are currently any > > comparisons. > > > > It's used as a data type in a few places under arm64: > > > > arch/arm64/include/asm/checksum.h: __uint128_t tmp; > > arch/arm64/include/asm/checksum.h: tmp = *(const __uint128_t *)iph; > > arch/arm64/include/asm/fpsimd.h: __uint128_t vregs[32]; > > arch/arm64/include/uapi/asm/ptrace.h: __uint128_t vregs[32]; > > arch/arm64/include/uapi/asm/sigcontext.h: __uint128_t vregs[32]; > > arch/arm64/kernel/signal32.c: __uint128_t raw; > > arch/arm64/kvm/guest.c: __uint128_t tmp; > > Then I think we just continue ignoring them for now :) > In the future we can extend kcov to trace 128-bits values. We will > need to add a special flag and write 2 consecutive entries for them. > Or something along these lines. Just wanted to make sure that we weren't backing ourselves into a corner w.r.t. ABI; that sounds fine to me. Thanks, Mark. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
