On Wed, Mar 25, 2020 at 01:21:27PM +0000, Mark Rutland wrote: > On Tue, Mar 24, 2020 at 01:32:31PM -0700, Kees Cook wrote: > > Allow for a randomized stack offset on a per-syscall basis, with roughly > > 5 bits of entropy. > > > > Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> > > Just to check, do you have an idea of the impact on arm64? Patch 3 had > figures for x86 where it reads the TSC, and it's unclear to me how > get_random_int() compares to that. I didn't do a measurement on arm64 since I don't have a good bare-metal test environment. I know Andy Lutomirki has plans for making get_random_get() as fast as possible, so that's why I used it here. I couldn't figure out if there was a comparable instruction like rdtsc in aarch64 (it seems there's a cycle counter, but I found nothing in the kernel that seemed to actually use it)? > Otherwise, this looks sound to me; I'd jsut like to know whether the > overhead is in the same ballpark. Thanks! -Kees -- Kees Cook
