On 06/01/2017 07:59 PM, Andrey Ryabinin wrote: > > > On 06/01/2017 07:52 PM, Mark Rutland wrote: >> On Thu, Jun 01, 2017 at 06:45:32PM +0200, Dmitry Vyukov wrote: >>> On Thu, Jun 1, 2017 at 6:34 PM, Mark Rutland <mark.rutland@xxxxxxx> wrote: >>>> On Thu, Jun 01, 2017 at 07:23:37PM +0300, Andrey Ryabinin wrote: >>>>> We used to read several bytes of the shadow memory in advance. >>>>> Therefore additional shadow memory mapped to prevent crash if >>>>> speculative load would happen near the end of the mapped shadow memory. >>>>> >>>>> Now we don't have such speculative loads, so we no longer need to map >>>>> additional shadow memory. >>>> >>>> I see that patch 1 fixed up the Linux helpers for outline >>>> instrumentation. >>>> >>>> Just to check, is it also true that the inline instrumentation never >>>> performs unaligned accesses to the shadow memory? >>> > > Correct, inline instrumentation assumes that all accesses are properly aligned as it > required by C standard. I knew that the kernel violates this rule in many places, > therefore I decided to add checks for unaligned accesses in outline case. > > >>> Inline instrumentation generally accesses only a single byte. >> >> Sorry to be a little pedantic, but does that mean we'll never access the >> additional shadow, or does that mean it's very unlikely that we will? >> >> I'm guessing/hoping it's the former! >> > > Outline will never access additional shadow byte: https://github.com/google/sanitizers/wiki/AddressSanitizerAlgorithm#unaligned-accesses s/Outline/inline of course. > >> 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>
