On Fri, 22 Jan 2021 at 22:15, Madhavan T. Venkataraman <madvenka@xxxxxxxxxxxxxxxxxxx> wrote: > > > > On 1/22/21 11:43 AM, Mark Brown wrote: > > On Thu, Jan 21, 2021 at 12:54:52PM -0600, Josh Poimboeuf wrote: > > > >> 2) The shadow stack idea sounds promising -- how hard would it be to > >> make a prototype reliable unwinder? > > > > In theory it doesn't look too hard and I can't see a particular reason > > not to try doing this - there's going to be edge cases but hopefully for > > reliable stack trace they're all in areas where we would be happy to > > just decide the stack isn't reliable anyway, things like nesting which > > allocates separate shadow stacks for each nested level for example. > > I'll take a look. > > > > I am a new comer to this discussion and I am learning. Just have some > questions. Pardon me if they are obvious or if they have already been > asked and answered. > > Doesn't Clang already have support for a shadow stack implementation for ARM64? > We could take a look at how Clang does it. > > Will there not be a significant performance hit? May be, some of it can be > mitigated by using a parallel shadow stack rather than a compact one. > > Are there any longjmp style situations in the kernel where the stack is > unwound by several frames? In these cases, the shadow stack must be unwound > accordingly. > Hello Madhavan, Let's discuss the details of shadow call stacks on a separate thread, instead of further hijacking Julien's series.
