On Tue, Apr 28, 2020 at 10:24 AM David Woodhouse <dw...@infradead.org> wrote: > > > > On 28 April 2020 17:14:49 BST, Peter Zijlstra <pet...@infradead.org> wrote: > >On Tue, Apr 28, 2020 at 02:41:33PM +0100, Andrew Cooper wrote: > >> Its fine to focus on userspace first, but the kernel is far more > >simple. > >> > >> Looking at that presentation, the only thing missing for kernel is > >the > >> notrack thunks, in the unlikely case that such code would be > >tolerated > >> (Frankly, I don't expect Xen or Linux to run with notrack enabled, as > >> there is no legacy code to be concerned with). > > > >Uhhh.. ftrace and kretprobes play dodgy games with the > >return stack, doesn't that make the CET thing slightly more > >interesting? > > Sure, there is work to do to enable CET. But Andy's point is that we > deliberately fixed up retpoline to be register-based *specifically* for the > purpose of being CET-compatible, so it's somewhat daft for GCC to be claiming > they are incompatible. >
GCC needs to be told that external thunk is CET compatible. -- H.J.
