On Wed, 2023-01-25 at 00:55 +0000, Sean Christopherson wrote: > On Wed, Oct 12, 2022, John Allen wrote: > > AMD Zen3 and newer processors support shadow stack, a feature > > designed to > > protect against ROP (return-oriented programming) attacks in which > > an attacker > > manipulates return addresses on the call stack in order to execute > > arbitrary > > code. To prevent this, shadow stacks can be allocated that are only > > used by > > control transfer and return instructions. When a CALL instruction > > is issued, it > > writes the return address to both the program stack and the shadow > > stack. When > > the subsequent RET instruction is issued, it pops the return > > address from both > > stacks and compares them. If the addresses don't match, a control- > > protection > > exception is raised. > > > > Shadow stack and a related feature, Indirect Branch Tracking (IBT), > > are > > collectively referred to as Control-flow Enforcement Technology > > (CET). However, > > current AMD processors only support shadow stack and not IBT. > > > > This series adds support for shadow stack in SVM guests and builds > > upon the > > support added in the CET guest support patch series [1] and the CET > > kernel > > patch series [2]. Additional patches are required to support shadow > > stack > > enabled guests in qemu [3] and glibc [4]. > > > > [1]: CET guest support patches > > https://lore.kernel.org/all/20220616084643.19564-1-weijiang.yang@xxxxxxxxx/ > > > > [2]: Latest CET kernel patches > > https://lore.kernel.org/all/20220929222936.14584-1-rick.p.edgecombe@xxxxxxxxx/ > > That dependency chain makes me sad. > > Outside of a very shallow comment on the last patch, I don't plan on > reviewing > this until the kernel side of things gets out of our way. When that > finally > does happen, I'll definitely prioritize reviewing and merging this > and the KVM > Intel series. I'd love to see this land. I think all KVM needs is a few patches from the beginning of the host series (the FPU stuff). At one point Weijiang and I had discussed with Paolo and x86 folks that those few could go up with the KVM series if desired.
