On Fri, 2020-05-15 at 19:53 -0700, Yu-cheng Yu wrote: > On Fri, 2020-05-15 at 16:56 -0700, Dave Hansen wrote: > > On 5/15/20 4:29 PM, Yu-cheng Yu wrote: > > > [...] > > > I have run them with CET enabled. All of them pass, except for the following: > > > Sigreturn from 64-bit to 32-bit fails, because shadow stack is at a 64-bit > > > address. This is understandable. > > [...] > > One a separate topic: You ran the selftests and one failed. This is a > > *MASSIVE* warning sign. It should minimally be described in your cover > > letter, and accompanied by a fix to the test case. It is absolutely > > unacceptable to introduce a kernel feature that causes a test to fail. > > You must either fix your kernel feature or you fix the test. > > > > This code can not be accepted until this selftests issue is rectified. The x86/sigreturn test constructs 32-bit ldt entries, and does sigreturn from 64-bit to 32-bit context. We do not have a way to construct a static 32-bit shadow stack. Why do we want that? I think we can simply run the test with CET disabled. Yu-cheng
