Re: [RFC PATCH v9 15/27] mm: Handle THP/HugeTLB Shadow Stack page fault

[Yu-cheng Yu]

On Tue, 2020-02-25 at 12:59 -0800, Kees Cook wrote:
> On Wed, Feb 05, 2020 at 10:19:23AM -0800, Yu-cheng Yu wrote:
> > This patch implements THP Shadow Stack (SHSTK) copying in the same way as
> > in the previous patch for regular PTE.
> > 
> > In copy_huge_pmd(), clear the dirty bit from the PMD to cause a page fault
> > upon the next SHSTK access to the PMD.  At that time, fix the PMD and
> > copy/re-use the page.
> 
> Now is as good a time as any to ask: do you have selftests for all this?
> It seems like it would be really nice to have a way to verify SHSTK is
> working correctly.

Yes, I have some simple tests at https://github.com/yyu168/cet-smoke-test.
I also run Linux/tools/testing/selftests/x86 and GLIBC tests with CET and THP
combinations.

Yu-cheng