Re: [RFC PATCH v9 01/27] Documentation/x86: Add CET description

H.J. Lu
2020-03-09T21:13:11Z

On Mon, Mar 9, 2020 at 1:59 PM Dave Hansen <dave.hansen@intel.com> wrote:
>
> On 3/9/20 1:54 PM, H.J. Lu wrote:
> >> If a program with the magic ELF CET flags missing can’t make a
> >> thread with IBT and/or SHSTK enabled, then I think we’ve made an
> >> error and should fix it.
> >>
> > A non-CET program can start a CET program and vice versa.
>
> Could we be specific here, please?
>
> HJ are you saying that:
> * CET program can execve() a non-CET program, and
> * a non-CET program can execve() a CET program
>
> ?

Yes.

> That's obvious.
>
> But what are the rules for clone()? Should there be rules for
> mismatches for CET enabling between threads if a process (not child
> processes)?

What did you mean? A threaded application is either CET enabled or not
CET enabled. A new thread from clone makes no difference.

--
H.J.