On Mar 9, 2020, at 2:13 PM, H.J. Lu [off-list ref] wrote:

On Mon, Mar 9, 2020 at 1:59 PM Dave Hansen [off-list ref] wrote:

quoted

On 3/9/20 1:54 PM, H.J. Lu wrote:

quoted

quoted

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.

quoted

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.

Why?  Dave’s example seems like a good reason to allow per-thread control.

-- 
H.J.