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

[Andy Lutomirski]

> On Mar 9, 2020, at 2:13 PM, H.J. Lu <hjl.tools@xxxxxxxxx> wrote:
> 
> ïOn Mon, Mar 9, 2020 at 1:59 PM Dave Hansen <dave.hansen@xxxxxxxxx> wrote:
>> 
>> On 3/9/20 1:54 PM, H.J. Lu wrote:
>>>> If a program with the magic ELF CET flags missing canât make a
>>>> thread with IBT and/or SHSTK enabled, then I think weâve 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.

Why?  Daveâs example seems like a good reason to allow per-thread control.



> 
> -- 
> H.J.