Re: [PATCH v7 03/14] x86/cet/ibt: Add IBT legacy code bitmap setup function

[Dave Hansen]

On 6/10/19 4:54 PM, Andy Lutomirski wrote:
> Another benefit of kernel management: we could plausibly auto-clear
> the bits corresponding to munmapped regions. Is this worth it?

I did it for MPX.  I think I even went to the trouble of zapping the
whole pages that got unused.

But, MPX tables took 80% of the address space, worst-case.  This takes
0.003% :)  The only case it would really matter would be a task was
long-running, used legacy executables/JITs, and was mapping/unmapping
text all over the address space.  That seems rather unlikely.