Re: [RFC PATCH v2 23/27] mm/mmap: Add IBT bitmap size to address space limit check

[Dave Hansen]

On 07/10/2018 03:26 PM, Yu-cheng Yu wrote:
> The indirect branch tracking legacy bitmap takes a large address
> space.  This causes may_expand_vm() failure on the address limit
> check.  For a IBT-enabled task, add the bitmap size to the
> address limit.

This appears to require that we set up
current->thread.cet.ibt_bitmap_size _before_ calling may_expand_vm().
What keeps the ibt_mmap() itself from hitting the address limit?