x86, mpx: extend MPX prctl() to pass in size of bounds directory
The MPX bounds tables are indexed by virtual address. A larger virtual
address space means that we need larger tables. But, we need to ensure
that userspace and the kernel agree about the size of these tables.
To do this, we require that userspace pass in the size of the tables
if they want a non-legacy size. They do this with a previously unused
(required to be 0) argument to the PR_MPX_ENABLE_MANAGEMENT ptctl().
This way, the kernel can make sure that the size of the tables is
consistent with the size of the address space and can return an error
if there is a mismatch.
There are essentially 3 table sizes that matter:
1. 32-bit table sized for a 32-bit address space
2. 64-bit table sized for a 48-bit address space
3. 64-bit table sized for a 57-bit address space
We cover all three of those cases.
FIXME: we also need to ensure that we check the current state of the
larger address space opt-in. If we've opted in to larger address spaces
we can not allow a small bounds directory to be used. Also, if we've
not opted in, we can not allow the larger bounds directory to be used.
5 files changed
