On Sat, Feb 18, 2023 at 01:14:12PM -0800, Rick Edgecombe wrote:

If a VMA has the VM_SHADOW_STACK flag, it is shadow stack memory. So
when it is made writable with pte_mkwrite(), it should create shadow
stack memory, not conventionally writable memory. Now that pte_mkwrite()
takes a VMA, and places where shadow stack memory might be created pass
one, pte_mkwrite() can know when it should do this.

So make pte_mkwrite() create shadow stack memory when the VMA has the
VM_SHADOW_STACK flag. Do the same thing for pmd_mkwrite().

This requires referencing VM_SHADOW_STACK in these functions, which are
currently defined in pgtable.h, however mm.h (where VM_SHADOW_STACK is
located) can't be pulled in without causing problems for files that
reference pgtable.h. So also move pte/pmd_mkwrite() into pgtable.c, where
they can safely reference VM_SHADOW_STACK.

Tested-by: Pengfei Xu <redacted>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>

Acked-by: Deepak Gupta <redacted>