arm64: Make sure permission updates happen for pmd/pud

Commit 15122ee2c515 ("arm64: Enforce BBM for huge IO/VMAP mappings")
disallowed block mappings for ioremap since that code does not honor
break-before-make. The same APIs are also used for permission updating
though and the extra checks prevent the permission updates from happening,
even though this should be permitted. This results in read-only permissions
not being fully applied. Visibly, this can occasionaly be seen as a failure
on the built in rodata test when the test data ends up in a section or
as an odd RW gap on the page table dump. Fix this by using
pgattr_change_is_safe instead of p*d_present for determining if the
change is permitted.

Reviewed-by: Kees Cook <keescook@chromium.org>
Tested-by: Peter Robinson <pbrobinson@gmail.com>
Reported-by: Peter Robinson <pbrobinson@gmail.com>
Fixes: 15122ee2c515 ("arm64: Enforce BBM for huge IO/VMAP mappings")
Signed-off-by: Laura Abbott <labbott@redhat.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Git-Commit: 82034c23fcbc2389c73d97737f61fa2dd6526413
Git-Repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Change-Id: I7cbc0366b5101ade51a527b4c9e72f0a39ea5246
[sudaraja@codeaurora.org: added definition for pfn_pud, merge conflict fixes]
Signed-off-by: Sudarshan Rajagopalan <sudaraja@codeaurora.org>
[guptap@codeaurora.org: added definition for pgattr_change_is_safe, merge conflict fixes]
Signed-off-by: Prakash Gupta <guptap@codeaurora.org>