powerpc: ability to associate pkey to a vma

arch-independent code expects the arch to  map
a  pkey  into the vma's protection bit setting.
The patch provides that ability.

Signed-off-by: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/mm/pkeys.c

@@ -34,6 +34,14 @@ int pkey_initialize(void)
 	BUILD_BUG_ON(PKEY_DISABLE_EXECUTE &
 		     (PKEY_DISABLE_ACCESS | PKEY_DISABLE_WRITE));
 
+	/*
+	 * pkey_to_vmflag_bits() assumes that the pkey bits are contiguous
+	 * in the vmaflag. Make sure that is really the case.
+	 */
+	BUILD_BUG_ON(__builtin_clzl(ARCH_VM_PKEY_FLAGS >> VM_PKEY_SHIFT) +
+		     __builtin_popcountl(ARCH_VM_PKEY_FLAGS >> VM_PKEY_SHIFT)
+				!= (sizeof(u64) * BITS_PER_BYTE));
+
 	/*
 	 * Disable the pkey system till everything is in place. A subsequent
 	 * patch will enable it.