powerpc: initial pkey plumbing

Basic  plumbing  to   initialize  the   pkey  system.
Nothing is enabled yet. A later patch will enable it
once all the infrastructure is in place.

Signed-off-by: Ram Pai <linuxram@us.ibm.com>
[mpe: Rework copyrights to use SPDX tags]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/pkeys.h

@@ -0,0 +1,51 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * PowerPC Memory Protection Keys management
+ *
+ * Copyright 2017, Ram Pai, IBM Corporation.
+ */
+
+#ifndef _ASM_POWERPC_KEYS_H
+#define _ASM_POWERPC_KEYS_H
+
+#include <linux/jump_label.h>
+
+DECLARE_STATIC_KEY_TRUE(pkey_disabled);
+#define ARCH_VM_PKEY_FLAGS 0
+
+static inline bool mm_pkey_is_allocated(struct mm_struct *mm, int pkey)
+{
+	return false;
+}
+
+static inline int mm_pkey_alloc(struct mm_struct *mm)
+{
+	return -1;
+}
+
+static inline int mm_pkey_free(struct mm_struct *mm, int pkey)
+{
+	return -EINVAL;
+}
+
+/*
+ * Try to dedicate one of the protection keys to be used as an
+ * execute-only protection key.
+ */
+static inline int execute_only_pkey(struct mm_struct *mm)
+{
+	return 0;
+}
+
+static inline int arch_override_mprotect_pkey(struct vm_area_struct *vma,
+					      int prot, int pkey)
+{
+	return 0;
+}
+
+static inline int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
+					    unsigned long init_val)
+{
+	return 0;
+}
+#endif /*_ASM_POWERPC_KEYS_H */