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/Kconfig

@@ -867,6 +867,21 @@ config SECCOMP
 
 	  If unsure, say Y. Only embedded should say N here.
 
+config PPC_MEM_KEYS
+	prompt "PowerPC Memory Protection Keys"
+	def_bool y
+	depends on PPC_BOOK3S_64
+	select ARCH_USES_HIGH_VMA_FLAGS
+	select ARCH_HAS_PKEYS
+	help
+	  Memory Protection Keys provides a mechanism for enforcing
+	  page-based protections, but without requiring modification of the
+	  page tables when an application changes protection domains.
+
+	  For details, see Documentation/vm/protection-keys.txt
+
+	  If unsure, say y.
+
 endmenu
 
 config ISA_DMA_API

arch/powerpc/include/asm/mmu_context.h

@@ -192,5 +192,6 @@ static inline bool arch_vma_access_permitted(struct vm_area_struct *vma,
 	/* by default, allow everything */
 	return true;
 }
+
 #endif /* __KERNEL__ */
 #endif /* __ASM_POWERPC_MMU_CONTEXT_H */

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 */

arch/powerpc/mm/Makefile

@@ -44,3 +44,4 @@ obj-$(CONFIG_PPC_COPRO_BASE)	+= copro_fault.o
 obj-$(CONFIG_SPAPR_TCE_IOMMU)	+= mmu_context_iommu.o
 obj-$(CONFIG_PPC_PTDUMP)	+= dump_linuxpagetables.o
 obj-$(CONFIG_PPC_HTDUMP)	+= dump_hashpagetable.o
+obj-$(CONFIG_PPC_MEM_KEYS)	+= pkeys.o

arch/powerpc/mm/hash_utils_64.c

@@ -36,6 +36,7 @@
 #include <linux/memblock.h>
 #include <linux/context_tracking.h>
 #include <linux/libfdt.h>
+#include <linux/pkeys.h>
 
 #include <asm/debugfs.h>
 #include <asm/processor.h>

arch/powerpc/mm/pkeys.c

@@ -0,0 +1,29 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * PowerPC Memory Protection Keys management
+ *
+ * Copyright 2017, Ram Pai, IBM Corporation.
+ */
+
+#include <linux/pkeys.h>
+
+DEFINE_STATIC_KEY_TRUE(pkey_disabled);
+bool pkey_execute_disable_supported;
+
+int pkey_initialize(void)
+{
+	/*
+	 * Disable the pkey system till everything is in place. A subsequent
+	 * patch will enable it.
+	 */
+	static_branch_enable(&pkey_disabled);
+
+	/*
+	 * Disable execute_disable support for now. A subsequent patch will
+	 * enable it.
+	 */
+	pkey_execute_disable_supported = false;
+	return 0;
+}
+
+arch_initcall(pkey_initialize);