mm, powerpc, x86: introduce an additional vma bit for powerpc pkey

Currently only 4bits are allocated in the vma flags to hold 16
keys. This is sufficient for x86. PowerPC  supports  32  keys,
which needs 5bits. This patch allocates an  additional bit.
Reviewed-by: NIngo Molnar <mingo@kernel.org>
Acked-by: NBalbir Singh <bsingharora@gmail.com>
Signed-off-by: NRam Pai <linuxram@us.ibm.com>
[mpe: Fold in #if VM_PKEY_BIT4 as noticed by Dave Hansen]
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

fs/proc/task_mmu.c

@@ -679,6 +679,9 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma)
 		[ilog2(VM_PKEY_BIT1)]	= "",
 		[ilog2(VM_PKEY_BIT2)]	= "",
 		[ilog2(VM_PKEY_BIT3)]	= "",
+#if VM_PKEY_BIT4
+		[ilog2(VM_PKEY_BIT4)]	= "",
+#endif
 #endif /* CONFIG_ARCH_HAS_PKEYS */
 	};
 	size_t i;

include/linux/mm.h

@@ -231,9 +231,14 @@ extern unsigned int kobjsize(const void *objp);
 #ifdef CONFIG_ARCH_HAS_PKEYS
 # define VM_PKEY_SHIFT	VM_HIGH_ARCH_BIT_0
 # define VM_PKEY_BIT0	VM_HIGH_ARCH_0	/* A protection key is a 4-bit value */
-# define VM_PKEY_BIT1	VM_HIGH_ARCH_1
+# define VM_PKEY_BIT1	VM_HIGH_ARCH_1	/* on x86 and 5-bit value on ppc64   */
 # define VM_PKEY_BIT2	VM_HIGH_ARCH_2
 # define VM_PKEY_BIT3	VM_HIGH_ARCH_3
+#ifdef CONFIG_PPC
+# define VM_PKEY_BIT4  VM_HIGH_ARCH_4
+#else
+# define VM_PKEY_BIT4  0
+#endif
 #endif /* CONFIG_ARCH_HAS_PKEYS */
 
 #if defined(CONFIG_X86)