mm: use ARCH_PKEY_BITS to define VM_PKEY_BITN

Use the new CONFIG_ARCH_PKEY_BITS to simplify setting these bits
for different architectures.
Signed-off-by: Joey Gouly <joey.gouly@arm.com>

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-fsdevel@vger.kernel.org
Cc: linux-mm@kvack.org
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Link: https://lore.kernel.org/r/20240822151113.1479789-4-joey.gouly@arm.comSigned-off-by: Will Deacon <will@kernel.org>

fs/proc/task_mmu.c

@@ -976,7 +976,9 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma)
 		[ilog2(VM_PKEY_BIT0)]	= "",
 		[ilog2(VM_PKEY_BIT1)]	= "",
 		[ilog2(VM_PKEY_BIT2)]	= "",
+#if VM_PKEY_BIT3
 		[ilog2(VM_PKEY_BIT3)]	= "",
+#endif
 #if VM_PKEY_BIT4
 		[ilog2(VM_PKEY_BIT4)]	= "",
 #endif

include/linux/mm.h

@@ -331,11 +331,15 @@ 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	/* on x86 and 5-bit value on ppc64   */
+# define VM_PKEY_BIT0  VM_HIGH_ARCH_0
+# define VM_PKEY_BIT1  VM_HIGH_ARCH_1
 # define VM_PKEY_BIT2  VM_HIGH_ARCH_2
+#if CONFIG_ARCH_PKEY_BITS > 3
 # define VM_PKEY_BIT3  VM_HIGH_ARCH_3
-#ifdef CONFIG_PPC
+#else
+# define VM_PKEY_BIT3  0
+#endif
+#if CONFIG_ARCH_PKEY_BITS > 4
 # define VM_PKEY_BIT4  VM_HIGH_ARCH_4
 #else
 # define VM_PKEY_BIT4  0