powerpc/book3s64/pkeys: Convert pkey_total to num_pkey

num_pkey now represents max number of keys supported such that we return
to userspace 0 - num_pkey - 1.
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200709032946.881753-11-aneesh.kumar@linux.ibm.com

arch/powerpc/include/asm/pkeys.h

@@ -12,7 +12,7 @@
 #include <asm/firmware.h>
 
 DECLARE_STATIC_KEY_FALSE(pkey_disabled);
-extern int pkeys_total; /* total pkeys as per device tree */
+extern int num_pkey;
 extern u32 initial_allocation_mask; /*  bits set for the initially allocated keys */
 extern u32 reserved_allocation_mask; /* bits set for reserved keys */
 
@@ -44,7 +44,10 @@ static inline int vma_pkey(struct vm_area_struct *vma)
 	return (vma->vm_flags & ARCH_VM_PKEY_FLAGS) >> VM_PKEY_SHIFT;
 }
 
-#define arch_max_pkey() pkeys_total
+static inline int arch_max_pkey(void)
+{
+	return num_pkey;
+}
 
 #define pkey_alloc_mask(pkey) (0x1 << pkey)
 

arch/powerpc/mm/book3s64/pkeys.c

@@ -13,7 +13,7 @@
 #include <linux/of_device.h>
 
 DEFINE_STATIC_KEY_FALSE(pkey_disabled);
-int  pkeys_total;		/* Total pkeys as per device tree */
+int  num_pkey;		/* Max number of pkeys supported */
 u32  initial_allocation_mask;   /* Bits set for the initially allocated keys */
 /*
  *  Keys marked in the reservation list cannot be allocated by  userspace
@@ -93,7 +93,7 @@ static int scan_pkey_feature(void)
 
 static int pkey_initialize(void)
 {
-	int os_reserved, i;
+	int pkeys_total, i;
 
 	/*
 	 * We define PKEY_DISABLE_EXECUTE in addition to the arch-neutral
@@ -133,12 +133,12 @@ static int pkey_initialize(void)
 	 * The OS can manage only 8 pkeys due to its inability to represent them
 	 * in the Linux 4K PTE. Mark all other keys reserved.
 	 */
-	os_reserved = pkeys_total - 8;
+	num_pkey = min(8, pkeys_total);
 #else
-	os_reserved = 0;
+	num_pkey = pkeys_total;
 #endif
 
-	if (unlikely((pkeys_total - os_reserved) <= execute_only_key)) {
+	if (unlikely(num_pkey <= execute_only_key)) {
 		/*
 		 * Insufficient number of keys to support
 		 * execute only key. Mark it unavailable.
@@ -185,10 +185,10 @@ static int pkey_initialize(void)
 	default_uamor &= ~(0x3ul << pkeyshift(1));
 
 	/*
-	 * Prevent the usage of OS reserved the keys. Update UAMOR
+	 * Prevent the usage of OS reserved keys. Update UAMOR
 	 * for those keys.
 	 */
-	for (i = (pkeys_total - os_reserved); i < pkeys_total; i++) {
+	for (i = num_pkey; i < pkeys_total; i++) {
 		reserved_allocation_mask |= (0x1 << i);
 		default_uamor &= ~(0x3ul << pkeyshift(i));
 	}