selftests: vm: pkeys: add helpers for pkey bits

This introduces some functions that help with setting or clearing bits of
a particular pkey.  This also adds an abstraction for getting a pkey's bit
position in the pkey register as this may vary across architectures.

Signed-off-by: Sandipan Das <sandipan@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Dave Hansen <dave.hansen@intel.com>
Cc: "Desnes A. Nunes do Rosario" <desnesn@linux.vnet.ibm.com>
Cc: Florian Weimer <fweimer@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Ram Pai <linuxram@us.ibm.com>
Cc: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Michal Suchanek <msuchanek@suse.de>
Cc: Shuah Khan <shuah@kernel.org>
Link: http://lkml.kernel.org/r/2ad9705f4f68ca7e72155cc583415e5a979546f1.1585646528.git.sandipan@linux.ibm.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

tools/testing/selftests/vm/pkey-helpers.h

@@ -80,6 +80,28 @@ extern void abort_hooks(void);
 #error Architecture not supported
 #endif /* arch */
 
+#define PKEY_MASK	(PKEY_DISABLE_ACCESS | PKEY_DISABLE_WRITE)
+
+static inline u64 set_pkey_bits(u64 reg, int pkey, u64 flags)
+{
+	u32 shift = pkey_bit_position(pkey);
+	/* mask out bits from pkey in old value */
+	reg &= ~((u64)PKEY_MASK << shift);
+	/* OR in new bits for pkey */
+	reg |= (flags & PKEY_MASK) << shift;
+	return reg;
+}
+
+static inline u64 get_pkey_bits(u64 reg, int pkey)
+{
+	u32 shift = pkey_bit_position(pkey);
+	/*
+	 * shift down the relevant bits to the lowest two, then
+	 * mask off all the other higher bits
+	 */
+	return ((reg >> shift) & PKEY_MASK);
+}
+
 extern u64 shadow_pkey_reg;
 
 static inline u64 _read_pkey_reg(int line)

tools/testing/selftests/vm/pkey-x86.h

@@ -118,6 +118,11 @@ static inline int cpu_has_pku(void)
 	return 1;
 }
 
+static inline u32 pkey_bit_position(int pkey)
+{
+	return pkey * PKEY_BITS_PER_PKEY;
+}
+
 #define XSTATE_PKEY_BIT	(9)
 #define XSTATE_PKEY	0x200
 

tools/testing/selftests/vm/protection_keys.c

@@ -334,25 +334,13 @@ pid_t fork_lazy_child(void)
 
 static u32 hw_pkey_get(int pkey, unsigned long flags)
 {
-	u32 mask = (PKEY_DISABLE_ACCESS|PKEY_DISABLE_WRITE);
 	u64 pkey_reg = __read_pkey_reg();
-	u64 shifted_pkey_reg;
-	u32 masked_pkey_reg;
 
 	dprintf1("%s(pkey=%d, flags=%lx) = %x / %d\n",
 			__func__, pkey, flags, 0, 0);
 	dprintf2("%s() raw pkey_reg: %016llx\n", __func__, pkey_reg);
 
-	shifted_pkey_reg = (pkey_reg >> (pkey * PKEY_BITS_PER_PKEY));
+	return (u32) get_pkey_bits(pkey_reg, pkey);
-	dprintf2("%s() shifted_pkey_reg: %016llx\n", __func__,
-			shifted_pkey_reg);
-	masked_pkey_reg = shifted_pkey_reg & mask;
-	dprintf2("%s() masked  pkey_reg: %x\n", __func__, masked_pkey_reg);
-	/*
-	 * shift down the relevant bits to the lowest two, then
-	 * mask off all the other high bits.
-	 */
-	return masked_pkey_reg;
 }
 
 static int hw_pkey_set(int pkey, unsigned long rights, unsigned long flags)
@@ -364,12 +352,8 @@ static int hw_pkey_set(int pkey, unsigned long rights, unsigned long flags)
 	/* make sure that 'rights' only contains the bits we expect: */
 	assert(!(rights & ~mask));
 
-	/* copy old pkey_reg */
+	/* modify bits accordingly in old pkey_reg and assign it */
-	new_pkey_reg = old_pkey_reg;
+	new_pkey_reg = set_pkey_bits(old_pkey_reg, pkey, rights);
-	/* mask out bits from pkey in old value: */
-	new_pkey_reg &= ~(mask << (pkey * PKEY_BITS_PER_PKEY));
-	/* OR in new bits for pkey: */
-	new_pkey_reg |= (rights << (pkey * PKEY_BITS_PER_PKEY));
 
 	__write_pkey_reg(new_pkey_reg);
 
@@ -403,7 +387,7 @@ void pkey_disable_set(int pkey, int flags)
 	ret = hw_pkey_set(pkey, pkey_rights, syscall_flags);
 	assert(!ret);
 	/* pkey_reg and flags have the same format */
-	shadow_pkey_reg |= flags << (pkey * 2);
+	shadow_pkey_reg = set_pkey_bits(shadow_pkey_reg, pkey, pkey_rights);
 	dprintf1("%s(%d) shadow: 0x%016llx\n",
 		__func__, pkey, shadow_pkey_reg);
 
@@ -437,7 +421,7 @@ void pkey_disable_clear(int pkey, int flags)
 	pkey_rights |= flags;
 
 	ret = hw_pkey_set(pkey, pkey_rights, 0);
-	shadow_pkey_reg &= ~(flags << (pkey * 2));
+	shadow_pkey_reg = set_pkey_bits(shadow_pkey_reg, pkey, pkey_rights);
 	pkey_assert(ret >= 0);
 
 	pkey_rights = hw_pkey_get(pkey, syscall_flags);
@@ -513,7 +497,8 @@ int alloc_pkey(void)
 			shadow_pkey_reg);
 	if (ret) {
 		/* clear both the bits: */
-		shadow_pkey_reg &= ~(0x3      << (ret * 2));
+		shadow_pkey_reg = set_pkey_bits(shadow_pkey_reg, ret,
+						~PKEY_MASK);
 		dprintf4("%s()::%d, ret: %d pkey_reg: 0x%016llx"
 				" shadow: 0x%016llx\n",
 				__func__,
@@ -523,7 +508,8 @@ int alloc_pkey(void)
 		 * move the new state in from init_val
 		 * (remember, we cheated and init_val == pkey_reg format)
 		 */
-		shadow_pkey_reg |=  (init_val << (ret * 2));
+		shadow_pkey_reg = set_pkey_bits(shadow_pkey_reg, ret,
+						init_val);
 	}
 	dprintf4("%s()::%d, ret: %d pkey_reg: 0x%016llx"
 			" shadow: 0x%016llx\n",