Subject: [patch V5 11/12] x86/futex: Convert to scoped user access

From: Thomas Gleixner <[email-masked]>
Date: Mon, 27 Oct 2025 09:44:02 +0100 (CET)

Replace the open coded implementation with the scoped user access
guards

No functional change intended.

Signed-off-by: Thomas Gleixner <[email-masked]>
Cc: [email-masked]
---
V4: Rename once more
    Use asm_inline - Andrew
V3: Adapt to scope changes
V2: Convert to scoped masked access
    Use RW access functions - Christophe
---
 arch/x86/include/asm/futex.h |   75 ++++++++++++++++++-------------------------
 1 file changed, 33 insertions(+), 42 deletions(-)
---
--- a/arch/x86/include/asm/futex.h
+++ b/arch/x86/include/asm/futex.h
@@ -46,38 +46,31 @@ do {								\
 } while(0)
 
 static __always_inline int arch_futex_atomic_op_inuser(int op, int oparg, int *oval,
-		u32 __user *uaddr)
+						       u32 __user *uaddr)
 {
-	if (can_do_masked_user_access())
-		uaddr = masked_user_access_begin(uaddr);
-	else if (!user_access_begin(uaddr, sizeof(u32)))
-		return -EFAULT;
-
-	switch (op) {
-	case FUTEX_OP_SET:
-		unsafe_atomic_op1("xchgl %0, %2", oval, uaddr, oparg, Efault);
-		break;
-	case FUTEX_OP_ADD:
-		unsafe_atomic_op1(LOCK_PREFIX "xaddl %0, %2", oval,
-				   uaddr, oparg, Efault);
-		break;
-	case FUTEX_OP_OR:
-		unsafe_atomic_op2("orl %4, %3", oval, uaddr, oparg, Efault);
-		break;
-	case FUTEX_OP_ANDN:
-		unsafe_atomic_op2("andl %4, %3", oval, uaddr, ~oparg, Efault);
-		break;
-	case FUTEX_OP_XOR:
-		unsafe_atomic_op2("xorl %4, %3", oval, uaddr, oparg, Efault);
-		break;
-	default:
-		user_access_end();
-		return -ENOSYS;
+	scoped_user_rw_access(uaddr, Efault) {
+		switch (op) {
+		case FUTEX_OP_SET:
+			unsafe_atomic_op1("xchgl %0, %2", oval, uaddr, oparg, Efault);
+			break;
+		case FUTEX_OP_ADD:
+			unsafe_atomic_op1(LOCK_PREFIX "xaddl %0, %2", oval, uaddr, oparg, Efault);
+			break;
+		case FUTEX_OP_OR:
+			unsafe_atomic_op2("orl %4, %3", oval, uaddr, oparg, Efault);
+			break;
+		case FUTEX_OP_ANDN:
+			unsafe_atomic_op2("andl %4, %3", oval, uaddr, ~oparg, Efault);
+			break;
+		case FUTEX_OP_XOR:
+			unsafe_atomic_op2("xorl %4, %3", oval, uaddr, oparg, Efault);
+			break;
+		default:
+			return -ENOSYS;
+		}
 	}
-	user_access_end();
 	return 0;
 Efault:
-	user_access_end();
 	return -EFAULT;
 }
 
@@ -86,21 +79,19 @@ static inline int futex_atomic_cmpxchg_i
 {
 	int ret = 0;
 
-	if (can_do_masked_user_access())
-		uaddr = masked_user_access_begin(uaddr);
-	else if (!user_access_begin(uaddr, sizeof(u32)))
-		return -EFAULT;
-	asm volatile("\n"
-		"1:\t" LOCK_PREFIX "cmpxchgl %3, %2\n"
-		"2:\n"
-		_ASM_EXTABLE_TYPE_REG(1b, 2b, EX_TYPE_EFAULT_REG, %0) \
-		: "+r" (ret), "=a" (oldval), "+m" (*uaddr)
-		: "r" (newval), "1" (oldval)
-		: "memory"
-	);
-	user_access_end();
-	*uval = oldval;
+	scoped_user_rw_access(uaddr, Efault) {
+		asm_inline volatile("\n"
+				    "1:\t" LOCK_PREFIX "cmpxchgl %3, %2\n"
+				    "2:\n"
+				    _ASM_EXTABLE_TYPE_REG(1b, 2b, EX_TYPE_EFAULT_REG, %0)
+				    : "+r" (ret), "=a" (oldval), "+m" (*uaddr)
+				    : "r" (newval), "1" (oldval)
+				    : "memory");
+		*uval = oldval;
+	}
 	return ret;
+Efault:
+	return -EFAULT;
 }
 
 #endif