[patch V3 11/12] x86/futex: Convert to scoped masked user access

[Andrew Cooper]

On 17/10/2025 11:09 am, Thomas Gleixner wrote:
> @@ -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_masked_user_rw_access(uaddr, 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");

Minor points, but as you're rewriting this, it wants to be asm_inline
volatile.

There's also a useless line continuation on the end of the ASM_EXTABLE
which can be dropped.

~Andrew