[patch V4 10/12] futex: Convert to scoped user access

Thomas Gleixner
2025-10-22T12:49:18Z

From: Thomas Gleixner <tglx@linutronix.de>

Replace the open coded implementation with the new get/put_user_scoped()
helpers.

No functional change intended

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Darren Hart <dvhart@infradead.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: "André Almeida" <andrealmeid@igalia.com>
---
V4: Rename once moar
V3: Adapt to scope changes
V2: Convert to scoped variant
---
kernel/futex/futex.h | 37 ++-----------------------------------
1 file changed, 2 insertions(+), 35 deletions(-)
---
--- a/kernel/futex/futex.h
+++ b/kernel/futex/futex.h
@@ -285,48 +285,15 @@ static inline int futex_cmpxchg_value_lo
* This does a plain atomic user space read, and the user pointer has
* already been verified earlier by get_futex_key() to be both aligned
* and actually in user space, just like futex_atomic_cmpxchg_inatomic().
- *
- * We still want to avoid any speculation, and while __get_user() is
- * the traditional model for this, it's actually slower than doing
- * this manually these days.
- *
- * We could just have a per-architecture special function for it,
- * the same way we do futex_atomic_cmpxchg_inatomic(), but rather
- * than force everybody to do that, write it out long-hand using
- * the low-level user-access infrastructure.
- *
- * This looks a bit overkill, but generally just results in a couple
- * of instructions.
*/
static __always_inline int futex_get_value(u32 *dest, u32 __user *from)
{
- u32 val;
-
- if (can_do_masked_user_access())
- from = masked_user_access_begin(from);
- else if (!user_read_access_begin(from, sizeof(*from)))
- return -EFAULT;
- unsafe_get_user(val, from, Efault);
- user_read_access_end();
- *dest = val;
- return 0;
-Efault:
- user_read_access_end();
- return -EFAULT;
+ return get_user_scoped(*dest, from) ? 0 : -EFAULT;
}

static __always_inline int futex_put_value(u32 val, u32 __user *to)
{
- if (can_do_masked_user_access())
- to = masked_user_access_begin(to);
- else if (!user_write_access_begin(to, sizeof(*to)))
- return -EFAULT;
- unsafe_put_user(val, to, Efault);
- user_write_access_end();
- return 0;
-Efault:
- user_write_access_end();
- return -EFAULT;
+ return put_user_scoped(val, to) ? 0 : -EFAULT;
}

static inline int futex_get_value_locked(u32 *dest, u32 __user *from)