v4.19.13 snapshot.
diff --git a/include/asm-generic/futex.h b/include/asm-generic/futex.h
new file mode 100644
index 0000000..fcb61b4
--- /dev/null
+++ b/include/asm-generic/futex.h
@@ -0,0 +1,147 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_GENERIC_FUTEX_H
+#define _ASM_GENERIC_FUTEX_H
+
+#include <linux/futex.h>
+#include <linux/uaccess.h>
+#include <asm/errno.h>
+
+#ifndef CONFIG_SMP
+/*
+ * The following implementation only for uniprocessor machines.
+ * It relies on preempt_disable() ensuring mutual exclusion.
+ *
+ */
+
+/**
+ * arch_futex_atomic_op_inuser() - Atomic arithmetic operation with constant
+ * argument and comparison of the previous
+ * futex value with another constant.
+ *
+ * @encoded_op: encoded operation to execute
+ * @uaddr: pointer to user space address
+ *
+ * Return:
+ * 0 - On success
+ * <0 - On error
+ */
+static inline int
+arch_futex_atomic_op_inuser(int op, u32 oparg, int *oval, u32 __user *uaddr)
+{
+ int oldval, ret;
+ u32 tmp;
+
+ preempt_disable();
+ pagefault_disable();
+
+ ret = -EFAULT;
+ if (unlikely(get_user(oldval, uaddr) != 0))
+ goto out_pagefault_enable;
+
+ ret = 0;
+ tmp = oldval;
+
+ switch (op) {
+ case FUTEX_OP_SET:
+ tmp = oparg;
+ break;
+ case FUTEX_OP_ADD:
+ tmp += oparg;
+ break;
+ case FUTEX_OP_OR:
+ tmp |= oparg;
+ break;
+ case FUTEX_OP_ANDN:
+ tmp &= ~oparg;
+ break;
+ case FUTEX_OP_XOR:
+ tmp ^= oparg;
+ break;
+ default:
+ ret = -ENOSYS;
+ }
+
+ if (ret == 0 && unlikely(put_user(tmp, uaddr) != 0))
+ ret = -EFAULT;
+
+out_pagefault_enable:
+ pagefault_enable();
+ preempt_enable();
+
+ if (ret == 0)
+ *oval = oldval;
+
+ return ret;
+}
+
+/**
+ * futex_atomic_cmpxchg_inatomic() - Compare and exchange the content of the
+ * uaddr with newval if the current value is
+ * oldval.
+ * @uval: pointer to store content of @uaddr
+ * @uaddr: pointer to user space address
+ * @oldval: old value
+ * @newval: new value to store to @uaddr
+ *
+ * Return:
+ * 0 - On success
+ * <0 - On error
+ */
+static inline int
+futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
+ u32 oldval, u32 newval)
+{
+ u32 val;
+
+ preempt_disable();
+ if (unlikely(get_user(val, uaddr) != 0)) {
+ preempt_enable();
+ return -EFAULT;
+ }
+
+ if (val == oldval && unlikely(put_user(newval, uaddr) != 0)) {
+ preempt_enable();
+ return -EFAULT;
+ }
+
+ *uval = val;
+ preempt_enable();
+
+ return 0;
+}
+
+#else
+static inline int
+arch_futex_atomic_op_inuser(int op, u32 oparg, int *oval, u32 __user *uaddr)
+{
+ int oldval = 0, ret;
+
+ pagefault_disable();
+
+ switch (op) {
+ case FUTEX_OP_SET:
+ case FUTEX_OP_ADD:
+ case FUTEX_OP_OR:
+ case FUTEX_OP_ANDN:
+ case FUTEX_OP_XOR:
+ default:
+ ret = -ENOSYS;
+ }
+
+ pagefault_enable();
+
+ if (!ret)
+ *oval = oldval;
+
+ return ret;
+}
+
+static inline int
+futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
+ u32 oldval, u32 newval)
+{
+ return -ENOSYS;
+}
+
+#endif /* CONFIG_SMP */
+#endif