v4.19.13 snapshot.
diff --git a/arch/sh/include/asm/futex.h b/arch/sh/include/asm/futex.h
new file mode 100644
index 0000000..6d192f4
--- /dev/null
+++ b/arch/sh/include/asm/futex.h
@@ -0,0 +1,79 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ASM_SH_FUTEX_H
+#define __ASM_SH_FUTEX_H
+
+#ifdef __KERNEL__
+
+#include <linux/futex.h>
+#include <linux/uaccess.h>
+#include <asm/errno.h>
+
+#if !defined(CONFIG_SMP)
+#include <asm/futex-irq.h>
+#elif defined(CONFIG_CPU_J2)
+#include <asm/futex-cas.h>
+#elif defined(CONFIG_CPU_SH4A)
+#include <asm/futex-llsc.h>
+#else
+#error SMP not supported on this configuration.
+#endif
+
+static inline int
+futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
+ u32 oldval, u32 newval)
+{
+ if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))
+ return -EFAULT;
+
+ return atomic_futex_op_cmpxchg_inatomic(uval, uaddr, oldval, newval);
+}
+
+static inline int arch_futex_atomic_op_inuser(int op, u32 oparg, int *oval,
+ u32 __user *uaddr)
+{
+ u32 oldval, newval, prev;
+ int ret;
+
+ pagefault_disable();
+
+ do {
+ ret = get_user(oldval, uaddr);
+
+ if (ret) break;
+
+ switch (op) {
+ case FUTEX_OP_SET:
+ newval = oparg;
+ break;
+ case FUTEX_OP_ADD:
+ newval = oldval + oparg;
+ break;
+ case FUTEX_OP_OR:
+ newval = oldval | oparg;
+ break;
+ case FUTEX_OP_ANDN:
+ newval = oldval & ~oparg;
+ break;
+ case FUTEX_OP_XOR:
+ newval = oldval ^ oparg;
+ break;
+ default:
+ ret = -ENOSYS;
+ break;
+ }
+
+ if (ret) break;
+
+ ret = futex_atomic_cmpxchg_inatomic(&prev, uaddr, oldval, newval);
+ } while (!ret && prev != oldval);
+
+ pagefault_enable();
+
+ if (!ret)
+ *oval = oldval;
+
+ return ret;
+}
+
+#endif /* __KERNEL__ */
+#endif /* __ASM_SH_FUTEX_H */