v4.19.13 snapshot.
diff --git a/arch/x86/include/asm/futex.h b/arch/x86/include/asm/futex.h
new file mode 100644
index 0000000..de4d688
--- /dev/null
+++ b/arch/x86/include/asm/futex.h
@@ -0,0 +1,88 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_X86_FUTEX_H
+#define _ASM_X86_FUTEX_H
+
+#ifdef __KERNEL__
+
+#include <linux/futex.h>
+#include <linux/uaccess.h>
+
+#include <asm/asm.h>
+#include <asm/errno.h>
+#include <asm/processor.h>
+#include <asm/smap.h>
+
+#define __futex_atomic_op1(insn, ret, oldval, uaddr, oparg) \
+ asm volatile("\t" ASM_STAC "\n" \
+ "1:\t" insn "\n" \
+ "2:\t" ASM_CLAC "\n" \
+ "\t.section .fixup,\"ax\"\n" \
+ "3:\tmov\t%3, %1\n" \
+ "\tjmp\t2b\n" \
+ "\t.previous\n" \
+ _ASM_EXTABLE(1b, 3b) \
+ : "=r" (oldval), "=r" (ret), "+m" (*uaddr) \
+ : "i" (-EFAULT), "0" (oparg), "1" (0))
+
+#define __futex_atomic_op2(insn, ret, oldval, uaddr, oparg) \
+ asm volatile("\t" ASM_STAC "\n" \
+ "1:\tmovl %2, %0\n" \
+ "\tmovl\t%0, %3\n" \
+ "\t" insn "\n" \
+ "2:\t" LOCK_PREFIX "cmpxchgl %3, %2\n" \
+ "\tjnz\t1b\n" \
+ "3:\t" ASM_CLAC "\n" \
+ "\t.section .fixup,\"ax\"\n" \
+ "4:\tmov\t%5, %1\n" \
+ "\tjmp\t3b\n" \
+ "\t.previous\n" \
+ _ASM_EXTABLE(1b, 4b) \
+ _ASM_EXTABLE(2b, 4b) \
+ : "=&a" (oldval), "=&r" (ret), \
+ "+m" (*uaddr), "=&r" (tem) \
+ : "r" (oparg), "i" (-EFAULT), "1" (0))
+
+static inline int arch_futex_atomic_op_inuser(int op, int oparg, int *oval,
+ u32 __user *uaddr)
+{
+ int oldval = 0, ret, tem;
+
+ pagefault_disable();
+
+ switch (op) {
+ case FUTEX_OP_SET:
+ __futex_atomic_op1("xchgl %0, %2", ret, oldval, uaddr, oparg);
+ break;
+ case FUTEX_OP_ADD:
+ __futex_atomic_op1(LOCK_PREFIX "xaddl %0, %2", ret, oldval,
+ uaddr, oparg);
+ break;
+ case FUTEX_OP_OR:
+ __futex_atomic_op2("orl %4, %3", ret, oldval, uaddr, oparg);
+ break;
+ case FUTEX_OP_ANDN:
+ __futex_atomic_op2("andl %4, %3", ret, oldval, uaddr, ~oparg);
+ break;
+ case FUTEX_OP_XOR:
+ __futex_atomic_op2("xorl %4, %3", ret, oldval, uaddr, oparg);
+ break;
+ 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 user_atomic_cmpxchg_inatomic(uval, uaddr, oldval, newval);
+}
+
+#endif
+#endif /* _ASM_X86_FUTEX_H */