v4.19.13 snapshot.
diff --git a/arch/arm/include/asm/futex.h b/arch/arm/include/asm/futex.h
new file mode 100644
index 0000000..ffebe7b
--- /dev/null
+++ b/arch/arm/include/asm/futex.h
@@ -0,0 +1,173 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_ARM_FUTEX_H
+#define _ASM_ARM_FUTEX_H
+
+#ifdef __KERNEL__
+
+#include <linux/futex.h>
+#include <linux/uaccess.h>
+#include <asm/errno.h>
+
+#define __futex_atomic_ex_table(err_reg) \
+ "3:\n" \
+ " .pushsection __ex_table,\"a\"\n" \
+ " .align 3\n" \
+ " .long 1b, 4f, 2b, 4f\n" \
+ " .popsection\n" \
+ " .pushsection .text.fixup,\"ax\"\n" \
+ " .align 2\n" \
+ "4: mov %0, " err_reg "\n" \
+ " b 3b\n" \
+ " .popsection"
+
+#ifdef CONFIG_SMP
+
+#define __futex_atomic_op(insn, ret, oldval, tmp, uaddr, oparg) \
+({ \
+ unsigned int __ua_flags; \
+ smp_mb(); \
+ prefetchw(uaddr); \
+ __ua_flags = uaccess_save_and_enable(); \
+ __asm__ __volatile__( \
+ "1: ldrex %1, [%3]\n" \
+ " " insn "\n" \
+ "2: strex %2, %0, [%3]\n" \
+ " teq %2, #0\n" \
+ " bne 1b\n" \
+ " mov %0, #0\n" \
+ __futex_atomic_ex_table("%5") \
+ : "=&r" (ret), "=&r" (oldval), "=&r" (tmp) \
+ : "r" (uaddr), "r" (oparg), "Ir" (-EFAULT) \
+ : "cc", "memory"); \
+ uaccess_restore(__ua_flags); \
+})
+
+static inline int
+futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
+ u32 oldval, u32 newval)
+{
+ unsigned int __ua_flags;
+ int ret;
+ u32 val;
+
+ if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))
+ return -EFAULT;
+
+ smp_mb();
+ /* Prefetching cannot fault */
+ prefetchw(uaddr);
+ __ua_flags = uaccess_save_and_enable();
+ __asm__ __volatile__("@futex_atomic_cmpxchg_inatomic\n"
+ "1: ldrex %1, [%4]\n"
+ " teq %1, %2\n"
+ " ite eq @ explicit IT needed for the 2b label\n"
+ "2: strexeq %0, %3, [%4]\n"
+ " movne %0, #0\n"
+ " teq %0, #0\n"
+ " bne 1b\n"
+ __futex_atomic_ex_table("%5")
+ : "=&r" (ret), "=&r" (val)
+ : "r" (oldval), "r" (newval), "r" (uaddr), "Ir" (-EFAULT)
+ : "cc", "memory");
+ uaccess_restore(__ua_flags);
+ smp_mb();
+
+ *uval = val;
+ return ret;
+}
+
+#else /* !SMP, we can work around lack of atomic ops by disabling preemption */
+
+#include <linux/preempt.h>
+#include <asm/domain.h>
+
+#define __futex_atomic_op(insn, ret, oldval, tmp, uaddr, oparg) \
+({ \
+ unsigned int __ua_flags = uaccess_save_and_enable(); \
+ __asm__ __volatile__( \
+ "1: " TUSER(ldr) " %1, [%3]\n" \
+ " " insn "\n" \
+ "2: " TUSER(str) " %0, [%3]\n" \
+ " mov %0, #0\n" \
+ __futex_atomic_ex_table("%5") \
+ : "=&r" (ret), "=&r" (oldval), "=&r" (tmp) \
+ : "r" (uaddr), "r" (oparg), "Ir" (-EFAULT) \
+ : "cc", "memory"); \
+ uaccess_restore(__ua_flags); \
+})
+
+static inline int
+futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
+ u32 oldval, u32 newval)
+{
+ unsigned int __ua_flags;
+ int ret = 0;
+ u32 val;
+
+ if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))
+ return -EFAULT;
+
+ preempt_disable();
+ __ua_flags = uaccess_save_and_enable();
+ __asm__ __volatile__("@futex_atomic_cmpxchg_inatomic\n"
+ "1: " TUSER(ldr) " %1, [%4]\n"
+ " teq %1, %2\n"
+ " it eq @ explicit IT needed for the 2b label\n"
+ "2: " TUSER(streq) " %3, [%4]\n"
+ __futex_atomic_ex_table("%5")
+ : "+r" (ret), "=&r" (val)
+ : "r" (oldval), "r" (newval), "r" (uaddr), "Ir" (-EFAULT)
+ : "cc", "memory");
+ uaccess_restore(__ua_flags);
+
+ *uval = val;
+ preempt_enable();
+
+ return ret;
+}
+
+#endif /* !SMP */
+
+static inline int
+arch_futex_atomic_op_inuser(int op, int oparg, int *oval, u32 __user *uaddr)
+{
+ int oldval = 0, ret, tmp;
+
+#ifndef CONFIG_SMP
+ preempt_disable();
+#endif
+ pagefault_disable();
+
+ switch (op) {
+ case FUTEX_OP_SET:
+ __futex_atomic_op("mov %0, %4", ret, oldval, tmp, uaddr, oparg);
+ break;
+ case FUTEX_OP_ADD:
+ __futex_atomic_op("add %0, %1, %4", ret, oldval, tmp, uaddr, oparg);
+ break;
+ case FUTEX_OP_OR:
+ __futex_atomic_op("orr %0, %1, %4", ret, oldval, tmp, uaddr, oparg);
+ break;
+ case FUTEX_OP_ANDN:
+ __futex_atomic_op("and %0, %1, %4", ret, oldval, tmp, uaddr, ~oparg);
+ break;
+ case FUTEX_OP_XOR:
+ __futex_atomic_op("eor %0, %1, %4", ret, oldval, tmp, uaddr, oparg);
+ break;
+ default:
+ ret = -ENOSYS;
+ }
+
+ pagefault_enable();
+#ifndef CONFIG_SMP
+ preempt_enable();
+#endif
+
+ if (!ret)
+ *oval = oldval;
+
+ return ret;
+}
+
+#endif /* __KERNEL__ */
+#endif /* _ASM_ARM_FUTEX_H */