diff --git a/Documentation/arm64/legacy_instructions.txt b/Documentation/arm64/legacy_instructions.txt
new file mode 100644
index 0000000000000000000000000000000000000000..49d4867c0c09e5603031384ad96ecb899a576378
--- /dev/null
+++ b/Documentation/arm64/legacy_instructions.txt
@@ -0,0 +1,33 @@
+The arm64 port of the Linux kernel provides infrastructure to support
+emulation of instructions which have been deprecated, or obsoleted in
+the architecture. The infrastructure code uses undefined instruction
+hooks to support emulation. Where available it also allows turning on
+the instruction execution in hardware.
+
+The emulation mode can be controlled by writing to sysctl nodes
+(/proc/sys/abi). The following explains the different execution
+behaviours and the corresponding values of the sysctl nodes -
+
+* Undef
+ Value: 0
+ Generates undefined instruction abort. Default for instructions that
+ have been obsoleted in the architecture, e.g., SWP
+
+* Emulate
+ Value: 1
+ Uses software emulation. To aid migration of software, in this mode
+ usage of emulated instruction is traced as well as rate limited
+ warnings are issued. This is the default for deprecated
+ instructions, .e.g., CP15 barriers
+
+* Hardware Execution
+ Value: 2
+ Although marked as deprecated, some implementations may support the
+ enabling/disabling of hardware support for the execution of these
+ instructions. Using hardware execution generally provides better
+ performance, but at the loss of ability to gather runtime statistics
+ about the use of the deprecated instructions.
+
+The default mode depends on the status of the instruction in the
+architecture. Deprecated instructions should default to emulation
+while obsolete instructions must be undefined by default.
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 1e0e4671dd2583b6cf586f6048308949f0cf66f8..aa8f4bea373869d878e72ba9eb4aceab365b026f 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -164,6 +164,24 @@ config ARCH_XGENE
help
This enables support for AppliedMicro X-Gene SOC Family
+comment "Processor Features"
+
+menuconfig ARMV8_DEPRECATED
+ bool "Emulate deprecated/obsolete ARMv8 instructions"
+ depends on COMPAT
+ help
+ Legacy software support may require certain instructions
+ that have been deprecated or obsoleted in the architecture.
+
+ Enable this config to enable selective emulation of these
+ features.
+
+ If unsure, say Y
+
+if ARMV8_DEPRECATED
+
+endif
+
endmenu
menu "Bus support"
diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
index a4d8671d6d111d55c4e05a90520aebab04ff91a5..84e9e5153efe73e10b8098f3e8a1611c2a500e23 100644
--- a/arch/arm64/kernel/Makefile
+++ b/arch/arm64/kernel/Makefile
@@ -32,6 +32,7 @@ arm64-obj-$(CONFIG_JUMP_LABEL) += jump_label.o
arm64-obj-$(CONFIG_KGDB) += kgdb.o
arm64-obj-$(CONFIG_EFI) += efi.o efi-stub.o efi-entry.o
arm64-obj-$(CONFIG_PCI) += pci.o
+arm64-obj-$(CONFIG_ARMV8_DEPRECATED) += armv8_deprecated.o
obj-y += $(arm64-obj-y) vdso/
obj-m += $(arm64-obj-m)
diff --git a/arch/arm64/kernel/armv8_deprecated.c b/arch/arm64/kernel/armv8_deprecated.c
new file mode 100644
index 0000000000000000000000000000000000000000..db3b79da6a4809773f9f41bde35fd31ff285abcc
--- /dev/null
+++ b/arch/arm64/kernel/armv8_deprecated.c
@@ -0,0 +1,216 @@
+/*
+ * Copyright (C) 2014 ARM Limited
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/init.h>
+#include <linux/list.h>
+#include <linux/slab.h>
+#include <linux/sysctl.h>
+
+#include <asm/traps.h>
+
+/*
+ * The runtime support for deprecated instruction support can be in one of
+ * following three states -
+ *
+ * 0 = undef
+ * 1 = emulate (software emulation)
+ * 2 = hw (supported in hardware)
+ */
+enum insn_emulation_mode {
+ INSN_UNDEF,
+ INSN_EMULATE,
+ INSN_HW,
+};
+
+enum legacy_insn_status {
+ INSN_DEPRECATED,
+ INSN_OBSOLETE,
+};
+
+struct insn_emulation_ops {
+ const char *name;
+ enum legacy_insn_status status;
+ struct undef_hook *hooks;
+ int (*set_hw_mode)(bool enable);
+};
+
+struct insn_emulation {
+ struct list_head node;
+ struct insn_emulation_ops *ops;
+ int current_mode;
+ int min;
+ int max;
+};
+
+static LIST_HEAD(insn_emulation);
+static int nr_insn_emulated;
+static DEFINE_RAW_SPINLOCK(insn_emulation_lock);
+
+static void register_emulation_hooks(struct insn_emulation_ops *ops)
+{
+ struct undef_hook *hook;
+
+ BUG_ON(!ops->hooks);
+
+ for (hook = ops->hooks; hook->instr_mask; hook++)
+ register_undef_hook(hook);
+
+ pr_notice("Registered %s emulation handler\n", ops->name);
+}
+
+static void remove_emulation_hooks(struct insn_emulation_ops *ops)
+{
+ struct undef_hook *hook;
+
+ BUG_ON(!ops->hooks);
+
+ for (hook = ops->hooks; hook->instr_mask; hook++)
+ unregister_undef_hook(hook);
+
+ pr_notice("Removed %s emulation handler\n", ops->name);
+}
+
+static int update_insn_emulation_mode(struct insn_emulation *insn,
+ enum insn_emulation_mode prev)
+{
+ int ret = 0;
+
+ switch (prev) {
+ case INSN_UNDEF: /* Nothing to be done */
+ break;
+ case INSN_EMULATE:
+ remove_emulation_hooks(insn->ops);
+ break;
+ case INSN_HW:
+ if (insn->ops->set_hw_mode) {
+ insn->ops->set_hw_mode(false);
+ pr_notice("Disabled %s support\n", insn->ops->name);
+ }
+ break;
+ }
+
+ switch (insn->current_mode) {
+ case INSN_UNDEF:
+ break;
+ case INSN_EMULATE:
+ register_emulation_hooks(insn->ops);
+ break;
+ case INSN_HW:
+ if (insn->ops->set_hw_mode && insn->ops->set_hw_mode(true))
+ pr_notice("Enabled %s support\n", insn->ops->name);
+ else
+ ret = -EINVAL;
+ break;
+ }
+
+ return ret;
+}
+
+static void register_insn_emulation(struct insn_emulation_ops *ops)
+{
+ unsigned long flags;
+ struct insn_emulation *insn;
+
+ insn = kzalloc(sizeof(*insn), GFP_KERNEL);
+ insn->ops = ops;
+ insn->min = INSN_UNDEF;
+
+ switch (ops->status) {
+ case INSN_DEPRECATED:
+ insn->current_mode = INSN_EMULATE;
+ insn->max = INSN_HW;
+ break;
+ case INSN_OBSOLETE:
+ insn->current_mode = INSN_UNDEF;
+ insn->max = INSN_EMULATE;
+ break;
+ }
+
+ raw_spin_lock_irqsave(&insn_emulation_lock, flags);
+ list_add(&insn->node, &insn_emulation);
+ nr_insn_emulated++;
+ raw_spin_unlock_irqrestore(&insn_emulation_lock, flags);
+
+ /* Register any handlers if required */
+ update_insn_emulation_mode(insn, INSN_UNDEF);
+}
+
+static int emulation_proc_handler(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp,
+ loff_t *ppos)
+{
+ int ret = 0;
+ struct insn_emulation *insn = (struct insn_emulation *) table->data;
+ enum insn_emulation_mode prev_mode = insn->current_mode;
+
+ table->data = &insn->current_mode;
+ ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
+
+ if (ret || !write || prev_mode == insn->current_mode)
+ goto ret;
+
+ ret = update_insn_emulation_mode(insn, prev_mode);
+ if (!ret) {
+ /* Mode change failed, revert to previous mode. */
+ insn->current_mode = prev_mode;
+ update_insn_emulation_mode(insn, INSN_UNDEF);
+ }
+ret:
+ table->data = insn;
+ return ret;
+}
+
+static struct ctl_table ctl_abi[] = {
+ {
+ .procname = "abi",
+ .mode = 0555,
+ },
+ { }
+};
+
+static void register_insn_emulation_sysctl(struct ctl_table *table)
+{
+ unsigned long flags;
+ int i = 0;
+ struct insn_emulation *insn;
+ struct ctl_table *insns_sysctl, *sysctl;
+
+ insns_sysctl = kzalloc(sizeof(*sysctl) * (nr_insn_emulated + 1),
+ GFP_KERNEL);
+
+ raw_spin_lock_irqsave(&insn_emulation_lock, flags);
+ list_for_each_entry(insn, &insn_emulation, node) {
+ sysctl = &insns_sysctl[i];
+
+ sysctl->mode = 0644;
+ sysctl->maxlen = sizeof(int);
+
+ sysctl->procname = insn->ops->name;
+ sysctl->data = insn;
+ sysctl->extra1 = &insn->min;
+ sysctl->extra2 = &insn->max;
+ sysctl->proc_handler = emulation_proc_handler;
+ i++;
+ }
+ raw_spin_unlock_irqrestore(&insn_emulation_lock, flags);
+
+ table->child = insns_sysctl;
+ register_sysctl_table(table);
+}
+
+/*
+ * Invoked as late_initcall, since not needed before init spawned.
+ */
+static int __init armv8_deprecated_init(void)
+{
+ register_insn_emulation_sysctl(ctl_abi);
+
+ return 0;
+}
+
+late_initcall(armv8_deprecated_init);