diff --git a/Documentation/arm64/legacy_instructions.txt b/Documentation/arm64/legacy_instructions.txt
index 5ab58614b7eddf75e5e9119d11fa4a80d0b73609..a3b3da2ec6edb4df31cfa10a773f2bf402715fdb 100644
--- a/Documentation/arm64/legacy_instructions.txt
+++ b/Documentation/arm64/legacy_instructions.txt
@@ -38,3 +38,8 @@ Supported legacy instructions
Node: /proc/sys/abi/swp
Status: Obsolete
Default: Undef (0)
+
+* CP15 Barriers
+Node: /proc/sys/abi/cp15_barrier
+Status: Deprecated
+Default: Emulate (1)
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 2b6213840ec86e2138e6a9a6bd3f1b603e991a1e..8e74dfe1e74da9d4e54f38d1614e97ae2092de39 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -201,6 +201,21 @@ config SWP_EMULATION
If unsure, say Y
+config CP15_BARRIER_EMULATION
+ bool "Emulate CP15 Barrier instructions"
+ help
+ The CP15 barrier instructions - CP15ISB, CP15DSB, and
+ CP15DMB - are deprecated in ARMv8 (and ARMv7). It is
+ strongly recommended to use the ISB, DSB, and DMB
+ instructions instead.
+
+ Say Y here to enable software emulation of these
+ instructions for AArch32 userspace code. When this option is
+ enabled, CP15 barrier usage is traced which can help
+ identify software that needs updating.
+
+ If unsure, say Y
+
endif
endmenu
diff --git a/arch/arm64/include/asm/insn.h b/arch/arm64/include/asm/insn.h
index 3ecc57c47c04ee9d5ccd03e98af8ae920a816efc..e2ff32a93b5cefc2c6fc2866d4d7befed27259fc 100644
--- a/arch/arm64/include/asm/insn.h
+++ b/arch/arm64/include/asm/insn.h
@@ -362,6 +362,8 @@ bool aarch32_insn_is_wide(u32 insn);
#define A32_RT2_OFFSET 0
u32 aarch32_insn_extract_reg_num(u32 insn, int offset);
+u32 aarch32_insn_mcr_extract_opc2(u32 insn);
+u32 aarch32_insn_mcr_extract_crm(u32 insn);
#endif /* __ASSEMBLY__ */
#endif /* __ASM_INSN_H */
diff --git a/arch/arm64/kernel/armv8_deprecated.c b/arch/arm64/kernel/armv8_deprecated.c
index 98865a7868f18fd2efb6c105501b384e2434dfc0..401c2e544ede4c7bf6207c8a899a4b8d31e7383a 100644
--- a/arch/arm64/kernel/armv8_deprecated.c
+++ b/arch/arm64/kernel/armv8_deprecated.c
@@ -6,6 +6,7 @@
* published by the Free Software Foundation.
*/
+#include <linux/cpu.h>
#include <linux/init.h>
#include <linux/list.h>
#include <linux/perf_event.h>
@@ -391,6 +392,133 @@ static struct insn_emulation_ops swp_ops = {
.set_hw_mode = NULL,
};
+static int cp15barrier_handler(struct pt_regs *regs, u32 instr)
+{
+ perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS, 1, regs, regs->pc);
+
+ switch (arm_check_condition(instr, regs->pstate)) {
+ case ARM_OPCODE_CONDTEST_PASS:
+ break;
+ case ARM_OPCODE_CONDTEST_FAIL:
+ /* Condition failed - return to next instruction */
+ goto ret;
+ case ARM_OPCODE_CONDTEST_UNCOND:
+ /* If unconditional encoding - not a barrier instruction */
+ return -EFAULT;
+ default:
+ return -EINVAL;
+ }
+
+ switch (aarch32_insn_mcr_extract_crm(instr)) {
+ case 10:
+ /*
+ * dmb - mcr p15, 0, Rt, c7, c10, 5
+ * dsb - mcr p15, 0, Rt, c7, c10, 4
+ */
+ if (aarch32_insn_mcr_extract_opc2(instr) == 5)
+ dmb(sy);
+ else
+ dsb(sy);
+ break;
+ case 5:
+ /*
+ * isb - mcr p15, 0, Rt, c7, c5, 4
+ *
+ * Taking an exception or returning from one acts as an
+ * instruction barrier. So no explicit barrier needed here.
+ */
+ break;
+ }
+
+ret:
+ pr_warn_ratelimited("\"%s\" (%ld) uses deprecated CP15 Barrier instruction at 0x%llx\n",
+ current->comm, (unsigned long)current->pid, regs->pc);
+
+ regs->pc += 4;
+ return 0;
+}
+
+#define SCTLR_EL1_CP15BEN (1 << 5)
+
+static inline void config_sctlr_el1(u32 clear, u32 set)
+{
+ u32 val;
+
+ asm volatile("mrs %0, sctlr_el1" : "=r" (val));
+ val &= ~clear;
+ val |= set;
+ asm volatile("msr sctlr_el1, %0" : : "r" (val));
+}
+
+static void enable_cp15_ben(void *info)
+{
+ config_sctlr_el1(0, SCTLR_EL1_CP15BEN);
+}
+
+static void disable_cp15_ben(void *info)
+{
+ config_sctlr_el1(SCTLR_EL1_CP15BEN, 0);
+}
+
+static int cpu_hotplug_notify(struct notifier_block *b,
+ unsigned long action, void *hcpu)
+{
+ switch (action) {
+ case CPU_STARTING:
+ case CPU_STARTING_FROZEN:
+ enable_cp15_ben(NULL);
+ return NOTIFY_DONE;
+ case CPU_DYING:
+ case CPU_DYING_FROZEN:
+ disable_cp15_ben(NULL);
+ return NOTIFY_DONE;
+ }
+
+ return NOTIFY_OK;
+}
+
+static struct notifier_block cpu_hotplug_notifier = {
+ .notifier_call = cpu_hotplug_notify,
+};
+
+static int cp15_barrier_set_hw_mode(bool enable)
+{
+ if (enable) {
+ register_cpu_notifier(&cpu_hotplug_notifier);
+ on_each_cpu(enable_cp15_ben, NULL, true);
+ } else {
+ unregister_cpu_notifier(&cpu_hotplug_notifier);
+ on_each_cpu(disable_cp15_ben, NULL, true);
+ }
+
+ return true;
+}
+
+static struct undef_hook cp15_barrier_hooks[] = {
+ {
+ .instr_mask = 0x0fff0fdf,
+ .instr_val = 0x0e070f9a,
+ .pstate_mask = COMPAT_PSR_MODE_MASK,
+ .pstate_val = COMPAT_PSR_MODE_USR,
+ .fn = cp15barrier_handler,
+ },
+ {
+ .instr_mask = 0x0fff0fff,
+ .instr_val = 0x0e070f95,
+ .pstate_mask = COMPAT_PSR_MODE_MASK,
+ .pstate_val = COMPAT_PSR_MODE_USR,
+ .fn = cp15barrier_handler,
+ },
+ { }
+};
+
+static struct insn_emulation_ops cp15_barrier_ops = {
+ .name = "cp15_barrier",
+ .status = INSN_DEPRECATED,
+ .hooks = cp15_barrier_hooks,
+ .set_hw_mode = cp15_barrier_set_hw_mode,
+};
+
/*
* Invoked as late_initcall, since not needed before init spawned.
*/
@@ -399,6 +527,9 @@ static int __init armv8_deprecated_init(void)
if (IS_ENABLED(CONFIG_SWP_EMULATION))
register_insn_emulation(&swp_ops);
+ if (IS_ENABLED(CONFIG_CP15_BARRIER_EMULATION))
+ register_insn_emulation(&cp15_barrier_ops);
+
register_insn_emulation_sysctl(ctl_abi);
return 0;
diff --git a/arch/arm64/kernel/insn.c b/arch/arm64/kernel/insn.c
index 63122dcd8524d2122984a032bbe4946e6769da67..819e409029ce5750fc11aa9337418fb804eed2f3 100644
--- a/arch/arm64/kernel/insn.c
+++ b/arch/arm64/kernel/insn.c
@@ -972,3 +972,16 @@ u32 aarch32_insn_extract_reg_num(u32 insn, int offset)
{
return (insn & (0xf << offset)) >> offset;
}
+
+#define OPC2_MASK 0x7
+#define OPC2_OFFSET 5
+u32 aarch32_insn_mcr_extract_opc2(u32 insn)
+{
+ return (insn & (OPC2_MASK << OPC2_OFFSET)) >> OPC2_OFFSET;
+}
+
+#define CRM_MASK 0xf
+u32 aarch32_insn_mcr_extract_crm(u32 insn)
+{
+ return insn & CRM_MASK;
+}