1 files changed, 53 insertions, 1 deletions

diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c
index 5346953e4382..9d3588450473 100644
--- a/arch/arm64/kernel/entry-common.c
+++ b/arch/arm64/kernel/entry-common.c
@@ -109,6 +109,55 @@ asmlinkage void noinstr exit_el1_irq_or_nmi(struct pt_regs *regs)
 		exit_to_kernel_mode(regs);
 }
 
+#ifdef CONFIG_ARM64_ERRATUM_1463225
+static DEFINE_PER_CPU(int, __in_cortex_a76_erratum_1463225_wa);
+
+static void cortex_a76_erratum_1463225_svc_handler(void)
+{
+	u32 reg, val;
+
+	if (!unlikely(test_thread_flag(TIF_SINGLESTEP)))
+		return;
+
+	if (!unlikely(this_cpu_has_cap(ARM64_WORKAROUND_1463225)))
+		return;
+
+	__this_cpu_write(__in_cortex_a76_erratum_1463225_wa, 1);
+	reg = read_sysreg(mdscr_el1);
+	val = reg | DBG_MDSCR_SS | DBG_MDSCR_KDE;
+	write_sysreg(val, mdscr_el1);
+	asm volatile("msr daifclr, #8");
+	isb();
+
+	/* We will have taken a single-step exception by this point */
+
+	write_sysreg(reg, mdscr_el1);
+	__this_cpu_write(__in_cortex_a76_erratum_1463225_wa, 0);
+}
+
+static bool cortex_a76_erratum_1463225_debug_handler(struct pt_regs *regs)
+{
+	if (!__this_cpu_read(__in_cortex_a76_erratum_1463225_wa))
+		return false;
+
+	/*
+	 * We've taken a dummy step exception from the kernel to ensure
+	 * that interrupts are re-enabled on the syscall path. Return back
+	 * to cortex_a76_erratum_1463225_svc_handler() with debug exceptions
+	 * masked so that we can safely restore the mdscr and get on with
+	 * handling the syscall.
+	 */
+	regs->pstate |= PSR_D_BIT;
+	return true;
+}
+#else /* CONFIG_ARM64_ERRATUM_1463225 */
+static void cortex_a76_erratum_1463225_svc_handler(void) { }
+static bool cortex_a76_erratum_1463225_debug_handler(struct pt_regs *regs)
+{
+	return false;
+}
+#endif /* CONFIG_ARM64_ERRATUM_1463225 */
+
 static void noinstr el1_abort(struct pt_regs *regs, unsigned long esr)
 {
 	unsigned long far = read_sysreg(far_el1);
@@ -186,7 +235,8 @@ static void noinstr el1_dbg(struct pt_regs *regs, unsigned long esr)
 		gic_write_pmr(GIC_PRIO_IRQON | GIC_PRIO_PSR_I_SET);
 
 	arm64_enter_el1_dbg(regs);
-	do_debug_exception(far, esr, regs);
+	if (!cortex_a76_erratum_1463225_debug_handler(regs))
+		do_debug_exception(far, esr, regs);
 	arm64_exit_el1_dbg(regs);
 }
 
@@ -362,6 +412,7 @@ static void noinstr el0_svc(struct pt_regs *regs)
 		gic_write_pmr(GIC_PRIO_IRQON | GIC_PRIO_PSR_I_SET);
 
 	enter_from_user_mode();
+	cortex_a76_erratum_1463225_svc_handler();
 	do_el0_svc(regs);
 }
 
@@ -439,6 +490,7 @@ static void noinstr el0_svc_compat(struct pt_regs *regs)
 		gic_write_pmr(GIC_PRIO_IRQON | GIC_PRIO_PSR_I_SET);
 
 	enter_from_user_mode();
+	cortex_a76_erratum_1463225_svc_handler();
 	do_el0_svc_compat(regs);
 }