feat(cpus): add sysreg_bit_toggle
Introduce a new helper to toggle bits in assembly. This allows us to
call the workaround twice, with the first call setting the workaround
and second undoing it. This allows the (errata) workaround functions to
be used to both apply and undo the mitigation.
This is applied to functions where the undo part will be required in
follow-up patches.
Change-Id: I058bad58f5949b2d5fe058101410e33b6be1b8ba
Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.com>
diff --git a/include/lib/cpus/aarch64/cpu_macros.S b/include/lib/cpus/aarch64/cpu_macros.S
index 0ce9c3c..ab60412 100644
--- a/include/lib/cpus/aarch64/cpu_macros.S
+++ b/include/lib/cpus/aarch64/cpu_macros.S
@@ -1,5 +1,5 @@
/*
- * Copyright (c) 2014-2024, Arm Limited and Contributors. All rights reserved.
+ * Copyright (c) 2014-2025, Arm Limited and Contributors. All rights reserved.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
@@ -402,6 +402,18 @@
msr \_reg, x1
.endm
+/*
+ * Toggle a bit in a system register. Can toggle multiple bits but is limited by
+ * the way the EOR instrucion encodes them.
+ *
+ * see sysreg_bit_set for usage
+ */
+.macro sysreg_bit_toggle _reg:req, _bit:req, _assert=1
+ mrs x1, \_reg
+ eor x1, x1, #\_bit
+ msr \_reg, x1
+.endm
+
.macro override_vector_table _table:req
adr x1, \_table
msr vbar_el3, x1