From 583a1da34888c6b300de1ddc61f4c8e60e782e90 Mon Sep 17 00:00:00 2001
From: Teufelchen1 <bennet.blischke@outlook.com>
Date: Fri, 19 May 2023 11:08:08 +0200
Subject: [PATCH] cpu/arm7: Fix undefined behavior based on invalid assembly

---
 cpu/arm7_common/common.s | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/cpu/arm7_common/common.s b/cpu/arm7_common/common.s
index 1df52e62d5..6094742cac 100644
--- a/cpu/arm7_common/common.s
+++ b/cpu/arm7_common/common.s
@@ -101,6 +101,10 @@ task_return:
 
     /* Restore all registers, PC & cpsr */
     ldmfd   r0, {r0-lr}^
+    /* According to ARM Architecture Reference Manual DDI 0100I,
+     * ldms which affect banked registers must be followed by a nop.
+     */
+    nop
 
     /* return to task */
     movs pc, lr