From 2c24e5b430cf67e3fb6e28bbc3b8911d0fd2c7b0 Mon Sep 17 00:00:00 2001
From: wanggang26 <wanggang26@xiaomi.com>
Date: Mon, 29 Jul 2024 13:45:26 +0800
Subject: [PATCH] arch/arm-m: Clear lr before jump to __start

to fix issue about https://github.com/apache/nuttx/issues/12687

Signed-off-by: wanggang26 <wanggang26@xiaomi.com>
---
 arch/arm/src/armv6-m/arm_vectors.c | 18 ++++++++++++++++--
 arch/arm/src/armv7-m/arm_vectors.c | 16 ++++++++++++++--
 arch/arm/src/armv8-m/arm_vectors.c | 16 ++++++++++++++--
 3 files changed, 44 insertions(+), 6 deletions(-)

diff --git a/arch/arm/src/armv6-m/arm_vectors.c b/arch/arm/src/armv6-m/arm_vectors.c
index eb4f27ebbd..8beb9443c1 100644
--- a/arch/arm/src/armv6-m/arm_vectors.c
+++ b/arch/arm/src/armv6-m/arm_vectors.c
@@ -57,13 +57,27 @@
 #endif
 
 /****************************************************************************
- * Public Functions
+ * Private Functions
  ****************************************************************************/
 
 /* Chip-specific entrypoint */
 
 extern void __start(void);
 
+static void start(void)
+{
+  /* Zero lr to mark the end of backtrace */
+
+  asm volatile ("mov lr, %0\n\t"
+                "bx      %1\n\t"
+                :
+                : "r"(0), "r"(__start));
+}
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
 /* Common exception entrypoint */
 
 extern void exception_common(void);
@@ -89,7 +103,7 @@ const void * const _vectors[] locate_data(".vectors") =
 
   /* Reset exception handler */
 
-  __start,
+  start,
 
   /* Vectors 2 - n point directly at the generic handler */
 
diff --git a/arch/arm/src/armv7-m/arm_vectors.c b/arch/arm/src/armv7-m/arm_vectors.c
index b5459ebd1d..c4674ab20f 100644
--- a/arch/arm/src/armv7-m/arm_vectors.c
+++ b/arch/arm/src/armv7-m/arm_vectors.c
@@ -49,13 +49,25 @@
 #define IDLE_STACK      (_ebss + CONFIG_IDLETHREAD_STACKSIZE)
 
 /****************************************************************************
- * Public Functions
+ * Private Functions
  ****************************************************************************/
 
 /* Chip-specific entrypoint */
 
 extern void __start(void);
 
+static void start(void)
+{
+  /* Zero lr to mark the end of backtrace */
+
+  asm volatile ("mov lr, #0\n\t"
+                "b  __start\n\t");
+}
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
 /* Common exception entrypoint */
 
 extern void exception_common(void);
@@ -82,7 +94,7 @@ const void * const _vectors[] locate_data(".vectors")
 
   /* Reset exception handler */
 
-  __start,
+  start,
 
   /* Vectors 2 - n point directly at the generic handler */
 
diff --git a/arch/arm/src/armv8-m/arm_vectors.c b/arch/arm/src/armv8-m/arm_vectors.c
index 7427b23a43..75308996e1 100644
--- a/arch/arm/src/armv8-m/arm_vectors.c
+++ b/arch/arm/src/armv8-m/arm_vectors.c
@@ -52,13 +52,25 @@
 #endif
 
 /****************************************************************************
- * Public Functions
+ * Private Functions
  ****************************************************************************/
 
 /* Chip-specific entrypoint */
 
 extern void __start(void);
 
+static void start(void)
+{
+  /* Zero lr to mark the end of backtrace */
+
+  asm volatile ("mov lr, #0\n\t"
+                "b  __start\n\t");
+}
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
 /* Common exception entrypoint */
 
 extern void exception_common(void);
@@ -84,7 +96,7 @@ const void * const _vectors[] locate_data(".vectors") =
 
   /* Reset exception handler */
 
-  __start,
+  start,
 
   /* Vectors 2 - n point directly at the generic handler */