HAL_ChibiOS: implement stack overflow hook

this needs C bindings to allow call from low level RTOS thread
switching code

libraries/AP_HAL_ChibiOS/hwdef/common/chconf.h

@@ -730,6 +730,15 @@
 } while(0)
 #endif
 
+/**
+ * @brief   stack overflow event hook.
+ * @details This hook is invoked when we have a stack overflow on task switch
+ */
+#define CH_CFG_STACK_OVERFLOW_HOOK(tp) {                                         \
+  extern void stack_overflow_hook(thread_t *tp); \
+  stack_overflow(tp); \
+}
+
 /**
  * @brief   Trace hook.
  * @details This hook is invoked each time a new record is written in the

libraries/AP_HAL_ChibiOS/hwdef/common/stm32_util.c

@@ -435,3 +435,13 @@ void system_halt_hook(void)
 #endif
 }
 
+// hook for stack overflow
+void stack_overflow(thread_t *tp)
+{
+    extern void AP_stack_overflow(const char *thread_name);
+    AP_stack_overflow(tp->name);
+    // if we get here then we are armed and got a stack overflow. We
+    // will report an internal error and keep trying to fly. We are
+    // quite likely to crash anyway due to memory corruption. The
+    // watchdog data should record the thread name and fault type
+}

libraries/AP_HAL_ChibiOS/hwdef/common/stm32_util.h

@@ -107,6 +107,9 @@ void fault_printf(const char *fmt, ...);
 // halt hook for printing panic message
 void system_halt_hook(void);
 
+// hook for stack overflow
+void stack_overflow(thread_t *tp);
+    
 #ifdef __cplusplus
 }
 #endif

libraries/AP_HAL_ChibiOS/system.cpp

@@ -56,16 +56,26 @@ void NMI_Handler(void) { while (1); }
 /*
   save watchdog data for a hard fault
  */
-    static void save_fault_watchdog(uint16_t line, FaultType fault_type, uint32_t fault_addr, uint32_t lr)
+static void save_fault_watchdog(uint16_t line, FaultType fault_type, uint32_t fault_addr, uint32_t lr)
 {
 #ifndef HAL_BOOTLOADER_BUILD
     bool using_watchdog = AP_BoardConfig::watchdog_enabled();
     if (using_watchdog) {
         AP_HAL::Util::PersistentData &pd = hal.util->persistent_data;
         pd.fault_line = line;
-        pd.fault_type = fault_type;
+        if (pd.fault_type == 0) {
+            // don't overwrite earlier fault
+            pd.fault_type = fault_type;
+        }
         pd.fault_addr = fault_addr;
-        pd.fault_thd_prio = chThdGetPriorityX();
+        thread_t *tp = chThdGetSelfX();
+        if (tp) {
+            pd.fault_thd_prio = tp->prio;
+            // get first 4 bytes of the name, but only of first fault
+            if (tp->name && pd.thread_name4[0] == 0) {
+                strncpy(pd.thread_name4, tp->name, 4);
+            }
+        }
         pd.fault_icsr = SCB->ICSR;
         pd.fault_lr = lr;
         stm32_watchdog_save((uint32_t *)&hal.util->persistent_data, (sizeof(hal.util->persistent_data)+3)/4);