fix(system): fixed potential double exception when booting on xtensa

Due to old windows from the startup flow being present after
switching to running freertos tasks  windowoverflow exceptions
could potentially try to save windows to the startup stack.

During this overflow they also values previously saved on the
startup stack to find earlier frames' stacks.
Since the start up stack was already recycled these values were
invalid and would cause a crash.

Closes https://github.com/espressif/esp-idf/issues/14406Y

Author: ESP-Marius

components/freertos/FreeRTOS-Kernel-SMP/portable/xtensa/port.c

@@ -348,6 +348,11 @@ BaseType_t xPortStartScheduler( void )
     }
 #endif // configNUM_CORES > 1
 
+    // Windows contain references to the startup stack which will be reclaimed by the main task
+    // Spill the windows to create a clean environment to ensure we do not carry over any such references
+    // to invalid SPs which will cause problems if main_task does a windowoverflow to them
+    xthal_window_spill();
+
     // Cannot be directly called from C; never returns
     __asm__ volatile ("call0    _frxt_dispatch\n");
 

components/freertos/FreeRTOS-Kernel/portable/xtensa/port.c

@@ -108,6 +108,11 @@ BaseType_t xPortStartScheduler( void )
 
     port_xSchedulerRunning[xPortGetCoreID()] = 1;
 
+    // Windows contain references to the startup stack which will be reclaimed by the main task
+    // Spill the windows to create a clean environment to ensure we do not carry over any such references
+    // to invalid SPs which will cause problems if main_task does a windowoverflow to them
+    xthal_window_spill();
+
     // Cannot be directly called from C; never returns
     __asm__ volatile ("call0    _frxt_dispatch\n");