Add functions to get top and limit stack

ports/atmel-samd/supervisor/port.c

@@ -271,6 +271,14 @@ void reset_cpu(void) {
     reset();
 }
 
+uint32_t *port_stack_get_limit(void) {
+    return &_ebss;
+}
+
+uint32_t *port_stack_get_top(void) {
+    return &_estack;
+}
+
 // Place the word to save 8k from the end of RAM so we and the bootloader don't clobber it.
 #ifdef SAMD21
 uint32_t* safe_word = (uint32_t*) (HMCRAMC0_ADDR + HMCRAMC0_SIZE - 0x2000);

ports/cxd56/supervisor/port.c

@@ -67,6 +67,14 @@ void reset_port(void) {
 void reset_to_bootloader(void) {
 }
 
+uint32_t *port_stack_get_limit(void) {
+    return &_ebss;
+}
+
+uint32_t *port_stack_get_top(void) {
+    return &_estack;
+}
+
 extern uint32_t _ebss;
 
 // Place the word to save just after our BSS section that gets blanked.

ports/nrf/supervisor/port.c

@@ -146,6 +146,14 @@ void reset_cpu(void) {
     NVIC_SystemReset();
 }
 
+uint32_t *port_stack_get_limit(void) {
+    return &_ebss;
+}
+
+uint32_t *port_stack_get_top(void) {
+    return &_estack;
+}
+
 extern uint32_t _ebss;
 // Place the word to save just after our BSS section that gets blanked.
 void port_set_saved_word(uint32_t value) {

ports/stm32f4/supervisor/port.c

@@ -67,6 +67,14 @@ void reset_cpu(void) {
 	NVIC_SystemReset();
 }
 
+uint32_t *port_stack_get_limit(void) {
+    return &_ebss;
+}
+
+uint32_t *port_stack_get_top(void) {
+    return &_estack;
+}
+
 extern uint32_t _ebss;
 // Place the word to save just after our BSS section that gets blanked.
 void port_set_saved_word(uint32_t value) {

supervisor/port.h

@@ -54,6 +54,12 @@ void reset_board(void);
 // Reset to the bootloader
 void reset_to_bootloader(void);
 
+// Get stack limit address
+uint32_t *port_stack_get_limit(void);
+
+// Get stack top address
+uint32_t *port_stack_get_top(void);
+
 // Save and retrieve a word from memory that is preserved over reset. Used for safe mode.
 void port_set_saved_word(uint32_t);
 uint32_t port_get_saved_word(void);