#include "stack.h"
#include <stdint.h>
#include <avr/interrupt.h>

extern uint8_t _end;
extern uint8_t __stack;

void __stack_canary_init(void)
	__attribute__ ((naked))
	__attribute__ ((section (".init1")));
void __stack_canary_init(void)
{
	__asm volatile ("    ldi r30,lo8(_end)\n"
			"    ldi r31,hi8(_end)\n"
			"    ldi r24,lo8(0xaa)\n" // canary
			"    ldi r25,hi8(__stack)\n"
			"    rjmp 2f\n"
			"1:\n"
			"    wdr\n"
			"    st Z+,r24\n"
			"2:\n"
			"    cpi r30,lo8(__stack)\n"
			"    cpc r31,r25\n"
			"    brlo 1b\n"
			"    breq 1b"
			:
			:
			: "memory");
}

/* return low level mark of free stack space */
uint16_t stack_min(void)
{
	const uint8_t *p;
	uint16_t c = 0;

	for (p = &_end; *p == 0xaa && p <= &__stack; p++)
		c++;
	return c;
}

/* return total amount of stack */
uint16_t stack_total(void)
{
	return &__stack - &_end;
}