lib.c

这是一个不到2000行的操作系统

#include "lib.h"

int exit(int error_code)
{
 	int ret;
 	__asm__(
 		"mov	r0, %1\n"
 		"swi	%2\n"
 		"mov	%0, r0\n"
 		:"=r"(ret)
 		:"r"(error_code),"M"(__NR_exit)
 		:"r0"
 		);
 	return ret;
}


int sleep(int time)
{
 	int ret;
 	__asm__(
 		"mov	r0, %1\n"
 		"swi	%2\n"
 		"mov	%0, r0\n"
 		:"=r"(ret)
 		:"r"(time),"M"(__NR_sleep)
		:"r0"
		);
	return ret;
}

int write(char *str)
{
 	int ret;
 	__asm__(
 		"mov	r0, %1\n"
 		"swi	%2\n"
 		"mov	%0, r0\n"
 		:"=r"(ret)
 		:"r"(str),"M"(__NR_write)
		:"r0"
		);
	return ret;
}