int cpu_state_machine() {
int state = 0;
while(state != ERROR) {
switch(state) {
case S0_FIRST_COMS:
if ( umc_first_com() == SUCCESS && kernel_first_com() == SUCCESS) { state = S1_GET_PCB; } else { state = ERROR; }
break;
case S1_GET_PCB:
if (get_pcb() == SUCCESS) { state = S2_CHANGE_ACTIVE_PROCESS; } else { state = ERROR; }
break;
case S2_CHANGE_ACTIVE_PROCESS:
if (change_active_process() == SUCCESS) { state = S3_EXECUTE; } else { state = ERROR; }
break;
case S3_EXECUTE:
if (execute_state_machine() == SUCCESS) { state = S4_RETURN_PCB; } else { state = ERROR; }
break;
case S4_RETURN_PCB:
if (return_pcb() == SUCCESS) { if(LAST_QUANTUM_FLAG) { return SUCCESS; } state = S1_GET_PCB; } else { state = ERROR; }
break;
default:
case ERROR:
return ERROR;
break;
}
}
return SUCCESS;
}
void init() {
struct pcb* p_kernel_pcb;
init_pcbs();
p_kernel_pcb = get_pcb(&p_free_pcb);
if (NULL == p_kernel_pcb)
return;
insert_pcb(&p_used_pcb, p_kernel_pcb);
p_kernel_pcb->stack = NULL;
p_pcb_now = p_kernel_pcb;
}
void create_task(void (*f)(), void* stack_bottom) {
unsigned short *sp = stack_bottom;
unsigned long *esp;
struct pcb *p_pcb = get_pcb(&p_free_pcb);
if (NULL == p_pcb)
return;
insert_pcb(&p_used_pcb, p_pcb);
/*prepare stack for task*/
*sp-- = 0x0202;//flags
*sp-- = 0;//cs
*sp = (unsigned short)f;//ip
esp = (unsigned long*)sp;
esp --;
*esp-- = 0xAAAAAAAA;//eax
*esp-- = 0xBBBBBBBB;//ebx
*esp-- = 0xCCCCCCCC;//ecx
*esp-- = 0xDDDDDDDD;//edx
*esp-- = 0xEEEEEEEE;//ebp
*esp-- = 0xFFFFFFFF;//esi
*esp = 0xABABABAB;//edi
p_pcb->stack = esp;
}
