system.c

/*
 * system.c - 
 */

#include <segment.h>
#include <types.h>
#include <interrupt.h>
#include <hardware.h>
#include <system.h>
#include <sched.h>
#include <mm.h>
#include <io.h>
#include <utils.h>
//#include <zeos_mm.h> /* TO BE DELETED WHEN ADDED THE PROCESS MANAGEMENT CODE TO BECOME MULTIPROCESS */

int (*usr_main)(void) = (void *)PH_USER_START;
unsigned int *p_sys_size = (unsigned int *)KERNEL_START;
unsigned int *p_usr_size = (unsigned int *)KERNEL_START + 1;
unsigned int *p_rdtr = (unsigned int *)KERNEL_START + 2;

/************************/
/** Auxiliar functions **/
/************************/
/**************************
 ** setSegmentRegisters ***
 **************************
 * Set properly all the registers, used
 * at initialization code.
 *   DS, ES, FS, GS <- DS
 *   SS:ESP <- DS:DATA_SEGMENT_SIZE
 *         (the stacks grows towards 0)
 *
 * cld -> gcc2 wants DF (Direction Flag (eFlags.df))
 *        always clear.
 */

/*
 * This function MUST be 'inline' because it modifies the %esp 
 */
inline void set_seg_regs(Word data_sel, Word stack_sel, DWord esp)
{
  esp = esp - 5 * sizeof(DWord); /* To avoid overwriting task 1 */
  __asm__ __volatile__(
      "cld\n\t"
      "mov %0,%%ds\n\t"
      "mov %0,%%es\n\t"
      "mov %0,%%fs\n\t"
      "mov %0,%%gs\n\t"
      "mov %1,%%ss\n\t"
      "mov %2,%%esp"
      : /* no output */
      : "r"(data_sel), "r"(stack_sel), "g"(esp));
}

/*
 *   Main entry point to ZEOS Operating System
 */
int __attribute__((__section__(".text.main")))
main(void)
{

  set_eflags();

  /* Define the kernel segment registers  and a stack to execute the 'main' code */
  // It is necessary to use a global static array for the stack, because the
  // compiler will know its final memory location. Otherwise it will try to use the
  // 'ds' register to access the address... but we are not ready for that yet
  // (we are still in real mode).
  set_seg_regs(__KERNEL_DS, __KERNEL_DS, (DWord)&protected_tasks[5]);

  /*** DO *NOT* ADD ANY CODE IN THIS ROUTINE BEFORE THIS POINT ***/

  printk("Kernel Loaded!    ");

  /* Initialize hardware data */
  setGdt(); /* Definicio de la taula de segments de memoria */
  setIdt(); /* Definicio del vector de interrupcions */
  setTSS(); /* Definicio de la TSS */

  /* Initialize Memory */
  init_mm();

  /* Initialize an address space to be used for the monoprocess version of ZeOS */

  //monoprocess_init_addr_space(); /* TO BE DELETED WHEN ADDED THE PROCESS MANAGEMENT CODE TO BECOME MULTIPROCESS */

  /* Initialize Scheduling */
  init_sched();

  /* Initialize idle task data */
  init_idle();
  /* Initialize task 1 data */
  init_task1();

  /* Move user code/data now (after the page table initialization) */
  copy_data((void *)KERNEL_START + *p_sys_size, usr_main, *p_usr_size);

  printk("Entering user mode...");

  enable_int();
  /*
   * We return from a 'theorical' call to a 'call gate' to reduce our privileges
   * and going to execute 'magically' at 'usr_main'...
   */
  return_gate(__USER_DS, __USER_DS, USER_ESP, __USER_CS, L_USER_START);

  /* The execution never arrives to this point */
  return 0;
}