hardware.c

/*
 * hardware.c 
 */

#include <types.h>

extern unsigned int *p_rdtr;
DWord get_eflags(void)
{
  register DWord flags;
  __asm__ __volatile__(
      "pushfl\n\t"
      "popl %0"
      : "=q"(flags));

  return flags;
}

void set_eflags(void)
{
  __asm__ __volatile__(
      "pushl $0\n\t"
      "popfl");
}

void set_idt_reg(Register *idt)
{
  __asm__ __volatile__(
      "lidtl (%0)"
      : /*no output*/
      : "r"(idt));
}

void set_gdt_reg(Register *gdt)
{
  __asm__ __volatile__(
      "lgdtl (%0)"
      : /*no output*/
      : "r"(gdt));
}

void set_ldt_reg(Selector ldt)
{
  __asm__ __volatile__(
      "lldtw %0"
      : /*no output*/
      : "r"(ldt));
}

void set_task_reg(Selector tr)
{
  __asm__ __volatile__(
      "ltrw %0"
      : /*no output*/
      : "r"(tr));
}

void return_gate(Word ds, Word ss, DWord esp, Word cs, DWord eip)
{
  __asm__ __volatile__(
      "mov %0,%%es\n\t"
      "mov %0,%%ds\n\t"
      "movl %2, %%eax\n\t"
      "addl $12, %%eax\n\t"
      "movl %5,(%%eax)\n\t"
      "pushl %1\n\t" /* user ss */
      "pushl %2\n\t" /* user esp */
      "pushl %3\n\t" /* user cs */
      "pushl %4\n\t" /* user eip */
      "lret"
      : /*no output*/
      : "m"(ds), "m"(ss), "m"(esp), "m"(cs), "m"(eip), "d"(*p_rdtr));
}

/*
 * enable_int: Set interruput mask
 *
 *    register 0x21:
 *    7 6 5 4 3 2 1 0
 *    x x x x x x x x
 *    
 *    bit 0 : Timer
 *    bit 1 : Keyboard
 *    bit 2 : PIC cascading
 *    bit 3 : 2nd Serial Port
 *    bit 4 : 1st Serial Port
 *    bit 5 : Reserved
 *    bit 6 : Floppy disk
 *    bit 7 : Reserved
 * 
 *
 *   x = 0 -> enabled
 *   x = 1 -> disabled
 */

void enable_int(void)
{
  __asm__ __volatile__(
      "movb %0,%%al\n\t"
      "outb %%al,$0x21\n\t"
      "call delay\n\t"
      "sti"
      :           /*no output*/
      : "i"(0xfc) /* 0xFF = 11111111 -> all bits disabled */
      : "%al");
}

void delay(void)
{
  __asm__ __volatile__(
      "jmp a\na:\t"
      :
      :);
}