.file "irq_pit.S"

.text

.extern switchKthread

.globl pit_handler
.type pit_handler, @function
pit_handler:         // already got eflags, cs and eip on stack thanks to CPU 
  pushl $0           // err_code     esp+12+8*4=44
  pushal             // (general reg) esp+12
  subl $2, %esp      // (alignment)  esp+10
  pushw %ss          //              esp+8
  pushw %ds          //              esp+6
  pushw %es          //              esp+4
  pushw %fs          //              esp+2
  pushw %gs          //              esp

  /* Send EOI to PIC */
  movb  $0x20, %al
  outb  %al, $0x20

  pushl %esp
  call pitIrqHandler
  movl %eax,%esp

  /* Restore the CPU context */
  popw %gs
  popw %fs
  popw %es
  popw %ds
  popw %ss
  addl $2,%esp
  popal
  addl $4, %esp /* Ignore "error code" */

  /* This restores the eflags, the cs and the eip registers */
  iret /* equivalent to: popfl ; ret */