os/arch/i686/interrupts/irq0.s

.global irq0
.extern _switch_task

.global jump_kernel
.global jump_user

.extern ss
.extern esp
.extern eflags
.extern cs
.extern eip 

.section .bss
.align 16 
task_stack_bottom:
.skip 4096
task_stack_top:

.skip 4

temp_esp:

.skip 4

.section .text
irq0:
mov %esp, (temp_esp)
mov $task_stack_top, %esp

pusha
mov temp_esp, %eax
push %eax
push 8(%eax)
push 4(%eax)
push  (%eax)

mov $0x10, %eax
mov %ax, %ds
mov %ax, %es
mov %ax, %fs
mov %ax, %gs

call _switch_task

iret

jump_kernel:
mov (ss), %eax
mov %ax, %ds
mov %ax, %es
mov %ax, %fs
mov %ax, %gs
mov %ax, %ss

pop %eax

mov $0x20, %eax
outb %al, $0x20

popa

mov (esp), %esp

push (eflags)
push (cs)
push (eip)

iret

jump_user:
mov (ss), %eax
mov %ax, %ds
mov %ax, %es
mov %ax, %fs
mov %ax, %gs

pop %eax

mov $0x20, %eax
outb %al, $0x20

popa

push (ss)
push (esp)
push (eflags)
push (cs)
push (eip)

iret