;
; traps.s provides entry points to the exception handlers
; as well as the system call interface.
;

global syscall_init
global traps_init
extern call_table
extern idt
extern panic
extern printf
extern register_isr

%macro SAVE 0
  pusha
  ; save the data segment selectors
  mov ax, ds
  push ax
  ; switch to kernel data segments
  mov ax, 0x10
  mov ds, ax
  mov es, ax
  mov fs, ax
  mov gs, ax
  ; restore EAX (needed for syscalls)
  mov eax, [esp+44]
%endmacro

%macro SAVE_ERR 0
  pusha
  ; fetch the error code that was pushed
  mov ebx, [esp+32]
  ; save the data segment selectors
  mov ax, ds
  push ax
  ; switch to kernel data segments
  mov ax, 0x10
  mov ds, ax
  mov es, ax
  mov fs, ax
  mov gs, ax
%endmacro

%macro RESTORE 0
  ; restore the data segment selectors
  pop ax
  mov ds, ax
  mov es, ax
  mov fs, ax
  mov gs, ax
  popa
  iret
%endmacro

%macro RESTORE_ERR 0
  ; restore the data segment selectors
  pop ax
  mov ds, ax
  mov es, ax
  mov fs, ax
  mov gs, ax
  popa
  add esp, 4
  iret
%endmacro

traps:
  dd exc_div
  dd exc_debug
  dd exc_nmi
  dd exc_brk
  dd exc_ovf
  dd exc_bounds
  dd exc_invop
  dd exc_nomath
  dd exc_dbf
  dd exc_coseg
  dd exc_invtss
  dd exc_segnotpres
  dd exc_stackf
  dd exc_gprot
  dd exc_pagef
  dd exc_reserved
  dd exc_mathf
  dd exc_alignchk
  dd exc_machinechk
  dd exc_simdfp
  dd exc_virt
  dd exc_reserved
  dd exc_reserved
  dd exc_reserved
  dd exc_reserved
  dd exc_reserved
  dd exc_reserved
  dd exc_reserved
  dd exc_reserved
  dd exc_reserved
  dd exc_reserved
  dd exc_reserved

traps_init:
  push ebp
  mov ebp, esp
  mov ecx, 0
  mov edx, idt
.loop:
  mov eax, ecx
  shl eax, 2
  add eax, traps
  mov eax, [eax]
  mov [edx], ax
  shr eax, 16
  mov [edx+6], ax
  mov word [edx+2], 0x08
  mov byte [edx+4], 0x00
  mov byte [edx+5], 0x8E
  inc ecx
  cmp ecx, 32
  je .end
  add edx, 8
  jmp .loop
.end:
  pop ebp
  ret

exc_div:
  SAVE
  RESTORE

exc_debug:
  SAVE
  RESTORE

exc_nmi:
  SAVE
  RESTORE

exc_brk:
  SAVE
  RESTORE

exc_ovf:
  SAVE
  RESTORE

exc_bounds:
  SAVE
  RESTORE

exc_invop:
  SAVE
  RESTORE

exc_nomath:
  SAVE
  RESTORE

exc_dbf:
  SAVE_ERR
  RESTORE_ERR

exc_coseg:
  SAVE
  RESTORE

exc_invtss:
  SAVE_ERR
  RESTORE_ERR

exc_segnotpres:
  SAVE_ERR
  RESTORE_ERR

exc_stackf:
  SAVE_ERR
  RESTORE_ERR

exc_gprot:
  SAVE_ERR
  RESTORE_ERR

exc_pagef:
  SAVE_ERR

  push ebx
  mov ebx, cr2
  push ebx
  push .fmt
  call printf
  add esp, 8
  call panic

  RESTORE_ERR
.fmt:
  db "Page Fault (illegal memory access: 0x%08x:0x%02x)", 10, 0

exc_mathf:
  SAVE
  RESTORE

exc_alignchk:
  SAVE
  RESTORE

exc_machinechk:
  SAVE
  RESTORE

exc_simdfp:
  SAVE
  RESTORE

exc_virt:
  SAVE
  RESTORE

exc_reserved:
  SAVE
  RESTORE

syscall_handler:
  SAVE

  push edx
  push ecx
  push ebx
  and eax, 0xFF
  shl eax, 2
  add eax, call_table
  call [eax]
  add esp, 12

  RESTORE


syscall_init:
  push ebp
  mov ebp, esp
  push syscall_handler
  push dword 3
  push dword 0x80
  call register_isr
  add esp, 12
  pop ebp
  ret