## 16-bit code

# Entry:
00:
  bd 00 90  # bp <- 0x9000
  89 ec  # sp <- bp

  bb 8f 7c  # bx <- MSG_REAL_MODE
  e8 38 00  # call print_string

  e8 02 00  # call switch_to_pm
  eb fe  # jump $  (should never get here)

# switch_to_pm:
10:
  fa  # cli
  0f 01 16 3d 7c  # lgdt [gdt_descriptor]
  0f 20 c0  # eax <- cr0
  66 83 c8 01  # eax <- or 0x1
  0f 22 c0  # cr0 <- eax
20:
  ea 53 7c 08 00  # jmp CODE_SEG:init_pm

# gdt_start:
# gdt_null:  mandatory null descriptor
  00 00 00 00 00 00 00 00
# gdt_code:
  ff ff 00
30:
  00 00 9a cf 00
# gdt_data:
  ff ff 00 00 00 92 cf 00
# gdt_end:

# gdt_descriptor:
3d:
  17 00  # limit
  25 7c 00 00  # start

# print_string:
43:
  60  # pusha
  b4 0e  # ah <- 0x0e
# loop:
  8a 07  # al <- *bx
  cd 10  # int 10h
  83 c3 01  # add bx, 1
  3c 00  # cmp al, 0
  75 f5  # jne loop
  61  # popa
  c3  # ret

## 32-bit code

# init_pm:
53:
  66 b8 10 00  # ax <- DATA_SEG
  8e d8  # ds <- ax
  8e d0  # ss <- ax
  8e c0  # es <- ax
  8e e0  # fs <- ax
  8e e8  # gs <- ax
61:
  bd 00 00 09 00  # ebp <- 0x90000
  89 ec  # esp <- ebp
  bb ab 7c 00 00  # ebx <- MSG_PROT_MODE
  e8 02 00 00 00  # call print_string_pm
  eb fe  # hang

# print_string_pm:
74:
  60  # pusha
  ba 00 80 0b 00 8a 03 b4 0f 3c 00
80:
  74 0b 66 89 02 83 c3 01 83 c2 02 eb ed 61 c3 53
90:
  74 61 72 74 65 64 20 69 6e 20 31 36 2d 62 69 74
a0:
  20 52 65 61 6c 20 4d 6f 64 65 00 53 75 63 63 65
b0:
  73 73 66 75 6c 6c 79 20 6c 61 6e 64 65 64 20 69
c0:
  6e 20 33 32 2d 62 69 74 20 50 72 6f 74 65 63 74
d0:
  65 64 20 4d 6f 64 65

# vim:ft=conf