kernel/entry.s

   1 bits 32
   2 extern kmain
   3 extern __STACK_BOTTOM__
   4
   5 section .text
   6 global _start
   7 _start:
   8         ; Here, the stack will look like:
   9         ; return address, map pointer, map size.
  10
  11         ; Skip the return address.
  12         add esp, 4
  13         ; Save the kernel arguments.
  14         ; Can this be done without the global variables?
  15         pop dword [e820_map]
  16         pop dword [e820_map_size]
  17         sub esp, 12
  18         ; Do the stack switch.
  19         mov ebp, __STACK_BOTTOM__
  20         mov esp, ebp
  21         ; Restore the kernel arguments.
  22         push dword [e820_map_size]
  23         push dword [e820_map]
  24         ; Call the actual kernel.
  25         call kmain
  26         hlt
  27         jmp $-1
  28
  29 ; Temporarily save arguments here to survive the upcoming stack switch.
  30 section .bss
  31 e820_map: resd 1
  32 e820_map_size: resd 1