apps/edit/start.asm

   1 ;  ZeX/OS
   2 ;  Copyright (C) 2007  Tomas 'ZeXx86' Jedrzejek (zexx86@gmail.com)
   3 ;
   4 ;  This program is free software: you can redistribute it and/or modify
   5 ;  it under the terms of the GNU General Public License as published by
   6 ;  the Free Software Foundation, either version 3 of the License, or
   7 ;  (at your option) any later version.
   8 ;
   9 ;  This program is distributed in the hope that it will be useful,
  10 ;  but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 ;  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 ;  GNU General Public License for more details.
  13 ;
  14 ;  You should have received a copy of the GNU General Public License
  15 ;  along with this program.  If not, see <http://www.gnu.org/licenses/>.
  16
  17
  18 ; This is the kernel's entry point. We could either call main here,
  19 ; or we can use this to setup the stack or other nice stuff, like
  20 ; perhaps setting up the GDT and segments. Please note that interrupts
  21 ; are disabled at this point: More on interrupts later!
  22 %macro  IMP 1
  23 %ifdef UNDERBARS
  24         EXTERN _%1
  25         %define %1 _%1
  26 %else
  27         EXTERN %1
  28 %endif
  29 %endmacro
  30
  31 %macro  EXP     1
  32         GLOBAL $_%1
  33         $_%1:
  34         GLOBAL $%1
  35         $%1:
  36 %endmacro
  37
  38 [BITS 32]
  39 global _start
  40 _start:
  41     ;mov esp, _sys_stack
  42         ; This points the stack to our new stack area
  43
  44     jmp stublet
  45
  46 ; This is an endless loop here. Make a note of this: Later on, we
  47 ; will insert an 'extern _main', followed by 'call _main', right
  48 ; before the 'jmp $'.
  49 stublet:
  50     IMP main
  51     call main
  52     ;jmp $
  53     ret
  54
  55 ; Here is the definition of our BSS section. Right now, we'll use
  56 ; it just to store the stack. Remember that a stack actually grows
  57 ; downwards, so we declare the size of the data before declaring
  58 ; the identifier '_sys_stack'
  59 SECTION .bss
  60     resb 512               ; This reserves 8KBytes of memory here
  61 ;_sys_stack: