kernel/testkernels etc/kernel.asm

   1 ;------------------------------------------------------------;
   2 ;                     BOS - test kernel                      ;
   3 ;------------------------------------------------------------;
   4 ;                                                            ;
   5 ;          by: Christoffer Bubach, 2003-2005                 ;
   6 ;   http://bos.asmhackers.net/      asmhacker@gmail.com      ;
   7 ;                                                            ;
   8 ;------------------------------------------------------------;
   9
  10 ;     16-bit mem map  (seg:off)
  11 ;  0x0000:0x0000 -> 0x0000:0x0500  BIOS stuff
  12 ;  0x0000:0x0500 -> 0x0000:0x2100  root
  13 ;  0x0000:0x2100 -> 0x0000:0x3300  fat
  14 ;  0x0000:0x3300 -> 0x0000:0x6c00  14,25kb free space
  15 ;  0x0000:0x6c00 -> 0x0000:0x7c00  IDT and GDT (256 desc. eatch)
  16 ;  0x0000:0x7c00 -> 0x0000:0x7e00  bootsector
  17 ;  0x0000:0x7e00 <- 0x0000:0xffff  ~32,5kb stack for boot
  18 ;  0x1000:0x0000 -> 0x9000:0xffff  576kb free space
  19 ;  0xa000:0x0000 -> .............  VGA mem etc.
  20
  21 use16
  22 org 0x0000
  23           jmp     start
  24
  25            include 'realmode/a20.inc'
  26            include 'realmode/variables.inc'
  27      ;----------------------------------------------------;
  28      ;  show a message and wait for a key before reboot   ;
  29      ;----------------------------------------------------;
  30      first:
  31           mov     bp, first16
  32           mov     ax, 0x1301
  33           mov     bx, 4
  34           mov     cx, 19
  35           mov     dx, 0x0401
  36           int     0x10
  37
  38           mov     ah, 0
  39           int     0x16
  40           ;int     0x19
  41           ret
  42
  43           first16     db  'Now in 16 bit mode.'
  44
  45
  46 ;------------------------------------------;
  47 ;   starting point of second stage code    ;
  48 ;------------------------------------------;
  49 start:
  50           cli
  51           mov     ax, 0x1000
  52           mov     ds, ax                              ; registers.
  53           mov     es, ax
  54           mov     ss, ax
  55           mov     sp, 0xFFFF                          ; Stack..
  56           sti
  57
  58
  59 ;----------------------;
  60 ;   enable a20 gate    ;
  61 ;----------------------;
  62 a20:                                                  ; Enable A20
  63           in      al, 0x64
  64           test    al, 2
  65           jnz     a20
  66           mov     al, 0xD1
  67           out     0x64, al
  68      .d6:
  69           in      al, 0x64
  70           and     ax, 2
  71           jnz     .d6
  72           mov     al, 0xDF
  73           out     0x60, al
  74
  75
  76 ;-----------------;
  77 ; display message ;
  78 ;-----------------;
  79           call    first
  80
  81
  82 ;------------------------;
  83 ;   enter 32-bit mode    ;
  84 ;------------------------;
  85 pmode:
  86     ;      xor     ebx, ebx
  87     ;      mov     bx, ds
  88     ;      shl     ebx, 4
  89     ;      mov     [BaseAddOn], ebx
  90     ;      mov     eax, ebx
  91
  92     ;      mov     [gdt.BOS_code + 2], ax
  93     ;      mov     [gdt.BOS_data + 2], ax
  94     ;      mov     [gdt.BOS_16code + 2], ax
  95     ;      mov     [gdt.BOS_16data + 2], ax
  96
  97     ;      shr     eax, 16
  98
  99     ;      mov     [gdt.BOS_code + 4], al
 100     ;      mov     [gdt.BOS_data + 4], al
 101     ;      mov     [gdt.BOS_16code + 4], al
 102     ;      mov     [gdt.BOS_16data + 4], al
 103
 104     ;      mov     [gdt.BOS_code + 7], ah
 105     ;      mov     [gdt.BOS_data + 7], ah
 106     ;      mov     [gdt.BOS_16code + 7], ah
 107     ;      mov     [gdt.BOS_16data + 7], ah
 108
 109     ;      add     ebx, gdt
 110
 111     ;      mov     [gdtr + 2], ebx
 112     ;      add     ebx, idt_start - gdt
 113     ;      mov     [idtr + 2], ebx
 114
 115         xor   ebx,ebx
 116         mov   bx,ds                            ; BX=segment
 117         shl   ebx,4                            ; BX="linear" address of segment base
 118         mov   eax,ebx
 119         mov   [sys_code_1 + 2],ax              ; set base address of 32-bit segments
 120         mov   [sys_data_1 + 2],ax
 121         mov   [Real_code_1 + 2],ax             ; set base address of 16-bit segments
 122         mov   [Real_data_1 + 2],ax
 123         shr   eax,16
 124         mov   [sys_code_1 + 4],al
 125         mov   [sys_data_1 + 4],al
 126         mov   [Real_code_1 + 4],al
 127         mov   [Real_data_1 + 4],al
 128
 129         mov   [sys_code_1 + 7],ah
 130         mov   [sys_data_1 + 7],ah
 131         mov   [Real_code_1 + 7],ah
 132         mov   [Real_data_1 + 7],ah
 133
 134         add   ebx,gdt                          ; EBX=linear address of gdt
 135         mov   [gdtr + 2],ebx
 136
 137         cli                                    ; Disable interrupts,
 138         mov   ax,cs
 139         mov   [RealModeCS],ax
 140         lgdt  [gdtr]                           ; Load the GDT descriptor
 141
 142         mov   eax, cr0                         ; Copy the contents of CR0 into EAX
 143         or    eax, 1                           ; Set bit 0
 144         mov   cr0, eax                         ; Copy the contents of EAX into CR0
 145
 146         ;jmp   10h:clear_pipe                   ; Jump to code segment, offset clear_pipe
 147
 148         ;  cli                                         ; set protected mode (32-bit)
 149         ;  lgdt    [gdtr]
 150         ;  mov     eax, cr0
 151         ;  or      eax, 1
 152         ;  mov     cr0, eax
 153
 154           jmp     0x08:flush
 155
 156 ;----------------------------------------;
 157 ; start of 32-bit area.                  ;
 158 ;     flush segments and jump to kernel  ;
 159 ;----------------------------------------;
 160 use32
 161 flush:
 162           mov     eax, 0x10                           ; refresh all segment registers
 163           mov     ds, eax
 164           mov     es, eax
 165           mov     fs, eax
 166           mov     gs, eax
 167           mov     ss, eax
 168           mov     esp, 0xfffc
 169
 170           mov     byte [ds:0B8502h], 'P'
 171           mov     byte [ds:0B8503h], 0x07             ; Assign a color code
 172
 173           jmp     $ ;hang
 174
 175
 176
 177 ;--------------------------------;
 178 ;  global descriptor table (gdt) ;
 179 ;--------------------------------;
 180 gdt:
 181     .null:           dw   0x0000, 0x0000, 0x0000, 0x0000
 182     .codesel:        dw   0xFFFF, 0x0000, 0x9800, 0x00CF
 183     .datasel:        dw   0xFFFF, 0x0000, 0x9200, 0x00CF
 184 gdt_end:
 185
 186 gdtr:
 187      .size:          dw   gdt_end - gdt - 1
 188      .address        dd   gdt ;+ 0x10000               ; 0x10000 is where we are in mem