minor stuff with the A20 line '-'

boot/elf/elf.c

@@ -0,0 +1,10 @@
+//----------------------------------------------------------------------------//
+//                           GNU GPL OS/K                                     //
+//                                                                            //
+//  Authors:    spectral`                                                     //
+//              NeoX                                                          //
+//                                                                            //
+//  Desc:       ELF64 Parser and Loader                                       //
+//----------------------------------------------------------------------------//
+
+

boot/loader.asm

@@ -33,13 +33,6 @@
 %define volumeLabel       bp+0x2b           ; Volume Label
 %define fatTypeLabel      bp+0x36           ; File system type 
 
-;; DISK BUFFER "SEGMENT"
-%define BUFFER_SEG 0x07c0                   ; (BUFFER_SEG << 4) + BUFFER_OFF = 0x07C00
-%define BUFFER_OFF 0x0000
-
-;; SECOND STAGE LOADER "SEGMENT"
-%define LOAD_SEG   LONG_SELECTOR-GDT64      ; (LOAD_SEG   << 4) + LOAD_OFF   = 0x070000
-%define LOAD_OFF   Kernel
 
 
 [BITS 16]
@@ -61,7 +54,7 @@ GDT64:
                         dd  0x0             ;            
 
         CODE_SELECTOR:    ;; 32-bit code selector (ring 0)
-                        dw     0x0FFFF      ; Segment Limit
+                        dw  0x0000FFFF      ; Segment Limit
                         db  0x0, 0x0, 0x0   ; Base Address
                         db  10011010b       ;    |7|6|5|4|3|2|1|0|
                                             ;     | | | | | | | `----- 1 when segment used. 
@@ -84,7 +77,7 @@ GDT64:
                         db  0x0             ; Base Address
                         
         DATA_SELECTOR:    ;; flat data selector (ring 0)
-                        dw     0x0FFFF      ; Segment Limit
+                        dw  0x0000FFFF      ; Segment Limit
                         db  0x0, 0x0, 0x0   ; Base Address
                         db  10010010b       ;    |7|6|5|4|3|2|1|0| 
                                             ;     | | | | | | | `----- 1 when segment used.  
@@ -107,7 +100,7 @@ GDT64:
                         db  0x0             ; Base Address
                         
         LONG_SELECTOR:    ;; 64-bit code selector (ring 0)
-                        dw     0x0FFFF      ;  Segment Limit
+                        dw  0x0000FFFF      ;  Segment Limit
                         db  0x0, 0x0, 0x0   ; Base Address
                         db  10011010b       ;    |7|6|5|4|3|2|1|0|
                                             ;     | | | | | | | `----- 1 when segment used. 
@@ -195,6 +188,21 @@ main32:
     pop dword [VGA_HEIGHT32]
     pop dword [VIDEO_MODE32]
     
+    ;; VERIFY A20
+    pushad
+    mov edi,0x112345  ;odd megabyte address.
+    mov esi,0x012345  ;even megabyte address.
+    mov [esi],esi     ;making sure that both addresses contain diffrent values.
+    mov [edi],edi     ;(if A20 line is cleared the two pointers would point to the address 0x012345 that would contain 0x112345 (edi)) 
+    cmpsd             ;compare addresses to see if the're equivalent.
+    popad
+    jne .A20_on       ;if not equivalent , A20 line is set.
+    mov WORD [A20_OK], 0
+    jmp .A20_end
+.A20_on:    
+    mov BYTE [A20_OK], 1
+.A20_end:
+
     ;; INITIALIZE PROTECTED MODE SEGMENT REGISTERS
     mov ax, DATA_SELECTOR-GDT64
     mov ds, ax
@@ -260,6 +268,7 @@ KernSearch      db  0x09, " Loading the Kernel in RAM...", 0
 txt             db  0x09, " Switching to Long Mode... ", 0
 Reinit          db  "Booting OS/K !", 0x0D, 0x0A, 0x0D, 0x0A, 0
 Pass            db  " OK", 0x0A, 0x0D, 0
+Fail            db  " FAIL!", 0x0A, 0x0D, 0
 msg             db  "The system is now in x64 mode. Is this not beautiful ?", 0x0A, 0x0D, 0
 
 NoLongMode      db   0x0A, 0x0D, "ERROR : Your computer is not designed for x64 OS", 0
@@ -278,6 +287,7 @@ NextTRAM        dq  0x0B8000                ; Last position of cursor
 VIDEO_MODE64    dq  0
 VGA_HEIGHT64    dq  0
 VGA_X           dq  0
+A20_OK          db  0
 
 main64:
     pop qword [VGA_HEIGHT64]
@@ -304,14 +314,13 @@ main64:
     mov esi, EnA20
     call write
 
-    mov bl, 0x0A
+    cmp BYTE [A20_OK], 1
-    mov esi, Pass
+    je .A20Success
+    mov bl, 0x0C
+    mov esi, Fail
     call write
-    
+    jmp Die
-    mov bl, 0x0F
+.A20Success:
-    mov esi, KernSearch
-    call write
-
     mov bl, 0x0A
     mov esi, Pass
     call write
@@ -328,6 +337,7 @@ main64:
     mov esi, msg
     call write
     
+    
     jmp Die
     
     ; times 1024 nop