diff options
| author | Miguel <m.i@gmx.at> | 2018-09-02 00:08:42 +0200 |
|---|---|---|
| committer | Miguel <m.i@gmx.at> | 2018-09-02 00:08:42 +0200 |
| commit | 8e3411139b27a3421e9ac75c13f14f99f6dd3137 (patch) | |
| tree | cf8b53ab02863117c310bde11ee4683e134cf1b2 /xxx/GDT.asm | |
| parent | 0fff2e6dc6fae82da1c7978918a490c25cc36f04 (diff) | |
syscalls
Diffstat (limited to 'xxx/GDT.asm')
| -rw-r--r-- | xxx/GDT.asm | 81 |
1 files changed, 81 insertions, 0 deletions
diff --git a/xxx/GDT.asm b/xxx/GDT.asm new file mode 100644 index 0000000..53458ba --- /dev/null +++ b/xxx/GDT.asm @@ -0,0 +1,81 @@ +;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; +;;;;;;; Miguel's FoolOS Helper Functions ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; +;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; +; +; Global Descriptor Table +; we have the null descriptor and a code and data block for a start +; +; 0x08 code segment +; 0x10 data segment +; +; this file contains pure data +; +; +; +; + +;global gdt_descriptor +;global gdt_start + +gdt_start: + +gdt_null: ;null descriptor (2 x 4 bytes) + dd 0x0 + dd 0x0 + +gdt_code: + ; flags: + ; present: 1 / privilege: 00 / type: 1 + ; code: 1 / conforming: 0 / readable: 1 / accessed: 0 + ; granularity: 1 / 16-bit default: 1 / 64-bit seg: 0 / AVL: 0 + dw 0xffff ;limit + dw 0x0 ;base + db 0x0 ;base + db 10011010b ;flags + db 11001111b ;flags & seg.limit + db 0x0 ;base + +gdt_data: + ; flags: + ; code: 0 / expand down: 0 / writable: 1 / accessed: 0 + dw 0xffff + dw 0x0 + db 0x0 + db 10010010b + db 11001111b + db 0x0 + +gdt16_code: + ; flags: + ; present: 1 / privilege: 00 / type: 1 + ; code: 1 / conforming: 0 / readable: 1 / accessed: 0 + ; granularity: 1 / 16-bit default: 1 / 64-bit seg: 0 / AVL: 0 + dw 0xffff ;limit + dw 0x0 ;base + db 0x0 ;base + db 10011010b ;flags + db 10001111b ;flags & seg.limit + db 0x0 ;base + +gdt16_data: + ; flags: + ; code: 0 / expand down: 0 / writable: 1 / accessed: 0 + dw 0xffff + dw 0x0 + db 0x0 + db 10010010b + db 10001111b + db 0x0 + +gdt_end: + +gdt_descriptor: + dw gdt_end-gdt_start-1 + dd gdt_start + +CODE_SEG equ gdt_code - gdt_start +DATA_SEG equ gdt_data - gdt_start +CODE16_SEG equ gdt16_code - gdt_start +DATA16_SEG equ gdt16_data - gdt_start + + |