diff options
| author | Michal Idziorek <m.i@gmx.at> | 2014-08-29 15:20:17 +0200 |
|---|---|---|
| committer | Michal Idziorek <m.i@gmx.at> | 2014-08-29 15:20:17 +0200 |
| commit | 659f1f1ae057c82a154a1fd32cc9dca040979daa (patch) | |
| tree | 41afd3afb1b3e29ea6bf8445e1a7b284e7043368 /boot/mbr.asm | |
| parent | 1cb4a8a202023958589d563ad132d701e27c008a (diff) | |
experimenting with a20 gate
Diffstat (limited to 'boot/mbr.asm')
| -rw-r--r-- | boot/mbr.asm | 28 |
1 files changed, 21 insertions, 7 deletions
diff --git a/boot/mbr.asm b/boot/mbr.asm index 26d13bf..4dd82d1 100644 --- a/boot/mbr.asm +++ b/boot/mbr.asm @@ -56,20 +56,23 @@ jmp boot_16 ;start boot process BOOT_DRIVE: db 0xff STR_VERSION: - db "Fool Boot Loader v0.3.1~",0 + db "v0.3.1~",0 VESA_CHECK1: - db " VESA: Get Info.",0 + db " V1.",0 VESA_CHECK2: - db " VESA: Get Mode Info.",0 + db " V2",0 VESA_CHECK3: - db " VESA: Set Mode.",0 + db " V2",0 +CHECK_A20: + db " A20",0 ;lets put our temporary GDT (Global Descriptor Table) here ;kernel should move this away %include "boot/GDT.asm" -;include 16-bit real mode routines (print_string, disk_load, vesa_setup) +;include 16-bit real mode routines (print_string, disk_load, vesa_setup,check_a20) %include "boot/disk_load_16.asm" +%include "boot/check_a20_16.asm" %include "boot/print_string_16.asm" %include "boot/vesa_setup_16.asm" @@ -112,6 +115,15 @@ boot_16: call BiosGetMemoryMap ; this will also put the number of entries ; of the memory map at MEMMAP_SIZE_OFFSET +a20check: + + mov bx, STR_VERSION + call print_string + + call check_a20 + cmp ax,0 + je a20check ;hang if a20 is disabled! + ;VESA: also setup vesa stuff before entering 32 bit protected mode call VesaSetup @@ -127,9 +139,11 @@ boot_32_pm: ;enable A20 ;http://www.brokenthorn.com/Resources/OSDev9.html ;Method 3.1: Enables A20 through keyboard controller + ;Not all keyboard controllers support this ;todo: check if this has any effect at all !?!? - mov al, 0xdd ; command 0xdd: enable a20 - out 0x64, al ; send command to controller + ;mov al, 0xdd ; command 0xdd: enable a20 + ;mov al, 0xdf ; command 0xdf: disable a20 + ;out 0x64, al ; send command to controller ;pic setup call pic_setup |