diff options
| -rw-r--r-- | src/boot/bootloader.asm | 70 |
1 files changed, 67 insertions, 3 deletions
diff --git a/src/boot/bootloader.asm b/src/boot/bootloader.asm index eb226a6..4b803fa 100644 --- a/src/boot/bootloader.asm +++ b/src/boot/bootloader.asm @@ -36,15 +36,13 @@ step2: or eax, 0x1 mov cr0, eax - jmp $ -; jmp CODE_SEG:start_32 + jmp CODE_SEG:start_32 ; GDT table description gdt_start: gdt_null: ; First segment Descriptor is always 0 dd 0x0 dd 0x0 - ;Second segment descriptor... Code segment - 0x8 gdt_code: dw 0xffff ; Segment limit 0-15 @@ -74,6 +72,72 @@ gdt_table: dw gdt_end - gdt_start - 1 dd gdt_start +[BITS 32] +start_32: + mov eax, 1 ; LBA addr to start from + mov ecx, 100 ; Num of sectors + mov edi, 0x00100000 ; Mem addr to load data read + call ata_lba_read + jmp CODE_SEG:0x0100000 + +ata_lba_read: + ; Write the high 8bits of the LBA to the disk controller + mov ebx, eax, + shr eax, 24 ; Get LBA high 8bits to send to the controller + or eax, 0xE0 ; Select the 'master' drive + mov dx, 0x1F6 ; Port number + out dx, al ; Write bits to the port + + ; Write the number of sectors to read to the disk controller + mov eax, ecx ; Num of sectors + mov dx, 0x1F2 ; Port number + out dx, al ; Send to the port + + ; Send LBA's first 0-7 bits + mov eax, ebx ; Get original LBA + mov dx, 0x1F3 ; Port number + out dx, al ; Write the low 8 bits to the controller + + ; Send LBA's bits 8-15 to the controller + mov eax, ebx ; Get original LBA + mov dx, 0x1F4 ; Port number + shr eax, 8 ; Get bits 8-15 + out dx, al ; Write 8 bits to controller + + ; Send LBA's bits 16-23 to the controller + mov eax, ebx ; Get original LBA + mov dx, 0x1F5 ; Port number + shr eax, 16 ; Get bits 16-23 + out dx, al ; Write to the controller + + ; No idea what it does yet + mov dx, 0x1F7 + mov al, 0x20 + out dx, al + + ; Read sectors into memory +.next_sector: + push ecx ; Save num of sectors + + ; Loop here until the controller is ready +.try_again: + mov dx, 0x1f7 + in al, dx + test al, 8 + jz .try_again + + mov ecx, 256 + mov dx, 0x1F0 + rep insw ; Read 256 words from the I/O port in DX into memory ES:EDI + ; EDI has been set to 0x100000 above + ; ecx controls how many words to read (w means word in ins) + ; 256 * 2 bytes-per-word - We read a whole sector + + pop ecx ; restor num of sectors + loop .next_sector ; This decrements ecx too + + ret + ; Fill in to the end and add bootloader signature times 510 - ($ - $$) db 0 dw 0xAA55 |