diff options
Diffstat (limited to 'src/stage2_real_functions.asm')
| -rw-r--r-- | src/stage2_real_functions.asm | 42 |
1 files changed, 25 insertions, 17 deletions
diff --git a/src/stage2_real_functions.asm b/src/stage2_real_functions.asm index f173ca3..1728b1a 100644 --- a/src/stage2_real_functions.asm +++ b/src/stage2_real_functions.asm @@ -9,7 +9,7 @@ SECTORS_PER_CYLINDER: db 0x3F ; detect parameters enters the correct value here (sectors + 1) ; if detection fails, force int13 to read ahead NOF_HEADS: - db 0x02 ; number of heads + 1 + db 0x01 ; number of heads + 1 SECTORS_TO_LOAD: db NOF_LOAD_SECTORS ; load NOF_LOAD_SECTORS sectors in total CURRENT_SECTOR: @@ -49,31 +49,39 @@ detect_disk_geometry: ret probe_and_fix_disk_geometry: - mov cl, 0xff ; from 63 down to 0 + mov cl, 0x1 ; from 1 to 63 + mov BYTE [SECTORS_PER_CYLINDER], cl .loop: + mov dl, [BOOT_DRIVE] mov ah, 0x02 ; read sectors from drive mov al, 1 ; read 1 sector + mov cl, BYTE [SECTORS_PER_CYLINDER] mov ch, BYTE 0 mov dh, BYTE 0 int 0x13 - jc .next_try - ; no errors anymore, so it must be the correct sector - inc cl - mov [SECTORS_PER_CYLINDER], BYTE cl - - mov al, '>' - call print_char - movzx dx, byte [SECTORS_PER_CYLINDER] - call print_hex - - ret - -.next_try: - dec cl ; next sector - jnz .loop + jnc .next_sector ; on error, remeber cl being the highest sector + +.fix_heads: + cmp [NOF_HEADS], BYTE 0 ; 0 heads, the BIOS is playing tricks to us! + je .illegal_heads + jmp .end + +.illegal_heads: + mov [NOF_HEADS], BYTE 1 + jmp .end + +.next_sector: + mov cl, BYTE [SECTORS_PER_CYLINDER] + inc cl ; next sector + mov BYTE [SECTORS_PER_CYLINDER], cl + cmp cl, 0x40 ; to a max of 63, if so, this is the default + jbe .loop + jmp .fix_heads + +.end: ret ; read the whole stage2 and kernel from the disk |