diff options
| author | hpa <hpa> | 2002-07-15 23:03:18 +0000 |
|---|---|---|
| committer | hpa <hpa> | 2002-07-15 23:03:18 +0000 |
| commit | 536024af947f9e06b19cc552a0838ea6cb8decb7 (patch) | |
| tree | b399eaabbef2481c9253846e736f994a27988803 | |
| parent | 2b289c41c404315a9fc6a87ae99837f8f21b69ce (diff) | |
| download | syslinux-536024af947f9e06b19cc552a0838ea6cb8decb7.tar.gz | |
Finally get around to fixing the MBR code.syslinux-2.00-pre6
| -rw-r--r-- | NEWS | 1 | ||||
| -rw-r--r-- | mbr.asm | 28 |
2 files changed, 14 insertions, 15 deletions
@@ -5,6 +5,7 @@ Changes in 2.00: * ALL: Add support for "COM32" (32-bit COMBOOT) images. * ALL: Add an API for COMBOOT/COM32 images. See comboot.doc for details. + * Fix mbr.asm so that it actually works. Changes in 1.75: * ALL: NASM 0.98.32 or later is now required to build @@ -48,7 +48,8 @@ _start: cli ; ; Now, jump to the copy at 0600h so we can load the boot sector at 7C00h. ; Since some BIOSes seem to think 0000:7C00h and 07C0:0000h are the same -; thing, use a far jump to canonicalize the address. +; thing, use a far jump to canonicalize the address. This also makes +; sure that it is a code speculation barrier. ; jmp 0:next ; Jump to copy at 0600h @@ -61,16 +62,14 @@ next: ; mov ah,08h ; Get drive parameters int 13h - mov [Heads],dh - mov dh,cl - and dh,3Fh ; Max sector number - dec dh ; Sector count - mov [Sectors],dh - mov dx,cx - xchg dh,dl - mov cl,6 - shr dh,cl - mov [Cylinders],dx + xor ax,ax + mov al,dh + inc ax ; From 0-based to count + mov [Heads],ax + and cl,3Fh ; Max sector number + mov [Sectors],cl + ; Note: we actually don't care about the number of + ; cylinders, since that's the highest-order division ; ; Now look for one (and only one) active partition. @@ -138,15 +137,15 @@ no_ebios: mov dh,dl ; Head # mov dl,[DriveNo] mov bx,7C00h - mov ah,02h ; Read + mov ax,0201h ; Read one sector common_tail: int 13h jc disk_error - pop di + pop si ; DS:SI -> partition table entry ; ; Verify that we have a boot sector, jump ; - test word [7C00h+510],0AA55h + cmp word [7C00h+510],0AA55h jne missing_os cli jmp 7C00h ; Jump to boot sector @@ -187,7 +186,6 @@ dapa: ; CHS information Heads: dw 0 Sectors: dw 0 -Cylinders: dw 0 ; Error messages missing_os_msg db 'Missing operating system', 13, 10, 0 |