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| author | H. Peter Anvin <hpa@zytor.com> | 2007-07-11 16:45:27 -0700 |
|---|---|---|
| committer | H. Peter Anvin <hpa@zytor.com> | 2007-07-11 16:45:27 -0700 |
| commit | a9a2963de68bfb52c51c793c5325608a99f60d91 (patch) | |
| tree | 747403938bef1df67bdf194e948baa2f5e4e04fa /mbr | |
| parent | d9139b2f937aac9b6ee08cc79da35afde4d832b4 (diff) | |
| download | syslinux-a9a2963de68bfb52c51c793c5325608a99f60d91.tar.gz | |
MBR: always do setup for EBIOS, makes stack handling easier and saves jmp
Diffstat (limited to 'mbr')
| -rw-r--r-- | mbr/mbr.S | 28 |
1 files changed, 14 insertions, 14 deletions
@@ -80,8 +80,8 @@ next: shrw %cx /* Bit 0 = fixed disk subset */ jnc 1f - /* We have EBIOS; patch in a jump to read_sector_ebios */ - movw $0xeb+((read_sector_ebios-read_sector_cbios-2)<< 8), (read_sector_cbios) + /* We have EBIOS; patch in jump to skip over read_sector_cbios */ + movw $0xeb+((read_common-read_sector_cbios-2)<< 8), (read_sector_cbios) 1: popw %dx @@ -111,9 +111,18 @@ next: */ read_sector: pushal - movw %sp, %bp xorl %edx, %edx movw $bootsec, %bx + pushl %edx /* MSW of LBA */ + pushl %eax /* LSW of LBA */ + pushw %es /* Buffer segment */ + pushw %bx /* Buffer offset */ + pushw $1 /* Sector count */ + pushw $16 /* Size of packet */ + movw %sp, %si + movb $0x42, %ah + + /* This chunk is skipped if we have ebios */ read_sector_cbios: divl (secpercyl) shlb $6, %ah @@ -125,20 +134,11 @@ read_sector_cbios: orb %ah, %cl incw %cx /* Sectors are 1-based */ movw $0x0201, %ax - jmp read_common -read_sector_ebios: - pushl %edx /* MSW of LBA */ - pushl %eax /* LSW of LBA */ - pushw %es /* Buffer segment */ - pushw %bx /* Buffer offset */ - pushw $1 /* Sector count */ - pushw $16 /* Size of packet */ - movw %sp, %si - movb $0x42, %ah + read_common: movb (driveno), %dl int $0x13 - movw %bp, %sp + addw $16, %sp /* Drop DAPA */ popal ret |