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Working with multi-sector reads

This commit is contained in:
Michael Brown 2007-07-05 13:30:49 +01:00
parent 66208dd65d
commit a0f078d7f5

View File

@ -10,29 +10,61 @@
#include "bootpart.S"
load_image:
movw $_rom_size, %bp
1: /* Truncate read length to end of track */
movzwl %bp, %eax
movw $1, %ax
/* Read sectors */
/* Get disk geometry */
pushal
pushw %es
movb $0x08, %ah
int $0x13
jc load_failed
movb %cl, max_sector
movb %dh, max_head
popw %es
popal
1: /* Read to end of current track */
movb %cl, %al
negb %al
addb max_sector, %al
incb %al
andb $0x3f, %al
movzbl %al, %eax
call *read_sectors
jc load_failed
/* Update %es */
movw %es, %bx
shll $5, %eax
addw %ax, %bx
movw %bx, %es
shrl $5, %eax
/* Update LBA address */
addl %eax, %edi
adcl $0, %esi
/* Update CHS address */
// hmmmm
andb $0xc0, %cl
orb $0x01, %cl
incb %dh
cmpb max_head, %dh
jbe 2f
xorb %dh, %dh
incb %ch
jnc 2f
addb $0xc0, %cl
2:
/* Loop until whole image is read */
subw %ax, %bp
jne 1b
subl %eax, load_length
ja 1b
ljmp $BOOT_SEG, $start_image
load_length:
.long _rom_size
max_sector:
.byte 0
max_head:
.byte 0
load_failed:
movw $10f, %si
jmp boot_error