From: Anthony Liguori <[EMAIL PROTECTED]>
In certain circumstances, the calculated CHS can result in a total number of
sectors that is less than the actual number of sectors. I'm not entirely
sure why this upsets grub, but it seems to be the source of the Grub Error 18
that sometimes occurs when using extboot.
The solution is to implement the read drive parameters function and return the
actual numbers of sectors. This requires changing the QEMU <=> extboot
interface as this was not previously passed to extboot.
Signed-off-by: Anthony Liguori <[EMAIL PROTECTED]>
Signed-off-by: Avi Kivity <[EMAIL PROTECTED]>
diff --git a/extboot/extboot.S b/extboot/extboot.S
index 584d36d..9eb9333 100644
--- a/extboot/extboot.S
+++ b/extboot/extboot.S
@@ -351,7 +351,7 @@ disk_reset:
sub $1, %ax
mov %ax, 4(%bp)
- alloca $8
+ alloca $16
movw $0, 0(%bx) /* read c,h,s */
push %bx
@@ -426,7 +426,7 @@ read_disk_drive_parameters:
push %bx
/* allocate memory for packet, pointer gets returned in bx */
- alloca $8
+ alloca $16
/* issue command */
movw $0, 0(%bx) /* cmd = 0, read c,h,s */
@@ -481,7 +481,7 @@ alternate_disk_reset:
read_disk_drive_size:
push %bx
- alloca $8
+ alloca $16
movw $0, 0(%bx) /* cmd = 0, read c,h,s */
push %bx
@@ -572,29 +572,20 @@ extended_write_sectors:
extended_read_write_sectors $0x02
get_extended_drive_parameters:
- mov $1, %ah
- stc
- ret
-#if 0
- /* this function is seriously borked */
-1:
push %ax
push %bp
push %cx
push %dx
- allocbpa $8
+ allocbpa $16
movw $0, 0(%bp) /* read c,h,s */
push %bp
call send_command
add $2, %sp
- /* check the size of the passed in data */
- cmpw $26, 0(%si)
- mov 0(%si), %ax
- dump %ax
- jle 0b
+ /* write size */
+ movw $26, 0(%si)
/* set flags to 2 */
movw $2, 2(%si)
@@ -617,46 +608,19 @@ get_extended_drive_parameters:
xor %ax, %ax
mov %ax, 14(%si)
- /* calculate total sectors */
-
- /* cx:dx = cylinders */
- mov 2(%bp), %dx
- xor %cx, %cx
-
- /* *= heads */
- push 4(%bp)
- push $0
- push %dx
- push %cx
- call mul32
- add $8, %sp
-
- /* *= sectors */
- push 6(%bp)
- push $0
- push %dx
- push %cx
- call mul32
- add $8, %sp
-
- /* total number of sectors */
- mov %dx, 16(%si)
- mov %cx, 18(%si)
- xor %ax, %ax
+ /* set total number of sectors */
+ mov 8(%bp), %ax
+ mov %ax, 16(%si)
+ mov 10(%bp), %ax
+ mov %ax, 18(%si)
+ mov 12(%bp), %ax
mov %ax, 20(%si)
+ mov 14(%bp), %ax
mov %ax, 22(%si)
/* number of bytes per sector */
movw $512, 24(%si)
- /* optional segmention:offset to EDD config */
- cmpw $30, 0(%si)
- jl 1f
-
- movw $0xFFFF, 26(%si)
- movw $0xFFFF, 28(%si)
-
-1:
freebpa
pop %dx
@@ -667,7 +631,6 @@ get_extended_drive_parameters:
mov $0, %ah
clc
ret
-#endif
terminate_disk_emulation:
mov $1, %ah
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