Displaying 11 results from an estimated 11 matches for "divb".
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2012 Aug 10
1
[PATCH 4/4] Support sectors >512
...er */
@@ -258,12 +274,12 @@ read_sector:
/* This chunk is skipped if we have ebios */
/* Do not clobber %es:%bx or %edx:%eax before this chunk! */
read_sector_cbios:
- divl -6(%bp) /* secpercyl */
+ divl -36(%bp) /* secpercyl */
shlb $6, %ah
movb %ah, %cl
movb %al, %ch
xchgw %dx, %ax
- divb -2(%bp) /* sectors */
+ divb -32(%bp) /* sectors */
movb %al, %dh
orb %ah, %cl
incw %cx /* Sectors are 1-based */
@@ -275,7 +291,7 @@ read_common:
leaw 16(%si), %sp /* Drop DAPA */
popal
jc disk_error
- addb $2, %bh /* bx += 512: point to the next buffer */
+ addb -5(%bp), %bh /* bx +...
2013 Feb 08
6
[PATCH] 4k_sector: Support dynamic sectors in GPT MBR
This patches add support for dynamic sectors to GPT MBR code.
First 3 patches are trick and optimizations to gain some space for the forth
patch.
I have a modified version of SeaBIOS, some code and some script o test it
I'll send on a different mail.
2017 Mar 22
3
"isolinux.bin missing or corrupt" when booting USB flash drive in old PC
Hi,
given the fact that the conversion has the factor HC*SH = "secpercyl",
which is invariant under swapping, there remains as suspect in
read_sector_cbios only this division:
divb (sectors)
There is a suspicious discrepancy in the code:
heads = (stack-16)
sectors = (stack-18)
...
/* here we computer CHS values or just do some dummy computation for EBIOS */
andw $0x3f, %cx /* Sector count */
popw %bx /* EBIOS flag */
pushw %cx /* -16: Save sectors on the stack...
2017 Mar 22
4
"isolinux.bin missing or corrupt" when booting USB flash drive in old PC
Hi,
funny or enlightening observation:
With my qemu-system-i386 it would work if the detected Heads/Cylinder and
Sectors/Head factors would change positions !
The effective read operation seems to use H/C = 32 , S/H = 63.
The correct LBA would be addressed by H/C = 63 , S/H = 32.
--------------------------------------------------------------------------
Reasoning:
I have transplanted the
2017 Mar 24
2
"isolinux.bin missing or corrupt" when booting USB flash drive in old PC
...-----------
MartinS wrote:
> Amazingly the size of the code in isohdpfd decreased by one byte
> although it's more informative!
I still did not find the spot in the Intel manual which tells me
the bytes sizes of instructions and their operands. Yesterday i riddled
which bytes after the DIVB instruction are the stack address:
f6 36 ee 7b
and whether to add or to subtract 2 with that address.
Finally isohdpfc.bin told me that "ee" must become "f0" to correct the bug.
(This would mean we can correct existing ISOs by this bash command
echo -n $'\xf0' |...
2009 Mar 30
2
[PATCH 1/1] v2 Add Diagnostic MBR for trouble-shooting
...tor_chs:
+ divl (sectors_cylinder) /* LBA in DX:AX inherited from above */
+ shlb $6, %ah /* quotient is the cylinder number */
+ movb %ah, %cl /* cylinder high bits (7-6) */
+ movb %al, %ch /* cylinder low bits (7-0) */
+ xchgw %dx, %ax /* remainder is the sector-offset into the cylinder */
+ divb (sectors)
+ movb %al, %dh /* head number */
+ orb %ah, %cl /* sector offset ORed into CL since CL(7-6) already contain two high bits of cylinder number */
+ incw %cx /* sector counts start at 1 not 0 */
+
+read_common:
+read_op = .+2 /* address of operand to be moved into AH (0x42 in the f...
2017 Mar 21
3
"isolinux.bin missing or corrupt" when booting USB flash drive in old PC
...t */
pushw $16 /* Size of packet */
movw %sp, %si
/* This chunk is skipped if we have ebios */
/* Do not clobber %eax before this chunk! */
/* This also relies on %bx and %edx as set up above. */
read_sector_cbios:
divl (secpercyl)
shlb $6, %ah
movb %ah, %cl
movb %al, %ch
xchgw %dx, %ax
divb (sectors)
movb %al, %dh
orb %ah, %cl
incw %cx /* Sectors are 1-based */
movw $0x0201, %ax
read_common:
movb (driveno), %dl
int $0x13
leaw 16(%si), %sp /* Drop DAPA */
popal
ret
disk_error:
call print_string
.ascii "Operating system load error.\r\n"
jmp boot_failure
/*
*...
2017 Mar 23
6
"isolinux.bin missing or corrupt" when booting USB flash drive in old PC
Hi,
Geert Stappers wrote:
> Contact David off-list, he did unsubscribe.
Can you tell when he unsubscribed (i.e. which of the messages he got
as last one) ?
> Martin posted elsewhere in this thread "Thomas, you found the bug"
> and provided a patch.
Open question is whether the fix helps with David's BIOS.
The newest answer from Martin indicates that a failure to read
2012 Sep 10
19
Initial support for sector size >512
This set of patches add some support for sector size >512.
Currently it fixes extlinux, MBR for GPT and ext partitions.
Other code is unaffected.
This set of patches has been tested on a read Dell machine running a beta
firmware.
2009 Mar 30
0
[PATCH 1/1] Add Diagnostic MBR for trouble-shooting
...tor_chs:
+ divl (sectors_cylinder) /* LBA in DX:AX inherited from above */
+ shlb $6, %ah /* quotient is the cylinder number */
+ movb %ah, %cl /* cylinder high bits (7-6) */
+ movb %al, %ch /* cylinder low bits (7-0) */
+ xchgw %dx, %ax /* remainder is the sector-offset into the cylinder */
+ divb (sectors)
+ movb %al, %dh /* head number */
+ orb %ah, %cl /* sector offset ORed into CL since CL(7-6) already contain two high bits of cylinder number */
+ incw %cx /* sector counts start at 1 not 0 */
+
+read_common:
+read_op = .+2 /* address of operand to be moved into AH (0x42 in the f...
2009 Mar 30
2
[PATCH 1/1] v3: Add Diagnostic MBR for trouble-shooting BIOS boot-order problems.
...tor_chs:
+ divl (sectors_cylinder) /* LBA in DX:AX inherited from above */
+ shlb $6, %ah /* quotient is the cylinder number */
+ movb %ah, %cl /* cylinder high bits (7-6) */
+ movb %al, %ch /* cylinder low bits (7-0) */
+ xchgw %dx, %ax /* remainder is the sector-offset into the cylinder */
+ divb (sectors)
+ movb %al, %dh /* head number */
+ orb %ah, %cl /* sector offset ORed into CL since CL(7-6) already contain two high bits of cylinder number */
+ incw %cx /* sector counts start at 1 not 0 */
+
+read_common:
+read_op = .+2 /* address of operand to be moved into AH (0x42 in the f...