search for: divb

...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 +...

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.

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...

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

...----------- 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' |...

...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...

...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 /* *...

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

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.

...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...

...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...