search for: checksumiso

Until Syslinux 3.86, isolinux.bin contained a checksum that was calculated by 'core/checksumiso.pl'. The checksum is related to the patching of the boot info table. During May 2009, a commit by Peter deleted the checksumiso.pl file. The commit is: core: LZO compress the PM part of the core repo.or.cz/syslinux.git/commit/0d82b71304d596d80f3c4520f9dcf90048ca50b7 And so, since ve...

Hi, Ady wrote: > During May 2009, a commit by Peter deleted the checksumiso.pl file. The > commit is: > core: LZO compress the PM part of the core > repo.or.cz/syslinux.git/commit/0d82b71304d596d80f3c4520f9dcf90048ca50b7 > And so, since version 4.00, the 'code/checksumiso.pl' file is no longer > included. > How is the checksum of isolinux.bin...

> Hi, > > Ady wrote: > > During May 2009, a commit by Peter deleted the checksumiso.pl file. The > > commit is: > > core: LZO compress the PM part of the core > > repo.or.cz/syslinux.git/commit/0d82b71304d596d80f3c4520f9dcf90048ca50b7 > > And so, since version 4.00, the 'code/checksumiso.pl' file is no longer > > included. > > How i...

...en beginning the checksum loop, if "start" is 64. > Since I am not a developer, I cannot avoid wondering whether patching > prepcore.c would have additional consequences. The change should only influence the checksum, which can hardly get worse. It comes to me that a run of old checksumiso.pl should have the same effect as putting isolinux.bin into an ISO. I.e. test would be whether the four bytes at offset 20 of a freshly built isolinux change by a run of checksumiso.pl. If they don't change, then we have a high probability of correct code in prepcore.c. Have a nice day :) Th...

Hi, i think i found a suspect in lzo/prepcore.c and it would indeed be a wrong range of checksumming (speculative congratulations to Ady). Looking at http://repo.or.cz/syslinux.git/blob/0d82b71304d596d80f3c4520f9dcf90048ca50b7:/lzo/prepcore.c it seems that this change in line 374 could yield correct checksums: unsigned int ptr; - for (ptr = 64; ptr < offset; ptr += 4) +

...;start" is 64. > > > > Since I am not a developer, I cannot avoid wondering whether patching > > prepcore.c would have additional consequences. > > The change should only influence the checksum, which can hardly get worse. > > It comes to me that a run of old checksumiso.pl should have the same > effect as putting isolinux.bin into an ISO. I.e. test would be whether > the four bytes at offset 20 of a freshly built isolinux change by a run > of checksumiso.pl. > If they don't change, then we have a high probability of correct code > in prepcore.c....

...for whichever reason (e.g. user lacking > knowledge), do not patch the boot info table. I agree and still riddle about the reason. > So, my question is whether there is some intentional reason for these > changes in isolinux.bin. I assume that hpa intended to move the functionality of checksumiso.pl into the "prepcore" helper program which compresses all or parts of the ./core/*.bin files. > What I'd like to know is what > happened with the "default" checksum in isolinux.bin, To my theory it fell victim to a bug. > how is/are the checksum(s) calculated n...

...aaf5b" \ -l isolinux.lsr -o isolinux.o isolinux.asm ld -m elf_i386 -T syslinux.ld -M -o isolinux.elf isolinux.o > isolinux.map objdump -h isolinux.elf > isolinux.sec perl lstadjust.pl isolinux.lsr isolinux.sec isolinux.lst objcopy -O binary isolinux.elf isolinux.bin perl checksumiso.pl isolinux.bin nasm -O9999 -f elf -g -F stabs -DDATE_STR="'pre11-112-g930881b*'" \ -DHEXDATE="0x49caaf5b" \ -l isolinux-debug.lsr -o isolinux-debug.o isolinux-debug.asm ld -m elf_i386 -T syslinux.ld -M -o isolinux-debug.elf isolinux-debu...

...ero. > > > Have a nice day :) > > Thomas > Since I am not a developer, I cannot avoid wondering whether patching prepcore.c would have additional consequences. Considering that LZO was brought into Syslinux by Peter, and he is also the author of the commit that replaced checksumiso.pl, I really wish Peter would show up and comment on this matter. Hpa? Any Syslinux developer (past or present)? TIA, Ady.