search for: bad_signature

...looks like the call to "error" (line 276) is made if a summation of > the bytes in the first four sectors of a partition don't add up to > HYBRID_MAGIC (?). HYBRID_MAGIC = 0x7078c0fb isolinux_hybrid_signature = 0x7c00+64 ... cmpl $HYBRID_MAGIC,(isolinux_hybrid_signature) jne bad_signature ... bad_signature: call error .ascii "isolinux.bin missing or corrupt.\r\n" No. It looks for the value HYBRID_MAGIC at position isolinux_hybrid_signature in memory. -- MartinS

Hi, > The ISO will boot successfully (when chainloaded from grub) on 2 and > 3, but not on 5 and 6. Did you try with a boot loader other than GRUB ? Afaik, the MBRs of newly bought USB sticks often contain code which hops on the MBR code of the partition that is marked by the boot flag. At least one could exclude that your problem is in a GRUB peculiarity. Have a nice day :) Thomas

...ode or know easy-to-grasp reference docs? (I left machine code programming when i gave up using my VIC-20.) The MBR template isohdppx.bin stems from http://git.zytor.com/syslinux/syslinux.git/tree/mbr/isohdpfx.S with macro PARTITION_SUPPORT defined. One can see the error message text in there: bad_signature: call error .ascii "isolinux.bin missing or corrupt.\r\n" It seems to be reached only if the seen isolinux.bin does not bear the magic number of isohybrid capable isolinux.bin. cmpl $HYBRID_MAGIC,(isolinux_hybrid_signature) jne bad_signature Since we know that the iso...

...> (I left machine code programming when i gave up using my VIC-20.) > > The MBR template isohdppx.bin stems from > http://git.zytor.com/syslinux/syslinux.git/tree/mbr/isohdpfx.S > with macro PARTITION_SUPPORT defined. > > One can see the error message text in there: > > bad_signature: > call error > .ascii "isolinux.bin missing or corrupt.\r\n" > > It seems to be reached only if the seen isolinux.bin does not bear the > magic number of isohybrid capable isolinux.bin. > > cmpl $HYBRID_MAGIC,(isolinux_hybrid_signature)...

Thomas Schmitt wrote: > I ponder whether it would be possible to create a diagnostic MBR > which does not necessarily have to boot but rather tells what the > isohybrid MBR would perceive: Presence of partition table, > EBIOS or CBIOS, block address used with INT 13, content of the block > read by the first INT 13, ... ... > The diagnostic MBR should only use 432 bytes because at

...call print_string .ascii "\r\n" dec %dx jnz 2b call print_string .ascii "Key?\r\n" xor %ax, %ax int $0x16 popa /* * Okay, that actually worked... update the stack pointer * and jump into isolinux.bin... */ cmpl $HYBRID_MAGIC,(isolinux_hybrid_signature) jne bad_signature cli movw $ebios_flag, %sp /* * Use a ljmpw here to work around a bug in some unknown version * of gas or ld when it comes to jumping to an absolute symbol... * * Look more closely into it if we ever are short on space. */ ljmpw $0, $isolinux_start_hybrid bad_signature: call print_...

...ry */ movb $0x08, %ah int $0x13 + + /* 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 */ @@ -223,9 +257,15 @@ next: ljmpw $0, $isolinux_start_hybrid bad_signature: - call error + call print_string .ascii "isolinux.bin missing or corrupt.\r\n" +boot_failure: + int $0x18 /* Boot failure */ +die: + hlt + jmp die + /* * read_sector: read a single sector pointed to by %eax to %es:%bx. * CF is set on error. All registers saved. @@ -266,15 +306...

...nerating the error >> message "isolinux.bin missing or corrupt". > > That would be the MBR code at bytes 0 to 432 of the ISO. > Source code (assembler) is at > http://git.zytor.com/syslinux/syslinux.git/tree/mbr/isohdpfx.S I see the source code for the error message: bad_signature: call error .ascii "isolinux.bin missing or corrupt.\r\n" And the machine code: 2017-03-18 18:06:56 root at cd2533 ~ # dd if=/var/local/data/dpchrist/iso/debian/8.7.1/i386/debian-8.7.1-i386-xfce-CD-1.iso bs=1 skip=177 count=37 2>/dev/null | hexdump -C 00000000 e8 83 00 69 73 6f...

On 03/18/2017 01:18 AM, Ady Ady via Syslinux wrote: > Some of the things you should / could (re)test / (re)try: > > _ Verify the md5sum of the ISO image. SHA256 verified for downloaded image and for contents of USB flash drive (see below). > _ Is this particular USB device _still_ capable of booting newer > computers? Yes. > What happens if you would try _again_ to boot a