[syslinux] Re; isohybrid question

[Thomas Schmitt]

Hi,

> Sorry for the late reply, I have been travelling.

I made a more elaborate proposal the same day:
  http://syslinux.zytor.com/archives/files/2010-March/013905.html


> b) patching the LBA of the boot file at (zero-based) offset 432
>    decimal;
> c) constructing the volume ID of the partition table at offsets
>    440-512.

It takes care of this by the headers
  Num-h: 64
  Num-s: 32
  Limit-cc: 1024
  Bin-block-field: 432
  Payload-size: 512
which i identified as the parameters which
libisofs needs to know to perform its adjustments
on the MBR.


> a) verifying the hybrid signature of the boot file;
> [...]
> The one thing that I'm wondering about is if we should have a more
> complete header of the boot file than the very simple signature I have
> now, to avoid future problems.  In particular, I'm wondering if there is
> anything we can do to avoid version mismatches between the System Area
> file and the rest of the boot file.

How about a signature header ?
  Signature: <Start-byte>,<Hex-bytes>[:<Start-byte>,<Hex-bytes>]

E.g.:
  Signature: 64,fbc07870
The ISO formatter then has to check 4 bytes of
magic beginning at byte 64 of the boot image
file.

This would give you the freedom to prescribe more
than one significant byte string to match.

In general the MBR template should be generated
by the same SYSLINUX version as the isolinux.bin.
So you could have a version stamp inside
isolinux.bin which must match the MBR template
header.


Have a nice day :)

Thomas