[syslinux] Re; isohybrid question

[H. Peter Anvin]

On 03/30/2010 01:55 PM, Thomas Schmitt wrote:
> 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
> 

I really don't like it, in large part because it embeds in the file
things that would be better passed directly to xorriso, and which are
user options which don't come out of the Syslinux build anyway.
Otherwise I need to add a CLI tool to manipulate these files just so the
user can set these options, which really doesn't make any sense whatsoever.

We could wrapper up the files out of the Syslinux build, perhaps using
an ar archive or something like that, but I'd like to see a good reason
for doing so.  The *only* reason I can think of at the moment is to make
sure the System Area file matches the boot file, or to allow a System
Area file to be created without the isohybrid extensions, but I think
that's already supported in the form of the -G option to mkisofs (I
assume xorriso is compatible with the mkisofs interface, although I
haven't looked myself.)

As such, the format of bytes 432..511 is fixed anyway.  Perhaps what we
can do is use those bytes in the System Area image to point to the
signature in the boot file:

- Offset 432 contains the offset within the boot image for the
  signature;
- Offset 436 contains the length of the signature;
- The remaining bytes is the content of the signature string.

If no signature checking is desired, the build can just leave these
bytes to be zero.

How does that sound?

	-hpa