[syslinux] port syslinux isohybrid perl script to C

H. Peter Anvin hpa at zytor.com
Tue Mar 30 15:37:15 PDT 2010


On 03/30/2010 02:03 PM, Thomas Schmitt wrote:
> Hi,
> 
>> The request is to port the isohybrid script, in the syslinux package,
>> from perl to C
> 
> If a major overhaul of isohybrid is done, then
> please also consider my proposal to produce MBR
> template files as alternative to image patching
> 
>   http://syslinux.zytor.com/archives/2010-March/013905.html
> 

That doesn't work, since creating the content of the MBR requires
knowing the content (at the very least the size) of the iso image; as
such, it belongs in the iso generator.  It cannot be pre-generated as a
template.

There really is nothing at all in bytes 432..511 that xorriso/libisofs
can't create based on defaults plus user options; the rest of the System
Area file just comes out of the Syslinux build as a plain binary.

In other words, the isohybrid support degenerates to the support already
there for the -G option, plus signature checking (see other email), plus
building the "extended" partition table (extended with the LBA to the
boot file.)

Note: the patching of the boot file LBA is really just a convenience.
This could be skipped entirely; the System Area is big enough that it
could contain a full-blown El Torito boot catalog parser, if you think
that is a better option.  Then the *only* difference between isohybrid
and -G would be the creation of the partition table.

	-hpa




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