Re: kern/59783: Can't mount the "special" SGI volume formatted cd9660

["Izumi Tsutsui via gnats" <gnats-admin%NetBSD.org@localhost>]

The following reply was made to PR kern/59783; it has been noted by GNATS.

From: Izumi Tsutsui <tsutsui%ceres.dti.ne.jp@localhost>
To: gnats-bugs%netbsd.org@localhost
Cc: tsutsui%ceres.dti.ne.jp@localhost
Subject: Re: kern/59783: Can't mount the "special" SGI volume formatted cd9660
Date: Sun, 23 Nov 2025 03:03:39 +0900

 > >Synopsis:       Can't mount the "special" SGI volume formatted cd9660
 
 > boot -f scsi(0)cdrom(5)rdisk(0)partition(8)ip2xboot
 > 
 > .. which means the SGI volume label is correct!
 > 
 > But they can't be mounted.
 
 This is because the CD-ROM image for sgimips includes
 teh SGI volume header before ISO9660 (for its ARC BIOS)
 and it has certain offset (more than 32KB for usual ISO9660).
 
 In most case ISO9660 images don't include explicit disklabel
 (i.e. raw struct cpu_disklabel) data in the disk image
 and it should be handled by MD disklabel routines.
 However most ports assume ISO9660 has no such offset.
 
 > >Fix:
 > from mlelstv on irc; I've tested this and it fixes it.
 
 IIRC one annoying issue is sector size on ISO (usually 2048).
 If we are trying to offset in actual disklabel, we have
 to check carefully all values are consistent (in 512 bytes
 or 2048 bytes etc).
 
 Thanks,
 ---
 Izumi Tsutsui