Re: Generic boot image support in makefs(8)

Hello,

isnetbsd.org writes:
> On Sun, Jan 13, 2008 at 04:42:24PM +0000, Nick Hudson
wrote:
> > Hi,
> > 
> > I added an option to makefs(8) to write a file
into the first 32K of a cd9660 
> > image. This can be used to create bootable
NetBSD/hp700 CDs.
> > 
> > Any comments before I commit?
> 
> I think this collides with SUN disklabels, needed for
bootable SUN CD's (Sun3,
> Sun3x,32 bit Sparc - I'm not totally sure about
Sparc64).

It is possible to have both SPARC disklabel and hp700 LIF
structure.
I did this when I was developing hp700 xxboot.

hp700 LIF uses bytes 0-1 (0x80 0x00) and 240-251 (points to
IPL location)
of the first sector.  The IPL itself is placed elsewhere.

SPARC disklabel starts at 128th byte (LABELOFFSET in
<sparc/disklabel.h>)
of the first sector.

<sys/disklabel.h> (added byte offsets):
struct disklabel {
	uint32_t d_magic;		/* 128: the magic number */
	uint16_t d_type;		/* 132: drive type */
	uint16_t d_subtype;		/* 134: controller/d_type specific */
	char	  d_typename[16];	/* 136: type name, e.g.
"eagle" */

	... (snip)

#define	NDDATA 5
	uint32_t d_drivedata[NDDATA];	/* 220: drive-type specific
information */
#define	NSPARE 5
	uint32_t d_spare[NSPARE];	/* 240: reserved for future use
*/
	uint32_t d_magic2;		/* 260: the magic number (again) */
	uint16_t d_checksum;		/* 264: xor of data incl. partitions
*/

			/* filesystem and partition information: */
	... (snip)
};

The hp700 LIF header (240-251) happen to fit in the spare
words (d_spare),
and does not damage SPARC disklabel (the checksum of the
disklabel needs
to be recalculated, though).

Just for your information.
-- 
ITOH Yasufumi