Russel King <rmk@arm.linux.org.uk>:
>And who's to say that the first four bytes of the first sector of a hard drive
>have any significance in any case? Some partition tables are stored in sector
>6, others in the first sector, etc.
My idea was based on information on page 179 of _Advanced
MSDOS Programming_, second edition, by Ray Duncan, which stated
that valid MSDOS boot sectors always started with one of these
two patterns (in hexademical):
E9 __ __ (real mode relative jump, 16 bits)
EB __ 90 (real mode relative jump, 8 bits + nop)
Checking four systems here, I see that their disks
start with:
FA EB 6C 00 (3 machines have this sequence)
EB 69 49 4C (1 machine has this sequence).
I am not sure what the FA opcode prefix does, but that
system's BIOS still attempts to boot it, so the BIOS apparently
still recognizes it.
Anyhow, using a scheme like this, it would be possible to
add something /etc/modules.conf (or /usr/share/modules/modules.conf.base):
alias partition-faeb???? msdos_part
alias partition-e[9b]?????? msdos_part
However, I am much more interested in a facility mentioned by
"Guest Section DW" (dwguest@win.tue.nl) where userland programs can
define the partitioning to the kernel directly. This would be much
better, since the code would not consume unswappable kernel space,
it would not have to be released with every new kernel, the would
not be copies for each kernel version in /lib/modules, it would be
more flexible, and it could more easily share code with fdisk-like
programs. Unfortunately, I am having trouble finding this facility,
since it looks like the only routines that call add_gd_partition are
those partitioning modules. Anyhow, if this facility really exists,
I would appreciate a pointer to it, because I would love to move
partition table reading entirely to userland.
Adam J. Richter __ ______________ 4880 Stevens Creek Blvd, Suite 104
adam@yggdrasil.com \ / San Jose, California 95129-1034
+1 408 261-6630 | g g d r a s i l United States of America
fax +1 408 261-6631 "Free Software For The Rest Of Us."
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