After yesterday’s post I received a tip that I may wish to try getting at the Xbox disc data using the low-level Linux SCSI layer– the facility commonly known as SCSI generic, or simply ‘sg’. In order to make use of this facility, it is necessary to configure your Linux kernel with the right support (CONFIG_CHR_DEV_SG, CONFIG_BLK_DEV_IDESCSI, but not CONFIG_BLK_DEV_IDECD). Download and install the SCSI generic utilities from here (which do not compile on my AMD64 machine; fortunately, the x86-compiled utilities and associated shared library drop into the system perfectly). There are about 30 little sg* utilities in the package. One that caught my attention was sg_dd– your typical ‘dd’ Unix command, but for interacting with a SCSI device. I tested it out on a typical Xbox DVD:
$ sudo sg_dd if=/dev/sg0 of=dvd bs=2048 bpt=1 count=20 20+0 records in 20+0 records out
And, indeed, the beginning of the disc has the markings of a typical DVD filesystem. So let’s try to read beyond the 6,992-sector limit on a standard Xbox disc:
$ sudo sg_dd if=/dev/sg0 of=dvd bs=2048 bpt=1 count=2 skip=6991
reading: SCSI status: Check Condition
Fixed format, current; Sense key: Illegal Request
Additional sense: Logical block address out of range
Raw sense data (in hex):
70 00 05 00 00 00 00 0a 00 00 00 00 21 00 00 00
00 00
plus...: Driver_status=0x08 [DRIVER_SENSE, SUGGEST_OK]
sg_read failed, seek=1
Some error occurred, remaining block count=1
1+0 records in
1+0 records out
I had to deal with all this SCSI nonsense in a previous life and I admit that this output is conjuring some sour memories. Anyway, it seems that the stock sg_dd command can not read beyond what the DVD header structure ostensibly reports as the size of the disc. There are a number of other utilities I need to investigate for potential. Failing that, it’s possible — with at least a modicum of effort — to program the sg layer. There may yet be a solution.
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