On Tue, Nov 4, 2008 at 4:04 PM, Greg Freemyer <greg.freemyer@xxxxxxxxx> wrote: > On Tue, Nov 4, 2008 at 2:13 PM, Mark Lord <liml@xxxxxx> wrote: >> Greg Freemyer wrote: >>> >>> On Tue, Nov 4, 2008 at 1:08 PM, Mark Lord <liml@xxxxxx> wrote: >> >> .. >>>> >>>> Mmm.. never thought about that much before now, >>>> but DCO is a nifty way to hide much of a drive from prying eyes. >>>> Eg. Use DCO to restrict the drive to LBA28 accessible sectors >>>> and also turn off LBA48 support, and then a lot of space becomes >>>> "hidden". >>>> Until now! >>> >>> Yeah, combine that with some HPA shenanigans and you can create two >>> complete disk partition layouts on one drive. >>> >>> ie. Two partition tables, the normal partition table for the first 128 >>> GiB is in sector 1. The partition table for the rest of the disk is >>> at sector 128 GiB + 1. Then use DCO to totally hide the upper section >>> of the drive. >>> >>> When you want access, use DCO commands to expose it, and then HPA >>> commands to make only the sectors beyond 128 GiB accessible. >> >> .. >> >> Now that one has me stumped. The only HPA commands I know of, >> permit setting only the maximum-LBA, not the minimum. >> Or is this a newish ATA9 (or last-minute ATA8) sort of thing ? >> .. >>> >>> to the end of the disk, then issue a "hpa swap" command. That will >>> hide the first 128 GiB and expose the rest of the disk. >> >> .. >> >> Yeah.. what's this "hpa swap" ? Possibly a vendor-specific op, perhaps? >> >> Cheers >> > Mark, > > I don't know the details, <snip> I got curious. It is in a 7 or 8 year old spec. T13 1407DT >From Draft 5: (http://www.t13.org/Documents/UploadedDocuments/project/d1407r5-Address-Offset.doc) 3. Address Offset Mode operation 3.1 Enable/Disable Address Offset Mode In devices that support the Address Offset feature, the SET FEATURES subcommand 09h Enable Address Offset Mode, offsets address Cylinder 0, Head 0, Sector 1, LBA 0, to the start of the non-volatile protected area established using the SET MAX ADDRESS Command. The Address Offset condition is cleared by the SET FEATURES subcommand 89h Disable Address Offset Mode, a hardware reset or a power-on reset. If Reverting to Power on Defaults has been enabled by a SET FEATURES command, it is cleared by software reset as well. Upon entering the Address Offset mode the capacity of the drive returned in the Identify device data is the size of the former protected area. A subsequent SET MAX ADDRESS command using the address returned by the READ NATIVE MAX ADDRESS command allows access to the entire drive. Addresses wrap so the entire drive remains addressable (see figure 1). If a non-volatile reserved area has not been established before the device receives a SET FEATURES Enable Address Offset Mode command, the command fails with Abort error status. The Disable Address Offset Mode removes the address offset and sets the size of the drive reported by the IDENTIFY DEVICE command back to the size specified in the last non-volatile SET MAX ADDRESS command. 3.2 IDENTIFY DEVICE IDENTIFY DEVICE word 83 bit 07, if set to one, indicates the device supports the Address Offset Mode. IDENTIFY DEVICE word 86 bit 07, if set to one, indicates the device is in Address Offset Mode. 3.3 SET MAX ADDRESS Issuing the SET MAX ADDRESS command with bit 0 in the Sector Count register set to one is not valid when the device is in Address Offset Mode. HTH Greg -- Greg Freemyer Litigation Triage Solutions Specialist http://www.linkedin.com/in/gregfreemyer First 99 Days Litigation White Paper - http://www.norcrossgroup.com/forms/whitepapers/99%20Days%20whitepaper.pdf The Norcross Group The Intersection of Evidence & Technology http://www.norcrossgroup.com -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
