Talk:PreDesktop Area

Use the HPA for GNU/Linux?

More interesting than removing the HPA (which includes a.o. Acces IBM Predesktop Area, some other tools and a backup of the pre-installed OS) would be to use this area for GNU/Linux too. At least, removing the HPA only saves 3,5 GB on my 60 GB hard disk. It would be worth a try to see whether the backup of the pre-installed OS on the largest PSA could be replaced by a backup of your favourite GNU/Linux distribution.

Elaborating on my ideas a few days later, I'd guess the following could be tried:

• see whether GRUB can be made to boot the Access IBM Predekstop Area (I guess by "chainloading" the bootsector of its PSA). Right now GRUB refuses to load sectors outside the partioned area. I've got absolutely no idea if it's possible to write a hack to overcome that restriction. Need to contact the GRUB people about that ...
• write a HPA or SPA driver. That driver should provide something like "/dev/hpa", "/dev/hpa0", etc or "/dev/spa", "/dev/spa0", whatever. The idea here is that it allows you to simply mount (ro!) the Hidden Protected Area (given the correct BIOS settings). Probably just an addaption of the current drivers for (IDE?) harddisks. (This might mean "/dev/hda" and "/dev/hpa" overlap: dangerous?) That would probably need - way - more coding skills than I have ...
• write some userspace tools for the HPA/the SPAs (things like: dumpbeer, printDoS).

It should be clear these are basically random ideas. Still feedback would be appreciated ...

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Hei,

interesting ideas, but i'd only see a point in it if one could keep Win and Linux rescue stuff in the HPA. That means it would need to be expandable or fit the stuff for both systems. Wyrfel 20:03, 15 Mar 2005 (CET)

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Thanks.

Short answer: that should be possible.

Long answer: I see little in the specs (as I understand them now) to stop one from adding (say) an extra 3 GB GNU/Linux-rescue PSA or something like that. We might try to do that first by changing the BEER and DoS manually. (Not sure whether Phoenix added some proprietary stuff to keep you from booting it. The PSA should always be accesable with the proper BIOS setting.) It might be mandatory to put it on a FAT filesystem. The hard part probably is to have it show up in the Access IBM Predesktop Area. (My guess is you need to regenerate the FirstSight "graphical shell". If that's correct we probably only can use the FirstWare tools "hidden" on their little PSA. That's no fun. Well it might a little fun if we try FreeDOS).

Paul Bolle (not logged in)

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Update: a trivial patch to grub allows it to also work outside the partioned area:

--- /var/tmp/rpm/BUILD/grub-0.95/stage2/disk_io.c.oud   2004-05-23 18:35:24.000000000 +0200
+++ /var/tmp/rpm/BUILD/grub-0.95/stage2/disk_io.c       2005-03-18 22:38:30.050907408 +0100
@@ -297,8 +297,8 @@
    *  Check partition boundaries
    */
   if (sector < 0
-      || ((sector + ((byte_offset + byte_len - 1) >> SECTOR_BITS))
-         >= part_length))
+      /*|| ((sector + ((byte_offset + byte_len - 1) >> SECTOR_BITS))
+         >= part_length)*/)
     {
       errnum = ERR_OUTSIDE_PART;
       return 0;

I made a grub CD with a grub patched with the above. Now I can "cat" the bootsector of the Predesktop Area from the grub shell (when booting of that grub CD). But I haven't yet managed to boot the Predesktop Area (dangerous stuff!) To be continued ...

Paul Bolle Fri Mar 18 22:42:43 CET 2005

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I've been playing around with the predesktop area tonight. I was simply trying to just leave the diagnostics stuff and remove the windows part. I wrote some programs to read/write the BEER data and stuff, but I wasn't able to get the system to boot it, it kept erroring "Authentication of System Services failed" (or something along those lines). I will play around with this some more later

Tim Nordell

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A quick look with a hexeditor gave me two instances of "Application authentication has failed!" in the FirstSight application. Does that sound familair?

Paul Bolle Fri Apr 1 19:35:30 CEST 2005

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Actually it wasn't that. I did a search of that too, the message itself was not in the predesktop area at all. What also is interesting is the fw*.exe utilities for manipulating the predesktop area, contains the string "MD5" which makes me wonder if there is an md5 hash of each "predesktop" partition. I know on the IBM whitepaper it states there being a signature so that non-signed applications can not be run. Could a simple "md5" be the signature?

Tim Nordell 12:01, 3 Apr 2005 (CEST)

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• What is it that you were trying to do (what did trigger the error you saw)?

• About ten of the fw*.exe utilities contain the phrase "MD5 Checksums do not match". So they could very well be using MD5 sums for some sort of validation. But they could use the MD5 sums in a lot of ways actually, so I won't yet speculate ...

Paul Bolle Sun Apr 3 15:11:10 CEST 2005

Predesktop Area

I made a program that takes the BEER record at the end, parses it out to a ".cfg" file, lets you modify it, recalibrate the start spots for the records, and write it out to disk again. It doesn't directly access hda, 'cept for reading the original beer record. It makes a script file to go with the files you have, to read in the HPA data, and to write it out again with the new record.

Anyways, I tried simply removing the last record from the BEER, which is the windows recovery partition. It didn't like that.

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Did you update the two's complement checksum at the end of the BEER?

Paul Bolle

TODO

• Ad a section on dmesg and hdparm -I output:

(...)
Commands/features:
       Enabled Supported:
(...)
          *    Host Protected Area feature set
(...)
               SET MAX security extension
               Address Offset Reserved Area Boot
(...)

• Check boot parameters: is hda=stroke still valid?

Kernel command line: ro root=LABEL=/ acpi=off hda=stroke
ide_setup: hda=stroke -- BAD OPTION

Paul Bolle