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

Ya

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