[syslinux] [syslinux:disklib] disklib: make CHS calculation match core/fs/diskio.c

[Gene Cumm]

On Mon, Oct 18, 2010 at 00:14, Shao Miller <Shao.Miller at yrdsb.edu.on.ca> wrote:
>> On 10/14/2010 09:08 AM, Shao Miller wrote:
>>>
>>> Somewhat unrelated: Some day in the far, far future, it might be nice to
>>> "re-image"[1] computers using INT 13h via one or more COMBOOT32
>>> programs.  - Shao
>>>
>>> [1] Apply a disk or filesystem snapshot/saved-state.
>>
>> That's not even very hard at all, at least not for the whole-disk case.
>
> Andrew Bobulsky wrote:
>>
>> Hello Shao, hpa,
>>
>
> Hello.
>
>> I thought it was really ironic that you guys mentioned this.  I remember
>> back when I was imaging XP, I was trying to work out specifically what I'd
>> want to do to get gPXE/PXELINUX/COMBOOT to simplify our imaging process
>> which at the time was using a very clunky XP live CD that took forever to
>> boot up...  I ultimately ended up booting DOS from iSCSI and imaging via
>> INT13 with Ghost 8, which worked pretty well.
>
> That seems very familiar...  Until (for Windows) working out a 210 MB non-PE
> XP RAM disk image and including NIC and SATA drivers; then there was a
> definite gain from 32-bit network drivers.
>
>> Still, while I was wrapping my head around the concepts I was trying to
>> exploit, I was browsing through all of these com32 modules in the SYSLINUX
>> package then hopped on IRC and said, "Hey guys, is there a COM32 module for
>> imaging disks?  Something like DD.c32?"
>
> That seems interesting, and as H. Peter mentions, probably fairly
> straight-forward to implement for sector imaging.  FS manipulation would be
> a different story. :S
>
>> While several people (you guys included I think) remarked that it was an
>> interesting idea, I never found anything...  Hence the Ghost 8 use :-D
>
> Well if we [Syslinux users/enthusiasts] had a DD.C32 COMBOOT32 module that
> did something useful like write an image from the Syslinux filesystem (TFTP:
> hmm...) to a disk via INT 0x13, that might be a tiny start.  There might be
> a challenge if a RAID/SCSI adapter was a BEV device and if the user
> PXE-boots but if that prevents the adapter's ROM from establishing an INT
> 0x13 hook.  I guess there's one way to find out.

Most (but probably all) of the disk controllers (built-in
RAID/SCSI/SAS/SATA, add-in Fibre Channel and RAID/SCSI) and
PXE-enabled NICs (always LoMs; LAN On Motherboard) I've used load
their BIOS extension before any boot entry is processed, granting
access to the RAID volume from any boot (CD, HDD, RAID, FC or PXE) via
INT 13h (until a driver is loaded, of course).

At that point, I think the obvious possible issue is software RAID.
This would require that the user know more about their environment and
how to manage it anyways so I'd consider it a non-issue.
Documentation should be distributed with dd.c32 to warn of this (use
at your own risk).

>> I do think it would be really nifty to have a DVD with ISOLINUX that boots
>> to a menu and images all via COM32...   no HAL issues or hardware
>> compatibility issues, no need to wait for a "thick" protected mode OS to
>> load.  Making modern operating systems easier to deploy by exploiting the
>> ubiquity of the "modern" BIOS implementations has a high geek-sexiness
>> factor to it ;)
>
> For Windows, HAL/kernel injection might require an FS driver (I'm thinking
> of NTFS) and write support.  A sneaky way might be to put magic in a
> BOOT.INI file with known contiguity and a known length, then overwrite it
> with a particular HAL/kernel choice...  What a hack.  But we don't know
> Windows XP Setup's logic for HAL/kernel choice (though perhaps we could
> guess).
>
> With Linux, of course, it's possible (and easy) to get a minimal environment
> with just what you need for re-imaging.  There is a project called
> "DeployStudio"[1] whose PC support happens to use PXELINUX and Linux for
> re-imaging, but I believe the environment supports Windows images, as well.
>
> There is definitely something nice about pre-OS control, where Syslinux and
> its wonderful shuffler can "get out of the way" and boot an OS after doing
> other useful things...  And of course UNDI+PXE and INT 0x13 are handy where
> one doesn't wish to manage tracking down and injecting drivers for a proper
> OS.
>
> - Shao Miller
>
> [1] http://www.deploystudio.com/Home.html

-- 
-Gene