Running Linux on an NCD HMX X-Terminal

Running Linux on an NCD HMX X-Terminal

[Adam Nielsen]

Hi,

I've got a few old NCD HMX X-Terminals and I'd like to see if I could get 
Linux running on them.  The reason I ask is that the units boot an ELF image 
over the network, and when running readelf on the image it appears than the 
terminals have an R3000 processor:

$ readelf -h Xncdhmx 
ELF Header:
  Magic:   7f 45 4c 46 01 02 01 00 00 00 00 00 00 00 00 00 
  Class:                             ELF32
  Data:                              2's complement, big endian
  Version:                           1 (current)
  OS/ABI:                            UNIX - System V
  ABI Version:                       0
  Type:                              EXEC (Executable file)
  Machine:                           MIPS R3000
  Version:                           0x1
  Entry point address:               0x40020000
  Start of program headers:          52 (bytes into file)
  Start of section headers:          2625644 (bytes into file)
  Flags:                             0x0
  Size of this header:               52 (bytes)
  Size of program headers:           32 (bytes)
  Number of program headers:         1
  Size of section headers:           40 (bytes)
  Number of section headers:         7
  Section header string table index: 6

Does anyone know what my chances would be of getting a Linux kernel on it?  I 
found a couple of precompiled MIPS kernel images (one was ELF32 but the other 
was ELF64), however when I tried to boot them the terminal simply said "Load 
address out of range" and aborted.  I was using the precompiled images 
because I really want to know whether it'll work before I go to the trouble 
of installing all the cross-compilation tools.

Any info would be greatly appreciated!

Thanks,
Adam.

Re: Running Linux on an NCD HMX X-Terminal

[Brad Parker]

Adam Nielsen wrote:
...
>Does anyone know what my chances would be of getting a Linux kernel on it?  I 
>found a couple of precompiled MIPS kernel images (one was ELF32 but the other 
>was ELF64), however when I tried to boot them the terminal simply said "Load 
>address out of range" and aborted.  I was using the precompiled images 
>because I really want to know whether it'll work before I go to the trouble 
>of installing all the cross-compilation tools.

I brought up linux on the PPC403 version of an NCD x-terminal.  As I recall I
had to write program to hack the elf header to get kernels to load.

The project is at http://sourceforge.net/projects/explora-linux/

And the program to hack the kernel elf file is 

http://cvs.sourceforge.net/viewcvs.py/explora-linux/ncdhack/ncdhack.c

You may get lucky and find they used the same format for MIPS...

-brad

Re: Running Linux on an NCD HMX X-Terminal

[Adam Nielsen]

> I brought up linux on the PPC403 version of an NCD x-terminal.  As I recall
> I had to write program to hack the elf header to get kernels to load.
> The project is at http://sourceforge.net/projects/explora-linux/

Hmm...this looks interesting!

> You may get lucky and find they used the same format for MIPS...

Well I am hopeful, given that they use the same manual for the HMX and the 
Explora, but running ncdhack on the kernel didn't seem to have any effect :-(

I did try some fiddling with the ELF files, just to see what would happen (but 
not having any experience with this, I was just guessing ;-))  The load 
address for the proper boot image is 0x40020000 but the kernel is 0x88002000 
which I think is partly why it doesn't work.  If I shrink the ELF file a 
little by removing a couple of the sections (by telling objcopy to ignore 
them) *and* I change the load address to 0x40020000 then the xterm actually 
downloads the image but then gives a "File corrupted CRC error" just as it 
goes to boot it.

I'm not sure why that happens, because manipulating the file properly with 
objcopy should adjust any CRC checksums accordingly.  I wonder whether the 
xterm is checking that the image is 'official'?

Cheers,
Adam.