[uCsimm] Himemloader for uCimm

From: Bernhard Kuhn (kuhn@lpr.e-technik.tu-muenchen.de)
Date: Sat Mar 17 2001 - 21:34:26 EST


Short:
------
Loading images for uCsimm to ram via ethernet/nfs.

Long:
-----
uClinux on uCsimm can be started from RAM
to simplyfy development, but you have to
download the image via the serial line
(afaik).

As i don't like to bother around with
minicom/fast/rx, i implemented a
"himemloader": instead of loading the image to
0x20000 via the serial line (fast/rx) within
the bootloader environement, the image is treated
as located in ROM and loaded to
0x600000 via ethernet/nfs within uClinux.
The usage of the command "himemloader" is similar to
"flashloader". To reserve the memory for the
new image, the "*.ld" files in
platforms/68EZ328/ucsimm are modified accordingly.
Additionaly, You have to be in "supervisor mode"
in order to start the loaded kernel. I remembered
a trick that was used 17 years ago at AmigaOS:
I implemented trap #10, that just sets the Supervisor bit
in the status register that is saved on the stack and
returns from exception. The RTE then restores the
modified sr :-)

The whole package can be downloaded at
http://www.rcs.ei.tum.de/~kuhn/uclinux/himemloader-patches.tgz
and consists of the following patches:

patch-2.0.38.1pre7-supervisor
  trap #10 implementation for setting supervisor mode
  in user space. Include asm/system.h that provides
  the function supervisor() to make things easier.

patch-2.0.38.1pre7-supervisor-himem
  apply this patch *after* applying the supervisor-patch
  to limit the Memory to 6 Mbyte to get 2 Mbyte to
  emulate some ROM. An option "Kernel executes from HIMEM"
  is added in the "platform dependant setup".

patch-boottools-himemloader
  This patch adds the "himemloader" command to the boottools
  directory.

patch-deftemplate.sh-himemloader
  This patch just adjusts the deftemplate.sh so that
  the himemloader is also copied to the romdisk when typing
  "make" within the project directory.

Bernhard
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