Windows CE on freerunner

[Vikas Saurabh]

Awesome details.

I would definitely give it a try. Not intereseted in font blitting, so would
stick to the morse code idea :).
Would send out the details (and wiki them).

--Vikas

On Fri, Aug 22, 2008 at 7:57 AM, Alex Osborne <ato at meshy.org> wrote:

> On 22/08/2008, at 11:41 AM, Vikas Saurabh wrote:
>
> > Why can't I fool the bootloader to think that I am a kernel. I
> > always thought boot loaders just load the kernel image, pass it
> > some parameters and start executing them.
>
> Indeed, that's exactly what it does.  It loads the kernel image into
> RAM, puts some parameters and a pointer to the ATAGS (which include
> stuff the kernel command-line) into registers and jumps to the start
> of the image.  See here for details:
>
> http://www.arm.linux.org.uk/developer/booting.php
>
> >
> > I had done this helloworld kind of thing with grub during
> > college...but then maybe grub is advanced. What puzzles me is how
> > exactly?
>
> Note that the Freerunner doesn't have a BIOS.  When you did it on x86
> you probably used the BIOS' printing routines.  If you want to do it
> on the FR you'll have to do your own font blitting etc.  If you have
> a debug board you could print it to a serial port.  You can then also
> use JTAG to debug your code and figure out what is going on.  If you
> don't have the debug board, I guess you could easily enough blink out
> hello world in morse code through an LED or by turning on and off the
> backlight or something.
>
> It might also be useful to play with it in qemu, just pass in your
> binary with the -kernel option, you can connect gdb to it and step
> through line by line (see the qemu documentation for how to do this).
>
> As to how to actually do it, it's a bit of a pain.  You'll probably
> need to write a little ARM assembler stub entry point to setup a
> stack and call your C code.  Although you might be able to just reuse
> u-boots stack, I guess.  Then you'll need to compile your code with -
> nostdlib and link it in a way that ensures your assembler code is at
> the start of the image, you might need to investigate custom linker
> scripts for this, I can't remember.  You can then use something like
> "objcopy -O binary mycode.elf mycode.bin" to pull the raw code out of
> the elf file the linker generated, so that you can give it to u-boot.
>
> Remember also that you won't have any standard library, so you'll
> have to write every function you want to use yourself (or use
> something like the OSKit C library) and if you code has a bug it's
> just going to hang or reset the CPU, unless you define your own error
> handling code.
>
> So yes, certainly doable and a good learning experience but it's not
> exactly straightforward.
>
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