GRUB on OLPC / XO

[Robert Millan]

Some comments on things that need polishing.  Some are more addressed at one
of the two lists than the others, but feel free to join in either case.

(also, if you feel this is off-topic in olpc-devel, feel free to ki^W let
me know)

btw, Mitch mentioned to me on IRC that the ELF loader on XO has some "weird"
modifications to support Minix.  Is this documented somewhere?

On Sat, Jan 12, 2008 at 02:42:30PM +0100, Robert Millan wrote:
> +void
> +grub_exit (void)
> +{
> +  /* Trap to Open Firmware.  */
> +  /* FIXME.  */
> +
> +  for (;;);
> +}

We used to run "trap" insttruction on powerpc.  I assume for exitting via trap
on i386 we need to generate an interrupt;  I'm just not sure which is the right
number for it.

>    /* Load pre-loaded modules and free the space.  */
>    grub_register_exported_symbols ();
> -  grub_load_modules ();
> +//  grub_load_modules ();

This generates an out of bounds exception.  GRUB puts modules above _end
(0x1000-aligned).  Is access to that address allowed by OFW ?
 
>    grub_ieee1275_finddevice ("/options", &options);
>    rc = grub_ieee1275_get_property (options, "real-mode?", &realmode,
>  				   sizeof realmode, 0);
> -  if ((rc >= 0) && realmode)
> +//  if ((rc >= 0) && realmode)
>      grub_ieee1275_set_flag (GRUB_IEEE1275_FLAG_REAL_MODE);

This OFW operates in what GRUB calls "real mode" (not to be confused with
x86 realmode!), but /options/real-mode? doesn't exist.  Should we probe
for the actual feature (/chosen/mmu IIRC), probe for firmware version, or
#ifdef it for x86 CPUs?

> -void cmain (uint32_t r3, uint32_t r4, uint32_t r5);
>  void
> -cmain (UNUSED uint32_t r3, UNUSED uint32_t r4, uint32_t r5)
> +cmain (void)
>  {
> -  grub_ieee1275_entry_fn = (int (*)(void *)) r5;
> -

This was the only powerpc-specific part of that file, that I can tell.  I
moved grub_ieee1275_entry_fn initialisation to startup.S.  I'd suggest doing
the same on powerpc/sparc and move cmain.c out of powerpc/ directory.


> diff -x '*.mk' -x '*~' -x CVS -x .svn -x configure -x config.h.in -Nurp ../../grub2/kern/powerpc/ieee1275/init.c ./kern/powerpc/ieee1275/init.c
> --- ../../grub2/kern/powerpc/ieee1275/init.c	2008-01-03 23:43:46.000000000 +0100
> +++ ./kern/powerpc/ieee1275/init.c	2008-01-12 03:26:06.000000000 +0100
> @@ -52,15 +52,6 @@ grub_millisleep (grub_uint32_t ms)
>    grub_millisleep_generic (ms);
>  }
>  
> -void
> -grub_exit (void)
> -{
> -  /* Trap to Open Firmware.  */
> -  asm ("trap");
> -
> -  for (;;);
> -}

Same here.

>    /* Decode each entry and call `hook'.  */
>    i = 0;
> -  while (i < sizeof (available))
> +  while (i < sizeof (available) && available[i])

Here we were attempting to claim a region that starts at 0x0 and
ends at INT_MAX !!  I suppose we just need to check for available property
length.  Need to look more into this.

> -      address = available[i++];
> +      address = grub_be_to_cpu32 (available[i++]);
>        if (address_cells == 2)
> -	address = (address << 32) | available[i++];
> +	address = (address << 32) | grub_be_to_cpu32 (available[i++]);
>  
> -      size = available[i++];
> +      size = grub_be_to_cpu32 (available[i++]);
>        if (size_cells == 2)
> -	size = (size << 32) | available[i++];
> +	size = (size << 32) | grub_be_to_cpu32 (available[i++]);

Integer properties are always in network byte order (thanks Mitch for
clarifiing).

I wonder if we should byteswap all callers of getprop or just mangle the
result in the getprop function instead (the latter seems cleaner, but it wasn't
obvious how to do it without breaking non-integer properties).

Ah, and for some reason address_cells is set to a garbage number.  Might be
a pointer dereference issue, will look into this.
 
> --- ../../grub2/term/ieee1275/ofconsole.c	2007-12-25 12:10:47.000000000 +0100
> +++ ./term/ieee1275/ofconsole.c	2008-01-12 03:09:02.000000000 +0100
> @@ -369,9 +369,6 @@ static struct grub_term grub_ofconsole_t
>      .getwh = grub_ofconsole_getwh,
>      .gotoxy = grub_ofconsole_gotoxy,
>      .cls = grub_ofconsole_cls,
> -    .setcolorstate = grub_ofconsole_setcolorstate,
> -    .setcolor = grub_ofconsole_setcolor,
> -    .getcolor = grub_ofconsole_getcolor,
>      .setcursor = grub_ofconsole_setcursor,
>      .refresh = grub_ofconsole_refresh,
>      .flags = 0,

Not really a porting issue, but when using serial terminal GRUB still tries to
set white/black color on it, which becomes very ugly in my black/white
gnome-terminal :-)

-- 
Robert Millan

<GPLv2> I know my rights; I want my phone call!
<DRM> What use is a phone call, if you are unable to speak?
(as seen on /.)