Re: [OpenBIOS] next-property

[Mark Cave-Ayland]

On 03/01/14 19:16, Olivier Danet wrote:
> On 03/01/2014 17:09, Artyom Tarasenko wrote:
> > On Thu, Jan 2, 2014 at 2:43 AM, Olivier Danet 
> > wrote:
> > > I may have found a bug in OpenBIOS.
> > >
> > > An OS uses the "nextprop" iterator to scan device properties, and
> > > eventually
> > > asks about nonexistant properties.
> > > "const char *obp_nextprop(int node, const char *name)"
> > > (arch/sparc32/romvec.c)
> > > calls the "next-property" forth code, then pops the result.
> > > According to the standard, next-property should return 0 if the property
> > > selected
> > > is the last _OR_ if the property does not exist.
> > > The current code in forth/admin/devices.fs returns nothing when the
> > > property
> > > does
> > > not exit.
> > >
> > > For example (SPARC 32) :
> > >
> > > cd screen
> > > " name" ?active-package next-property drop cr type
> > > --> returns "device_type"
> > >
> > > " interrupts" ?active-package next-property
> > > --> returns 0, this is the last property.
> > >
> > > " bozo" ?active-package next-property
> > > --> returns nothing. Which, imho, is wrong.
> >
> > Actually this matches pretty much with what OBP does:
> >
> > ok showstack
> > ok " model" current-device next-property
> > fffe61e8 4 ffffffffffffffff ok drop type
> > name
> > ok " bozo" current-device next-property
> > ok
> >
> > Artyom
> > > Here is a patch, I am not quite sure about it (debuting Forth)
> > > but it helps the target OS :
> > > Index: forth/device/property.fs
> > >
> > > --- forth/device/property.fs (révision 1246)
> > > +++ forth/device/property.fs (copie de travail)
> > > @@ -70,7 +70,7 @@
> > > 2drop r> >dn.properties @
> > > else
> > > r> find-property dup if @ then
> > > ?dup if >prop.next @ then
> > > dup if >prop.next @ then
> > >
> > > then
> > > ?dup if
> > >
> > > The standard asks for a pointer to a zero lenght string instead of zero,
> > > the C code obp_nextprop() expects a zero. I don't know if it makes a
> > > difference.
> > >
> > > Olivier
> > > (Btw, the OS is NetBSD :-)
>
> You are right.
> I tried on an Ultra 10 with OpenBoot 3.12.
>
> next-property returns nothing when the property is unknown and also when
> the property is the last one.
> This contradicts Sun own documentation "Writing FCode 3.x Programs".
>
> Puzzled, I tried then on a Apple iBook G3 :
> dev screen
> " <something>" active-package next-property
>
> This laptop returns :
> true and a forth string when the property is not the last one
> true and "0 0" when the property is the last one
> false when the property does not exist.
>
> Anyway, whatever method is chosen (return nothing, return zero...),
> OpenBIOS forth and/or C code ("opb_nextprop()") should be modifed to
> avoid page faults.

Hi Olivier,

Do you have a revised version of this patch based upon the discussion in 
this thread?

I'm wondering whether we should simply use a [IFDEF] SPARC32 ... [ENDIF] 
block so that your change only takes effect on SPARC32?

ATB,

Mark.