[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 <odanet at caramail.com>
>> 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 :-)
>>>
>>>
>>> --
>>> OpenBIOS http://openbios.org/
>>> Mailinglist: http://lists.openbios.org/mailman/listinfo
>>> Free your System - May the Forth be with you
>>
>>
> 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.