Re: asm in OF? YES!

Re: asm in OF? YES!

[Bruce Anderson]

On Thu, Aug 31, 2000 2:52 AM, Gabriel Paubert <mailto:paubert@iram.es>
wrote:
>
>You've just got to love OF portability across machines and architecture
>independance :-( Add to this the fact that I have somewhere a FirmWorks
>document which claims that on PPC the top of the stack is always in r28,
>r20/r21 are scratch registers. r31 is still the stack pointer (and r30 the
>return stack AFAIR).
>
>

Your asumption about OF portability is in error. Apple does not
use FirmWorks OF code.  Apple created their own "OF" version that
resembles FirmWorks OF vocabulary.



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Re: asm in OF?

[Gabriel Paubert]

	Hi Michel,


> > All the OF I have seen had the capability to build new words in asm, with
> > a `code' definition IIRC. Maybe Apple's OF are crippled ?
>
> Apple's OF seems to have that capability as well (I think, guess and hope ;-).
> However, it does _not_ seem to have an assembler built-in. The 'code' word
> is defined all right.

You don't have any ppc-assembler vocabulary or similar, then ?

> When I do a 'see hido@', I only get:
>  >0 see hid0@ code hid0 ok
>  >0

Ok, how can something this close to the machine be delivered without an
assembler ?

> What I can do is look at the hex dump of the hid0@ word, and that gives me asm
> statements like for you (except that in Apple's OF, r20 holds the top stack
> item ;-). The fact that ' ' hid0@ dis' gives me a hex dump and not a
> disassembly is another evidence that Apple's OF doesn't know anything about
> asm....

Well, sincee you can type in hex, there is still some hope...

> > The syntax to build with an unknwown SPR is strange:
> > code ictc@
> > stwu r28,-4(r31)
> > 33f mfspr r28,*
> > bcctr 20,0
> >
> > generates the correct code, since I don't have ictc spr defined.
> > Otherwise mfspr 28,ictc might work.
>
> I will try this tonight, but I doubt I will be able to enter this as asm
> words. Do you know the alternate syntax? Would something lime this work:
>
> code 60000000 l, 6000000 l,

I think so, let me try:

ok code ictc@ ok 979ffffc l, 7f99faa6 l, 4e800420 l, ;code
ok see ictc@
code ictc@
edcc5c     stwu    r28,-4(r31)
edcc60     mfspr   r28,spr1017
edcc64     bcctr   always
ok ictc@ .
264d2
ok

It just works and returns garbage on a 603e, everytime a different value.

> as a sequence of 2 NOP's? How do you terminate a 'code' sequence?

Oops, forgot about it, my bad. With ';code', isn't it obvious ?

	Gabriel.


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Re: asm in OF? YES!

[Michel Lanners]

Hi all,

Yep, it works! I can boot off mesh again ;-)

On  30 Aug, this message from Gabriel Paubert echoed through cyberspace:
>> Apple's OF seems to have that capability as well (I think, guess and hope ;-).
>> However, it does _not_ seem to have an assembler built-in. The 'code' word
>> is defined all right.
>
> You don't have any ppc-assembler vocabulary or similar, then ?

Nope. Definitely not. We have hexdump and l, , isn't that enough? No
real hacker would use an assembler; thats for lamers ;-)

> Ok, how can something this close to the machine be delivered without an
> assembler ?

See above ;-))

> Well, sincee you can type in hex, there is still some hope...

Hex worked.

>> I will try this tonight, but I doubt I will be able to enter this as asm
>> words. Do you know the alternate syntax? Would something lime this work:
>>
>> code 60000000 l, 6000000 l,
>
> I think so, let me try:
>
> ok code ictc@ ok 979ffffc l, 7f99faa6 l, 4e800420 l, ;code
> ok see ictc@
> code ictc@
> edcc5c     stwu    r28,-4(r31)
> edcc60     mfspr   r28,spr1017

1017 is actually l2cr, but never mind...

> edcc64     bcctr   always
> ok ictc@ .
> 264d2
> ok

>> How do you terminate a 'code' sequence?
>
> Oops, forgot about it, my bad. With ';code', isn't it obvious ?

Hm, doesn't work in Apple's OF 1.0.5. end-code is the answer ;-). Here
is my ictc! implementation, if anyone's interested:

code ictc!
        7e9bfba6 l, 829f0000 l, 3bff0004 l, 4e800020 l,
end-code

That is roughly this in asm:

	mtictc	r20	(or mtspr 1019,r20)
	lwz	r20,0(r31)
	addi	r31,r31,4
	blr

Verifyed to slow the system on a busy loop:

: loop
	begin
	1- dup 0<
	until
	drop
;

11 ictc! slows this loop by a factor of 4.

Now, go figure why this helps the MESH driver... It seems to use some
busy loop timing somewhere; however there is the ms word available which
uses the timebase and is accurate even on my upgraded box.... That would
have been the better choice, unless the driver uses sub-1ms loops. Which
would explain...

Anyway, thanks for your help, Gabriel!

Cheers

Michel

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Re: asm in OF? YES!

[Gabriel Paubert]

On Wed, 30 Aug 2000, Michel Lanners wrote:

	Hi,

> Yep, it works! I can boot off mesh again ;-)

Glad it helped...

> > ok code ictc@ ok 979ffffc l, 7f99faa6 l, 4e800420 l, ;code
> > ok see ictc@
> > code ictc@
> > edcc5c     stwu    r28,-4(r31)
> > edcc60     mfspr   r28,spr1017
>
> 1017 is actually l2cr, but never mind...

Right, anyway the 603e has neither ictc nor l2cr so I presume it would
work in ay case...

> >> How do you terminate a 'code' sequence?
> >
> > Oops, forgot about it, my bad. With ';code', isn't it obvious ?
>
> Hm, doesn't work in Apple's OF 1.0.5. end-code is the answer ;-). Here
> is my ictc! implementation, if anyone's interested:

You've just got to love OF portability across machines and architecture
independance :-( Add to this the fact that I have somewhere a FirmWorks
document which claims that on PPC the top of the stack is always in r28,
r20/r21 are scratch registers. r31 is still the stack pointer (and r30 the
return stack AFAIR).

>
> code ictc!
>         7e9bfba6 l, 829f0000 l, 3bff0004 l, 4e800020 l,
> end-code
[snipped]
>
> 11 ictc! slows this loop by a factor of 4.
>
> Now, go figure why this helps the MESH driver... It seems to use some
> busy loop timing somewhere; however there is the ms word available which
> uses the timebase and is accurate even on my upgraded box.... That would
> have been the better choice, unless the driver uses sub-1ms loops. Which
> would explain...

Indeed, to find it you might simply try to `see' all the words in the mesh
driver, but it may be large. BTW there is another interesting word in my
OF (apart from the even more interesting bugs ;-)):

' some_word .calls

will show all Forth words which call some_word (with a few false positives
to make things more entertaining). Does Apple's OF have something similar
or is it also crippled ?

> Anyway, thanks for your help, Gabriel!

De nada.

	Regards,
	Gabriel.


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