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On 02.08.2017 21:10, Maxime Villard wrote:
> Le 02/08/2017 à 16:42, Kamil Rytarowski a écrit :
>> On 02.08.2017 15:27, Johnny Billquist wrote:
>>> On 2017-08-02 14:44, Maxime Villard wrote:
>>>> Le 02/08/2017 à 14:21, Kamil Rytarowski a écrit :
>>>>> On 02.08.2017 11:34, Maxime Villard wrote:
>>>>>> Hi,
>>>>>> I see that the Vax GENERIC kernel has COMPAT_IBCS2 enabled by
>>>>>> default.
>>>>>> But what
>>>>>> exactly is it doing here? iBCS2 is a standard designed for x86 CPUs,
>>>>>> and
>>>>>> it has
>>>>>> nothing to do with Vax.
>>>>>> Is there something that I'm missing? If so, it would be good to
>>>>>> enlighten the
>>>>>> man page.
>>>>>> Thanks,
>>>>>> Maxime
>>>>> This looks like SVR3 compatibility, x86 variation of it is called
>>>>> IBCS2.
>>>> Yes, I guessed that when reading the entry in GENERIC; but shouldn't
>>>> it be
>>>> renamed, or at least, made a little less confusing? In the man page for
>>>> example, we could say that iBCS2 stands for SVR3 on Vax, even if it is
>>>> called
>>>> iBCS2...
>>> I would vote for renaming. iBCS2 is something that is totally cryptic to
>>> me. SVR3 is something I would expect most people to understand what
>>> it is.
>>> But I suspect that also means renaming it for the x86 folks, and I
>>> wonder how easy it might be to get them onboard.
>>>    Johnny
>> I would keep it as it is, and improve documentation.
> That's what I would do too.
> In fact, I don't understand for which specific purpose compat_ibcs2 was
> written. Was it written to be a compat for SVR3, but called iBCS2 for some
> reason? (in which case, it would be suspicious to have it on i386.) Or
> was it
> intended to be the real x86-specific iBCS2? (in which case, it would be
> suspicious to have it on Vax.)

It started as compat_ibcs2 which was SVR4 (ELF) i386.
It was extended with SCO UNIX SVR3 (IBCS2 COFF) i386.
Later there was added SCO UNIX SVR3 (IBCS2 XAOUT) i386.

The compat_ibcs2 i386 code was reused for DEC VAX SVR3.

> The man page is not particularly enlightening, and I fear that in order to
> figure out which compat (or which mix of both) compat_ibcs2 was meant to
> be,
> we will have to read the code and compare it with the iBCS2
> specification. I
> couldn't find this spec on the internet.

It started as SVR4 i386. IBCS2 ELF was renamed to compat_svr4, and
compat_ibcs2 was used for i386 SVR3.

I think that the ibcs2 evaluated as an alias for SVR3. I don't know
whether somebody reused this name on original VAX UNIX.

I proposed to keep it as it is, because there are more aliases like i386
that have not clear meaning.

> Maxime

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