Few simple A/UX questions

[Paul Campbell]

In article <2791 at sequent.cs.qmw.ac.uk> liam at cs.qmw.ac.uk (William Roberts) writes:
>I do understand the benefit, and I also recognise that A/UX has missed the
>boat - unless the UNXI ABI for 680x0 includes the myriad different schemes
>for getting syscall arguments into the kernel (if you don't already know
>about this mess, consider pipe, read, semop and socketpair: yes - they
>are ALL different).

Well yes and no (read on it doesn't really matter ...).

'Yes' because there are a couple of ABIs out there - the first one called the
68000BCS (Binary Compatability Standard) which was promoted by Motorola
about 3 years ago codifies system call parameters, trap codes etc for
Posix implementation it codified the system call practices in use at
that time in the standard Unix porting base (from which A/UX is derived)
[I wrote a large chunk of it so I remember it in terrible detail :-]. It
was rather still-born because most of the 68K Unix vendors at that time were
in the process of moving to RISC. There is a similar 88K BCS document.

'No' because the current evolving standards (new unixes etc) use shared
libraries to handle this. The standards describe how applications find
system calls in the libraries (ie 'read', shmop' etc as well as non-system
call routines such as 'printf' etc) how the calls in the library actually
call the kernel are up to a particular implementation and are irrelevant
to the issue of ABIs.

Note that one of the things that came out in the BCS development was that
system call schemes are relatively independant of function - this means that
a system can have more than one built-in system call scheme (for example
it can have two system call traps - one that passes system parameters in
registers, another that passes them on the stack (A/UX actually does have
these) - or even traps with different numbers for system calls, or even
different parameters etc etc).


	Paul

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