[TUHS] Design of the AT&T assembly syntax

[Robert Clausecker]

Hi Alexander,

On Tue, Oct 29, 2019 at 12:48:29AM +0300, Alexander Voropay wrote:
> Robert Clausecker <fuz at fuz.su>wrote:
> 
> > The one thing in this chain I have never found is an AT&T style
> > assembler for x86 before ELF was introduced.
> 
> There were alot of AT&T codebase ports to x86 architecture except Xenix:
> Microport, INTERACTIVE, Everex, Wyse e.t.c. using AT&T x86 syntax.
> 
> I've tried Microport SystemV /386 (SysV R3.2). It uses COFF
> as format for executables:
> See:
> http://www.vcfed.org/forum/showthread.php?67736-History-behind-the-disk-images-of-AT-amp-T-UNIX-System-V-Release-4-Version-2-1-for-386&p=560039#post560039
> (Rather interesting kernel ABI/Call convention)

Nice find!  It seems to use lcall to selector 7 for system calls.  A
similar choice was made in 386BSD all the way through FreeBSD 2.2.8
where it was replaced with int $0x80 as in Linux.

> and
> https://gunkies.org/wiki/Unix_SYSVr3
> 
> There were also SystemV R2 to i286 ports i.e.:
> https://gunkies.org/wiki/Microport_System_V
> with a.out binary format.

I'll have a look at that.

Thank you for the help!

Yours,
Robert Clausecker

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