So, in:
http://minnie.tuhs.org/cgi-bin/utree.pl?file=V6/usr/source/s2/mv.c
what's the point of this piece of code:
p = place;
p1 = p;
while(*p++ = *argp3++);
p2 = p;
while(*p++ = *argp4++);
execl("/bin/cp","cp", p1, p2, 0);
I mean, I get that it's copying the two strings pointed to by 'argp3' and
'argp4' into a temporary buffer at 'place', and leaving 'p1' and 'p2' as
pointers to the copies of said strings, but... why is it doing that?
I at first thought that maybe the execl() call was smashing the stack (and
thus the copies pointed to by 'argp3' and 'argp4'), or something, but I don't
think it does that. So why couldn't the code have just been:
execl("/bin/cp","cp", argp3, argp4, 0);
Is this code maybe just a left-over from some previous variant?
Noel
> From: Dave Horsfall <dave(a)horsfall.org>
> I'd like to see it handle "JSR PC,@(SP)+"...
Heh!
But that does point out that the general concept is kind of confused - at
least, if you hope to get a fully working program out the far end. The only
way to do that is build (effectively) a simulator, one that _exactly_
re-creates the effects on the memory and registers of the original program.
Only instead of reading binary machine code, this one's going to read in the
machine language source, and produce a custom simulator, one that can run only
one program - the one fed into it.
Think of it as a 'simulator compiler'! :-)
Noel
>> I was wondering what it would take to convert the v6/v7 basic program
>> into something that can be run today.
>
> Hmmm... If it were C-generated then it would be (somewhat) easy, but it's
> hand-written and hand-optimised... You'd have to do some functional
> analysis on it e.g. what does this routine do, etc.
>
>> Its 2128 lines. It doesn't have that fun instruction in it :)
>
> I know! Say ~2,000 lines, say ~100 people on this list, distributed
> computing to the rescue! That's only 20 lines each, so it ought to be a
> piece of cake :-)
I'm up for that! However, only if the resulting C program can be compiled/run
on a V6/PDP11 again.
Let's assume that reverse engineering a subroutine of 20 lines takes
an hour. That then makes for 100 hours. If 10 people participate and
contribute one hour/routine per week, it will be done by May.
However, the initial analysis of the code architecture is a (time) hurdle.
Paul
PS: the Fortran66 of V6 is also assembler only...
IMO:
1) It kinda did catch on, in the form of macOS, but there was a time
when it was nearly dead as the major vendors moved to System V. For
some reason, Sun was the last major vendor to make the move, but they
caught most of the flack.
2) I think the main reason BSD nearly died, was the AT&T lawsuit. At
the time, Linux appeared to be a safer bet legally.
3) Linux got a reputation as an OS you had to be an expert to install,
so lots of people started it to install it to "prove themselves".
This was sort of true back when Linux came as 2 floppy images, but
didn't remain true for very long.
4) I believe the SCO lawsuit "against Linux" was too little, too late
to kill Linux's first mover advantage in the opensource *ix
department.
5) I think FreeBSD's ports and similar huge-source-tree approaches
didn't work out as well Linux developers contributing their changes
upstream.
Hi all,
Would anyone here be able to help me troubleshoot my qd32 controller? I
have a pdp11/73 that's mostly working, boots 2.11 from rl02 okay, but I
need my big disk to work so I can load the rest of the distro.
I've been following the manual for the qd32 to enter the geometry of my
real working m2333 (jumpered correctly according to the manuals), but when
I load the special command into the qd32's SP register that's supposed to
load the geometry table from the pdp11 memory to the novram, I get a bad
status value from the qd32's SP register and it remains unresponsive when I
try to store the geometry. If I go ahead and try the built-in qd32 format
command, it responds similarly. When I pull in mkfs from tape (vtserver)
and try anyway, despite the failures, to run mkfs on the m2333, I get an
!online error from the standalone unix mkfs. The disk does respond (the
select light flashes and I can hear heads actuating), but without geometry
and format, I'm obviously dead in the water.
Any suggestions on how to proceed?
thx
jake
> Why is it that umount(2) took the device special file name rather than the mount point directory name, anyway?
Symmetry. You unmount what you mount.
A competing model is that of links. Link makes an old file available
under a new name. But you unlink by the new name. Necessarily so,
because there may be many new names for one old file.
This is reminiscent of Don Norman's screed about the unnaturalness
of Unix. He didn't like strcpy because the arguments come in the
opposite order to those of cp. But stcpy is part of C, and in
C the destination of assignment comes before the source. But Norman
didn't rail at C. You pays your money and takes your choice.
Doug
these were in by the time I can along but I was wondering when they got it.
They've also always felt a bit like a thing that did not fit to me. I'm
pretty sure I was not alone, given that the Unix authors worked out a way
to get rid of them in later efforts. I know what came after, in Plan 9;
what came before, in Unix, that led to special files?
We lost computer pioneer John von Neumann on this day in 1957; the "von
Neumann" architecture (stored program etc) is the basis of all modern
computers, and he almost certainly borrowed it from Charles Babbage.
--
Dave Horsfall DTM (VK2KFU) "Those who don't understand security will suffer."
