TUHS January 2015

tuhs@tuhs.org

47 participants
32 discussions

by jnc＠mercury.lcs.mit.edu

> From: Noel Chiappa > For some reason, the code for /etc/init .. bashes the command line so > it just has '-' in it, so it looks just like a shell. BTW, that may be accidental, not a deliberate choice - e.g. someone copied another line of code which exec'd a shell, and didn't change the second arg. > I fixed my copy so it says "/etc/init", or something like that. ... I > can upload the 'fixed' code tomorrow. The change is pretty minor: in this piece of code: case reboot: termall(); execl(init, minus, 0); reset(); just change the execl() line to say: execl(init, init, 0); >> I'm not sure if unix of the v6 or v5 era was designed to go from multi >> user to single user mode and then back again. > I seem to recall there's some issue, something like in some cases > there's an extra shell left running attached to the console So the bug is that in going from single-user to multi-user, by using "kill -1 1" in single-user with the switch register set for multi-user, it doesn't kill the running single-user shell on the console. The workaround to that bug which I use is to set the CSWR and then ^D the running shell. In general, the code in init.c isn't quite as clean/clear as would be optimal (which is part of why I haven't tried to fix the above bug), but _in general_ it does support going back and forth. > From: Ronald Natalie > our init checked the switch register to determine whether to bring up > single or multiuser I think that's standard from Bell, actually. > I believe our system shutdown if you kill -1-1 (HUP to init). The 'stock' behaviour is that when that happens, it checks the switch register, and there are three options (the code is a little hard to follow, but I'm pretty sure this is right): - if it's set for single-user, it shuts down all the other children, and brings up a console shell; when done, it does the next - if it's set for 'reboot', it just shuts down all children, and restarts the init process (presumably so one can switch to a new version of the init without restarting the whole machine); - if it's not set for either, it re-reads /etc/ttys, and for any lines which have switched state in that file, it starts/kills the process listening to that line (this allows one to add/drop lines dynamically). > From: Clem Cole > it's probably worth digging up the v6 version of fsck. That's on that MIT V6 tape, too. Speaking of which, time to write the code to grok the tape... Noel

9 years, 11 months

Re: [TUHS] single user mode in v5 & v6

by jnc＠mercury.lcs.mit.edu

> From: Mark Longridge <cubexyz(a)gmail.com> > I've finally managed to get Unix v5 and v6 to go into single user mode > while running under simh. > ... > dep system sr 173030 (simh command) Just out of curiousity, why don't you set the SR before you boot the machine? That way it'll come up single user, and you can icheck/dcheck before you go to multi-user mode. I prefer doing it that way, there's as little as possible going on, in case the disk is slightly 'confused', so less chance any bit-rot will spread... > Now I'm in muti user mode .. but then if I do a "ps -alx" I get: > > TTY F S UID PID PRI ADDR SZ WCHAN COMMAND > ?: 3 S 0 0-100 1227 2 5676 ???? > ?: 1 W 0 1 40 1324 6 5740 - > The ps command doesn't show the /etc/init process explicitly, although > I'm pretty sure it is running. No, it's there: the second line (PID 1). For some reason, the code for /etc/init (in V6 at least, I don't know anything about V5) bashes the command line so it just has '-' in it, so it looks just like a shell. I fixed my copy so it says "/etc/init", or something like that. The machine my source is on is powered down at the moment; if you want, I can upload the 'fixed' code tomorrow. > I'm not sure if unix of the v6 or v5 era was designed to go from multi > user to single user mode and then back again. I seem to recall there's some issue, something like in some cases there's an extra shell left running attached to the console, but I don't recall the details (too lazy to look for the note I made about the bug; I can look it up if you really want to know). > Would it be safer to just go to single user and then shut it down? I don't usually bother; I just log out all the shells except the one on the console, so the machine is basically idle; then do a 'sync', and shortly after than completes, I just halt the machine. Noel

9 years, 11 months

Re: [TUHS] COHERENT sources released under 3-clause BSD license.

by Rico Pajarola

adding the list back On Tue, Jan 6, 2015 at 10:42 AM, Michael Kerpan <mjkerpan(a)kerpan.com> wrote: > This is a cool development. Does this code build into a working version of > Coherent or is this mainly useful to study? Either way, it should be > interesting to look at the code for a clone specifically aimed at low-end > hardware. > > Mike >

9 years, 11 months

single user mode in v5 & v6

by Mark Longridge

Ok, I've finally managed to get Unix v5 and v6 to go into single user mode while running under simh. I boot up unix as normal, that is to say in multi-user mode. Then a ctrl-e and dep system sr 173030 (simh command) then c to continue execution of the operating system and finally "kill -1 1". This gets me from multi user mode to single user mode. I can also go back to multi user mode with: ctrl-e and dep system sr 000000 then once again c to continue execution of the operating system and "kill -1 1". Now I'm in muti user mode, and I can telnet in as another user so it seems to be working but then if I do a "ps -alx" I get: TTY F S UID PID PRI ADDR SZ WCHAN COMMAND ?: 3 S 0 0-100 1227 2 5676 ???? ?: 1 W 0 1 40 1324 6 5740 - 8: 1 W 0 51 40 2456 19 5766 - ?: 1 W 0 55 10 1377 6 42066 - ?: 1 W 0 5 90 1734 5 5440 /etc/update ?: 1 W 0 32 10 2001 6 42126 - ?: 1 W 0 33 10 2054 6 42166 - ?: 1 W 0 34 10 2127 6 42226 - ?: 1 W 0 35 10 2202 6 42266 - ?: 1 W 0 36 10 2255 6 42326 - ?: 1 W 0 37 10 2330 6 42366 - ?: 1 W 0 38 10 2403 6 42426 - 8: 1 R 0 59 104 1472 17 ps alx The ps command doesn't show the /etc/init process explicitly, although I'm pretty sure it is running. I'm not sure if unix of the v6 or v5 era was designed to go from multi user to single user mode and then back again. Would it be safer to just go to single user and then shut it down? Mark

9 years, 11 months

VAX faxing?

by Cory Smelosky

Friend asked an odd question: Were VAXen ever used to send/receive faxes large-scale? What software was used and how was it configured? Was any of this run on any of the UCB VAXen? -- Cory Smelosky http://gewt.net Personal stuff http://gimme-sympathy.org Projects

9 years, 11 months

Misread on my part, or is there really a notable gcc port? Was: (Re: COHERENT sources released under 3-clause BSD license.)

by Jacob Ritorto

Andrzej wrote: > > I have ported gcc-2.8.1,2.95.3,3.2.3 and 4.2.x. > Ported them to what?

9 years, 11 months

Re: [TUHS] pdp11 UNIX memory allocation.

by Johnny Billquist

On 2015-01-06 23:56, Clem Cole<clemc(a)ccc.com> wrote: > > On Tue, Jan 6, 2015 at 5:45 PM, Noel Chiappa<jnc(a)mercury.lcs.mit.edu> > wrote: > >> >I have no idea why DEC didn't put it in the 60 - probably helped kill that >> >otherwise intersting machine, with its UCS, early... >> > > ?"Halt and confuse ucode" had a lot to do with it IMO. > > FYI: The 60 set the record of going from production to "traditional > products" faster than? anything else in DEC's history. As I understand > it, the 11/60 was expected to a business system and run RSTS. Why the WCS > was put in, I never understood, other than I expect the price of static RAM > had finally dropped and DEC was buying it in huge quantities for the > Vaxen. The argument was that they could update the ucode cheaply in the > field (which to my knowledge the never did). But I asked that question > many years ago to one of the HW manager, who explained to me that it was > felt separate I/D was not needed for the targeted market and would have > somehow increased cost. I don't understand why it would have cost any > more but I guess it was late. No, field upgrade of microcode can not have been it. The WCS for the 11/60 was an option. Very few machines actually had it. It was for writing your own extra microcode as addition to the architecture. The basic microcode for the machine was in ROM, just like on all the other PDP-11s. And DEC sold a compiler and other programs required to develop microcode for the 11/60. Not that I know of anyone who had them. I've "owned" four PDP-11/60 systems in my life. I still have a set of boards for the 11/60 CPU, but nothing else left around. The 11/60 was, by the way, not the only PDP-11 with WCS. The 11/03 (if I remember right) also had such an option. Obviously the microcode was not compatible between the two machines, so you couldn't move it over from one to the other. Also, reportedly, someone at DEC implemented a PDP-8 on the 11/60, making it the fastest PDP-8 ever manufactured. I probably have some notes about it somewhere, but I'd have to do some serious searching if I were to dig that up. But yes, the 11/60 went from product to "traditional" extremely fast. Split I/D space was one omission from the machine, but even more serious was the decision to only do 18-bit addressing on it. That killed it very fast. Someone else mentioned the MFPI/MFPD instructions as a way of getting around the I/D restrictions. As far as I know (can tell), they are possible to use to read/write instruction space on a machine. I would assume that any OS would set both current and previous mode to user when executing in user space. The documentation certainly claims they will work. I didn't think of those previously, but they would allow you to read/write to instruction space even when you have split I/D space enabled. Johnny -- Johnny Billquist || "I'm on a bus || on a psychedelic trip email: bqt(a)softjar.se || Reading murder books pdp is alive! || tryin' to stay hip" - B. Idol

9 years, 11 months

Re: [TUHS] pdp11 UNIX memory allocation.

by jnc＠mercury.lcs.mit.edu

> From: Ronald Natalie <ron(a)ronnatalie.com> > Yep, the only time this was ever trully useful was so you could put an > a.out directly into the boot block I think. Well, sort of. If you had non position-independent code, it would blow out (it would be off by 020). Also, some bootstraps (e.g. the RL, IIRC) were so close to 512. bytes long that the extra 020 was a problem. And it was so easy to strip off: dd if=a.out of=fooboot bs=1 skip=16 I'm not sure that anything actually used the fact that 407 was 'br .+020', by the V6 era; I think it was just left over from older Unixes (where it was not in fact stripped on loading). Not just on executables running under Unix; the boot-loader also stripped it, so it wasn't even necessary to strip the a.out header off /unix. Noel

9 years, 11 months

Re: [TUHS] pdp11 UNIX memory allocation.

by Johnny Billquist

On 2015-01-06 20:57, Milo Velimirovi?<milov(a)cs.uwlax.edu> wrote: > Bringing a conversation back online. > On Jan 6, 2015, at 6:22 AM,arnold(a)skeeve.com wrote: > >>> >>Peter Jeremy scripsit: >>>> >>>But you pay for the size of $TERMCAP in every process you run. >> > >> >John Cowan<cowan(a)mercury.ccil.org> wrote: >>> >>A single termcap line doesn't cost that much, less than a KB in most cases. >> > >> >In 1981 terms, this has more weight. On a non-split I/D PDP-11 you only >> >have 32KB to start with. (The discussion a few weeks ago about cutting >> >yacc down to size comes to mind?) > (Or even earlier than ?81.) How did pdp11 UNIXes handle per process memory? It?s suggested above that there was a 50-50 split of the 64KB address space between instructions and data. My own recollection is that you got any combination of instruction and data space that was <64KB. This would also be subject to limits of pdp11 memory management unit. > > Anyone have a definitive answer or pointer to appropriate man page or source code? You are conflating two things. :-) A standard PDP-11 have 64Kb of virtual memory space. This can be divided any way you want between data and code. Later model PDP-11 processors had a hardware feature called split I/D space. This meant that you could have one 64Kb virtual memory space for instructions, and one 64Kb virtual memory space for data. (This also means that the text you quoted was incorrect, as it stated that you had 32Kb, which is incorrect. It was/is 32 Kword.) Johnny -- Johnny Billquist || "I'm on a bus || on a psychedelic trip email: bqt(a)softjar.se || Reading murder books pdp is alive! || tryin' to stay hip" - B. Idol

9 years, 11 months

Re: [TUHS] pdp11 UNIX memory allocation

by Johnny Billquist

On 2015-01-06 22:59, random832(a)fastmail.us wrote: > On Tue, Jan 6, 2015, at 15:20, Johnny Billquist wrote: >> >Later model PDP-11 processors had a hardware feature called split I/D >> >space. This meant that you could have one 64Kb virtual memory space for >> >instructions, and one 64Kb virtual memory space for data. > Was it possible to read/write to the instruction space, or execute the > data space? From what I've seen, the calling convention for PDP-11 Unix > system calls read their arguments from directly after the trap > instruction (which would mean that the C wrappers for the system calls > would have to write their arguments there, even if assembly programs > could have them hardcoded.) Nope. A process cannot read or write to instruction space, nor can it execute from data space. It's inherent in the MMU. All references related to the PC will be done from I-space, while everything else will be done through D-space. So the MMU have two sets of page registers. One set maps I-space, and another maps D-space. Of course, you can have them overlap, in which case you get the traditional appearance of older models. The versions of Unix I am aware of push arguments on the stack. But of course, the kernel can remap memory, and so can of course read the instruction space. But the user program itself would not be able to write anything after the trap instruction. Johnny -- Johnny Billquist || "I'm on a bus || on a psychedelic trip email: bqt(a)softjar.se || Reading murder books pdp is alive! || tryin' to stay hip" - B. Idol

9 years, 11 months

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TUHS January 2015