[TUHS] A Census of /etc and /sys Prior to V4

[segaloco via TUHS]

There are the s2-bits binaries that I'm slowly disassembling.  I don't think there is a kernel image down in there though.  That said, there is a "core" file included, I wonder if kernel text is swept up in that.

In any case, if there are other binaries floating around, disassembly is one of my oldest techie hobbies, so happy to go mining for information.

Also, I've mentioned it a few times but in busier emails: The s1-bits source code fragments appear to be later than the s2-bits binaries, evidenced both by /etc/passwd subbed for /etc/uids in the former and likewise ac and mq EAE registers are still in use in s2-bits binaries but have been replaced by s1-bits. All in all that pegs the s1-bits fragments as being closer in character to V3 while the binaries are closer in character to V2.  As my V2 disassembly progresses I'll try and put together a more detailed list of differences between these two bits of code as well as the Bashkow init and sh sources, with V5 as a later reference.

- Matt G.

------- Original Message -------
On Friday, May 19th, 2023 at 7:36 AM, jnc at mercury.lcs.mit.edu <jnc at mercury.lcs.mit.edu> wrote:


> > From: Matt G.
> 
> 
> > Given the movement of UNIX to the 11/45 and then to C, does the Third
> 
> > Edition represent a version of UNIX for the 11/45 with protection but
> 
> > written in assembly, not C?
> 
> 
> I think so (evidence detailed below). The support may not have been quite
> identical to that in V4 (e.g. there was no support for pure texts in V3 -
> below), though.
> 
> > is there any other information such as documents, code, etc. concerning
> 
> > the 11/45 assembly version?
> 
> 
> This is the real problem, of course; all we have for V3 is some man pages.
> (And in relying on them, we have to hope that they were updated to match the
> then-current system - which is not guaranteed, but in general at this point
> in time, man pages do seem to match whats's in the code.)
> 
> > Was work completed on the 11/45 kernel changes in the context of this
> 
> > version and then simply "ported" to the C version or were there
> 
> > concepts that were cropping up in one or the other and varying amounts
> 
> > of transportation back and forth as 11/45 and C aspects were
> 
> > implemented?
> 
> 
> Without a lot more information, which is now almost certainly lost, we are
> unlikely to be able to tell. But let me start by laying out what we do know.
> 
> 
> To start with, it's important to realize that support for protection (and
> relocation - i.e. memory that looks, to user code, like it's at 0,
> is actually at, say, 060000 in physical terms) in PDP-11 UNIX pre-dates the
> -11/45. DEC had a rare, and now almost forgotten "Memory Protect & Relocate"
> option for the -11/20, the KS11:
> 
> https://gunkies.org/wiki/KS11_Memory_Protection_and_Relocation_option
> 
> What exactly it did, and how, is now uncertain (no documentation, or code
> that used it, appeats to have survived - all we have are a couple of vague
> recollections), but it is certain that that the UNIX group's -11/20 had it:
> 
> https://www.bell-labs.com/usr/dmr/www/odd.html
> 
> and Ken has said that he wrote the code to use it.
> 
> It's also important to remember that not all the machines running UNIX would
> have had their hardware updated simultaneously: e.g. the patent group's
> -11/20 would not have needed the KS11 as much, since it was runnng mature
> applications. So UNIX was probably conditionalized to run with and without
> the KS11. As late as V3, there were apparently still UNIX machines without
> relocation hardware: "The purpose of this command is to simplify the
> preparation of object programs for systems which have no relocation
> hardware.":
> 
> http://squoze.net/UNIX/v3man/man1/reloc
> 
> When the support for the KS11 appeared is uncertain. It's not in the extant
> V1 code; but V2 seems to have had it: "the current system, which has
> relocation and protection hardware":
> 
> http://squoze.net/UNIX/v2man/man5/core
> 
> V2 also seems to have started looking forward to the -11/45 - "a trap is
> simulated by the floating point simulator" (ditto); "if they correspond to
> 11/45 floating point instructions":
> 
> http://squoze.net/UNIX/v2man/man3/fptrap
> 
> It is possible that they already had the -11/45 at this point, but I would
> tend to doubt it: "immediate mode ((pc)+) is not supported, since the
> PDP-11/45 handbook is not clear on what to do about it." (If they had it, a
> simple experiment would have produced the answer.) And "Double precision
> results are probably less correct than the hardware will be" (note tense).
> (All from v2man/man3/fptrap.)
> 
> 
> V3 seems to have the -11/45: "it depends on what hardware is present (EAE,
> floating-point option)":
> 
> http://squoze.net/UNIX/v3man/man5/core
> 
> The "floating-point option" would only have been on the -11/45. (And again we
> see that V3 still ran on -11/20's; the -11/45 would not have had an EAE:
> 
> https://gunkies.org/wiki/KE11-A_Extended_Arithmetic_Element
> 
> since all the EAE operations - except normalization, but that's only needed
> for floating-point - were in the basic -11/45.)
> 
> Probably the protection and relocation provided to UNIX processes on the
> 11/45 was very similar to that provided with the KS11. Do note that thememory
> management was not exactly the same as V4's: "In the future the text segment
> will be write-protected and shared.":
> 
> http://squoze.net/UNIX/v3man/man5/a.out
> 
> However, it was keeping multiple processes in main memory at the same time:
> "only processes whose core images are on disk have visible names":
> 
> http://squoze.net/UNIX/v3man/man8/ps
> 
> 
> So we can actually tell a fair amount about the evolution through V2 and V3
> from the few scraps that are left to us. I do live in hope that a V2 or V3
> listing will turn up one day; the system changed a lot in that period, and
> many questions aren't answered definitively by the man pages.
> 
> (One big one is details of how the process' address space was laid out -
> ld(III) and exec(II) simply say nothing at all. I assume it started at 0 -
> but who knows? In V1, it must have started at a higher address - as on
> MINI-UNIX:
> 
> https://gunkies.org/wiki/MINI-UNIX#Implementation_details
> 
> which I am fairly familiar with - but again, neither V1's ld(III) or exec(II)
> mentions this detail. I suppose I could work it out from the V1 source, but
> I'm not that interested... :-))
> 
> It is possible that the evolution started with just protection (if the KS11
> could do that), and relocation was added later. It seems clear that the
> step from the KS11 to the -11/45 was probably not large.
> 
> 
> If anyone has a V2 or V3 listing, please sing up! That would be an
> incredibly valuable thing to add to the historical record.
> 
> Noel