Re: [TUHS] Fwd: Choice of Unix for 11/03 and 11/23+ Systems

[jnc@mercury.lcs.mit.edu (Noel Chiappa)]

    > From: jay-tuhs9915

    > Are there any notes you can share on how to get to the point you're at?

Well, there are three areas where the /03 version needs work, over the /05:

- No LTC clock register
- No switch register
- PS access only via MFPS/MTPS instructions

For the first two, the needed changes are identical to the ones detailed here:

  http://gunkies.org/wiki/Running_UNIX_V6_on_an_-11/23

These have all been tested on the /23. Rather than anyone make the exact same
changes independently, I can put up the modified versions of the MiniUnix
files for them (low.s, main.c and param.h).

For the third, I have an mch.s with a conditional assembly flag that _should_
do it all; like I said, there are also really minor edits to bio.c, clock.c,
slp.c, and tty.c. Again, I can upload the mch.s which is already done.

I haven't been able to _confirm_ that these work, but it should be mostly good;
the changes are pretty straight-foward.


    > The code is doing a string comparison between the name in the current
    > directory entry (u_dent) and the current pathname component (in
    > u_dbuf). The expression in brackets is the relative distance between the
    > two name fields within the u struct.

Yeah, I'd worked that out (the immediately preceding comment in the code -
"String compare the directory entry and the current component" - indicates
what it's doing, and as my "the term inside the []'s seems to be an offset
.. into the copy of the current directory entry" indicates, I'd worked out how
it did that. I was still puzzled by some othet aspects of the code, I just
included that to give a flavour of the code.

    > In what way does it fail? Is it simply that namei() doesn't find the
    > file its looking for?

Right. It's looking for 'etc' in the root directory (only one block), and
it looks at the following entries:

  9 146 '05mx'
  8 130 'usr'
  7 114 'tmp'
  6 98 'mnt'
  5 82 'lib'

(I put a printf() in the loop; I've added prf.c to the load so I can do
that. The numbers are the index, u.u_count - although it's already been
descremented at that point, so it will be '0' when doing the last entry - and
location of that entry in the directory, given next to it. For some reason, I
can't get the entry to print from u.u_dent.u_name, so I'm printing it straight
from the block buffer, bp->b_addr[]. I can print the _inode number_,
u.u_dent.u_ino as a string, but not the dir entry. Wierd.)

Anyway, after printing the entry for 5, it goes to 'done', with u_error
containing '2'. I can't see how it could do that.

I'm using printf() because I'm too lazy to figure out how to build a kernel
with a debugger like DDT included. (We never did that when we were working
on V6 at MIT BITD; ISR we mostly just used printf() back then, too.)

   Noel