30 Apr
2008
30 Apr
'08
4:21 p.m.
Guys, I'm writing a PDP-11 a.out disassember. I think it will be useful for
a couple of reasons:
- we will be able to convert the extant 1972 binaries back into some form
of source code. It won't be as good as the real thing, but it will be
better than the binary.
- we have some source code in fragmentary form on the s1 tape, see
http://minnie.tuhs.org/UnixTree/1972_stuff/. Some of the fragments
are identifiable, some are not. We might be able to use the
diassembled binaries to identify some of the fragments, and even
reconstruct a hybrid original/diassembled version of the source
for some of the 1972 applications.
Right now, here's what I've got: disassembly of the top of 1972 ls:
sys break: 00
mov $01,044260
mov sp,r5
mov (r5)+,043732
tst (r5)+
dec 043732
mov 043732,043734
bgt 040056
mov $042542,r5
mov (r5)+,r4
cmpb (r4)+,$055
bne 040174
dec 043734
and the top of the frag19 file:
sys break; end+512.
mov $1,obuf
mov sp,r5
mov (r5)+,count
tst (r5)+
dec count
mov count,ocount
bgt loop
mov $dotp,r5
loop:
mov (r5)+,r4
cmpb (r4)+,$'-
bne 1f
dec ocount
At the moment it's a 1-pass disassembler. I want to make it 2-pass: on the
first pass I will try to identify labels for branches, functions, strings and
variable locations (and given them arbitrary names); on the second pass
I'll print out the instructions with reference to the labels.
None of the binaries have symbol tables, unfortunately.
It's a start, anyway.
Warren