23 Jan
2016
23 Jan
'16
11:25 p.m.
I had a pdp-11/73 on which I ran 7th Edition. I debugged with print’s out the console.
Usually I had a subroutine that would dump the registers including the PC, so I knew where
it was. I used adb to get the absolute addresses.
The ’73 also had a very simple debugger, ODT, built into the microcode. I never used it
much, preferring to use printf in the C code and puts, puthex and snap in the assembler
code.
I still use this technique working with our Plan 9 system today.
Brantley
On Jan 23, 2016, at 11:58 AM, Will Senn
<will.senn(a)gmail.com> wrote:
All,
I'm finally returning to my study of v6 after digging a bit further into assembly
language and "other" pdp-11 operating systems. I even managed to get hello,
world working in assembly in v6 and interestingly enough, I actually see how it works...
for the most part :). Mini-note here:
http://decuser.blogspot.com/2016/01/hello-world-in-assembly-on-research.html
My question for y'all today is as follows (asked previously with a much larger gap
in understanding):
How did folks debug assembly routines in Unix v6, back in the day?
I realize that most folks didn't do assembly, but some did and I'm curious what
their approach might have been.
After having worked with RT-11 for a bit, I can see how I might develop using RT-11 and
then "port" a program across, but that seems less than ideal. Here is my short
list of missing features as I see them:
1. No listing file/cross reference list created by as.
2. No map file created by ld.
3. No debugger that I can find.
4. This is not a missing feature, but it deserves inclusion in the list, the command as
has possibly the most terse error messages I have ever seen - B 12? Really? Thankfully,
the awesome man command comes to the rescue with the list of error codes.
My workarounds include using OD to view the generated machine code and adding mesg
calls.
Thoughts?
Will