23 Jan
2016
23 Jan
'16
10:58 p.m.
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
23 Jan
23 Jan
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
11:30 p.m.
below...
On Sat, 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?
3 questions here... how did you debug the pre-boot world (aka standalone
system), how to debug the kernel itself and a user program.
Couple of them that I used were:
1. T.lights&switches in the PMS notation (ie. the front console of the
processor) - very helpful for kernel debugging. In fact, certain patterns
were definitely recognizable. Plus people wrote programs the ran specific
patterns in the console during certain times like the idle loop. For the
11 this was definitely used to debug the preboot world but it helped on the
kernel (see below)
2. printf or equiv
3. a debugger when possible (adb came from AT&T, there is a ddt clone on
one of the USENIX tapes - which I liked better and IIRC adb is not around
with v5). When I was mostly using v6, we used the ddt program, because I
was also doing PDP-10 and a little VMS programming at CMU. When I left
CMU,went the V7 and later BSD 4.x and became pretty much 100% Unix, the ddt
program had issues including no Vax port, so instead of fixing it, I learn
adb and never went back.
In fact to help debug the kernel, we even put adb into the core resident
port of V7 which was tricky - Noel I seem to remember we (probably Steve
Zimmerman or maybe Geoff Peck) stole that from you guys at MIT (Steve
definitely spliced adb into the Masscomp kernel say in '84ish. But I
remember having had something before that.
Clem
Side bar --- most of the Masscomp HW team came from the 780, 750 or 11/34
teams at DEC. Dave Cane (Mr. 750), was the HW lead. I remember a big
argument at Masscomp because the SW team wanted a real console at least as
a option and Dave hated them (for system debugging). The best we ever got
was a set of macros for a logic analyzer hanging off of system in Eric
Finger's office.
I realize that most folks didn't do assembly, but some did and I'm curious
what their approach might have been.
Use the USENIX Macro-11 assembler clone.
Funny, we were talking about this at lunch just yesterday!! Later with the
Vax, post DEC putting the Fortran on BSD, you had the VMS linker on BSD.
Its still there and works.
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.
Check the USENIX tapes
2. No map file created by ld.
Yup - I never had one for the 11.
I seem to remember somebody (* Goble at Purdue I think) hacked a ld to
generate them. Check USENIX and Purdue tools. George's Microprocessor
tools for the Z80, 8080, 6800, 6502 etc... had an ld that did just this.
3. No debugger that I can find.
From research, until V7 correct. But check the USENIX tapes, Harvard, CU
or Columbia did a ddt clone that was pretty good.
4. This is not a missing feature, but it deserves
inclusion in the list,
the command as has possibly the most terse error messages
No ed(1) has beats it. You just get a ? printed. Google "Brian
Kernightan's dashboard"
Clem
11:39 p.m.
On Sat, Jan 23, 2016 at 12:30 PM, Clem Cole <clemc(a)ccc.com> wrote:
3. No debugger that I can find.
From research, until V7 correct. But
check the USENIX tapes, Harvard,
CU or Columbia did a ddt clone that was pretty good.
Just read Noel's message -- sounds like the ddt came from Stanford and
MIT. I don't remember the assembler version of it, but we definitely had
a C version for the 11 before V7.
I also had forgotten about db and cdb - I could not tell you when they
appeared in the source stream without poking at Warren's archives.
BTW: I was thinking that the ddt came from the CU folks because they were
the folks that first got the DEC FTN to run on UNIX. Since they did not
have access to PDP-10 to run the BLISS compiler, the simulated it. They
wrote a number of tools for the 11 and 10 in that project what were much
like the DEC tools from the PDP-10.
Clem
3256
days inactive
3256
days old
3 comments
3 participants
participants (3)
-
Brantley Coile -
Clem Cole -
Will Senn