From mboxrd@z Thu Jan 1 00:00:00 1970 From: will.senn@gmail.com (Will Senn) Date: Sat, 23 Jan 2016 11:38:06 -0600 Subject: [TUHS] v6 debugging In-Reply-To: <20160123171851.F423518C0D3@mercury.lcs.mit.edu> References: <20160123171851.F423518C0D3@mercury.lcs.mit.edu> Message-ID: <56A3BA7E.5040905@gmail.com> On 1/23/16 11:18 AM, Noel Chiappa wrote: > > From: Will Senn > > > How did folks debug assembly routines in Unix v6, back in the day? > > There are three different questions here, although you may not realize it: > > - How did folks debug assembly routines in user programs in Unix v6 > - How did folks debug assembly routines in the kernel in Unix v6 > - How did folks debug assembly routines in PDP-11 standalone code created > with Unix v6 > > I did all three, and I used different methods for each. > > For user code, there was no source-level debugger, so debugging C programs > and debugging code written in assembler were the same thing. I used 'adb' > (which is, stricly speaking, slightly post-V6 - our system at MIT was > actually sort of an early PWB clone), but V6 itself provides 'db' (and also, > IIRC, 'cdb'); all three are very similar. > > For standalone code (in my case, a packet switch that ran on PDP-11's), I > used a version of DDT that was linked in with the rest of the code. The > original version was one in MACRO-11 which I inherited from Jim Mathis at > SRI, but I eventually re-wrote it in portable C, and it was used on the 68K, > uVax and 29K. > > For kernel assembler code... I can't remember what I did! Although I wrote a > fair amount of it (I modified m45.s very extensively, to work with the Able > ENABLE card), so I must have done _something_, but I have no idea what. In > theory I could have linked DDT in with the kernel, but I don't think I ever > did so? > > Recently I was debugging some kernel code (the splice() system call we were > discussing here), and I debugged it using... printf()'s! It was written in C, > but I don't really differentiate between debugging C code, and assembler. > > > > 2. No map file created by ld. > > LD normally includes a symbol table in the output file, which 'nm' can dump. > > > 3. No debugger that I can find. > > See above. > > > My workarounds include using OD to view the generated machine code > > Use db/cdb/adb if you want to look at compiled code. Also, for 'cc', use the > -S flag. > > Noel I have cdb, it works. How do I exit it. %, CTRL-C, CTRL-D, CTRL-Z, Break, CTRL-Break, and so on just result in a ? being displayed. I checked the man page, no joy. It is possible to use %r to run the program at which point it exits, but I'm hoping there's a magic key combination... db works too and it's exit is simply %. Thanks, Will