labath accepted this revision. labath added inline comments. This revision is now accepted and ready to land.
================ Comment at: lldb/examples/python/scripted_process/scripted_platform.py:31 + def list_processes(self): + """ Get a list of processes that can be ran on the platform. + ---------------- mib wrote: > labath wrote: > > mib wrote: > > > labath wrote: > > > > mib wrote: > > > > > labath wrote: > > > > > > mib wrote: > > > > > > > labath wrote: > > > > > > > > mib wrote: > > > > > > > > > mib wrote: > > > > > > > > > > mib wrote: > > > > > > > > > > > labath wrote: > > > > > > > > > > > > I am surprised that you want to go down the "run" path > > > > > > > > > > > > for this functionality. I think most of the launch > > > > > > > > > > > > functionality does not make sense for this use case > > > > > > > > > > > > (e.g., you can't provide arguments to these processes, > > > > > > > > > > > > when you "run" them, can you?), and it is not > > > > > > > > > > > > consistent with what the "process listing" > > > > > > > > > > > > functionality does for regular platforms. > > > > > > > > > > > > > > > > > > > > > > > > OTOH, the "attach" flow makes perfect sense here -- you > > > > > > > > > > > > take the pid of an existing process, attach to it, and > > > > > > > > > > > > stop it at a random point in its execution. You can't > > > > > > > > > > > > customize anything about how that process is run > > > > > > > > > > > > (because it's already running) -- all you can do is > > > > > > > > > > > > choose how you want to select the target process. > > > > > > > > > > > For now, there is no support for attaching to a scripted > > > > > > > > > > > process, because we didn't have any use for it quite yet: > > > > > > > > > > > cripted processes were mostly used for doing post-mortem > > > > > > > > > > > debugging, so we "ran" them artificially in lldb by > > > > > > > > > > > providing some launch options (the name of the class > > > > > > > > > > > managing the process and an optional user-provided > > > > > > > > > > > dictionary) through the command line or using an > > > > > > > > > > > `SBLaunchInfo` object. > > > > > > > > > > > > > > > > > > > > > > I guess I'll need to extend the `platform process > > > > > > > > > > > launch/attach` commands and `SBAttachInfo` object to also > > > > > > > > > > > support these options since they're required for the > > > > > > > > > > > scripted process instantiation. > > > > > > > > > > > > > > > > > > > > > > Note that we aren't really attaching to the real running > > > > > > > > > > > process, we're creating a scripted process that knows how > > > > > > > > > > > to read memory to mock the real process. > > > > > > > > > > @labath, I'll do that work on a follow-up patch > > > > > > > > > @labath here D139945 :) > > > > > > > > Thanks. However, are you still planning to use the launch path > > > > > > > > for your feature? Because if you're not, then I think this > > > > > > > > comment should say "Get a list of processes that **are > > > > > > > > running**" (or that **can be attached to**). > > > > > > > > > > > > > > > > And if you are, then I'd like to hear your thoughts on the > > > > > > > > discrepancy between what "launching" means for scripted and > > > > > > > > non-scripted platforms. > > > > > > > > > > > > > > > The way I see it is that the scripted platform will create a > > > > > > > process with the right process plugin. In the case of scripted > > > > > > > processes, the `ProcessLaunchInfo` argument should have the > > > > > > > script class name set (which automatically sets the process > > > > > > > plugin name to "ScriptedProcess" in the launch info). Once the > > > > > > > process is instantiated (before the launch), the scripted > > > > > > > platform will need to redirect to process stop events through its > > > > > > > event multiplexer. So the way I see it essentially, running a > > > > > > > regular process with the scripted platform should be totally > > > > > > > transparent. > > > > > > > > > > > > > > Something that is also worth discussing IMO, is the discrepancy > > > > > > > between launching and attaching from the scripted platform: > > > > > > > > > > > > > > One possibility could be that `platform process launch` would > > > > > > > launch all the scripted processes listed by the scripted platform > > > > > > > and set them up with the multiplexer, whereas `platform process > > > > > > > attach` would just create a scripted process individually. I know > > > > > > > this doesn't match the current behavior of the platform commands > > > > > > > so if you guys think we should preserve the expected behavior, I > > > > > > > guess. > > > > > > > > > > > > > > May be @jingham has some opinion about this ? > > > > > > Before we do that, maybe we could take a step back. Could you > > > > > > explain why you chose to use the "launch" flow for this use case? > > > > > > > > > > > > To me, it just seems confusing to be using "launching" for any of > > > > > > this, particularly given that "attaching" looks like a much better > > > > > > match for what is happening here: > > > > > > - launch allows you to specify process cmdline arguments, attach > > > > > > does not - I don't think you will be able to specify cmdline > > > > > > arguments for these scripted processes > > > > > > - launch allows you to specify env vars, attach does not -- ditto > > > > > > - launch allows you to stop-at-entry, attach does not -- you cannot > > > > > > stop at entry for these processes, as they have been started already > > > > > > - attach allows you to specify a pid, launch does not -- you (I > > > > > > think) want to be able to choose the process (pid) that you want to > > > > > > create a scripted process for > > > > > > > > > > > > For me, the choice is obvious, particularly considering that there > > > > > > *is* an obvious equivalent for "launching" for the kernel > > > > > > co-debugging use case. One could actually have the kernel create a > > > > > > new process --and then it **would** make sense to specify cmdline > > > > > > arguments, environment, and all of the other launch flags. I don't > > > > > > expect anyone to actually support this, as creating a brand new > > > > > > process like this is going to be very tricky, but one could still > > > > > > conceivably do that. > > > > > > > > > > > > Now, I don't want to be designing the feature for you, but I do > > > > > > have a feeling that building the scripted platform feature around > > > > > > this "launch-is-attach" model is going to limit its usefulness to > > > > > > other, more conventional use cases. However, if the feature you're > > > > > > looking for is "launching all processes", then I don't see a > > > > > > problem with adding something like `attach --all`, which would > > > > > > attach to all (attachable) processes. It's probably not something > > > > > > one would want to use for normal platforms very often (so we may > > > > > > want to implement some kind of a "are you sure?" dialog), but > > > > > > functionally that makes sense to me regardless of the platform. > > > > > I don't have any strong opinion for one over the other. The reason > > > > > I'm going with launch is because this is what Scripted Processes > > > > > already support. Originally, Scripted Processes were made for > > > > > post-mortem debugging, so "re-launching" the process made sense to > > > > > me, instead of attaching to a non-running process. > > > > > > > > > > Regarding passing command line arguments, env variables, etc. this > > > > > could be done using the `-k/-v` options or a structured data > > > > > dictionary in the `Process{Launch,Attach}Info`, so both cases should > > > > > be covered. > > > > > > > > > > For the `attach --all` suggestion, I was thinking of something > > > > > similar and I actually like it :) That would iterate over every > > > > > process on the platform and call the attach method on it. For > > > > > scripted processes, the process attach behavior could be customized > > > > > by the implementor. > > > > Well, I do have a medium-strong opinion on that. :) > > > > I believe you that you can make it work through the launch code path. > > > > The -k/-v thing is a stringly typed api, and you can pass anything > > > > through that. But I have to ask: why would you be doing that, if you > > > > already have a bespoke api to do that? My concern is two fold: > > > > - Even if "process launch" does an "attach" to userspace process and > > > > the process-to-attach is specified using -k/-v pairs, the user can > > > > still pass "launchy" arguments (cmdline, env) to that command. So you > > > > now have to either ignore them, or do extra work to make sure they are > > > > rejected > > > > - Doing it this way would mean duplicating some existing lldb > > > > functionality. The attach command already supports attach-by-pid and > > > > attach-by-name modes, and I would expect that the users would want to > > > > use that in a scripted scenario as well. If they are meant to go > > > > through the launch path, then the launch code would have to support > > > > that as well. > > > > > > > > I think that, for the post-mortem use case, the "load-core" flow (which > > > > actually uses parts of the attach code under the hood) would make more > > > > sense. I'm not sure what it would take to make that usable from a > > > > script. > > > Hi @labath, I just getting back to this, and I'm a bit confused by what > > > changes you're asking for exactly. Would you mind clarifying ? Thanks! > > Ideally, I would like you to say "I'm not going to implement the > > 'user/kernel co-debugging feature' using the 'launch' flow" :D. I don't > > know if you already decided that, but if you have, I was not aware of that. > > If you really do want to go with the launch approach, I'd appreciate some > > response my concerns above (i.e., what are you going to do if the user > > specifies arguments when "launching" these processes? Will you be > > duplicating the attach-by-name functionality?) Or just some general > > description of how will the launch look like (e.g. what arguments will the > > user be providing to launch a given process). > > > > In terms of this patch, I think the only part that's rubbing me the wrong > > way is the function description highlighted above -- specifically the "ran > > or" part. If a platform reports running processes (like normal platforms > > do), then you cannot "run" them again. I think we should drop that part and > > say "can be attached" (or simply "are running"). `help platform process > > list` says "List processes on a remote platform by name, pid, or many other > > matching attributes." and I think this should say something effectively > > equivalent to that (modulo the filtering part, as that does not happen > > here). > > > Done! I had misunderstood what you were asking for originally, but I actually > think it makes more sense to use `attach` instead of `launch` in the context > of user/kernel co-debugging :-) So just to recap, Scripted Platform will have > both affordances but we will use `attach` for the co-debugging part. > > Awesome. I'm glad we're in agreement. Thanks. CHANGES SINCE LAST ACTION https://reviews.llvm.org/D139250/new/ https://reviews.llvm.org/D139250 _______________________________________________ lldb-commits mailing list lldb-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-commits