Thank you that was a huge help. I'm making some progress now. Though I wonder, is there any documentation of the GDB packet format? The reason I ask is that I'm trying to figure out to get the process name from vAttach.
I've looked at how debugserver does it, namely the method GetProcessNameFrom_vAttach [1], and I cannot seem to find the equivalent method in StringExtractorGDBRemote or StringExtractor (though I'll admit that it might be obvious and I'm just missing it). If that's the case I imagine I'll have to implement it and I would like to at least understand the packet format to do that. [1] https://github.com/apple/swift-lldb/blob/a8c149f75a8cba674bead048cd9c80ddc8166a8a/tools/debugserver/source/RNBRemote.cpp#L3585 On Tue, Jun 5, 2018, at 9:03 PM, Jim Ingham wrote: > Except for Windows and FreeBSD, lldb uses a server program to do the > actual debugging - either debugserver on Darwin or lldb-server > elsewhere. The interface to these servers (and to the in-process > debugging in Windows & FreeBSD) is abstracted being Process Plugins, > which the generic code uses. Target::Attach is in generic code, it > won't know anything about the actual method used to attach, wait for > attach, whatever. That will be dispatched to the currently active > ProcessPlugin. > > ProcessGDBRemote is the plugin that is used on Linux & Darwin. It is > the code that actually talks to debugserver or lldb-rpc-server from > within lldb. And that's the code in lldb that sends the vAttachWait > gdb-remote protocol packet to instruct the above-mentioned servers to > implement attach-wait. That request works on Darwin because debugserver > handles the vAttachWait packet, but doesn't work on Linux because lldb- > rpc-server doesn't know currently respond to the vAttachWait packet. So > all you should need to do is teach lldb-server to handle the vAttachWait > packet. > > Jim > > > > On Jun 5, 2018, at 5:44 PM, Ryan Lovelett via lldb-dev > > <lldb-dev@lists.llvm.org> wrote: > > > > I think I might be a little lost. I built a lldb in debug mode and I am > > running lldb in an lldb debugger (very meta). > > > > Earlier in the thread you said "we need a better error message when > > vAttachWait returns unsupported" I have found where the error message, > > e.g., "error: attach failed: lost connection" is constructed. The "attach > > failed: " comes from here [1] and the "lost connection" comes from here [2]. > > > > What do you mean by "vAttachWait"? Am I missing something obvious? > > > > It seems like you are expecting lldb-server to be the place where the fix > > will be implemented. Though in the debugger I'm seeing the method > > Target::Attach() [3] as the place where the connection attempt is made and > > fails. > > > > [1] > > https://github.com/apple/swift-lldb/blob/a8c149f75a8cba674bead048cd9c80ddc8166a8a/source/Commands/CommandObjectProcess.cpp#L518 > > [2] > > https://github.com/apple/swift-lldb/blob/a8c149f75a8cba674bead048cd9c80ddc8166a8a/source/Target/Target.cpp#L3444-L3445 > > [3] > > https://github.com/apple/swift-lldb/blob/a8c149f75a8cba674bead048cd9c80ddc8166a8a/source/Target/Target.cpp#L3374 > > > > On Mon, Jun 4, 2018, at 7:04 PM, Greg Clayton wrote: > >> I will be too busy this week to get to this, so please do have a stab at > >> it. > >> > >> Basically the flow that debug server does is: > >> 1 - get a list of all processes whose basename matches and remember those > >> pids so we don't try to attach to them since we are waiting for a new > >> process to show up > >> 2 - poll the OS for the process list and wait for a new pid to show up > >> with the basename and attach to the first one that matches whose pid isn't > >> i the list from step #1 > >> > >> On MacOSX we don't have a way to be notified of new processes are spawned, > >> not sure on other unix variants. If it is possible, we would want change > >> to: > >> 1 - sign up to be notified about new processes > >> 2 - as each process gets launched, check for a match and attach as quickly > >> as possible > >> > >> Hope this helps and I look forward to seeing your patch! > >> > >> Greg > >> > >>> On Jun 4, 2018, at 5:56 AM, Ryan Lovelett <r...@lovelett.me> wrote: > >>> > >>> Greg, > >>> > >>> Is there anything I can do to help you implement or test this feature? > >>> Obviously I'm willing to roll-up my sleeves and work on this myself too > >>> if you've become more busy than you expected. That happens to us all and > >>> I completely understand. > >>> > >>> Not being able to debug in this manner is blocking me from adding Linux > >>> support to a Swift program. As you might imagine, I'm a little antsy to > >>> get past this so I can start writing some code. > >>> > >>> On Thu, May 31, 2018, at 5:08 PM, Greg Clayton wrote: > >>>> > >>>> > >>>>> On May 31, 2018, at 12:40 PM, Ryan Lovelett <r...@lovelett.me> wrote: > >>>>> > >>>>> Well at least there is a little good news. I understood way more of > >>>>> those logs than I thought I did. > >>>>> > >>>>>> So two issues here: > >>>>>> 1 - we need a better error message when vAttachWait returns unsupported > >>>>>> 2 - fix lldb-server to support vAttachWait > >>>>> > >>>>> A few questions. > >>>>> > >>>>> What is the protocol here? Can/should I report the issues at > >>>>> https://bugs.llvm.org/ ? Or is that something that a project member > >>>>> needs to do? Assuming that I can, would this be two seperate issues or > >>>>> one "large" issue? > >>>>> > >>>>> Barring that this is not something someone else might implement > >>>>> better/faster than me. Considering I have zero LLDB development > >>>>> experience is this something that I could tackle? > >>>> > >>>> I didn't realize this functionality was missing in lldb-server. I can > >>>> take a stab at implementing it and see what I can do. Stay tuned. > >>>> > >>>>> > >>>>> On Thu, May 31, 2018, at 3:02 PM, Greg Clayton wrote: > >>>>>> lldb-server claims it doesn't support it: > >>>>>> > >>>>>> lldb < 48> send packet: > >>>>>> $vAttachWait;6c616e677365727665722d7377696674#d6 > >>>>>> lldb < 4> read packet: $#00 > >>>>>> > >>>>>> > >>>>>> Returning the empty packet ("$#00") means it is not supported, but we > >>>>>> really should give a better error message than this. > >>>>>> > >>>>>> It isn't that hard to implement. It would be easy to copy the code > >>>>>> that is in debugserver in DNB.cpp in the DNBProcessAttachWait > >>>>>> function. Most of it is probably posix style stuff. > >>>>>> > >>>>>> So two issues here: > >>>>>> 1 - we need a better error message when vAttachWait returns unsupported > >>>>>> 2 - fix lldb-server to support vAttachWait > >>>>>> > >>>>>> Greg > >>>>>> > >>>>>> > >>>>>>> On May 31, 2018, at 11:04 AM, Ryan Lovelett <r...@lovelett.me> wrote: > >>>>>>> > >>>>>>>> It might be a lldb-server issue? > >>>>>>> > >>>>>>> How would one go about determining this? > >>>>>>> > >>>>>>> (lldb) log enable -f /tmp/packates.txt gdb-remote packets > >>>>>>> (lldb) process attach --name "<name>" --waitfor > >>>>>>> error: attach failed: lost connection > >>>>>>> > >>>>>>> Attached the log output. Maybe it'll make more sense to you than me. > >>>>>>> > >>>>>>> That escalated quickly. So I've read through that log. I found > >>>>>>> something that says $qVAttachOrWaitSupported#38 with the following > >>>>>>> response being $#00. Perhaps I'm reading too much but is it that it's > >>>>>>> reporting that it is not supported? > >>>>>>> > >>>>>>> Does lldb-server need to be compiled in a certain way to add support > >>>>>>> for attach wait? > >>>>>>> > >>>>>>> On Thu, May 31, 2018, at 1:49 PM, Greg Clayton wrote: > >>>>>>>> Try enabling logging with: > >>>>>>>> > >>>>>>>> (lldb) log enable -f /tmp/packets.txt gdb-remote packets > >>>>>>>> > >>>>>>>> And the try the attach. It might be a lldb-server issue? > >>>>>>>> > >>>>>>>>> On May 31, 2018, at 9:02 AM, Ryan Lovelett via lldb-dev > >>>>>>>>> <lldb-dev@lists.llvm.org> wrote: > >>>>>>>>> > >>>>>>>>> I am attempting to use: process attach --name "<name>" --waitfor > >>>>>>>>> > >>>>>>>>> The problem is that it immediately returns error: attach failed: > >>>>>>>>> lost connection. > >>>>>>>>> > >>>>>>>>> Is this something I can troubleshoot further? Or is this not > >>>>>>>>> supported on Linux? > >>>>>>>>> > >>>>>>>>> -- > >>>>>>>>> Ryan Lovelett > >>>>>>>>> _______________________________________________ > >>>>>>>>> lldb-dev mailing list > >>>>>>>>> lldb-dev@lists.llvm.org > >>>>>>>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev > >>>>>>> <packates.txt> > > > > _______________________________________________ > > lldb-dev mailing list > > lldb-dev@lists.llvm.org > > http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev > _______________________________________________ lldb-dev mailing list lldb-dev@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev
