[lldb-dev] lldb-gdbserver (llgs) is here! Light FAQ.

[Todd Fiala]

Looks like this introduced a build break on Windows. We're working to fix that up now.

-Todd

> On Jun 30, 2014, at 3:03 PM, Todd Fiala <todd.fiala at gmail.com> wrote:
> 
> Hi all,
> 
> Revision 212069 in the llvm.org lldb trunk brings in lldb-gdbserver to lldb TOT.
> 
> Here is the abbreviated FAQ on lldb-gdbserver:
> 
> WHAT IS IT?
> 
> lldb-gdbserver is intended to be a drop-in replacement for debugserver on platforms that support it.  It supports debugging an executable running on a remote machine.  It is the portion that runs on the remote machine, talking to an lldb client running on a local machine.
> 
> WHAT PLATFORMS DOES IT SUPPORT?
> 
> Currently it supports Linux x86_64 running llgs on the remote end, and has only been tested officially when run from an lldb running on Linux x86_64.  (This will change in the future, but we're taking it one step at a time).
> 
> WHY DIDN'T YOU JUST USE DEBUGSERVER?
> 
> After some discussion with Greg Clayton, we decided it would be easier to create an lldb-gdbserver piece that runs off a new abstraction called NativeProcessProtocol (with NativeThreadProtocol and NativeRegisterContext).  The existing debugserver code was also heavily dependent on MacOS/iOS-specific constructs, and we were looking to move towards a more platform-neutral code base.
> 
> Native*Protocol classes allow us to move towards supporting an OS/Architecture in one place (in the OS/Architecture-specific Native*Protocol classes) and get remote/local debugging at the same time without duplicating code.  We have follow-on steps that need to happen before we can realize this goal - namely, we need to rework lldb's local debugging to work in terms of the Native* classes.  For the short term, we're looking to work the kinks out of those Native* classes using llgs.
> 
> DOES LLDB-PLATFORM SUPPORT LLDB-GDBSERVER?
> 
> Not yet.  Coming very soon.
> 
> HOW DO I USE IT?
> 
> You can fire up a lldb-gdbserver instance on a system similar to the instructions for debugserver:
> 
> remote-system $ lldb-gdbserver host-system:5432
> 
> host-system $ lldb -- /bin/ls
> (lldb) gdb-remote remote-system:5432
> (lldb) run
> 
> You can also attach by process id (pid), or have lldb-gdbserver launch the process.
> 
> IS IT READY FOR PRIMETIME?
> 
> It needs to pass the remote test suite at an acceptable level before it's ready for heavy usage.  I'm going to get lldb-platform working next, a pre-requisite for running the lldb test suite in remote mode.  I expect this step will shake out a number of bugs we'll want to fix.  Any testing you can give it and any bugs you file on incorrect behavior will be helpful.
> 
> WHAT WORKS?
> 
> I've been able to do the following:
> Start/stop processes.
> Use breakpoints.
> Evaluate expressions.
> Observe program exits, kill processes, etc.
> There is likely to be a bunch of things that don't work - I'll fix them in priority order as soon as we find them.  Please file any bugs you find while using lldb-gdbserver when running on Linux x86_64 while using a Linux x86_64 lldb as a client.
> 
> HOW DO I FILE A BUG?
> 
> File at llvm.org's bugzilla.  Tag them with the lldb project and include "llgs" or "lldb-gdbserver" in the subject.
> 
> HOW ABOUT OTHER PLATFORMS?
> 
> Ed Maste is working on getting this running on FreeBSD.  Greg mentioned Apple will look into moving over to lldb-gdbserver after we work the kinks out of it and reach a reasonable level of compatibility with debugserver.
> 
> CAN WE CONNECT TO LLGS WITH OTHER LLDB PLATFORMS OR IDEs?
> 
> I've focused on Linux x86_64 llgs and lldb side.  I have started fixing code that is broken when attempting to connect across OS/Architectures.  Regarding IDEs and other debugger hosts for lldb, YMMV.  I am doing some work there but nothing interesting to say yet.  We are definitely driving to ensure an lldb on one architecture/OS can attach to an llgs of a different architecture/OS.  Some of this work landed earlier last week.
> 
> WHAT'S NEXT?
> lldb-platform support for Linux x86_64.
> More Linux platforms.
> Android support.
> Bug fixes.
> Thanks, all!
> 
> Sincerely,
> Todd Fiala
> 
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