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

[Todd Fiala]

Changes coming in shortly...


On Mon, Jun 30, 2014 at 4:13 PM, Todd Fiala <todd.fiala at gmail.com> wrote:

> 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
>
>


-- 
-Todd
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