Your project will be great! Below I will outline a few things to keep you on
track:
Core file kernel debugging:
- You shouldn't have to do too much to the current ProcessELFCore except help
it to locate hint address for the list of shared libraries and the main kernel
file in memory. This is done in:
virtual lldb::addr_t
ProcessELFCore::GetImageInfoAddress ();
- Most of the work will be done in your DynamicLoader subclass that then uses
the hint from the ProcessELFCore::GetImageInfoAddress() as to where the shared
libraries are. This new DynamicLoader subclass will be used for both live
kernel debugging and for Core file debugging and should be able to track down
all kernel extensions that are loaded.
Live kernel debugging:
- You will make a new process subclass like you were saying unless the GDB
remote protocol is used to talk to the kernel?
- You should re-use your dynamic loader from the Core file step here
Extra credit:
- Get threads that are context switched in memory to show up. In the MacOSX
kernel debugger we have the notion of 1 core we can talk to through the KDP
interface which is the code that runs the debugger. There are tons of threads
in the kernel that are sitting in memory. We have a python plugin that will
supply a list of memory threads back to lldb. So even though the kernel debug
interface only supports N cores, we might also be able to show M number of
memory threads and see their backtraces, registers, etc. The MacOSX kernel
implements this using python code that can use kernel globals to get the list
of in memory threads and create them on the fly. There is a very simple example
of this in:
svn cat
http://llvm.org/svn/llvm-project/lldb/trunk/examples/python/operating_system.py
Let us know if you have any questions as far as implementation and architecture
goes. The MacOSX kernel process subclass does things correctly so keep an eye
on that plug-in when you have questions or need guidance.
Greg Clayton
> On May 22, 2014, at 2:03 AM, Mike Ma <[email protected]> wrote:
>
> Hi there,
>
> I'm a google summer of code student this year, on FreeBSD part.
>
> And I'm writing to introduce my project, we are aiming to support kernel
> debugging on FreeBSD for LLDB.
> Ed Maste ([email protected]) is my mentor for this project, I'll be working
> closely with him.
>
> Here is the project page:
> https://wiki.freebsd.org/SummerOfCode2014/LLDB_KernelDebugging
>
> This is my LLDB fork:
> https://github.com/cosql/lldb
>
> Any comments are more than welcome.
>
> --
> Cheers,
> Mike
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