[okl4-developer] Debug Tools

[Carl van Schaik]

Hi Gary,

Ease of debugging is something we take very seriously ... mostly because 
it not only helps our customers, but our own engineers as well. I'll try 
explain the current state of debugging and some things we have done in 
the past, but keep in mind we are actively working to improve our 
debugging capabilities.

It is true that we often use software systems to debug the L4 kernel and 
Linux kernel. This is mostly done through simulators as you say (we 
often edit simulators to provide the exact debug we require) and 
software debug interfaces built into the kernel. This is however mainly 
due to the fact that we are internally often working on kernel features 
and which need to be debugged quickly and this software debugging helps 
us the most. Often, tools like GDB can't help in the low level debugging 
such as the kernel, or glibc.

Debugging at a higher level such as applications on L4 and Linux can be 
debugged more simply with GDB type tools. We use GDB for debugging in OK 
Linux and have in the past supported GDB debugging of L4 threads.

We also use JTAG tools to debug, although often the case is not enough 
hardware for everyone thus its typically used for bringing up new 
hardware and performance debugging, however we have done serious 
kernel/application debugging with these tools. We have tried a variety 
of JTAG tools, but mostly have experience with Trace32. It is fairly 
easy to use these tools to debug our software and they can be extended 
to support context-sensitive debugging. Tools however that already 
provide Linux-sensitive debugging, require modification to understand 
that Linux is being run as an application on L4 and that other threads 
and applications run in parallel to it.

regards,
Carl

Gary Gibson wrote:
> Howdy!
>  
> I am starting off a project using L4 that will entail kernel mods and 
> porting to an ARM1176 platform and am curious to know what debug tools 
> are being used successfully in the OKL4 Universe. From what I have 
> read it appears that most of the kernel debug is being done with the 
> debug facilities built into software emulators (Skyeye/QEMU) and 
> Kernel Debugger.
>  
> Are any of you using remote gdb debugging or JTAG based tools (e.g., 
> Albatron / American Arium / ARM) or their ETM based trace tools while 
> debugging on target hardware ?
>  
>  
> How about at the Linux Kernel Level (OKLinux/Wombat) ?
>  
> Thanks!
> Gary
>  
>  
>  
>  
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