GDB Improvements for Telecom System

GDB’s Strengths, Today

• Primary debugger for Linux

• Used by Eclipse for C, C++ debugging– Eclipse communicates with GDB via MI

(‘Machine Interface’) protocol

• Debug multi-threaded programs

• Supports remote debugging

• GDB is Open Source

GDB’s Limitations, Today

• When any thread stops, all must stop

• Can debug only one process at a time

• No support for telecom OS like DICOS

• CodeSourcery’s work for Ericsson will remove all these limitations under DICOS, and most under Linux

Non-Stop Debugging Mode

• When one thread stops, others can continue to run

• GDB reports breakpoint hits, etc. even while waiting for user commands

• User can stop or run each thread independently

• Natural behavior for Eclipse debugging

Non-stop Benefits

• Reduced impact on debuggee

• Allows inspection of live systems

• Can synthesize other useful behaviors:– Together with multi-process debugging:

Stop all threads in this process, but leave other processes running

– Dedicated debugger interaction threads

Multi-Process Debugging

• GDB can attach to or detach from each process independently

• GDB can follow both parent and child after a fork

• Breakpoints can be global to all attached processes

Multi-Process Debugging:Limitations

• GDB still has only a single address space map

• For DICOS, this is not a problem, since code and data are global to all processes

• On Linux, GDB will only handle families of processes with identical address maps: fork, but no exec, no dlopen/dlclose

DICOS Support

• Connect to DICOS processor via GDB’s remote protocol over TCP/IP

• List processes and capsules, attach and detach

• GDB can attach automatically to new processes that hit global breakpoints

Additional improvements

• Optimization Analysis

• Tracepoints

• Process-specific breakpoints

• Linux multi-process debugging