What does 0x0800f298 in ?? () mean?
You have two problems:


Your debugger does not know about ARMv7-M exceptions.
Your code triggers a fault probably due to a programming error, like forgetting to enable a peripherial clock.


In this case the debugger gets confused by the magic 0xFFFFFFFx value in LR. You could try to manually inspect the register values saved on the stack to locate the original PC value. 

The address 0x0800f498 might be in the Hard Fault exception handler. I ususally use my own handler with a special LED blinking sequence so I know when things went wrong.

The gdb in Sourcery CodeBench has support for this exception model, but you may need a target.xml file to enable it.