I've been doing some testing of the MIPS Function Tracer functionality on the 3.3 kernel. I was surprised to find that the option to generate frame pointers was required for tracing. When I don't enable FRAME_POINTER along with FUNCTION_TRACER, the kernel hangs on boot. I also noticed that a checkin to the 3.4 kernel (b732d439cb43336cd6d7e804ecb2c81193ef63b0) no longer forces on FRAME_POINTER when FUNCTION_TRACER is selected. I was wondering how it works in 3.4 and beyond, so I built a Malta kernel from the latest MIPS tree with FUNCTION_TRACING enabled and tested it with QEMU. The kernel hung the same way. I can think of 2 reasons for this: 1. Function tracing is broken for MIPS in 3.4 and beyond. 2. The 4.5.3 GNU C compiler I'm using is generating different code for function tracing. I was wondering if anyone has MIPS function tracing working in 3.4 or later? I did figure out why it's hanging and I have some changes that will allow the function tracer to run without frame pointers, but before I proceed I want to rule out compiler differences. Thanks
