If you don't use one of the oskit ENTRY macros, then your function's symbol may not be declared properly. If you want to do it by hand, then declare the symbol:
.globl symbol_name
.type symbol_name,@function
Note that this is taken care of for you by the macros in asm.h if you simply declare a function with ENTRY(x) or NON_GPROF_ENTRY(x).