symbol:const char*[K] - the symbol that is being hooked.
trampoline:const char*[K] - the name/address of the ftrace trampoline.
callback:const char*[K] - the callback name/address that will be called once the symbol is being executed.
callback_offset:off_t[K] - the callback offset (inside the function).
callback_owner:const char*[K] - the owner of the callback (kernel module name if applicable etc)
flags:const char*[K] - the flags for ftrace. R: registers are passed to the callback; I: callback can change the RIP register value; D: direct call to the function; O: callsite-specific ops; M: the function had I or D.
count:unsigned long[K] - the number of callbacks registered with the symbol.