tracing/probes: Support field specifier option for typecast

Add a field specifier option for the typecast. This works like
container_of() macro.

    (STRUCT[,FIELD[.FIELD2...]])VAR

This is equivalent to :

    container_of(VAR, struct STRUCT, FIELD[.FIELD2...])

For example:

 echo "f tick_nohz_handler next_tick=(tick_sched,sched_timer)timer->next_tick" >> dynamic_events

This will trace tick_nohz_handler() with its tick_sched::next_tick which
is converted from @timer by contianer_of(tick, struct tick_sched, sched_timer).
So, if you enabkle both fprobes:tick_nohz_handler__entry and
timer:hrtimer_expire_entry events, we will see something like:


          <idle>-0       [002] d.h1.  3778.087272: hrtimer_expire_entry: hrtimer=00000000d63db328 f
unction=tick_nohz_handler now=3777450051040
          <idle>-0       [002] d.h1.  3778.087281: tick_nohz_handler__entry: (tick_nohz_handler+0x4
/0x140) next_tick=3777450000000


Link: https://lore.kernel.org/all/178271365745.1176915.725923927180862257.stgit@devnote2/

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

0 files changed, 0 insertions, 0 deletions