fprobe: Pass return address to the handlers

Pass return address as 'ret_ip' to the fprobe entry and return handlers
so that the fprobe user handler can get the reutrn address without
analyzing arch-dependent pt_regs.

Link: https://lore.kernel.org/all/168507467664.913472.11642316698862778600.stgit@mhiramat.roam.corp.google.com/

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

fprobe: Skip exit_handler if entry_handler returns !0

Skip hooking function return and calling exit_handler if the
entry_handler() returns !0.

Link: https://lkml.kernel.org/r/167526699798.433354.10998365726830117303.stgit@mhiramat.roam.corp.google.com

Cc: Florent Revest <revest@chromium.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

fprobe: Pass entry_data to handlers

Pass the private entry_data to the entry and exit handlers so that
they can share the context data, something like saved function
arguments etc.
User must specify the private entry_data size by @entry_data_size
field before registering the fprobe.

Link: https://lkml.kernel.org/r/167526696173.433354.17408372048319432574.stgit@mhiramat.roam.corp.google.com

Cc: Florent Revest <revest@chromium.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

fprobe/samples: Make sample_probe static

This symbol is not used outside of fprobe_example.c, so marks it static.

Fixes the following warning:

sparse warnings: (new ones prefixed by >>)
>> samples/fprobe/fprobe_example.c:23:15: sparse: sparse: symbol 'sample_probe'
was not declared. Should it be static?

Link: https://lkml.kernel.org/r/20220606075659.674556-1-sunliming@kylinos.cn

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: sunliming <sunliming@kylinos.cn>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

fprobe, samples: Add module parameter descriptions

Add module parameter descriptions for the fprobe_example module.

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/165602349520.56016.1314423560740428008.stgit@devnote2

fprobe, samples: Add use_trace option and show hit/missed counter

Add use_trace option to use trace_printk() instead of pr_info()
so that the handler doesn't involve the RCU operations.
And show the hit and missed counter so that the user can check
how many times the probe handler hit and missed.

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/bpf/165461826247.280167.11939123218334322352.stgit@devnote2

fprobe: Add sample program for fprobe

Add a sample program for the fprobe. The sample_fprobe puts a fprobe on
kernel_clone() by default. This dump stack and some called address info
at the function entry and exit.

The sample_fprobe.ko gets 2 parameters.
- symbol: you can specify the comma separated symbols or wildcard symbol
pattern (in this case you can not use comma)
- stackdump: a bool value to enable or disable stack dump in the fprobe
handler.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Tested-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/164735291987.1084943.4449670993752806840.stgit@devnote2