linux.git/kernel/trace/fprobe.c, branch v6.4-rc2

fprobe: Skip exit_handler if entry_handler returns !0

2023-03-28T22:52:22+00:00

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 
Cc: Mark Rutland 
Cc: Will Deacon 
Signed-off-by: Masami Hiramatsu (Google) 
Signed-off-by: Steven Rostedt (Google)

fprobe: Add nr_maxactive to specify rethook_node pool size

2023-03-28T22:52:22+00:00

Add nr_maxactive to specify rethook_node pool size. This means
the maximum number of actively running target functions concurrently
for probing by exit_handler. Note that if the running function is
preempted or sleep, it is still counted as 'active'.

Link: https://lkml.kernel.org/r/167526697917.433354.17779774988245113106.stgit@mhiramat.roam.corp.google.com

Cc: Florent Revest 
Cc: Mark Rutland 
Cc: Will Deacon 
Signed-off-by: Masami Hiramatsu (Google) 
Signed-off-by: Steven Rostedt (Google)

fprobe: Pass entry_data to handlers

2023-03-28T22:52:22+00:00

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 
Cc: Mark Rutland 
Cc: Will Deacon 
Signed-off-by: Masami Hiramatsu (Google) 
Signed-off-by: Steven Rostedt (Google)

tracing/fprobe: Fix to check whether fprobe is registered correctly

2022-11-03T23:50:07+00:00

Since commit ab51e15d535e ("fprobe: Introduce FPROBE_FL_KPROBE_SHARED flag
for fprobe") introduced fprobe_kprobe_handler() for fprobe::ops::func,
unregister_fprobe() fails to unregister the registered if user specifies
FPROBE_FL_KPROBE_SHARED flag.
Moreover, __register_ftrace_function() is possible to change the
ftrace_ops::func, thus we have to check fprobe::ops::saved_func instead.

To check it correctly, it should confirm the fprobe::ops::saved_func is
either fprobe_handler() or fprobe_kprobe_handler().

Link: https://lore.kernel.org/all/166677683946.1459107.15997653945538644683.stgit@devnote3/

Fixes: cad9931f64dc ("fprobe: Add ftrace based probe APIs")
Cc: stable@vger.kernel.org
Signed-off-by: Masami Hiramatsu (Google)

fprobe: Check rethook_alloc() return in rethook initialization

2022-11-03T23:50:00+00:00

Check if fp->rethook succeeded to be allocated. Otherwise, if
rethook_alloc() fails, then we end up dereferencing a NULL pointer in
rethook_add_node().

Link: https://lore.kernel.org/all/20221025031209.954836-1-rafaelmendsr@gmail.com/

Fixes: 5b0ab78998e3 ("fprobe: Add exit_handler support")
Cc: stable@vger.kernel.org
Signed-off-by: Rafael Mendonca 
Acked-by: Steven Rostedt (Google) 
Acked-by: Masami Hiramatsu (Google) 
Signed-off-by: Masami Hiramatsu (Google)

fprobe: Resolve symbols with ftrace_lookup_symbols

2022-05-10T21:42:06+00:00

Using ftrace_lookup_symbols to speed up symbols lookup
in register_fprobe_syms API.

Acked-by: Masami Hiramatsu 
Signed-off-by: Jiri Olsa 
Link: https://lore.kernel.org/r/20220510122616.2652285-4-jolsa@kernel.org
Signed-off-by: Alexei Starovoitov

fprobe: Fix sparse warning for acccessing __rcu ftrace_hash

2022-03-29T02:05:40+00:00

Since ftrace_ops::local_hash::filter_hash field is an __rcu pointer,
we have to use rcu_access_pointer() to access it.

Reported-by: kernel test robot 
Signed-off-by: Masami Hiramatsu 
Signed-off-by: Alexei Starovoitov 
Link: https://lore.kernel.org/bpf/164802093635.1732982.4938094876018890866.stgit@devnote2

fprobe: Fix smatch type mismatch warning

2022-03-29T02:05:40+00:00

Fix the type mismatching warning of 'rethook_node vs fprobe_rethook_node'
found by Smatch.

Reported-by: Dan Carpenter 
Signed-off-by: Masami Hiramatsu 
Signed-off-by: Alexei Starovoitov 
Link: https://lore.kernel.org/bpf/164802092611.1732982.12268174743437084619.stgit@devnote2

fprobe: Introduce FPROBE_FL_KPROBE_SHARED flag for fprobe

2022-03-18T03:17:02+00:00

Introduce FPROBE_FL_KPROBE_SHARED flag for sharing fprobe callback with
kprobes safely from the viewpoint of recursion.

Since the recursion safety of the fprobe (and ftrace) is a bit different
from the kprobes, this may cause an issue if user wants to run the same
code from the fprobe and the kprobes.

The kprobes has per-cpu 'current_kprobe' variable which protects the
kprobe handler from recursion in any case. On the other hand, the fprobe
uses only ftrace_test_recursion_trylock(), which will allow interrupt
context calls another (or same) fprobe during the fprobe user handler is
running.

This is not a matter in cases if the common callback shared among the
kprobes and the fprobe has its own recursion detection, or it can handle
the recursion in the different contexts (normal/interrupt/NMI.)
But if it relies on the 'current_kprobe' recursion lock, it has to check
kprobe_running() and use kprobe_busy_*() APIs.

Fprobe has FPROBE_FL_KPROBE_SHARED flag to do this. If your common callback
code will be shared with kprobes, please set FPROBE_FL_KPROBE_SHARED
*before* registering the fprobe, like;

 fprobe.flags = FPROBE_FL_KPROBE_SHARED;

 register_fprobe(&fprobe, "func*", NULL);

This will protect your common callback from the nested call.

Signed-off-by: Masami Hiramatsu 
Signed-off-by: Steven Rostedt (Google) 
Tested-by: Steven Rostedt (Google) 
Signed-off-by: Alexei Starovoitov 
Link: https://lore.kernel.org/bpf/164735293127.1084943.15687374237275817599.stgit@devnote2

fprobe: Add exit_handler support

2022-03-18T03:16:52+00:00

Add exit_handler to fprobe. fprobe + rethook allows us to hook the kernel
function return. The rethook will be enabled only if the
fprobe::exit_handler is set.

Signed-off-by: Masami Hiramatsu 
Signed-off-by: Steven Rostedt (Google) 
Tested-by: Steven Rostedt (Google) 
Signed-off-by: Alexei Starovoitov 
Link: https://lore.kernel.org/bpf/164735290790.1084943.10601965782208052202.stgit@devnote2