[for-next,07/25] docs: tracing: Update fprobe documentation
Commit Message
From: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Update fprobe.rst for
- the private entry_data argument
- the return value of the entry handler
- the nr_rethook_node field.
Link: https://lkml.kernel.org/r/167526701579.433354.3057889264263546659.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>
---
Documentation/trace/fprobe.rst | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)
@@ -87,14 +87,16 @@ returns as same as unregister_ftrace_function().
The fprobe entry/exit handler
=============================
-The prototype of the entry/exit callback function is as follows:
+The prototype of the entry/exit callback function are as follows:
.. code-block:: c
- void callback_func(struct fprobe *fp, unsigned long entry_ip, struct pt_regs *regs);
+ int entry_callback(struct fprobe *fp, unsigned long entry_ip, struct pt_regs *regs, void *entry_data);
-Note that both entry and exit callbacks have same ptototype. The @entry_ip is
-saved at function entry and passed to exit handler.
+ void exit_callback(struct fprobe *fp, unsigned long entry_ip, struct pt_regs *regs, void *entry_data);
+
+Note that the @entry_ip is saved at function entry and passed to exit handler.
+If the entry callback function returns !0, the corresponding exit callback will be cancelled.
@fp
This is the address of `fprobe` data structure related to this handler.
@@ -113,6 +115,12 @@ saved at function entry and passed to exit handler.
to use @entry_ip. On the other hand, in the exit_handler, the instruction
pointer of @regs is set to the currect return address.
+@entry_data
+ This is a local storage to share the data between entry and exit handlers.
+ This storage is NULL by default. If the user specify `exit_handler` field
+ and `entry_data_size` field when registering the fprobe, the storage is
+ allocated and passed to both `entry_handler` and `exit_handler`.
+
Share the callbacks with kprobes
================================