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docs: tracing: Update fprobe documentation

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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>
This commit is contained in:
Masami Hiramatsu (Google) 2023-02-02 00:56:55 +09:00 committed by Steven Rostedt (Google)
parent 87de2163a3
commit 8be098a9eb
1 changed files with 12 additions and 4 deletions
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16
Documentation/trace/fprobe.rst
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@ -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
================================