[PATCH v5 11/12] Documentation: probes: Update fprobe document to use ftrace_regs

Masami Hiramatsu (Google)
2023-09-24T13:38:46Z

Update fprobe document so that the entry/exit handler uses ftrace_regs
instead of pt_regs.

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Florent Revest <revest@chromium.org>
---
Documentation/trace/fprobe.rst | 14 ++++++--------
1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/Documentation/trace/fprobe.rst b/Documentation/trace/fprobe.rst
index 196f52386aaa..64ef522f7a64 100644
--- a/Documentation/trace/fprobe.rst
+++ b/Documentation/trace/fprobe.rst
@@ -91,9 +91,9 @@ The prototype of the entry/exit callback function are as follows:

.. code-block:: c

- int entry_callback(struct fprobe *fp, unsigned long entry_ip, unsigned long ret_ip, struct pt_regs *regs, void *entry_data);
+ int entry_callback(struct fprobe *fp, unsigned long entry_ip, unsigned long ret_ip, struct ftrace_regs *fregs, void *entry_data);

- void exit_callback(struct fprobe *fp, unsigned long entry_ip, unsigned long ret_ip, struct pt_regs *regs, void *entry_data);
+ void exit_callback(struct fprobe *fp, unsigned long entry_ip, unsigned long ret_ip, struct ftrace_regs *fregs, 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.
@@ -112,12 +112,10 @@ If the entry callback function returns !0, the corresponding exit callback will
This is the return address that the traced function will return to,
somewhere in the caller. This can be used at both entry and exit.

-@regs
- This is the `pt_regs` data structure at the entry and exit. Note that
- the instruction pointer of @regs may be different from the @entry_ip
- in the entry_handler. If you need traced instruction pointer, you need
- to use @entry_ip. On the other hand, in the exit_handler, the instruction
- pointer of @regs is set to the current return address.
+@fregs
+ This is the `ftrace_regs` data structure at the entry and exit. Note that
+ the instruction pointer of @fregs may be incorrect in entry handler and
+ exit handler, so you have to use @entry_ip and @ret_ip instead.

@entry_data
This is a local storage to share the data between entry and exit handlers.