[PATCH v5 02/12] Documentation: probes: Add a new ret_ip callback parameter

Masami Hiramatsu (Google)
2023-09-24T13:36:18Z

Add a new ret_ip callback parameter description.

Fixes: cb16330d1274 ("fprobe: Pass return address to the handlers")
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Florent Revest <revest@chromium.org>
---
Changes in v4:
- Update ret_ip description (Thanks Florent!)
---
Documentation/trace/fprobe.rst | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/Documentation/trace/fprobe.rst b/Documentation/trace/fprobe.rst
index 7a895514b537..196f52386aaa 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, struct pt_regs *regs, void *entry_data);
+ int entry_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, struct pt_regs *regs, void *entry_data);
+ void exit_callback(struct fprobe *fp, unsigned long entry_ip, unsigned long ret_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.
@@ -108,6 +108,10 @@ If the entry callback function returns !0, the corresponding exit callback will
Note that this may not be the actual entry address of the function but
the address where the ftrace is instrumented.

+@ret_ip
+ 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