linux-kernel - [PATCH v3 8/8] Documentations: probes: Update fprobe document to use ftrace

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Message-Id: <169181869006.505132.4695602314698748304.stgit@devnote2>
Date:   Sat, 12 Aug 2023 14:38:10 +0900
From:   "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Florent Revest <revest@...omium.org>
Cc:     linux-trace-kernel@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        bpf <bpf@...r.kernel.org>, Sven Schnelle <svens@...ux.ibm.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Alan Maguire <alan.maguire@...cle.com>,
        Mark Rutland <mark.rutland@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH v3 8/8] Documentations: probes: Update fprobe document to use ftrace_regs

From: Masami Hiramatsu (Google) <mhiramat@...nel.org>

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

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@...nel.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 a6d682478147..8eee88eda4e6 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 of the traced function. This can be used
         at both entry and exit.
 
-@...s
-        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 currect return address.
+@...gs
+        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.