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From:   "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
To:     Alexei Starovoitov <alexei.starovoitov@gmail.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Florent Revest <revest@chromium.org>
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        LKML <linux-kernel@vger.kernel.org>,
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        Jiri Olsa <jolsa@kernel.org>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
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        Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Guo Ren <guoren@kernel.org>
Subject: [PATCH v5 03/12] tracing: Add a comment about the requirements of the ftrace_regs
Date:   Sun, 24 Sep 2023 22:36:23 +0900
Message-Id: <169556258347.146934.12248055282843332442.stgit@devnote2>
In-Reply-To: <169556254640.146934.5654329452696494756.stgit@devnote2>
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From: Masami Hiramatsu (Google) <mhiramat@kernel.org>

Add a comment about the requirements of the ftrace_regs if it is
implemented on the arch-dependent code with
CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS.

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
 include/linux/ftrace.h |    8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index e8921871ef9a..5da70f238645 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -118,6 +118,14 @@ extern int ftrace_enabled;
 
 #ifndef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS
 
+/*
+ * The ftrace_regs will be just a wrapper of the pt_regs if
+ * CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS is not set. If it is set on an
+ * architecture, it has to define the ftrace_regs data structure.
+ * The ftrace_regs is expected to save the registers for the function
+ * arguments, the registers for stack dump (e.g. stack pointer and the
+ * frame pointer) and the instruction pointer for reference.
+ */
 struct ftrace_regs {
 	struct pt_regs		regs;
 };