linux-kernel - [PATCH v2] ftrace: Hide a extra entry in stack trace

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Message-ID: <20240926061311.25625-1-tatsuya.s2862@gmail.com>
Date: Thu, 26 Sep 2024 15:13:07 +0900
From: Tatsuya S <tatsuya.s2862@...il.com>
To: Steven Rostedt <rostedt@...dmis.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: Tatsuya S <tatsuya.s2862@...il.com>,
	linux-kernel@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org
Subject: [PATCH v2] ftrace: Hide a extra entry in stack trace

A extra entry is shown on stack trace(CONFIG_UNWINDER_ORC=y).

    [003] .....   110.171589: vfs_write <-__x64_sys_write
    [003] .....   110.171600: <stack trace>
 => XXXXXXXXX (Wrong function name)
 => vfs_write
 => __x64_sys_write
 => do_syscall_64
 => entry_SYSCALL_64_after_hwframe

To resolve this, increment skip in __ftrace_trace_stack().
The reason why skip is incremented in __ftrace_trace_stack()
is because __ftrace_trace_stack() in stack trace is the only function
that wasn't skipped from anywhere.

Signed-off-by: Tatsuya S <tatsuya.s2862@...il.com>
---
 kernel/trace/trace.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index c3b2c7dfadef..0f2e255f563c 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2916,10 +2916,8 @@ static void __ftrace_trace_stack(struct trace_buffer *buffer,
 	 * Add one, for this function and the call to save_stack_trace()
 	 * If regs is set, then these functions will not be in the way.
 	 */
-#ifndef CONFIG_UNWINDER_ORC
-	if (!regs)
+	if (IS_ENABLED(CONFIG_UNWINDER_ORC) || !regs)
 		skip++;
-#endif
 
 	preempt_disable_notrace();
 
-- 
2.46.1