linux-kernel - [PATCH] ftrace: Handle TRACE_BPUTS in print_graph

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Message-Id: <20160901024354.13720-1-namhyung@kernel.org>
Date:   Thu,  1 Sep 2016 11:43:54 +0900
From:   Namhyung Kim <namhyung@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...nel.org>
Subject: [PATCH] ftrace: Handle TRACE_BPUTS in print_graph_comment

It missed to handle TRACE_BPUTS so messages recorded by trace_bputs()
will be shown with symbol info unnecessarily.

You can see it with the trace_printk sample code:

  # cd /sys/kernel/tracing/
  # echo sys_sync > set_graph_function
  # echo 1 > options/sym-offset
  # echo function_graph > current_tracer

Note that the sys_sync filter was there to prevent recording other
functions and the sym-offset option was needed since the first message
was called from a module init function so kallsyms doesn't have the
symbol and omitted in the output.

  # cd ~/build/kernel
  # insmod samples/trace_printk/trace-printk.ko

  # cd -
  # head trace

Before:

  # tracer: function_graph
  #
  # CPU  DURATION                  FUNCTION CALLS
  # |     |   |                     |   |   |   |
   1)               |  /* 0xffffffffa0002000: This is a static string that will use trace_bputs */
   1)               |  /* This is a dynamic string that will use trace_puts */
   1)               |  /* trace_printk_irq_work+0x5/0x7b [trace_printk]: (irq) This is a static string that will use trace_bputs */
   1)               |  /* (irq) This is a dynamic string that will use trace_puts */
   1)               |  /* (irq) This is a static string that will use trace_bprintk() */
   1)               |  /* (irq) This is a dynamic string that will use trace_printk */

After:

  # tracer: function_graph
  #
  # CPU  DURATION                  FUNCTION CALLS
  # |     |   |                     |   |   |   |
   1)               |  /* This is a static string that will use trace_bputs */
   1)               |  /* This is a dynamic string that will use trace_puts */
   1)               |  /* (irq) This is a static string that will use trace_bputs */
   1)               |  /* (irq) This is a dynamic string that will use trace_puts */
   1)               |  /* (irq) This is a static string that will use trace_bprintk() */
   1)               |  /* (irq) This is a dynamic string that will use trace_printk */

Signed-off-by: Namhyung Kim <namhyung@...nel.org>
---
 kernel/trace/trace_functions_graph.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index 9c7ffa4df5a8..4e480e870474 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -1182,6 +1182,11 @@ print_graph_comment(struct trace_seq *s, struct trace_entry *ent,
 	trace_seq_puts(s, "/* ");
 
 	switch (iter->ent->type) {
+	case TRACE_BPUTS:
+		ret = trace_print_bputs_msg_only(iter);
+		if (ret != TRACE_TYPE_HANDLED)
+			return ret;
+		break;
 	case TRACE_BPRINT:
 		ret = trace_print_bprintk_msg_only(iter);
 		if (ret != TRACE_TYPE_HANDLED)
-- 
2.9.3