linux-kernel - [PATCH] tracing/user_events: Use print_format

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Date:   Tue, 28 Mar 2023 15:14:13 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     LKML <linux-kernel@...r.kernel.org>,
        Linux Trace Kernel <linux-trace-kernel@...r.kernel.org>
Cc:     Masami Hiramatsu <mhiramat@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Beau Belgrave <beaub@...ux.microsoft.com>
Subject: [PATCH] tracing/user_events: Use print_format_fields() for trace
 output

From: "Steven Rostedt (Google)" <rostedt@...dmis.org>

Currently, user events are shown using the "hex" output for "safety"
reasons as one cannot trust user events behaving nicely. But the hex
output is not the only utility for safe outputting of trace events. The
print_event_fields() is just as safe and gives user readable output.

Before:
         example-839     [001] .....    43.222244:
00000000: b1 06 00 00 47 03 00 00 00 00 00 00              ....G.......
         example-839     [001] .....    43.564433:
00000000: b1 06 00 00 47 03 00 00 01 00 00 00              ....G.......
         example-839     [001] .....    43.763917:
00000000: b1 06 00 00 47 03 00 00 02 00 00 00              ....G.......
         example-839     [001] .....    43.967929:
00000000: b1 06 00 00 47 03 00 00 03 00 00 00              ....G.......

After:

         example-837     [006] .....    55.739249: test: count=0x0 (0)
         example-837     [006] .....   111.104784: test: count=0x1 (1)
         example-837     [006] .....   111.268444: test: count=0x2 (2)
         example-837     [006] .....   111.416533: test: count=0x3 (3)
         example-837     [006] .....   111.542859: test: count=0x4 (4)

Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---

This depends on:

   https://lore.kernel.org/linux-trace-kernel/20230328145156.497651be@gandalf.local.home/

 kernel/trace/trace_events_user.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c
index 11922f7cf496..b8fb67448e00 100644
--- a/kernel/trace/trace_events_user.c
+++ b/kernel/trace/trace_events_user.c
@@ -22,8 +22,9 @@
 #include <linux/highmem.h>
 #include <linux/init.h>
 #include <linux/user_events.h>
-#include "trace.h"
 #include "trace_dynevent.h"
+#include "trace_output.h"
+#include "trace.h"
 
 #define USER_EVENTS_PREFIX_LEN (sizeof(USER_EVENTS_PREFIX)-1)
 
@@ -1198,11 +1199,7 @@ static enum print_line_t user_event_print_trace(struct trace_iterator *iter,
 						int flags,
 						struct trace_event *event)
 {
-	/* Unsafe to try to decode user provided print_fmt, use hex */
-	trace_print_hex_dump_seq(&iter->seq, "", DUMP_PREFIX_OFFSET, 16,
-				 1, iter->ent, iter->ent_size, true);
-
-	return trace_handle_return(&iter->seq);
+	return print_event_fields(iter, event);
 }
 
 static struct trace_event_functions user_event_funcs = {
-- 
2.39.1