linux-kernel - [PATCH] tracing: fix trace_print

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Message-ID: <4A4B2351.5010300@cn.fujitsu.com>
Date:	Wed, 01 Jul 2009 16:50:25 +0800
From:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Eduard - Gabriel Munteanu <eduard.munteanu@...ux360.ro>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH] tracing: fix trace_print_seq()

We will lose something if trace_seq->buffer[0] is 0, because the copy length
is calculated by strlen() in seq_puts(), so using seq_write() instead of 
seq_puts().

There have a example:
after reboot:
# echo kmemtrace > current_tracer
# echo 0 > options/kmem_minimalistic
# cat trace
# tracer: kmemtrace
#
#
Nothing is exported, because the first byte of trace_seq->buffer[ ]
is KMEMTRACE_USER_ALLOC.
( the value of KMEMTRACE_USER_ALLOC is zero, seeing
  kmemtrace_print_alloc_user() in kernel/trace/kmemtrace.c)

Signed-off-by: Xiao Guangrong <xiaoguangrong@...fujitsu.com>
---
 kernel/trace/trace_output.c |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index 7938f3a..e0c2545 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -27,8 +27,7 @@ void trace_print_seq(struct seq_file *m, struct trace_seq *s)
 {
 	int len = s->len >= PAGE_SIZE ? PAGE_SIZE - 1 : s->len;
 
-	s->buffer[len] = 0;
-	seq_puts(m, s->buffer);
+	seq_write(m, s->buffer, len);
 
 	trace_seq_init(s);
 }
-- 
1.6.1.2

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