linux-kernel - [tip:tracing/urgent] tracing: Fix trace_print

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Message-ID: <tip-5c37f525657e879a17a27c83021602cd55837531@git.kernel.org>
Date:	Wed, 1 Jul 2009 14:06:32 GMT
From:	tip-bot for Xiao Guangrong <xiaoguangrong@...fujitsu.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com,
	penberg@...helsinki.fi, eduard.munteanu@...ux360.ro,
	xiaoguangrong@...fujitsu.com, fweisbec@...il.com,
	rostedt@...dmis.org, tglx@...utronix.de, mingo@...e.hu
Subject: [tip:tracing/urgent] tracing: Fix trace_print_seq()

Commit-ID:  5c37f525657e879a17a27c83021602cd55837531
Gitweb:     http://git.kernel.org/tip/5c37f525657e879a17a27c83021602cd55837531
Author:     Xiao Guangrong <xiaoguangrong@...fujitsu.com>
AuthorDate: Wed, 1 Jul 2009 16:50:25 +0800
Committer:  Ingo Molnar <mingo@...e.hu>
CommitDate: Wed, 1 Jul 2009 16:03:50 +0200

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>
Acked-by: Frederic Weisbecker <fweisbec@...il.com>
Cc: Eduard - Gabriel Munteanu <eduard.munteanu@...ux360.ro>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Pekka Enberg <penberg@...helsinki.fi>
LKML-Reference: <4A4B2351.5010300@...fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@...e.hu>


---
 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);
 }
--
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