lkml.org 
[lkml]   [2017]   [Jul]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[RFC V2] printk: add warning while drop partial text in msg
Date
If the buffer pass to msg_print_text is not big enough to put both all
prefixes and log_text(msg), kernel will quietly break.
That means the user may not have the chance to know whether the
log_text(msg) is fully printed into buffer or not.

In this patch, once above case happened, we try to calculate how many
characters of log_text(msg) are dropped and add warning for debugging
purpose.

Signed-off-by: pierre Kuo <vichy.kuo@gmail.com>
---
Changes since v2:
* fix typo in commit message from "waring for debugging purpose" to "warning for debugging purpose"

kernel/printk/printk.c | 23 ++++++++++++++++++++++-
1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index fc47863..6cbb3699 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -558,6 +558,12 @@ static u32 msg_used_size(u16 text_len, u16 dict_len, u32 *pad_len)
#define MAX_LOG_TAKE_PART 4
static const char trunc_msg[] = "<truncated>";

+/*
+ * Define max drop msg length that we put in next msg
+ */
+#define MAX_DROP_MSG_LENGTH 32
+static char drop_msg[MAX_DROP_MSG_LENGTH];
+
static u32 truncate_msg(u16 *text_len, u16 *trunc_msg_len,
u16 *dict_len, u32 *pad_len)
{
@@ -1264,8 +1270,23 @@ static size_t msg_print_text(const struct printk_log *msg, bool syslog, char *bu

if (buf) {
if (print_prefix(msg, syslog, NULL) +
- text_len + 1 >= size - len)
+ text_len + 1 >= size - len) {
+ /* below stores dropped characters
+ * related information in next msg
+ */
+ size_t drop_len;
+
+ drop_len = scnprintf(drop_msg,
+ MAX_DROP_MSG_LENGTH,
+ "<%u characters dropped>",
+ (next) ?
+ (unsigned int)(text_size + next - text) :
+ (unsigned int)text_size);
+ drop_msg[drop_len] = 0;
+ log_store(msg->facility, msg->level, msg->flags,
+ 0, NULL, 0, drop_msg, strlen(drop_msg));
break;
+ }

len += print_prefix(msg, syslog, buf + len);
memcpy(buf + len, text, text_len);
--
1.9.1
\
 
 \ /
  Last update: 2017-07-30 15:38    [W:0.114 / U:10.860 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site