[PATCH v3] printk: add console output tracing

Johannes Berg
2011-11-24T19:03:14Z

From: Johannes Berg <johannes.berg@intel.com>

Add a printk.console trace point to record any printk
messages into the trace, regardless of the current
console loglevel. This can help correlate (existing)
printk debugging with other tracing.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
---
v2: remove extra file
v3: simplify length of __dynamic_array, thanks Frederic

include/trace/events/printk.h | 41 +++++++++++++++++++++++++++++++++++++++++
kernel/printk.c | 5 +++++
2 files changed, 46 insertions(+)

--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ b/include/trace/events/printk.h 2011-11-24 20:02:21.000000000 +0100
@@ -0,0 +1,41 @@
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM printk
+
+#if !defined(_TRACE_PRINTK_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_PRINTK_H
+
+#include <linux/tracepoint.h>
+
+TRACE_EVENT_CONDITION(console,
+ TP_PROTO(const char *log_buf, unsigned start, unsigned end,
+ unsigned log_buf_len),
+
+ TP_ARGS(log_buf, start, end, log_buf_len),
+
+ TP_CONDITION(start != end),
+
+ TP_STRUCT__entry(
+ __dynamic_array(char, msg, end - start + 1)
+ ),
+
+ TP_fast_assign(
+ if ((start & (log_buf_len - 1)) > (end & (log_buf_len - 1))) {
+ memcpy(__get_dynamic_array(msg),
+ log_buf + (start & (log_buf_len - 1)),
+ log_buf_len - (start & (log_buf_len - 1)));
+ memcpy((char *)__get_dynamic_array(msg) +
+ log_buf_len - (start & (log_buf_len - 1)),
+ log_buf, end & (log_buf_len - 1));
+ } else
+ memcpy(__get_dynamic_array(msg),
+ log_buf + (start & (log_buf_len - 1)),
+ end - start);
+ ((char *)__get_dynamic_array(msg))[end - start] = 0;
+ ),
+
+ TP_printk("%s", __get_str(msg))
+);
+#endif /* _TRACE_PRINTK_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>
--- a/kernel/printk.c 2011-11-24 09:38:53.000000000 +0100
+++ b/kernel/printk.c 2011-11-24 09:42:37.000000000 +0100
@@ -44,6 +44,9 @@

#include <asm/uaccess.h>

+#define CREATE_TRACE_POINTS
+#include <trace/events/printk.h>
+
/*
* Architectures can override it:
*/
@@ -542,6 +545,8 @@ MODULE_PARM_DESC(ignore_loglevel, "ignor
static void _call_console_drivers(unsigned start,
unsigned end, int msg_log_level)
{
+ trace_console(&LOG_BUF(0), start, end, log_buf_len);
+
if ((msg_log_level < console_loglevel || ignore_loglevel) &&
console_drivers && start != end) {
if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {