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Subject[PATCH v2] printk: add console output tracing
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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
include/trace/events/printk.h | 44 ++++++++++++++++++++++++++++++++++++++++++
kernel/printk.c | 5 ++++
2 files changed, 49 insertions(+)
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ b/include/trace/events/printk.h 2011-11-16 23:18:35.000000000 +0100
@@ -0,0 +1,44 @@
+#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 + log_buf_len) &
+ (log_buf_len - 1)) + 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 + log_buf_len) & (log_buf_len - 1));
+ ((char *)__get_dynamic_array(msg))[(end - start + log_buf_len) &
+ (log_buf_len - 1)] = 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 2011-11-16 22:25:43.000000000 +0100
+++ b/kernel/printk.c 2011-11-17 16:19:19.000000000 +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)) {



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