1 files changed, 40 insertions, 1 deletions

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index bc5392a326ab..a3a5574a61fc 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -514,7 +514,8 @@ do {									\
  *
  * This is intended as a debugging tool for the developer only.
  * Please refrain from leaving trace_printks scattered around in
- * your code.
+ * your code. (Extra memory is used for special buffers that are
+ * allocated when trace_printk() is used)
  */
 
 #define trace_printk(fmt, args...)                                      \
@@ -537,6 +538,44 @@ int __trace_bprintk(unsigned long ip, const char *fmt, ...);
 extern __printf(2, 3)
 int __trace_printk(unsigned long ip, const char *fmt, ...);
 
+/**
+ * trace_puts - write a string into the ftrace buffer
+ * @str: the string to record
+ *
+ * Note: __trace_bputs is an internal function for trace_puts and
+ *       the @ip is passed in via the trace_puts macro.
+ *
+ * This is similar to trace_printk() but is made for those really fast
+ * paths that a developer wants the least amount of "Heisenbug" affects,
+ * where the processing of the print format is still too much.
+ *
+ * This function allows a kernel developer to debug fast path sections
+ * that printk is not appropriate for. By scattering in various
+ * printk like tracing in the code, a developer can quickly see
+ * where problems are occurring.
+ *
+ * This is intended as a debugging tool for the developer only.
+ * Please refrain from leaving trace_puts scattered around in
+ * your code. (Extra memory is used for special buffers that are
+ * allocated when trace_puts() is used)
+ *
+ * Returns: 0 if nothing was written, positive # if string was.
+ *  (1 when __trace_bputs is used, strlen(str) when __trace_puts is used)
+ */
+
+extern int __trace_bputs(unsigned long ip, const char *str);
+extern int __trace_puts(unsigned long ip, const char *str, int size);
+#define trace_puts(str) ({                                              \
+        static const char *trace_printk_fmt                             \
+                __attribute__((section("__trace_printk_fmt"))) =        \
+                __builtin_constant_p(str) ? str : NULL;                 \
+                                                                        \
+        if (__builtin_constant_p(str))                                  \
+                __trace_bputs(_THIS_IP_, trace_printk_fmt);             \
+        else                                                            \
+                __trace_puts(_THIS_IP_, str, strlen(str));              \
+})
+
 extern void trace_dump_stack(void);
 
 /*