tracing/core: drop the old trace_printk() implementation in favour of trace_bprintk()

Impact: faster and lighter tracing

Now that we have trace_bprintk() which is faster and consume lesser
memory than trace_printk() and has the same purpose, we can now drop
the old implementation in favour of the binary one from trace_bprintk(),
which means we move all the implementation of trace_bprintk() to
trace_printk(), so the Api doesn't change except that we must now use
trace_seq_bprintk() to print the TRACE_PRINT entries.

Some changes result of this:

- Previously, trace_bprintk depended of a single tracer and couldn't
  work without. This tracer has been dropped and the whole implementation
  of trace_printk() (like the module formats management) is now integrated
  in the tracing core (comes with CONFIG_TRACING), though we keep the file
  trace_printk (previously trace_bprintk.c) where we can find the module
  management. Thus we don't overflow trace.c

- changes some parts to use trace_seq_bprintk() to print TRACE_PRINT entries.

- change a bit trace_printk/trace_vprintk macros to support non-builtin formats
  constants, and fix 'const' qualifiers warnings. But this is all transparent for
  developers.

- etc...

V2:

- Rebase against last changes
- Fix mispell on the changelog

V3:

- Rebase against last changes (moving trace_printk() to kernel.h)

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <1236356510-8381-5-git-send-email-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

include/linux/kernel.h

@@ -423,6 +423,16 @@ extern void ftrace_off_permanent(void);
 extern void
 ftrace_special(unsigned long arg1, unsigned long arg2, unsigned long arg3);
 
+static inline void __attribute__ ((format (printf, 1, 2)))
+____trace_printk_check_format(const char *fmt, ...)
+{
+}
+#define __trace_printk_check_format(fmt, args...)			\
+do {									\
+	if (0)								\
+		____trace_printk_check_format(fmt, ##args);		\
+} while (0)
+
 /**
  * trace_printk - printf formatting in the ftrace buffer
  * @fmt: the printf format for printing
@@ -439,13 +449,31 @@ ftrace_special(unsigned long arg1, unsigned long arg2, unsigned long arg3);
  * Please refrain from leaving trace_printks scattered around in
  * your code.
  */
-# define trace_printk(fmt...) __trace_printk(_THIS_IP_, fmt)
+
+#define trace_printk(fmt, args...)					\
+do {									\
+	static const char *trace_printk_fmt				\
+	__attribute__((section("__trace_printk_fmt")));			\
+	trace_printk_fmt = fmt;					\
+	__trace_printk_check_format(fmt, ##args);			\
+	__trace_printk(_THIS_IP_, trace_printk_fmt, ##args);		\
+} while (0)
+
 extern int
 __trace_printk(unsigned long ip, const char *fmt, ...)
 	__attribute__ ((format (printf, 2, 3)));
-# define ftrace_vprintk(fmt, ap) __trace_printk(_THIS_IP_, fmt, ap)
+
+#define ftrace_vprintk(fmt, vargs)					\
+do {									\
+	static const char *trace_printk_fmt				\
+	__attribute__((section("__trace_printk_fmt")));			\
+	trace_printk_fmt = fmt;					\
+	__ftrace_vprintk(_THIS_IP_, trace_printk_fmt, vargs);		\
+} while (0)
+
 extern int
 __ftrace_vprintk(unsigned long ip, const char *fmt, va_list ap);
+
 extern void ftrace_dump(void);
 #else
 static inline void
@@ -467,7 +495,7 @@ ftrace_vprintk(const char *fmt, va_list ap)
 	return 0;
 }
 static inline void ftrace_dump(void) { }
-#endif
+#endif /* CONFIG_TRACING */
 
 /*
  *      Display an IP address in readable format.