Add support for the tracing infastructure in coreboot.

The compiler is forced to emmit special functions on every
entry/exit of the function. Add a compile time option
to support it. Function entries will be printed in
the console. The CONFIG_TRACE has more documentation.

Patch for userspace tools will follow.

Change-Id: I2cbeb3f104892b034c8756f86ed05bf71187c3f3
Signed-off-by: Rudolf Marek <r.marek@assembler.cz>
Reviewed-on: http://review.coreboot.org/178
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

src/console/vsprintf.c

@@ -22,6 +22,7 @@
 #include <string.h>
 #include <smp/spinlock.h>
 #include <console/vtxprintf.h>
+#include <trace.h>
 
 DECLARE_SPIN_LOCK(vsprintf_lock)
 
@@ -37,6 +38,7 @@ static int vsprintf(char *buf, const char *fmt, va_list args)
 {
 	int i;
 
+	DISABLE_TRACE;
 	spin_lock(&vsprintf_lock);
 
 	str_buf = buf;
@@ -44,6 +46,7 @@ static int vsprintf(char *buf, const char *fmt, va_list args)
 	*str_buf = '\0';
 
 	spin_unlock(&vsprintf_lock);
+	ENABLE_TRACE;
 
 	return i;
 }