tracing/ftrace: give an entry on the config for boot tracer

Bring the entry to choose the boot tracer on the kernel config.
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

kernel/trace/Kconfig

@@ -116,6 +116,18 @@ config CONTEXT_SWITCH_TRACER
 	  This tracer gets called from the context switch and records
 	  all switching of tasks.
 
+config BOOT_TRACER
+	bool "Trace boot initcalls"
+	depends on HAVE_FTRACE
+	depends on DEBUG_KERNEL
+	select TRACING
+	help
+	  This tracer helps developers to optimize boot times: it records
+	  the timings of the initcalls. Its aim is to be parsed by the
+	  /scripts/bootgraph.pl tool to produce pretty graphics about
+	  boot inefficiencies, giving a visual representation of the
+	  delays during initcalls.
+
 config STACK_TRACER
 	bool "Trace max stack"
 	depends on HAVE_FTRACE

kernel/trace/Makefile

@@ -22,5 +22,6 @@ obj-$(CONFIG_SCHED_TRACER) += trace_sched_wakeup.o
 obj-$(CONFIG_NOP_TRACER) += trace_nop.o
 obj-$(CONFIG_STACK_TRACER) += trace_stack.o
 obj-$(CONFIG_MMIOTRACE) += trace_mmiotrace.o
+obj-$(CONFIG_BOOT_TRACER) += trace_boot.o
 
 libftrace-y := ftrace.o