x86: Initialize stack canary in secondary start

Some secondary clockevent setup code needs to call request_irq, which
will cause fake stack check failure in schedule() if voluntary
preemption model is chosen.  It is safe to have stack canary
initialized here early, since start_secondary() does not return.
Signed-off-by: Jacob Pan <jacob.jun.pan@intel.com>
LKML-Reference: <43F901BD926A4E43B106BF17856F07559FB80D02@orsmsx508.amr.corp.intel.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

arch/x86/kernel/smpboot.c

@@ -48,6 +48,7 @@
 #include <linux/err.h>
 #include <linux/nmi.h>
 #include <linux/tboot.h>
+#include <linux/stackprotector.h>
 
 #include <asm/acpi.h>
 #include <asm/desc.h>
@@ -324,6 +325,9 @@ notrace static void __cpuinit start_secondary(void *unused)
 	/* enable local interrupts */
 	local_irq_enable();
 
+	/* to prevent fake stack check failure in clock setup */
+	boot_init_stack_canary();
+
 	x86_cpuinit.setup_percpu_clockev();
 
 	wmb();