NMI sampling

- if profile --nmi kernel uses NMI watchdog based sampling based on
  Intel architecture performance counters

- using NMI makes kernel profiling possible

- watchdog kernel lockup detection is disabled while sampling as we
  may get unpredictable interrupts in kernel and thus possibly many
  false positives

- if watchdog is not enabled at boot time, profiling enables it and
  turns it of again when done

kernel/profile.h

@@ -5,12 +5,17 @@
 
 #if SPROFILE	/* statistical profiling */
 
+#include "arch_watchdog.h"
+
 EXTERN int sprofiling;			/* whether profiling is running */
+EXTERN int sprofiling_type;			/* whether profiling is running */
 EXTERN int sprof_mem_size;		/* available user memory for data */
 EXTERN struct sprof_info_s sprof_info;	/* profiling info for user program */
 EXTERN vir_bytes sprof_data_addr_vir;	/* user address to write data */
 EXTERN endpoint_t sprof_ep;		/* user process */
 
+_PROTOTYPE(void nmi_sprofile_handler, (struct nmi_frame * frame));
+
 #endif /* SPROFILE */