tsc.c

 1// SPDX-License-Identifier: GPL-2.0
 2
 3#include <linux/types.h>
 4
 5#include "../../../util/tsc.h"
 6
 7u64 rdtsc(void)
 8{
 9	u64 val;
10
11	/*
12	 * According to ARM DDI 0487F.c, from Armv8.0 to Armv8.5 inclusive, the
13	 * system counter is at least 56 bits wide; from Armv8.6, the counter
14	 * must be 64 bits wide.  So the system counter could be less than 64
15	 * bits wide and it is attributed with the flag 'cap_user_time_short'
16	 * is true.
17	 */
18	asm volatile("mrs %0, cntvct_el0" : "=r" (val));
19
20	return val;
21}