1 // SPDX-License-Identifier: GPL-2.0
2
3 #include <linux/types.h>
4
5 #include "../../../util/tsc.h"
6
7 u64 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 }
22
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