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