gettime_perf.c

  1// SPDX-License-Identifier: GPL-2.0
  2#define _GNU_SOURCE
  3#include <sys/types.h>
  4#include <sys/stat.h>
  5#include <errno.h>
  6#include <fcntl.h>
  7#include <sched.h>
  8#include <time.h>
  9#include <stdio.h>
 10#include <unistd.h>
 11#include <sys/syscall.h>
 12#include <dlfcn.h>
 13
 14#include "log.h"
 15#include "timens.h"
 16
 17typedef int (*vgettime_t)(clockid_t, struct timespec *);
 18
 19vgettime_t vdso_clock_gettime;
 20
 21static void fill_function_pointers(void)
 22{
 23	void *vdso = dlopen("linux-vdso.so.1",
 24			    RTLD_LAZY | RTLD_LOCAL | RTLD_NOLOAD);
 25	if (!vdso)
 26		vdso = dlopen("linux-gate.so.1",
 27			      RTLD_LAZY | RTLD_LOCAL | RTLD_NOLOAD);
 28	if (!vdso)
 29		vdso = dlopen("linux-vdso32.so.1",
 30			      RTLD_LAZY | RTLD_LOCAL | RTLD_NOLOAD);
 31	if (!vdso)
 32		vdso = dlopen("linux-vdso64.so.1",
 33			      RTLD_LAZY | RTLD_LOCAL | RTLD_NOLOAD);
 34	if (!vdso) {
 35		pr_err("[WARN]\tfailed to find vDSO\n");
 36		return;
 37	}
 38
 39	vdso_clock_gettime = (vgettime_t)dlsym(vdso, "__vdso_clock_gettime");
 40	if (!vdso_clock_gettime)
 41		vdso_clock_gettime = (vgettime_t)dlsym(vdso, "__kernel_clock_gettime");
 42	if (!vdso_clock_gettime)
 43		pr_err("Warning: failed to find clock_gettime in vDSO\n");
 44
 45}
 46
 47static void test(clock_t clockid, char *clockstr, bool in_ns)
 48{
 49	struct timespec tp, start;
 50	long i = 0;
 51	const int timeout = 3;
 52
 53	vdso_clock_gettime(clockid, &start);
 54	tp = start;
 55	for (tp = start; start.tv_sec + timeout > tp.tv_sec ||
 56			 (start.tv_sec + timeout == tp.tv_sec &&
 57			  start.tv_nsec > tp.tv_nsec); i++) {
 58		vdso_clock_gettime(clockid, &tp);
 59	}
 60
 61	ksft_test_result_pass("%s:\tclock: %10s\tcycles:\t%10ld\n",
 62			      in_ns ? "ns" : "host", clockstr, i);
 63}
 64
 65int main(int argc, char *argv[])
 66{
 67	time_t offset = 10;
 68	int nsfd;
 69
 70	ksft_print_header();
 71
 72	ksft_set_plan(8);
 73
 74	fill_function_pointers();
 75
 76	test(CLOCK_MONOTONIC, "monotonic", false);
 77	test(CLOCK_MONOTONIC_COARSE, "monotonic-coarse", false);
 78	test(CLOCK_MONOTONIC_RAW, "monotonic-raw", false);
 79	test(CLOCK_BOOTTIME, "boottime", false);
 80
 81	nscheck();
 82
 83	if (unshare_timens())
 84		return 1;
 85
 86	nsfd = open("/proc/self/ns/time_for_children", O_RDONLY);
 87	if (nsfd < 0)
 88		return pr_perror("Can't open a time namespace");
 89
 90	if (_settime(CLOCK_MONOTONIC, offset))
 91		return 1;
 92	if (_settime(CLOCK_BOOTTIME, offset))
 93		return 1;
 94
 95	if (setns(nsfd, CLONE_NEWTIME))
 96		return pr_perror("setns");
 97
 98	test(CLOCK_MONOTONIC, "monotonic", true);
 99	test(CLOCK_MONOTONIC_COARSE, "monotonic-coarse", true);
100	test(CLOCK_MONOTONIC_RAW, "monotonic-raw", true);
101	test(CLOCK_BOOTTIME, "boottime", true);
102
103	ksft_exit_pass();
104	return 0;
105}