testcases/kernel/syscalls/getrandom/getrandom02.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright (C) 2015 Cedric Hnyda <ced.hnyda@gmail.com>
 *
 * Calls getrandom(2), checks that the buffer is filled with random bytes
 * and expects success.
 */

#include "lapi/getrandom.h"
#include "lapi/syscalls.h"
#include "tst_test.h"

static int modes[] = { 0, GRND_RANDOM, GRND_NONBLOCK,
		       GRND_RANDOM | GRND_NONBLOCK };

static int check_content(unsigned char *buf, int nb)
{
	int table[256];
	int i, index, max;

	memset(table, 0, sizeof(table));

	max = 6 + nb * 0.2;

	for (i = 0; i < nb; i++) {
		index = buf[i];
		table[index]++;
	}

	for (i = 0; i < nb; i++) {
		if (max > 0 && table[i] > max)
			return 0;
	}
	return 1;
}

static void verify_getrandom(unsigned int n)
{
	unsigned char buf[256];

	memset(buf, 0, sizeof(buf));

	do {
		TEST(tst_syscall(__NR_getrandom, buf, sizeof(buf), modes[n]));
	} while ((modes[n] & GRND_NONBLOCK) && TST_RET == -1
		  && TST_ERR == EAGAIN);

	if (!check_content(buf, TST_RET))
		tst_res(TFAIL | TTERRNO, "getrandom failed");
	else
		tst_res(TPASS, "getrandom returned %ld", TST_RET);
}

static struct tst_test test = {
	.tcnt = ARRAY_SIZE(modes),
	.test = verify_getrandom,
};