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-rw-r--r--tests/qtest/npcm7xx_rng-test.c278
1 files changed, 278 insertions, 0 deletions
diff --git a/tests/qtest/npcm7xx_rng-test.c b/tests/qtest/npcm7xx_rng-test.c
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+++ b/tests/qtest/npcm7xx_rng-test.c
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+/*
+ * QTest testcase for the Nuvoton NPCM7xx Random Number Generator
+ *
+ * Copyright 2020 Google LLC
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * for more details.
+ */
+
+#include "qemu/osdep.h"
+
+#include <math.h>
+
+#include "libqtest-single.h"
+#include "qemu/bitops.h"
+
+#define RNG_BASE_ADDR 0xf000b000
+
+/* Control and Status Register */
+#define RNGCS 0x00
+# define DVALID BIT(1) /* Data Valid */
+# define RNGE BIT(0) /* RNG Enable */
+/* Data Register */
+#define RNGD 0x04
+/* Mode Register */
+#define RNGMODE 0x08
+# define ROSEL_NORMAL (2) /* RNG only works in this mode */
+
+/* Number of bits to collect for randomness tests. */
+#define TEST_INPUT_BITS (128)
+
+static void rng_writeb(unsigned int offset, uint8_t value)
+{
+ writeb(RNG_BASE_ADDR + offset, value);
+}
+
+static uint8_t rng_readb(unsigned int offset)
+{
+ return readb(RNG_BASE_ADDR + offset);
+}
+
+/* Disable RNG and set normal ring oscillator mode. */
+static void rng_reset(void)
+{
+ rng_writeb(RNGCS, 0);
+ rng_writeb(RNGMODE, ROSEL_NORMAL);
+}
+
+/* Reset RNG and then enable it. */
+static void rng_reset_enable(void)
+{
+ rng_reset();
+ rng_writeb(RNGCS, RNGE);
+}
+
+/* Wait until Data Valid bit is set. */
+static bool rng_wait_ready(void)
+{
+ /* qemu_guest_getrandom may fail. Assume it won't fail 10 times in a row. */
+ int retries = 10;
+
+ while (retries-- > 0) {
+ if (rng_readb(RNGCS) & DVALID) {
+ return true;
+ }
+ }
+
+ return false;
+}
+
+/*
+ * Perform a frequency (monobit) test, as defined by NIST SP 800-22, on the
+ * sequence in buf and return the P-value. This represents the probability of a
+ * truly random sequence having the same proportion of zeros and ones as the
+ * sequence in buf.
+ *
+ * An RNG which always returns 0x00 or 0xff, or has some bits stuck at 0 or 1,
+ * will fail this test. However, an RNG which always returns 0x55, 0xf0 or some
+ * other value with an equal number of zeroes and ones will pass.
+ */
+static double calc_monobit_p(const uint8_t *buf, unsigned int len)
+{
+ unsigned int i;
+ double s_obs;
+ int sn = 0;
+
+ for (i = 0; i < len; i++) {
+ /*
+ * Each 1 counts as 1, each 0 counts as -1.
+ * s = cp - (8 - cp) = 2 * cp - 8
+ */
+ sn += 2 * ctpop8(buf[i]) - 8;
+ }
+
+ s_obs = abs(sn) / sqrt(len * BITS_PER_BYTE);
+
+ return erfc(s_obs / sqrt(2));
+}
+
+/*
+ * Perform a runs test, as defined by NIST SP 800-22, and return the P-value.
+ * This represents the probability of a truly random sequence having the same
+ * number of runs (i.e. uninterrupted sequences of identical bits) as the
+ * sequence in buf.
+ */
+static double calc_runs_p(const unsigned long *buf, unsigned int nr_bits)
+{
+ unsigned int j;
+ unsigned int k;
+ int nr_ones = 0;
+ int vn_obs = 0;
+ double pi;
+
+ g_assert(nr_bits % BITS_PER_LONG == 0);
+
+ for (j = 0; j < nr_bits / BITS_PER_LONG; j++) {
+ nr_ones += __builtin_popcountl(buf[j]);
+ }
+ pi = (double)nr_ones / nr_bits;
+
+ for (k = 0; k < nr_bits - 1; k++) {
+ vn_obs += !(test_bit(k, buf) ^ test_bit(k + 1, buf));
+ }
+ vn_obs += 1;
+
+ return erfc(fabs(vn_obs - 2 * nr_bits * pi * (1.0 - pi))
+ / (2 * sqrt(2 * nr_bits) * pi * (1.0 - pi)));
+}
+
+/*
+ * Verifies that DVALID is clear, and RNGD reads zero, when RNGE is cleared,
+ * and DVALID eventually becomes set when RNGE is set.
+ */
+static void test_enable_disable(void)
+{
+ /* Disable: DVALID should not be set, and RNGD should read zero */
+ rng_reset();
+ g_assert_cmphex(rng_readb(RNGCS), ==, 0);
+ g_assert_cmphex(rng_readb(RNGD), ==, 0);
+
+ /* Enable: DVALID should be set, but we can't make assumptions about RNGD */
+ rng_writeb(RNGCS, RNGE);
+ g_assert_true(rng_wait_ready());
+ g_assert_cmphex(rng_readb(RNGCS), ==, DVALID | RNGE);
+
+ /* Disable: DVALID should not be set, and RNGD should read zero */
+ rng_writeb(RNGCS, 0);
+ g_assert_cmphex(rng_readb(RNGCS), ==, 0);
+ g_assert_cmphex(rng_readb(RNGD), ==, 0);
+}
+
+/*
+ * Verifies that the RNG only produces data when RNGMODE is set to 'normal'
+ * ring oscillator mode.
+ */
+static void test_rosel(void)
+{
+ rng_reset_enable();
+ g_assert_true(rng_wait_ready());
+ rng_writeb(RNGMODE, 0);
+ g_assert_false(rng_wait_ready());
+ rng_writeb(RNGMODE, ROSEL_NORMAL);
+ g_assert_true(rng_wait_ready());
+ rng_writeb(RNGMODE, 0);
+ g_assert_false(rng_wait_ready());
+}
+
+/*
+ * Verifies that a continuous sequence of bits collected after enabling the RNG
+ * satisfies a monobit test.
+ */
+static void test_continuous_monobit(void)
+{
+ uint8_t buf[TEST_INPUT_BITS / BITS_PER_BYTE];
+ unsigned int i;
+
+ rng_reset_enable();
+ for (i = 0; i < sizeof(buf); i++) {
+ g_assert_true(rng_wait_ready());
+ buf[i] = rng_readb(RNGD);
+ }
+
+ g_assert_cmpfloat(calc_monobit_p(buf, sizeof(buf)), >, 0.01);
+}
+
+/*
+ * Verifies that a continuous sequence of bits collected after enabling the RNG
+ * satisfies a runs test.
+ */
+static void test_continuous_runs(void)
+{
+ union {
+ unsigned long l[TEST_INPUT_BITS / BITS_PER_LONG];
+ uint8_t c[TEST_INPUT_BITS / BITS_PER_BYTE];
+ } buf;
+ unsigned int i;
+
+ rng_reset_enable();
+ for (i = 0; i < sizeof(buf); i++) {
+ g_assert_true(rng_wait_ready());
+ buf.c[i] = rng_readb(RNGD);
+ }
+
+ g_assert_cmpfloat(calc_runs_p(buf.l, sizeof(buf) * BITS_PER_BYTE), >, 0.01);
+}
+
+/*
+ * Verifies that the first data byte collected after enabling the RNG satisfies
+ * a monobit test.
+ */
+static void test_first_byte_monobit(void)
+{
+ /* Enable, collect one byte, disable. Repeat until we have 100 bits. */
+ uint8_t buf[TEST_INPUT_BITS / BITS_PER_BYTE];
+ unsigned int i;
+
+ rng_reset();
+ for (i = 0; i < sizeof(buf); i++) {
+ rng_writeb(RNGCS, RNGE);
+ g_assert_true(rng_wait_ready());
+ buf[i] = rng_readb(RNGD);
+ rng_writeb(RNGCS, 0);
+ }
+
+ g_assert_cmpfloat(calc_monobit_p(buf, sizeof(buf)), >, 0.01);
+}
+
+/*
+ * Verifies that the first data byte collected after enabling the RNG satisfies
+ * a runs test.
+ */
+static void test_first_byte_runs(void)
+{
+ /* Enable, collect one byte, disable. Repeat until we have 100 bits. */
+ union {
+ unsigned long l[TEST_INPUT_BITS / BITS_PER_LONG];
+ uint8_t c[TEST_INPUT_BITS / BITS_PER_BYTE];
+ } buf;
+ unsigned int i;
+
+ rng_reset();
+ for (i = 0; i < sizeof(buf); i++) {
+ rng_writeb(RNGCS, RNGE);
+ g_assert_true(rng_wait_ready());
+ buf.c[i] = rng_readb(RNGD);
+ rng_writeb(RNGCS, 0);
+ }
+
+ g_assert_cmpfloat(calc_runs_p(buf.l, sizeof(buf) * BITS_PER_BYTE), >, 0.01);
+}
+
+int main(int argc, char **argv)
+{
+ int ret;
+
+ g_test_init(&argc, &argv, NULL);
+ g_test_set_nonfatal_assertions();
+
+ qtest_add_func("npcm7xx_rng/enable_disable", test_enable_disable);
+ qtest_add_func("npcm7xx_rng/rosel", test_rosel);
+ qtest_add_func("npcm7xx_rng/continuous/monobit", test_continuous_monobit);
+ qtest_add_func("npcm7xx_rng/continuous/runs", test_continuous_runs);
+ qtest_add_func("npcm7xx_rng/first_byte/monobit", test_first_byte_monobit);
+ qtest_add_func("npcm7xx_rng/first_byte/runs", test_first_byte_runs);
+
+ qtest_start("-machine npcm750-evb");
+ ret = g_test_run();
+ qtest_end();
+
+ return ret;
+}
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