Adding upstream version 1:115.7.0.upstream/1%115.7.0upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 791 insertions, 0 deletions

diff --git a/comm/third_party/libgcrypt/random/jitterentropy-base.c b/comm/third_party/libgcrypt/random/jitterentropy-base.c
new file mode 100644
index 0000000000..ba435e1bdb
--- /dev/null
+++ b/comm/third_party/libgcrypt/random/jitterentropy-base.c
@@ -0,0 +1,791 @@
+/*
+ * Non-physical true random number generator based on timing jitter.
+ *
+ * Copyright Stephan Mueller <smueller@chronox.de>, 2014 - 2017
+ *
+ * Design
+ * ======
+ *
+ * See documentation in doc/ folder.
+ *
+ * Interface
+ * =========
+ *
+ * See documentation in doc/ folder.
+ *
+ * License
+ * =======
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, and the entire permission notice in its entirety,
+ *    including the disclaimer of warranties.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote
+ *    products derived from this software without specific prior
+ *    written permission.
+ *
+ * ALTERNATIVELY, this product may be distributed under the terms of
+ * the GNU General Public License, in which case the provisions of the GPL2 are
+ * required INSTEAD OF the above restrictions.  (This clause is
+ * necessary due to a potential bad interaction between the GPL and
+ * the restrictions contained in a BSD-style copyright.)
+ *
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
+ * WHICH ARE HEREBY DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
+ * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
+ * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
+ * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH
+ * DAMAGE.
+ */
+
+#undef _FORTIFY_SOURCE
+#pragma GCC optimize ("O0")
+
+#include "jitterentropy.h"
+
+#ifndef CONFIG_CRYPTO_CPU_JITTERENTROPY_STAT
+ /* only check optimization in a compilation for real work */
+ #ifdef __OPTIMIZE__
+  #error "The CPU Jitter random number generator must not be compiled with optimizations. See documentation. Use the compiler switch -O0 for compiling jitterentropy-base.c."
+ #endif
+#endif
+
+#define MAJVERSION 2 /* API / ABI incompatible changes, functional changes that
+		      * require consumer to be updated (as long as this number
+		      * is zero, the API is not considered stable and can
+		      * change without a bump of the major version) */
+#define MINVERSION 1 /* API compatible, ABI may change, functional
+		      * enhancements only, consumer can be left unchanged if
+		      * enhancements are not considered */
+#define PATCHLEVEL 0 /* API / ABI compatible, no functional changes, no
+		      * enhancements, bug fixes only */
+
+/**
+ * jent_version() - Return machine-usable version number of jent library
+ *
+ * The function returns a version number that is monotonic increasing
+ * for newer versions. The version numbers are multiples of 100. For example,
+ * version 1.2.3 is converted to 1020300 -- the last two digits are reserved
+ * for future use.
+ *
+ * The result of this function can be used in comparing the version number
+ * in a calling program if version-specific calls need to be make.
+ *
+ * Return: Version number of kcapi library
+ */
+JENT_PRIVATE_STATIC
+unsigned int jent_version(void)
+{
+	unsigned int version = 0;
+
+	version =  MAJVERSION * 1000000;
+	version += MINVERSION * 10000;
+	version += PATCHLEVEL * 100;
+
+	return version;
+}
+
+/**
+ * Update of the loop count used for the next round of
+ * an entropy collection.
+ *
+ * Input:
+ * @ec entropy collector struct -- may be NULL
+ * @bits is the number of low bits of the timer to consider
+ * @min is the number of bits we shift the timer value to the right at
+ * 	the end to make sure we have a guaranteed minimum value
+ *
+ * @return Newly calculated loop counter
+ */
+static uint64_t jent_loop_shuffle(struct rand_data *ec,
+				  unsigned int bits, unsigned int min)
+{
+	uint64_t time = 0;
+	uint64_t shuffle = 0;
+	unsigned int i = 0;
+	unsigned int mask = (1<<bits) - 1;
+
+	jent_get_nstime(&time);
+	/*
+	 * Mix the current state of the random number into the shuffle
+	 * calculation to balance that shuffle a bit more.
+	 */
+	if (ec)
+		time ^= ec->data;
+	/*
+	 * We fold the time value as much as possible to ensure that as many
+	 * bits of the time stamp are included as possible.
+	 */
+	for (i = 0; (DATA_SIZE_BITS / bits) > i; i++) {
+		shuffle ^= time & mask;
+		time = time >> bits;
+	}
+
+	/*
+	 * We add a lower boundary value to ensure we have a minimum
+	 * RNG loop count.
+	 */
+	return (shuffle + (1<<min));
+}
+
+/***************************************************************************
+ * Noise sources
+ ***************************************************************************/
+
+/**
+ * CPU Jitter noise source -- this is the noise source based on the CPU
+ * 			      execution time jitter
+ *
+ * This function injects the individual bits of the time value into the
+ * entropy pool using an LFSR.
+ *
+ * The code is deliberately inefficient with respect to the bit shifting
+ * and shall stay that way. This function is the root cause why the code
+ * shall be compiled without optimization. This function not only acts as
+ * folding operation, but this function's execution is used to measure
+ * the CPU execution time jitter. Any change to the loop in this function
+ * implies that careful retesting must be done.
+ *
+ * Input:
+ * @ec entropy collector struct -- may be NULL
+ * @time time stamp to be injected
+ * @loop_cnt if a value not equal to 0 is set, use the given value as number of
+ *	     loops to perform the folding
+ *
+ * Output:
+ * updated ec->data
+ *
+ * @return Number of loops the folding operation is performed
+ */
+static uint64_t jent_lfsr_time(struct rand_data *ec, uint64_t time,
+			       uint64_t loop_cnt)
+{
+	unsigned int i;
+	uint64_t j = 0;
+	uint64_t new = 0;
+#define MAX_FOLD_LOOP_BIT 4
+#define MIN_FOLD_LOOP_BIT 0
+	uint64_t fold_loop_cnt =
+		jent_loop_shuffle(ec, MAX_FOLD_LOOP_BIT, MIN_FOLD_LOOP_BIT);
+
+	/*
+	 * testing purposes -- allow test app to set the counter, not
+	 * needed during runtime
+	 */
+	if (loop_cnt)
+		fold_loop_cnt = loop_cnt;
+	for (j = 0; j < fold_loop_cnt; j++) {
+		new = ec->data;
+		for (i = 1; (DATA_SIZE_BITS) >= i; i++) {
+			uint64_t tmp = time << (DATA_SIZE_BITS - i);
+
+			tmp = tmp >> (DATA_SIZE_BITS - 1);
+
+			/*
+			* Fibonacci LSFR with polynomial of
+			*  x^64 + x^61 + x^56 + x^31 + x^28 + x^23 + 1 which is
+			*  primitive according to
+			*   http://poincare.matf.bg.ac.rs/~ezivkovm/publications/primpol1.pdf
+			* (the shift values are the polynomial values minus one
+			* due to counting bits from 0 to 63). As the current
+			* position is always the LSB, the polynomial only needs
+			* to shift data in from the left without wrap.
+			*/
+			new ^= tmp;
+			new ^= ((new >> 63) & 1);
+			new ^= ((new >> 60) & 1);
+			new ^= ((new >> 55) & 1);
+			new ^= ((new >> 30) & 1);
+			new ^= ((new >> 27) & 1);
+			new ^= ((new >> 22) & 1);
+			new = rol64(new, 1);
+		}
+	}
+	ec->data = new;
+
+	return fold_loop_cnt;
+}
+
+/**
+ * Memory Access noise source -- this is a noise source based on variations in
+ * 				 memory access times
+ *
+ * This function performs memory accesses which will add to the timing
+ * variations due to an unknown amount of CPU wait states that need to be
+ * added when accessing memory. The memory size should be larger than the L1
+ * caches as outlined in the documentation and the associated testing.
+ *
+ * The L1 cache has a very high bandwidth, albeit its access rate is  usually
+ * slower than accessing CPU registers. Therefore, L1 accesses only add minimal
+ * variations as the CPU has hardly to wait. Starting with L2, significant
+ * variations are added because L2 typically does not belong to the CPU any more
+ * and therefore a wider range of CPU wait states is necessary for accesses.
+ * L3 and real memory accesses have even a wider range of wait states. However,
+ * to reliably access either L3 or memory, the ec->mem memory must be quite
+ * large which is usually not desirable.
+ *
+ * Input:
+ * @ec Reference to the entropy collector with the memory access data -- if
+ *     the reference to the memory block to be accessed is NULL, this noise
+ *     source is disabled
+ * @loop_cnt if a value not equal to 0 is set, use the given value as number of
+ *	     loops to perform the folding
+ *
+ * @return Number of memory access operations
+ */
+static unsigned int jent_memaccess(struct rand_data *ec, uint64_t loop_cnt)
+{
+	unsigned int wrap = 0;
+	uint64_t i = 0;
+#define MAX_ACC_LOOP_BIT 7
+#define MIN_ACC_LOOP_BIT 0
+	uint64_t acc_loop_cnt =
+		jent_loop_shuffle(ec, MAX_ACC_LOOP_BIT, MIN_ACC_LOOP_BIT);
+
+	if (NULL == ec || NULL == ec->mem)
+		return 0;
+	wrap = ec->memblocksize * ec->memblocks;
+
+	/*
+	 * testing purposes -- allow test app to set the counter, not
+	 * needed during runtime
+	 */
+	if (loop_cnt)
+		acc_loop_cnt = loop_cnt;
+
+	for (i = 0; i < (ec->memaccessloops + acc_loop_cnt); i++) {
+		unsigned char *tmpval = ec->mem + ec->memlocation;
+		/*
+		 * memory access: just add 1 to one byte,
+		 * wrap at 255 -- memory access implies read
+		 * from and write to memory location
+		 */
+		*tmpval = (*tmpval + 1) & 0xff;
+		/*
+		 * Addition of memblocksize - 1 to pointer
+		 * with wrap around logic to ensure that every
+		 * memory location is hit evenly
+		 */
+		ec->memlocation = ec->memlocation + ec->memblocksize - 1;
+		ec->memlocation = ec->memlocation % wrap;
+	}
+	return i;
+}
+
+/***************************************************************************
+ * Start of entropy processing logic
+ ***************************************************************************/
+
+/**
+ * Stuck test by checking the:
+ * 	1st derivation of the jitter measurement (time delta)
+ * 	2nd derivation of the jitter measurement (delta of time deltas)
+ * 	3rd derivation of the jitter measurement (delta of delta of time deltas)
+ *
+ * All values must always be non-zero.
+ *
+ * Input:
+ * @ec Reference to entropy collector
+ * @current_delta Jitter time delta
+ *
+ * @return
+ * 	0 jitter measurement not stuck (good bit)
+ * 	1 jitter measurement stuck (reject bit)
+ */
+static int jent_stuck(struct rand_data *ec, uint64_t current_delta)
+{
+	int64_t delta2 = ec->last_delta - current_delta;
+	int64_t delta3 = (uint64_t)delta2 - (uint64_t)ec->last_delta2;
+
+	ec->last_delta = current_delta;
+	ec->last_delta2 = delta2;
+
+	if (!current_delta || !delta2 || !delta3)
+		return 1;
+
+	return 0;
+}
+
+/**
+ * This is the heart of the entropy generation: calculate time deltas and
+ * use the CPU jitter in the time deltas. The jitter is injected into the
+ * entropy pool.
+ *
+ * WARNING: ensure that ->prev_time is primed before using the output
+ * 	    of this function! This can be done by calling this function
+ * 	    and not using its result.
+ *
+ * Input:
+ * @entropy_collector Reference to entropy collector
+ *
+ * @return: result of stuck test
+ */
+static int jent_measure_jitter(struct rand_data *ec)
+{
+	uint64_t time = 0;
+	uint64_t current_delta = 0;
+	int stuck;
+
+	/* Invoke one noise source before time measurement to add variations */
+	jent_memaccess(ec, 0);
+
+	/*
+	 * Get time stamp and calculate time delta to previous
+	 * invocation to measure the timing variations
+	 */
+	jent_get_nstime(&time);
+	current_delta = time - ec->prev_time;
+	ec->prev_time = time;
+
+	/* Now call the next noise sources which also injects the data */
+	jent_lfsr_time(ec, current_delta, 0);
+
+	/* Check whether we have a stuck measurement. */
+	stuck = jent_stuck(ec, current_delta);
+
+	/*
+	 * Rotate the data buffer by a prime number (any odd number would
+	 * do) to ensure that every bit position of the input time stamp
+	 * has an even chance of being merged with a bit position in the
+	 * entropy pool. We do not use one here as the adjacent bits in
+	 * successive time deltas may have some form of dependency. The
+	 * chosen value of 7 implies that the low 7 bits of the next
+	 * time delta value is concatenated with the current time delta.
+	 */
+	if (!stuck)
+		ec->data = rol64(ec->data, 7);
+
+	return stuck;
+}
+
+/**
+ * Shuffle the pool a bit by mixing some value with a bijective function (XOR)
+ * into the pool.
+ *
+ * The function generates a mixer value that depends on the bits set and the
+ * location of the set bits in the random number generated by the entropy
+ * source. Therefore, based on the generated random number, this mixer value
+ * can have 2**64 different values. That mixer value is initialized with the
+ * first two SHA-1 constants. After obtaining the mixer value, it is XORed into
+ * the random number.
+ *
+ * The mixer value is not assumed to contain any entropy. But due to the XOR
+ * operation, it can also not destroy any entropy present in the entropy pool.
+ *
+ * Input:
+ * @entropy_collector Reference to entropy collector
+ */
+static void jent_stir_pool(struct rand_data *entropy_collector)
+{
+	/*
+	 * to shut up GCC on 32 bit, we have to initialize the 64 variable
+	 * with two 32 bit variables
+	 */
+	union c {
+		uint64_t uint64;
+		uint32_t uint32[2];
+	};
+	/*
+	 * This constant is derived from the first two 32 bit initialization
+	 * vectors of SHA-1 as defined in FIPS 180-4 section 5.3.1
+	 */
+	union c constant;
+	/*
+	 * The start value of the mixer variable is derived from the third
+	 * and fourth 32 bit initialization vector of SHA-1 as defined in
+	 * FIPS 180-4 section 5.3.1
+	 */
+	union c mixer;
+	unsigned int i = 0;
+
+	/* Ensure that the function implements a constant time operation. */
+	union c throw_away;
+
+	/*
+	 * Store the SHA-1 constants in reverse order to make up the 64 bit
+	 * value -- this applies to a little endian system, on a big endian
+	 * system, it reverses as expected. But this really does not matter
+	 * as we do not rely on the specific numbers. We just pick the SHA-1
+	 * constants as they have a good mix of bit set and unset.
+	 */
+	constant.uint32[1] = 0x67452301;
+	constant.uint32[0] = 0xefcdab89;
+	mixer.uint32[1] = 0x98badcfe;
+	mixer.uint32[0] = 0x10325476;
+
+	for (i = 0; i < DATA_SIZE_BITS; i++) {
+		/*
+		 * get the i-th bit of the input random number and only XOR
+		 * the constant into the mixer value when that bit is set
+		 */
+		if ((entropy_collector->data >> i) & 1)
+			mixer.uint64 ^= constant.uint64;
+		else
+			throw_away.uint64 ^= constant.uint64;
+		mixer.uint64 = rol64(mixer.uint64, 1);
+	}
+	entropy_collector->data ^= mixer.uint64;
+}
+
+/**
+ * Generator of one 64 bit random number
+ * Function fills rand_data->data
+ *
+ * Input:
+ * @ec Reference to entropy collector
+ */
+static void jent_gen_entropy(struct rand_data *ec)
+{
+	unsigned int k = 0;
+
+	/* priming of the ->prev_time value */
+	jent_measure_jitter(ec);
+
+	while (1) {
+		/* If a stuck measurement is received, repeat measurement */
+		if (jent_measure_jitter(ec))
+			continue;
+
+		/*
+		 * We multiply the loop value with ->osr to obtain the
+		 * oversampling rate requested by the caller
+		 */
+		if (++k >= (DATA_SIZE_BITS * ec->osr))
+			break;
+	}
+	if (ec->stir)
+		jent_stir_pool(ec);
+}
+
+/**
+ * The continuous test required by FIPS 140-2 -- the function automatically
+ * primes the test if needed.
+ *
+ * Return:
+ * 0 if FIPS test passed
+ * < 0 if FIPS test failed
+ */
+static int jent_fips_test(struct rand_data *ec)
+{
+	if (ec->fips_enabled == -1)
+		return 0;
+
+	if (ec->fips_enabled == 0) {
+		if (!jent_fips_enabled()) {
+			ec->fips_enabled = -1;
+			return 0;
+		} else
+			ec->fips_enabled = 1;
+	}
+
+	/* prime the FIPS test */
+	if (!ec->old_data) {
+		ec->old_data = ec->data;
+		jent_gen_entropy(ec);
+	}
+
+	if (ec->data == ec->old_data)
+		return -1;
+
+	ec->old_data = ec->data;
+
+	return 0;
+}
+
+/**
+ * Entry function: Obtain entropy for the caller.
+ *
+ * This function invokes the entropy gathering logic as often to generate
+ * as many bytes as requested by the caller. The entropy gathering logic
+ * creates 64 bit per invocation.
+ *
+ * This function truncates the last 64 bit entropy value output to the exact
+ * size specified by the caller.
+ *
+ * Input:
+ * @ec Reference to entropy collector
+ * @data pointer to buffer for storing random data -- buffer must already
+ *        exist
+ * @len size of the buffer, specifying also the requested number of random
+ *       in bytes
+ *
+ * @return number of bytes returned when request is fulfilled or an error
+ *
+ * The following error codes can occur:
+ *	-1	entropy_collector is NULL
+ *	-2	FIPS test failed
+ */
+JENT_PRIVATE_STATIC
+ssize_t jent_read_entropy(struct rand_data *ec, char *data, size_t len)
+{
+	char *p = data;
+	size_t orig_len = len;
+
+	if (NULL == ec)
+		return -1;
+
+	while (0 < len) {
+		size_t tocopy;
+
+		jent_gen_entropy(ec);
+		if (jent_fips_test(ec))
+			return -2;
+
+		if ((DATA_SIZE_BITS / 8) < len)
+			tocopy = (DATA_SIZE_BITS / 8);
+		else
+			tocopy = len;
+		memcpy(p, &ec->data, tocopy);
+
+		len -= tocopy;
+		p += tocopy;
+	}
+
+	/*
+	 * To be on the safe side, we generate one more round of entropy
+	 * which we do not give out to the caller. That round shall ensure
+	 * that in case the calling application crashes, memory dumps, pages
+	 * out, or due to the CPU Jitter RNG lingering in memory for long
+	 * time without being moved and an attacker cracks the application,
+	 * all he reads in the entropy pool is a value that is NEVER EVER
+	 * being used for anything. Thus, he does NOT see the previous value
+	 * that was returned to the caller for cryptographic purposes.
+	 */
+	/*
+	 * If we use secured memory, do not use that precaution as the secure
+	 * memory protects the entropy pool. Moreover, note that using this
+	 * call reduces the speed of the RNG by up to half
+	 */
+#ifndef CONFIG_CRYPTO_CPU_JITTERENTROPY_SECURE_MEMORY
+	jent_gen_entropy(ec);
+#endif
+	return orig_len;
+}
+
+/***************************************************************************
+ * Initialization logic
+ ***************************************************************************/
+
+JENT_PRIVATE_STATIC
+struct rand_data *jent_entropy_collector_alloc(unsigned int osr,
+					       unsigned int flags)
+{
+	struct rand_data *entropy_collector;
+
+	entropy_collector = jent_zalloc(sizeof(struct rand_data));
+	if (NULL == entropy_collector)
+		return NULL;
+
+	if (!(flags & JENT_DISABLE_MEMORY_ACCESS)) {
+		/* Allocate memory for adding variations based on memory
+		 * access
+		 */
+		entropy_collector->mem =
+			(unsigned char *)jent_zalloc(JENT_MEMORY_SIZE);
+		if (NULL == entropy_collector->mem) {
+			jent_zfree(entropy_collector, sizeof(struct rand_data));
+			return NULL;
+		}
+		entropy_collector->memblocksize = JENT_MEMORY_BLOCKSIZE;
+		entropy_collector->memblocks = JENT_MEMORY_BLOCKS;
+		entropy_collector->memaccessloops = JENT_MEMORY_ACCESSLOOPS;
+	}
+
+	/* verify and set the oversampling rate */
+	if (0 == osr)
+		osr = 1; /* minimum sampling rate is 1 */
+	entropy_collector->osr = osr;
+
+	entropy_collector->stir = 1;
+	if (flags & JENT_DISABLE_STIR)
+		entropy_collector->stir = 0;
+	if (flags & JENT_DISABLE_UNBIAS)
+		entropy_collector->disable_unbias = 1;
+
+	/* fill the data pad with non-zero values */
+	jent_gen_entropy(entropy_collector);
+
+	return entropy_collector;
+}
+
+JENT_PRIVATE_STATIC
+void jent_entropy_collector_free(struct rand_data *entropy_collector)
+{
+	if (NULL != entropy_collector) {
+		if (NULL != entropy_collector->mem) {
+			jent_zfree(entropy_collector->mem, JENT_MEMORY_SIZE);
+			entropy_collector->mem = NULL;
+		}
+		jent_zfree(entropy_collector, sizeof(struct rand_data));
+	}
+}
+
+JENT_PRIVATE_STATIC
+int jent_entropy_init(void)
+{
+	int i;
+	uint64_t delta_sum = 0;
+	uint64_t old_delta = 0;
+	int time_backwards = 0;
+	int count_mod = 0;
+	int count_stuck = 0;
+	struct rand_data ec;
+
+	memset(&ec, 0, sizeof(ec));
+
+	/* We could perform statistical tests here, but the problem is
+	 * that we only have a few loop counts to do testing. These
+	 * loop counts may show some slight skew and we produce
+	 * false positives.
+	 *
+	 * Moreover, only old systems show potentially problematic
+	 * jitter entropy that could potentially be caught here. But
+	 * the RNG is intended for hardware that is available or widely
+	 * used, but not old systems that are long out of favor. Thus,
+	 * no statistical tests.
+	 */
+
+	/*
+	 * We could add a check for system capabilities such as clock_getres or
+	 * check for CONFIG_X86_TSC, but it does not make much sense as the
+	 * following sanity checks verify that we have a high-resolution
+	 * timer.
+	 */
+	/*
+	 * TESTLOOPCOUNT needs some loops to identify edge systems. 100 is
+	 * definitely too little.
+	 */
+#define TESTLOOPCOUNT 300
+#define CLEARCACHE 100
+	for (i = 0; (TESTLOOPCOUNT + CLEARCACHE) > i; i++) {
+		uint64_t time = 0;
+		uint64_t time2 = 0;
+		uint64_t delta = 0;
+		unsigned int lowdelta = 0;
+		int stuck;
+
+		/* Invoke core entropy collection logic */
+		jent_get_nstime(&time);
+		ec.prev_time = time;
+		jent_lfsr_time(&ec, time, 0);
+		jent_get_nstime(&time2);
+
+		/* test whether timer works */
+		if (!time || !time2)
+			return ENOTIME;
+		delta = time2 - time;
+		/*
+		 * test whether timer is fine grained enough to provide
+		 * delta even when called shortly after each other -- this
+		 * implies that we also have a high resolution timer
+		 */
+		if (!delta)
+			return ECOARSETIME;
+
+		stuck = jent_stuck(&ec, delta);
+
+		/*
+		 * up to here we did not modify any variable that will be
+		 * evaluated later, but we already performed some work. Thus we
+		 * already have had an impact on the caches, branch prediction,
+		 * etc. with the goal to clear it to get the worst case
+		 * measurements.
+		 */
+		if (CLEARCACHE > i)
+			continue;
+
+		if (stuck)
+			count_stuck++;
+
+		/* test whether we have an increasing timer */
+		if (!(time2 > time))
+			time_backwards++;
+
+		/* use 32 bit value to ensure compilation on 32 bit arches */
+		lowdelta = time2 - time;
+		if (!(lowdelta % 100))
+			count_mod++;
+
+		/*
+		 * ensure that we have a varying delta timer which is necessary
+		 * for the calculation of entropy -- perform this check
+		 * only after the first loop is executed as we need to prime
+		 * the old_data value
+		 */
+		if (delta > old_delta)
+			delta_sum += (delta - old_delta);
+		else
+			delta_sum += (old_delta - delta);
+		old_delta = delta;
+	}
+
+	/*
+	 * we allow up to three times the time running backwards.
+	 * CLOCK_REALTIME is affected by adjtime and NTP operations. Thus,
+	 * if such an operation just happens to interfere with our test, it
+	 * should not fail. The value of 3 should cover the NTP case being
+	 * performed during our test run.
+	 */
+	if (3 < time_backwards)
+		return ENOMONOTONIC;
+
+	/*
+	 * Variations of deltas of time must on average be larger
+	 * than 1 to ensure the entropy estimation
+	 * implied with 1 is preserved
+	 */
+	if ((delta_sum) <= 1)
+		return EMINVARVAR;
+
+	/*
+	 * Ensure that we have variations in the time stamp below 10 for at least
+	 * 10% of all checks -- on some platforms, the counter increments in
+	 * multiples of 100, but not always
+	 */
+	if ((TESTLOOPCOUNT/10 * 9) < count_mod)
+		return ECOARSETIME;
+
+	/*
+	 * If we have more than 90% stuck results, then this Jitter RNG is
+	 * likely to not work well.
+	 */
+	if (JENT_STUCK_INIT_THRES(TESTLOOPCOUNT) < count_stuck)
+		return ESTUCK;
+
+	return 0;
+}
+
+/***************************************************************************
+ * Statistical test logic not compiled for regular operation
+ ***************************************************************************/
+
+#ifdef CONFIG_CRYPTO_CPU_JITTERENTROPY_STAT
+/*
+ * Statistical test: return the time duration for the folding operation. If min
+ * is set, perform the given number of LFSR ops. Otherwise, allow the
+ * loop count shuffling to define the number of LFSR ops.
+ */
+JENT_PRIVATE_STATIC
+uint64_t jent_lfsr_var_stat(struct rand_data *ec, unsigned int min)
+{
+	uint64_t time = 0;
+	uint64_t time2 = 0;
+
+	jent_get_nstime(&time);
+	jent_memaccess(ec, min);
+	jent_lfsr_time(ec, time, min);
+	jent_get_nstime(&time2);
+	return ((time2 - time));
+}
+#endif /* CONFIG_CRYPTO_CPU_JITTERENTROPY_STAT */