Adding upstream version 5.10.209.upstream/5.10.209upstream

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

1 files changed, 855 insertions, 0 deletions

diff --git a/crypto/jitterentropy.c b/crypto/jitterentropy.c
new file mode 100644
index 000000000..37c4c3083
--- /dev/null
+++ b/crypto/jitterentropy.c
@@ -0,0 +1,855 @@
+/*
+ * Non-physical true random number generator based on timing jitter --
+ * Jitter RNG standalone code.
+ *
+ * Copyright Stephan Mueller <smueller@chronox.de>, 2015 - 2020
+ *
+ * Design
+ * ======
+ *
+ * See https://www.chronox.de/jent.html
+ *
+ * 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.
+ */
+
+/*
+ * This Jitterentropy RNG is based on the jitterentropy library
+ * version 2.2.0 provided at https://www.chronox.de/jent.html
+ */
+
+#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.c."
+#endif
+
+typedef	unsigned long long	__u64;
+typedef	long long		__s64;
+typedef	unsigned int		__u32;
+#define NULL    ((void *) 0)
+
+/* The entropy pool */
+struct rand_data {
+	/* all data values that are vital to maintain the security
+	 * of the RNG are marked as SENSITIVE. A user must not
+	 * access that information while the RNG executes its loops to
+	 * calculate the next random value. */
+	__u64 data;		/* SENSITIVE Actual random number */
+	__u64 old_data;		/* SENSITIVE Previous random number */
+	__u64 prev_time;	/* SENSITIVE Previous time stamp */
+#define DATA_SIZE_BITS ((sizeof(__u64)) * 8)
+	__u64 last_delta;	/* SENSITIVE stuck test */
+	__s64 last_delta2;	/* SENSITIVE stuck test */
+	unsigned int osr;	/* Oversample rate */
+#define JENT_MEMORY_BLOCKS 64
+#define JENT_MEMORY_BLOCKSIZE 32
+#define JENT_MEMORY_ACCESSLOOPS 128
+#define JENT_MEMORY_SIZE (JENT_MEMORY_BLOCKS*JENT_MEMORY_BLOCKSIZE)
+	unsigned char *mem;	/* Memory access location with size of
+				 * memblocks * memblocksize */
+	unsigned int memlocation; /* Pointer to byte in *mem */
+	unsigned int memblocks;	/* Number of memory blocks in *mem */
+	unsigned int memblocksize; /* Size of one memory block in bytes */
+	unsigned int memaccessloops; /* Number of memory accesses per random
+				      * bit generation */
+
+	/* Repetition Count Test */
+	int rct_count;			/* Number of stuck values */
+
+	/* Adaptive Proportion Test for a significance level of 2^-30 */
+#define JENT_APT_CUTOFF		325	/* Taken from SP800-90B sec 4.4.2 */
+#define JENT_APT_WINDOW_SIZE	512	/* Data window size */
+	/* LSB of time stamp to process */
+#define JENT_APT_LSB		16
+#define JENT_APT_WORD_MASK	(JENT_APT_LSB - 1)
+	unsigned int apt_observations;	/* Number of collected observations */
+	unsigned int apt_count;		/* APT counter */
+	unsigned int apt_base;		/* APT base reference */
+	unsigned int apt_base_set:1;	/* APT base reference set? */
+
+	unsigned int health_failure:1;	/* Permanent health failure */
+};
+
+/* Flags that can be used to initialize the RNG */
+#define JENT_DISABLE_MEMORY_ACCESS (1<<2) /* Disable memory access for more
+					   * entropy, saves MEMORY_SIZE RAM for
+					   * entropy collector */
+
+/* -- error codes for init function -- */
+#define JENT_ENOTIME		1 /* Timer service not available */
+#define JENT_ECOARSETIME	2 /* Timer too coarse for RNG */
+#define JENT_ENOMONOTONIC	3 /* Timer is not monotonic increasing */
+#define JENT_EVARVAR		5 /* Timer does not produce variations of
+				   * variations (2nd derivation of time is
+				   * zero). */
+#define JENT_ESTUCK		8 /* Too many stuck results during init. */
+#define JENT_EHEALTH		9 /* Health test failed during initialization */
+#define JENT_ERCT		10 /* RCT failed during initialization */
+
+#include "jitterentropy.h"
+
+/***************************************************************************
+ * Adaptive Proportion Test
+ *
+ * This test complies with SP800-90B section 4.4.2.
+ ***************************************************************************/
+
+/**
+ * Reset the APT counter
+ *
+ * @ec [in] Reference to entropy collector
+ */
+static void jent_apt_reset(struct rand_data *ec, unsigned int delta_masked)
+{
+	/* Reset APT counter */
+	ec->apt_count = 0;
+	ec->apt_base = delta_masked;
+	ec->apt_observations = 0;
+}
+
+/**
+ * Insert a new entropy event into APT
+ *
+ * @ec [in] Reference to entropy collector
+ * @delta_masked [in] Masked time delta to process
+ */
+static void jent_apt_insert(struct rand_data *ec, unsigned int delta_masked)
+{
+	/* Initialize the base reference */
+	if (!ec->apt_base_set) {
+		ec->apt_base = delta_masked;
+		ec->apt_base_set = 1;
+		return;
+	}
+
+	if (delta_masked == ec->apt_base) {
+		ec->apt_count++;
+
+		if (ec->apt_count >= JENT_APT_CUTOFF)
+			ec->health_failure = 1;
+	}
+
+	ec->apt_observations++;
+
+	if (ec->apt_observations >= JENT_APT_WINDOW_SIZE)
+		jent_apt_reset(ec, delta_masked);
+}
+
+/***************************************************************************
+ * Stuck Test and its use as Repetition Count Test
+ *
+ * The Jitter RNG uses an enhanced version of the Repetition Count Test
+ * (RCT) specified in SP800-90B section 4.4.1. Instead of counting identical
+ * back-to-back values, the input to the RCT is the counting of the stuck
+ * values during the generation of one Jitter RNG output block.
+ *
+ * The RCT is applied with an alpha of 2^{-30} compliant to FIPS 140-2 IG 9.8.
+ *
+ * During the counting operation, the Jitter RNG always calculates the RCT
+ * cut-off value of C. If that value exceeds the allowed cut-off value,
+ * the Jitter RNG output block will be calculated completely but discarded at
+ * the end. The caller of the Jitter RNG is informed with an error code.
+ ***************************************************************************/
+
+/**
+ * Repetition Count Test as defined in SP800-90B section 4.4.1
+ *
+ * @ec [in] Reference to entropy collector
+ * @stuck [in] Indicator whether the value is stuck
+ */
+static void jent_rct_insert(struct rand_data *ec, int stuck)
+{
+	/*
+	 * If we have a count less than zero, a previous RCT round identified
+	 * a failure. We will not overwrite it.
+	 */
+	if (ec->rct_count < 0)
+		return;
+
+	if (stuck) {
+		ec->rct_count++;
+
+		/*
+		 * The cutoff value is based on the following consideration:
+		 * alpha = 2^-30 as recommended in FIPS 140-2 IG 9.8.
+		 * In addition, we require an entropy value H of 1/OSR as this
+		 * is the minimum entropy required to provide full entropy.
+		 * Note, we collect 64 * OSR deltas for inserting them into
+		 * the entropy pool which should then have (close to) 64 bits
+		 * of entropy.
+		 *
+		 * Note, ec->rct_count (which equals to value B in the pseudo
+		 * code of SP800-90B section 4.4.1) starts with zero. Hence
+		 * we need to subtract one from the cutoff value as calculated
+		 * following SP800-90B.
+		 */
+		if ((unsigned int)ec->rct_count >= (31 * ec->osr)) {
+			ec->rct_count = -1;
+			ec->health_failure = 1;
+		}
+	} else {
+		ec->rct_count = 0;
+	}
+}
+
+/**
+ * Is there an RCT health test failure?
+ *
+ * @ec [in] Reference to entropy collector
+ *
+ * @return
+ * 	0 No health test failure
+ * 	1 Permanent health test failure
+ */
+static int jent_rct_failure(struct rand_data *ec)
+{
+	if (ec->rct_count < 0)
+		return 1;
+	return 0;
+}
+
+static inline __u64 jent_delta(__u64 prev, __u64 next)
+{
+#define JENT_UINT64_MAX		(__u64)(~((__u64) 0))
+	return (prev < next) ? (next - prev) :
+			       (JENT_UINT64_MAX - prev + 1 + next);
+}
+
+/**
+ * Stuck test by checking the:
+ * 	1st derivative of the jitter measurement (time delta)
+ * 	2nd derivative of the jitter measurement (delta of time deltas)
+ * 	3rd derivative of the jitter measurement (delta of delta of time deltas)
+ *
+ * All values must always be non-zero.
+ *
+ * @ec [in] Reference to entropy collector
+ * @current_delta [in] 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, __u64 current_delta)
+{
+	__u64 delta2 = jent_delta(ec->last_delta, current_delta);
+	__u64 delta3 = jent_delta(ec->last_delta2, delta2);
+
+	ec->last_delta = current_delta;
+	ec->last_delta2 = delta2;
+
+	/*
+	 * Insert the result of the comparison of two back-to-back time
+	 * deltas.
+	 */
+	jent_apt_insert(ec, current_delta);
+
+	if (!current_delta || !delta2 || !delta3) {
+		/* RCT with a stuck bit */
+		jent_rct_insert(ec, 1);
+		return 1;
+	}
+
+	/* RCT with a non-stuck bit */
+	jent_rct_insert(ec, 0);
+
+	return 0;
+}
+
+/**
+ * Report any health test failures
+ *
+ * @ec [in] Reference to entropy collector
+ *
+ * @return
+ * 	0 No health test failure
+ * 	1 Permanent health test failure
+ */
+static int jent_health_failure(struct rand_data *ec)
+{
+	/* Test is only enabled in FIPS mode */
+	if (!jent_fips_enabled())
+		return 0;
+
+	return ec->health_failure;
+}
+
+/***************************************************************************
+ * Noise sources
+ ***************************************************************************/
+
+/**
+ * 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 __u64 jent_loop_shuffle(struct rand_data *ec,
+			       unsigned int bits, unsigned int min)
+{
+	__u64 time = 0;
+	__u64 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 - 1) / 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));
+}
+
+/**
+ * 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.
+ *
+ * @ec [in] entropy collector struct
+ * @time [in] time stamp to be injected
+ * @loop_cnt [in] if a value not equal to 0 is set, use the given value as
+ *		  number of loops to perform the folding
+ * @stuck [in] Is the time stamp identified as stuck?
+ *
+ * Output:
+ * updated ec->data
+ *
+ * @return Number of loops the folding operation is performed
+ */
+static void jent_lfsr_time(struct rand_data *ec, __u64 time, __u64 loop_cnt,
+			   int stuck)
+{
+	unsigned int i;
+	__u64 j = 0;
+	__u64 new = 0;
+#define MAX_FOLD_LOOP_BIT 4
+#define MIN_FOLD_LOOP_BIT 0
+	__u64 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++) {
+			__u64 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.
+			*/
+			tmp ^= ((new >> 63) & 1);
+			tmp ^= ((new >> 60) & 1);
+			tmp ^= ((new >> 55) & 1);
+			tmp ^= ((new >> 30) & 1);
+			tmp ^= ((new >> 27) & 1);
+			tmp ^= ((new >> 22) & 1);
+			new <<= 1;
+			new ^= tmp;
+		}
+	}
+
+	/*
+	 * If the time stamp is stuck, do not finally insert the value into
+	 * the entropy pool. Although this operation should not do any harm
+	 * even when the time stamp has no entropy, SP800-90B requires that
+	 * any conditioning operation (SP800-90B considers the LFSR to be a
+	 * conditioning operation) to have an identical amount of input
+	 * data according to section 3.1.5.
+	 */
+	if (!stuck)
+		ec->data = new;
+}
+
+/**
+ * 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.
+ *
+ * @ec [in] 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 [in] if a value not equal to 0 is set, use the given value
+ *		  number of loops to perform the LFSR
+ */
+static void jent_memaccess(struct rand_data *ec, __u64 loop_cnt)
+{
+	unsigned int wrap = 0;
+	__u64 i = 0;
+#define MAX_ACC_LOOP_BIT 7
+#define MIN_ACC_LOOP_BIT 0
+	__u64 acc_loop_cnt =
+		jent_loop_shuffle(ec, MAX_ACC_LOOP_BIT, MIN_ACC_LOOP_BIT);
+
+	if (NULL == ec || NULL == ec->mem)
+		return;
+	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;
+	}
+}
+
+/***************************************************************************
+ * Start of entropy processing logic
+ ***************************************************************************/
+/**
+ * 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.
+ *
+ * @ec [in] Reference to entropy collector
+ *
+ * @return result of stuck test
+ */
+static int jent_measure_jitter(struct rand_data *ec)
+{
+	__u64 time = 0;
+	__u64 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 = jent_delta(ec->prev_time, time);
+	ec->prev_time = time;
+
+	/* Check whether we have a stuck measurement. */
+	stuck = jent_stuck(ec, current_delta);
+
+	/* Now call the next noise sources which also injects the data */
+	jent_lfsr_time(ec, current_delta, 0, stuck);
+
+	return stuck;
+}
+
+/**
+ * Generator of one 64 bit random number
+ * Function fills rand_data->data
+ *
+ * @ec [in] 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;
+	}
+}
+
+/**
+ * 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.
+ *
+ * @ec [in] Reference to entropy collector
+ * @data [in] pointer to buffer for storing random data -- buffer must already
+ *	      exist
+ * @len [in] size of the buffer, specifying also the requested number of random
+ *	     in bytes
+ *
+ * @return 0 when request is fulfilled or an error
+ *
+ * The following error codes can occur:
+ *	-1	entropy_collector is NULL
+ *	-2	RCT failed
+ *	-3	APT test failed
+ */
+int jent_read_entropy(struct rand_data *ec, unsigned char *data,
+		      unsigned int len)
+{
+	unsigned char *p = data;
+
+	if (!ec)
+		return -1;
+
+	while (0 < len) {
+		unsigned int tocopy;
+
+		jent_gen_entropy(ec);
+
+		if (jent_health_failure(ec)) {
+			int ret;
+
+			if (jent_rct_failure(ec))
+				ret = -2;
+			else
+				ret = -3;
+
+			/*
+			 * Re-initialize the noise source
+			 *
+			 * If the health test fails, the Jitter RNG remains
+			 * in failure state and will return a health failure
+			 * during next invocation.
+			 */
+			if (jent_entropy_init())
+				return ret;
+
+			/* Set APT to initial state */
+			jent_apt_reset(ec, 0);
+			ec->apt_base_set = 0;
+
+			/* Set RCT to initial state */
+			ec->rct_count = 0;
+
+			/* Re-enable Jitter RNG */
+			ec->health_failure = 0;
+
+			/*
+			 * Return the health test failure status to the
+			 * caller as the generated value is not appropriate.
+			 */
+			return ret;
+		}
+
+		if ((DATA_SIZE_BITS / 8) < len)
+			tocopy = (DATA_SIZE_BITS / 8);
+		else
+			tocopy = len;
+		jent_memcpy(p, &ec->data, tocopy);
+
+		len -= tocopy;
+		p += tocopy;
+	}
+
+	return 0;
+}
+
+/***************************************************************************
+ * Initialization logic
+ ***************************************************************************/
+
+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 (!entropy_collector)
+		return NULL;
+
+	if (!(flags & JENT_DISABLE_MEMORY_ACCESS)) {
+		/* Allocate memory for adding variations based on memory
+		 * access
+		 */
+		entropy_collector->mem = jent_zalloc(JENT_MEMORY_SIZE);
+		if (!entropy_collector->mem) {
+			jent_zfree(entropy_collector);
+			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;
+
+	/* fill the data pad with non-zero values */
+	jent_gen_entropy(entropy_collector);
+
+	return entropy_collector;
+}
+
+void jent_entropy_collector_free(struct rand_data *entropy_collector)
+{
+	jent_zfree(entropy_collector->mem);
+	entropy_collector->mem = NULL;
+	jent_zfree(entropy_collector);
+}
+
+int jent_entropy_init(void)
+{
+	int i;
+	__u64 delta_sum = 0;
+	__u64 old_delta = 0;
+	unsigned int nonstuck = 0;
+	int time_backwards = 0;
+	int count_mod = 0;
+	int count_stuck = 0;
+	struct rand_data ec = { 0 };
+
+	/* Required for RCT */
+	ec.osr = 1;
+
+	/* 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.
+	 *
+	 * SP800-90B requires at least 1024 initial test cycles.
+	 */
+#define TESTLOOPCOUNT 1024
+#define CLEARCACHE 100
+	for (i = 0; (TESTLOOPCOUNT + CLEARCACHE) > i; i++) {
+		__u64 time = 0;
+		__u64 time2 = 0;
+		__u64 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, 0);
+		jent_get_nstime(&time2);
+
+		/* test whether timer works */
+		if (!time || !time2)
+			return JENT_ENOTIME;
+		delta = jent_delta(time, time2);
+		/*
+		 * 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 JENT_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++;
+		else {
+			nonstuck++;
+
+			/*
+			 * Ensure that the APT succeeded.
+			 *
+			 * With the check below that count_stuck must be less
+			 * than 10% of the overall generated raw entropy values
+			 * it is guaranteed that the APT is invoked at
+			 * floor((TESTLOOPCOUNT * 0.9) / 64) == 14 times.
+			 */
+			if ((nonstuck % JENT_APT_WINDOW_SIZE) == 0) {
+				jent_apt_reset(&ec,
+					       delta & JENT_APT_WORD_MASK);
+				if (jent_health_failure(&ec))
+					return JENT_EHEALTH;
+			}
+		}
+
+		/* Validate RCT */
+		if (jent_rct_failure(&ec))
+			return JENT_ERCT;
+
+		/* 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 JENT_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 JENT_EVARVAR;
+
+	/*
+	 * 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 JENT_ECOARSETIME;
+
+	/*
+	 * If we have more than 90% stuck results, then this Jitter RNG is
+	 * likely to not work well.
+	 */
+	if ((TESTLOOPCOUNT/10 * 9) < count_stuck)
+		return JENT_ESTUCK;
+
+	return 0;
+}