Hi, On 1/9/20 12:34 AM, Stephan Müller wrote: > --- > drivers/char/lrng/Kconfig | 11 +++++ > drivers/char/lrng/Makefile | 1 + > drivers/char/lrng/lrng_jent.c | 87 +++++++++++++++++++++++++++++++++++ > 3 files changed, 99 insertions(+) > create mode 100644 drivers/char/lrng/lrng_jent.c > > diff --git a/drivers/char/lrng/lrng_jent.c b/drivers/char/lrng/lrng_jent.c > new file mode 100644 > index 000000000000..97c0d192e9c8 > --- /dev/null > +++ b/drivers/char/lrng/lrng_jent.c > @@ -0,0 +1,87 @@ > +// SPDX-License-Identifier: GPL-2.0 OR BSD-2-Clause > +/* > + * LRNG Fast Noise Source: Jitter RNG > + * > + * Copyright (C) 2016 - 2020, Stephan Mueller <smueller@xxxxxxxxxx> > + */ > + > +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt > + > +#include <linux/types.h> > +#include <crypto/internal/jitterentropy.h> > + > +#include "lrng_internal.h" > + > +/* > + * Estimated entropy of data is a 16th of LRNG_DRNG_SECURITY_STRENGTH_BITS. > + * Albeit a full entropy assessment is provided for the noise source indicating > + * that it provides high entropy rates and considering that it deactivates > + * when it detects insufficient hardware, the chosen under estimation of > + * entropy is considered to be acceptable to all reviewers. > + */ > +static u32 jitterrng = LRNG_DRNG_SECURITY_STRENGTH_BITS>>4; > +module_param(jitterrng, uint, 0644); > +MODULE_PARM_DESC(jitterrng, "Entropy in bits of 256 data bits from Jitter " > + "RNG noise source"); > + > +/** > + * Get Jitter RNG entropy > + * > + * @outbuf buffer to store entropy > + * @outbuflen length of buffer > + * @return > 0 on success where value provides the added entropy in bits > + * 0 if no fast source was available > + */ Don't begin the comment block with /** or convert it to Linux kernel-doc notation format. > +static struct rand_data *lrng_jent_state; > + > +u32 lrng_get_jent(u8 *outbuf, unsigned int outbuflen) > +{ > + int ret; > + u32 ent_bits = jitterrng; > + unsigned long flags; > + static DEFINE_SPINLOCK(lrng_jent_lock); > + static int lrng_jent_initialized = 0; > + > + spin_lock_irqsave(&lrng_jent_lock, flags); > + > + if (!ent_bits || (lrng_jent_initialized == -1)) { > + spin_unlock_irqrestore(&lrng_jent_lock, flags); > + return 0; > + } > + > + if (!lrng_jent_initialized) { > + lrng_jent_state = jent_lrng_entropy_collector(); > + if (!lrng_jent_state) { > + jitterrng = 0; > + lrng_jent_initialized = -1; > + spin_unlock_irqrestore(&lrng_jent_lock, flags); > + pr_info("Jitter RNG unusable on current system\n"); > + return 0; > + } > + lrng_jent_initialized = 1; > + pr_debug("Jitter RNG working on current system\n"); > + } > + ret = jent_read_entropy(lrng_jent_state, outbuf, outbuflen); > + spin_unlock_irqrestore(&lrng_jent_lock, flags); > + > + if (ret) { > + pr_debug("Jitter RNG failed with %d\n", ret); > + return 0; > + } > + > + /* Obtain entropy statement */ > + if (outbuflen != LRNG_DRNG_SECURITY_STRENGTH_BYTES) > + ent_bits = (ent_bits * outbuflen<<3) / > + LRNG_DRNG_SECURITY_STRENGTH_BITS; > + /* Cap entropy to buffer size in bits */ > + ent_bits = min_t(u32, ent_bits, outbuflen<<3); > + pr_debug("obtained %u bits of entropy from Jitter RNG noise source\n", > + ent_bits); > + > + return ent_bits; > +} > + > +u32 lrng_jent_entropylevel(void) > +{ > + return min_t(u32, jitterrng, LRNG_DRNG_SECURITY_STRENGTH_BITS); > +} > thanks. -- ~Randy