Re: [PATCH v27 09/12] LRNG - add Jitter RNG fast noise source

Am Freitag, 10. Januar 2020, 01:24:47 CET schrieb Randy Dunlap:

Hi Randy,

Hi,

On 1/9/20 12:34 AM, Stephan Müller wrote:

quoted

---

 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@chronox.de>
+ */
+
+#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.

Yes, the colons are missing and there is no @return. It will be fixed with the 
next patch set.

Thank you.

quoted

+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.

Ciao
Stephan