Adding upstream version 6.1.76.upstream/6.1.76

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

1 files changed, 911 insertions, 0 deletions

diff --git a/arch/s390/crypto/prng.c b/arch/s390/crypto/prng.c
new file mode 100644
index 000000000..a077087bc
--- /dev/null
+++ b/arch/s390/crypto/prng.c
@@ -0,0 +1,911 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright IBM Corp. 2006, 2015
+ * Author(s): Jan Glauber <jan.glauber@de.ibm.com>
+ *	      Harald Freudenberger <freude@de.ibm.com>
+ * Driver for the s390 pseudo random number generator
+ */
+
+#define KMSG_COMPONENT "prng"
+#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
+
+#include <linux/fs.h>
+#include <linux/fips.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/device.h>
+#include <linux/miscdevice.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/mutex.h>
+#include <linux/cpufeature.h>
+#include <linux/random.h>
+#include <linux/slab.h>
+#include <linux/sched/signal.h>
+
+#include <asm/debug.h>
+#include <linux/uaccess.h>
+#include <asm/timex.h>
+#include <asm/cpacf.h>
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("IBM Corporation");
+MODULE_DESCRIPTION("s390 PRNG interface");
+
+
+#define PRNG_MODE_AUTO	  0
+#define PRNG_MODE_TDES	  1
+#define PRNG_MODE_SHA512  2
+
+static unsigned int prng_mode = PRNG_MODE_AUTO;
+module_param_named(mode, prng_mode, int, 0);
+MODULE_PARM_DESC(prng_mode, "PRNG mode: 0 - auto, 1 - TDES, 2 - SHA512");
+
+
+#define PRNG_CHUNKSIZE_TDES_MIN   8
+#define PRNG_CHUNKSIZE_TDES_MAX   (64*1024)
+#define PRNG_CHUNKSIZE_SHA512_MIN 64
+#define PRNG_CHUNKSIZE_SHA512_MAX (64*1024)
+
+static unsigned int prng_chunk_size = 256;
+module_param_named(chunksize, prng_chunk_size, int, 0);
+MODULE_PARM_DESC(prng_chunk_size, "PRNG read chunk size in bytes");
+
+
+#define PRNG_RESEED_LIMIT_TDES		 4096
+#define PRNG_RESEED_LIMIT_TDES_LOWER	 4096
+#define PRNG_RESEED_LIMIT_SHA512       100000
+#define PRNG_RESEED_LIMIT_SHA512_LOWER	10000
+
+static unsigned int prng_reseed_limit;
+module_param_named(reseed_limit, prng_reseed_limit, int, 0);
+MODULE_PARM_DESC(prng_reseed_limit, "PRNG reseed limit");
+
+static bool trng_available;
+
+/*
+ * Any one who considers arithmetical methods of producing random digits is,
+ * of course, in a state of sin. -- John von Neumann
+ */
+
+static int prng_errorflag;
+
+#define PRNG_GEN_ENTROPY_FAILED  1
+#define PRNG_SELFTEST_FAILED	 2
+#define PRNG_INSTANTIATE_FAILED  3
+#define PRNG_SEED_FAILED	 4
+#define PRNG_RESEED_FAILED	 5
+#define PRNG_GEN_FAILED		 6
+
+struct prng_ws_s {
+	u8  parm_block[32];
+	u32 reseed_counter;
+	u64 byte_counter;
+};
+
+struct prno_ws_s {
+	u32 res;
+	u32 reseed_counter;
+	u64 stream_bytes;
+	u8  V[112];
+	u8  C[112];
+};
+
+struct prng_data_s {
+	struct mutex mutex;
+	union {
+		struct prng_ws_s prngws;
+		struct prno_ws_s prnows;
+	};
+	u8 *buf;
+	u32 rest;
+	u8 *prev;
+};
+
+static struct prng_data_s *prng_data;
+
+/* initial parameter block for tdes mode, copied from libica */
+static const u8 initial_parm_block[32] __initconst = {
+	0x0F, 0x2B, 0x8E, 0x63, 0x8C, 0x8E, 0xD2, 0x52,
+	0x64, 0xB7, 0xA0, 0x7B, 0x75, 0x28, 0xB8, 0xF4,
+	0x75, 0x5F, 0xD2, 0xA6, 0x8D, 0x97, 0x11, 0xFF,
+	0x49, 0xD8, 0x23, 0xF3, 0x7E, 0x21, 0xEC, 0xA0 };
+
+
+/*** helper functions ***/
+
+/*
+ * generate_entropy:
+ * This function fills a given buffer with random bytes. The entropy within
+ * the random bytes given back is assumed to have at least 50% - meaning
+ * a 64 bytes buffer has at least 64 * 8 / 2 = 256 bits of entropy.
+ * Within the function the entropy generation is done in junks of 64 bytes.
+ * So the caller should also ask for buffer fill in multiples of 64 bytes.
+ * The generation of the entropy is based on the assumption that every stckf()
+ * invocation produces 0.5 bits of entropy. To accumulate 256 bits of entropy
+ * at least 512 stckf() values are needed. The entropy relevant part of the
+ * stckf value is bit 51 (counting starts at the left with bit nr 0) so
+ * here we use the lower 4 bytes and exor the values into 2k of bufferspace.
+ * To be on the save side, if there is ever a problem with stckf() the
+ * other half of the page buffer is filled with bytes from urandom via
+ * get_random_bytes(), so this function consumes 2k of urandom for each
+ * requested 64 bytes output data. Finally the buffer page is condensed into
+ * a 64 byte value by hashing with a SHA512 hash.
+ */
+static int generate_entropy(u8 *ebuf, size_t nbytes)
+{
+	int n, ret = 0;
+	u8 *pg, pblock[80] = {
+		/* 8 x 64 bit init values */
+		0x6A, 0x09, 0xE6, 0x67, 0xF3, 0xBC, 0xC9, 0x08,
+		0xBB, 0x67, 0xAE, 0x85, 0x84, 0xCA, 0xA7, 0x3B,
+		0x3C, 0x6E, 0xF3, 0x72, 0xFE, 0x94, 0xF8, 0x2B,
+		0xA5, 0x4F, 0xF5, 0x3A, 0x5F, 0x1D, 0x36, 0xF1,
+		0x51, 0x0E, 0x52, 0x7F, 0xAD, 0xE6, 0x82, 0xD1,
+		0x9B, 0x05, 0x68, 0x8C, 0x2B, 0x3E, 0x6C, 0x1F,
+		0x1F, 0x83, 0xD9, 0xAB, 0xFB, 0x41, 0xBD, 0x6B,
+		0x5B, 0xE0, 0xCD, 0x19, 0x13, 0x7E, 0x21, 0x79,
+		/* 128 bit counter total message bit length */
+		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x80, 0x00 };
+
+	/* allocate one page stckf buffer */
+	pg = (u8 *) __get_free_page(GFP_KERNEL);
+	if (!pg) {
+		prng_errorflag = PRNG_GEN_ENTROPY_FAILED;
+		return -ENOMEM;
+	}
+
+	/* fill the ebuf in chunks of 64 byte each */
+	while (nbytes) {
+		/* fill lower 2k with urandom bytes */
+		get_random_bytes(pg, PAGE_SIZE / 2);
+		/* exor upper 2k with 512 stckf values, offset 4 bytes each */
+		for (n = 0; n < 512; n++) {
+			int offset = (PAGE_SIZE / 2) + (n * 4) - 4;
+			u64 *p = (u64 *)(pg + offset);
+			*p ^= get_tod_clock_fast();
+		}
+		/* hash over the filled page */
+		cpacf_klmd(CPACF_KLMD_SHA_512, pblock, pg, PAGE_SIZE);
+		n = (nbytes < 64) ? nbytes : 64;
+		memcpy(ebuf, pblock, n);
+		ret += n;
+		ebuf += n;
+		nbytes -= n;
+	}
+
+	memzero_explicit(pblock, sizeof(pblock));
+	memzero_explicit(pg, PAGE_SIZE);
+	free_page((unsigned long)pg);
+	return ret;
+}
+
+
+/*** tdes functions ***/
+
+static void prng_tdes_add_entropy(void)
+{
+	__u64 entropy[4];
+	unsigned int i;
+
+	for (i = 0; i < 16; i++) {
+		cpacf_kmc(CPACF_KMC_PRNG, prng_data->prngws.parm_block,
+			  (char *) entropy, (char *) entropy,
+			  sizeof(entropy));
+		memcpy(prng_data->prngws.parm_block, entropy, sizeof(entropy));
+	}
+}
+
+
+static void prng_tdes_seed(int nbytes)
+{
+	char buf[16];
+	int i = 0;
+
+	BUG_ON(nbytes > sizeof(buf));
+
+	get_random_bytes(buf, nbytes);
+
+	/* Add the entropy */
+	while (nbytes >= 8) {
+		*((__u64 *)prng_data->prngws.parm_block) ^= *((__u64 *)(buf+i));
+		prng_tdes_add_entropy();
+		i += 8;
+		nbytes -= 8;
+	}
+	prng_tdes_add_entropy();
+	prng_data->prngws.reseed_counter = 0;
+}
+
+
+static int __init prng_tdes_instantiate(void)
+{
+	int datalen;
+
+	pr_debug("prng runs in TDES mode with "
+		 "chunksize=%d and reseed_limit=%u\n",
+		 prng_chunk_size, prng_reseed_limit);
+
+	/* memory allocation, prng_data struct init, mutex init */
+	datalen = sizeof(struct prng_data_s) + prng_chunk_size;
+	prng_data = kzalloc(datalen, GFP_KERNEL);
+	if (!prng_data) {
+		prng_errorflag = PRNG_INSTANTIATE_FAILED;
+		return -ENOMEM;
+	}
+	mutex_init(&prng_data->mutex);
+	prng_data->buf = ((u8 *)prng_data) + sizeof(struct prng_data_s);
+	memcpy(prng_data->prngws.parm_block, initial_parm_block, 32);
+
+	/* initialize the PRNG, add 128 bits of entropy */
+	prng_tdes_seed(16);
+
+	return 0;
+}
+
+
+static void prng_tdes_deinstantiate(void)
+{
+	pr_debug("The prng module stopped "
+		 "after running in triple DES mode\n");
+	kfree_sensitive(prng_data);
+}
+
+
+/*** sha512 functions ***/
+
+static int __init prng_sha512_selftest(void)
+{
+	/* NIST DRBG testvector for Hash Drbg, Sha-512, Count #0 */
+	static const u8 seed[] __initconst = {
+		0x6b, 0x50, 0xa7, 0xd8, 0xf8, 0xa5, 0x5d, 0x7a,
+		0x3d, 0xf8, 0xbb, 0x40, 0xbc, 0xc3, 0xb7, 0x22,
+		0xd8, 0x70, 0x8d, 0xe6, 0x7f, 0xda, 0x01, 0x0b,
+		0x03, 0xc4, 0xc8, 0x4d, 0x72, 0x09, 0x6f, 0x8c,
+		0x3e, 0xc6, 0x49, 0xcc, 0x62, 0x56, 0xd9, 0xfa,
+		0x31, 0xdb, 0x7a, 0x29, 0x04, 0xaa, 0xf0, 0x25 };
+	static const u8 V0[] __initconst = {
+		0x00, 0xad, 0xe3, 0x6f, 0x9a, 0x01, 0xc7, 0x76,
+		0x61, 0x34, 0x35, 0xf5, 0x4e, 0x24, 0x74, 0x22,
+		0x21, 0x9a, 0x29, 0x89, 0xc7, 0x93, 0x2e, 0x60,
+		0x1e, 0xe8, 0x14, 0x24, 0x8d, 0xd5, 0x03, 0xf1,
+		0x65, 0x5d, 0x08, 0x22, 0x72, 0xd5, 0xad, 0x95,
+		0xe1, 0x23, 0x1e, 0x8a, 0xa7, 0x13, 0xd9, 0x2b,
+		0x5e, 0xbc, 0xbb, 0x80, 0xab, 0x8d, 0xe5, 0x79,
+		0xab, 0x5b, 0x47, 0x4e, 0xdd, 0xee, 0x6b, 0x03,
+		0x8f, 0x0f, 0x5c, 0x5e, 0xa9, 0x1a, 0x83, 0xdd,
+		0xd3, 0x88, 0xb2, 0x75, 0x4b, 0xce, 0x83, 0x36,
+		0x57, 0x4b, 0xf1, 0x5c, 0xca, 0x7e, 0x09, 0xc0,
+		0xd3, 0x89, 0xc6, 0xe0, 0xda, 0xc4, 0x81, 0x7e,
+		0x5b, 0xf9, 0xe1, 0x01, 0xc1, 0x92, 0x05, 0xea,
+		0xf5, 0x2f, 0xc6, 0xc6, 0xc7, 0x8f, 0xbc, 0xf4 };
+	static const u8 C0[] __initconst = {
+		0x00, 0xf4, 0xa3, 0xe5, 0xa0, 0x72, 0x63, 0x95,
+		0xc6, 0x4f, 0x48, 0xd0, 0x8b, 0x5b, 0x5f, 0x8e,
+		0x6b, 0x96, 0x1f, 0x16, 0xed, 0xbc, 0x66, 0x94,
+		0x45, 0x31, 0xd7, 0x47, 0x73, 0x22, 0xa5, 0x86,
+		0xce, 0xc0, 0x4c, 0xac, 0x63, 0xb8, 0x39, 0x50,
+		0xbf, 0xe6, 0x59, 0x6c, 0x38, 0x58, 0x99, 0x1f,
+		0x27, 0xa7, 0x9d, 0x71, 0x2a, 0xb3, 0x7b, 0xf9,
+		0xfb, 0x17, 0x86, 0xaa, 0x99, 0x81, 0xaa, 0x43,
+		0xe4, 0x37, 0xd3, 0x1e, 0x6e, 0xe5, 0xe6, 0xee,
+		0xc2, 0xed, 0x95, 0x4f, 0x53, 0x0e, 0x46, 0x8a,
+		0xcc, 0x45, 0xa5, 0xdb, 0x69, 0x0d, 0x81, 0xc9,
+		0x32, 0x92, 0xbc, 0x8f, 0x33, 0xe6, 0xf6, 0x09,
+		0x7c, 0x8e, 0x05, 0x19, 0x0d, 0xf1, 0xb6, 0xcc,
+		0xf3, 0x02, 0x21, 0x90, 0x25, 0xec, 0xed, 0x0e };
+	static const u8 random[] __initconst = {
+		0x95, 0xb7, 0xf1, 0x7e, 0x98, 0x02, 0xd3, 0x57,
+		0x73, 0x92, 0xc6, 0xa9, 0xc0, 0x80, 0x83, 0xb6,
+		0x7d, 0xd1, 0x29, 0x22, 0x65, 0xb5, 0xf4, 0x2d,
+		0x23, 0x7f, 0x1c, 0x55, 0xbb, 0x9b, 0x10, 0xbf,
+		0xcf, 0xd8, 0x2c, 0x77, 0xa3, 0x78, 0xb8, 0x26,
+		0x6a, 0x00, 0x99, 0x14, 0x3b, 0x3c, 0x2d, 0x64,
+		0x61, 0x1e, 0xee, 0xb6, 0x9a, 0xcd, 0xc0, 0x55,
+		0x95, 0x7c, 0x13, 0x9e, 0x8b, 0x19, 0x0c, 0x7a,
+		0x06, 0x95, 0x5f, 0x2c, 0x79, 0x7c, 0x27, 0x78,
+		0xde, 0x94, 0x03, 0x96, 0xa5, 0x01, 0xf4, 0x0e,
+		0x91, 0x39, 0x6a, 0xcf, 0x8d, 0x7e, 0x45, 0xeb,
+		0xdb, 0xb5, 0x3b, 0xbf, 0x8c, 0x97, 0x52, 0x30,
+		0xd2, 0xf0, 0xff, 0x91, 0x06, 0xc7, 0x61, 0x19,
+		0xae, 0x49, 0x8e, 0x7f, 0xbc, 0x03, 0xd9, 0x0f,
+		0x8e, 0x4c, 0x51, 0x62, 0x7a, 0xed, 0x5c, 0x8d,
+		0x42, 0x63, 0xd5, 0xd2, 0xb9, 0x78, 0x87, 0x3a,
+		0x0d, 0xe5, 0x96, 0xee, 0x6d, 0xc7, 0xf7, 0xc2,
+		0x9e, 0x37, 0xee, 0xe8, 0xb3, 0x4c, 0x90, 0xdd,
+		0x1c, 0xf6, 0xa9, 0xdd, 0xb2, 0x2b, 0x4c, 0xbd,
+		0x08, 0x6b, 0x14, 0xb3, 0x5d, 0xe9, 0x3d, 0xa2,
+		0xd5, 0xcb, 0x18, 0x06, 0x69, 0x8c, 0xbd, 0x7b,
+		0xbb, 0x67, 0xbf, 0xe3, 0xd3, 0x1f, 0xd2, 0xd1,
+		0xdb, 0xd2, 0xa1, 0xe0, 0x58, 0xa3, 0xeb, 0x99,
+		0xd7, 0xe5, 0x1f, 0x1a, 0x93, 0x8e, 0xed, 0x5e,
+		0x1c, 0x1d, 0xe2, 0x3a, 0x6b, 0x43, 0x45, 0xd3,
+		0x19, 0x14, 0x09, 0xf9, 0x2f, 0x39, 0xb3, 0x67,
+		0x0d, 0x8d, 0xbf, 0xb6, 0x35, 0xd8, 0xe6, 0xa3,
+		0x69, 0x32, 0xd8, 0x10, 0x33, 0xd1, 0x44, 0x8d,
+		0x63, 0xb4, 0x03, 0xdd, 0xf8, 0x8e, 0x12, 0x1b,
+		0x6e, 0x81, 0x9a, 0xc3, 0x81, 0x22, 0x6c, 0x13,
+		0x21, 0xe4, 0xb0, 0x86, 0x44, 0xf6, 0x72, 0x7c,
+		0x36, 0x8c, 0x5a, 0x9f, 0x7a, 0x4b, 0x3e, 0xe2 };
+
+	u8 buf[sizeof(random)];
+	struct prno_ws_s ws;
+
+	memset(&ws, 0, sizeof(ws));
+
+	/* initial seed */
+	cpacf_prno(CPACF_PRNO_SHA512_DRNG_SEED,
+		   &ws, NULL, 0, seed, sizeof(seed));
+
+	/* check working states V and C */
+	if (memcmp(ws.V, V0, sizeof(V0)) != 0
+	    || memcmp(ws.C, C0, sizeof(C0)) != 0) {
+		pr_err("The prng self test state test "
+		       "for the SHA-512 mode failed\n");
+		prng_errorflag = PRNG_SELFTEST_FAILED;
+		return -EIO;
+	}
+
+	/* generate random bytes */
+	cpacf_prno(CPACF_PRNO_SHA512_DRNG_GEN,
+		   &ws, buf, sizeof(buf), NULL, 0);
+	cpacf_prno(CPACF_PRNO_SHA512_DRNG_GEN,
+		   &ws, buf, sizeof(buf), NULL, 0);
+
+	/* check against expected data */
+	if (memcmp(buf, random, sizeof(random)) != 0) {
+		pr_err("The prng self test data test "
+		       "for the SHA-512 mode failed\n");
+		prng_errorflag = PRNG_SELFTEST_FAILED;
+		return -EIO;
+	}
+
+	return 0;
+}
+
+
+static int __init prng_sha512_instantiate(void)
+{
+	int ret, datalen, seedlen;
+	u8 seed[128 + 16];
+
+	pr_debug("prng runs in SHA-512 mode "
+		 "with chunksize=%d and reseed_limit=%u\n",
+		 prng_chunk_size, prng_reseed_limit);
+
+	/* memory allocation, prng_data struct init, mutex init */
+	datalen = sizeof(struct prng_data_s) + prng_chunk_size;
+	if (fips_enabled)
+		datalen += prng_chunk_size;
+	prng_data = kzalloc(datalen, GFP_KERNEL);
+	if (!prng_data) {
+		prng_errorflag = PRNG_INSTANTIATE_FAILED;
+		return -ENOMEM;
+	}
+	mutex_init(&prng_data->mutex);
+	prng_data->buf = ((u8 *)prng_data) + sizeof(struct prng_data_s);
+
+	/* selftest */
+	ret = prng_sha512_selftest();
+	if (ret)
+		goto outfree;
+
+	/* generate initial seed, we need at least  256 + 128 bits entropy. */
+	if (trng_available) {
+		/*
+		 * Trng available, so use it. The trng works in chunks of
+		 * 32 bytes and produces 100% entropy. So we pull 64 bytes
+		 * which gives us 512 bits entropy.
+		 */
+		seedlen = 2 * 32;
+		cpacf_trng(NULL, 0, seed, seedlen);
+	} else {
+		/*
+		 * No trng available, so use the generate_entropy() function.
+		 * This function works in 64 byte junks and produces
+		 * 50% entropy. So we pull 2*64 bytes which gives us 512 bits
+		 * of entropy.
+		 */
+		seedlen = 2 * 64;
+		ret = generate_entropy(seed, seedlen);
+		if (ret != seedlen)
+			goto outfree;
+	}
+
+	/* append the seed by 16 bytes of unique nonce */
+	store_tod_clock_ext((union tod_clock *)(seed + seedlen));
+	seedlen += 16;
+
+	/* now initial seed of the prno drng */
+	cpacf_prno(CPACF_PRNO_SHA512_DRNG_SEED,
+		   &prng_data->prnows, NULL, 0, seed, seedlen);
+	memzero_explicit(seed, sizeof(seed));
+
+	/* if fips mode is enabled, generate a first block of random
+	   bytes for the FIPS 140-2 Conditional Self Test */
+	if (fips_enabled) {
+		prng_data->prev = prng_data->buf + prng_chunk_size;
+		cpacf_prno(CPACF_PRNO_SHA512_DRNG_GEN,
+			   &prng_data->prnows,
+			   prng_data->prev, prng_chunk_size, NULL, 0);
+	}
+
+	return 0;
+
+outfree:
+	kfree(prng_data);
+	return ret;
+}
+
+
+static void prng_sha512_deinstantiate(void)
+{
+	pr_debug("The prng module stopped after running in SHA-512 mode\n");
+	kfree_sensitive(prng_data);
+}
+
+
+static int prng_sha512_reseed(void)
+{
+	int ret, seedlen;
+	u8 seed[64];
+
+	/* We need at least 256 bits of fresh entropy for reseeding */
+	if (trng_available) {
+		/* trng produces 256 bits entropy in 32 bytes */
+		seedlen = 32;
+		cpacf_trng(NULL, 0, seed, seedlen);
+	} else {
+		/* generate_entropy() produces 256 bits entropy in 64 bytes */
+		seedlen = 64;
+		ret = generate_entropy(seed, seedlen);
+		if (ret != sizeof(seed))
+			return ret;
+	}
+
+	/* do a reseed of the prno drng with this bytestring */
+	cpacf_prno(CPACF_PRNO_SHA512_DRNG_SEED,
+		   &prng_data->prnows, NULL, 0, seed, seedlen);
+	memzero_explicit(seed, sizeof(seed));
+
+	return 0;
+}
+
+
+static int prng_sha512_generate(u8 *buf, size_t nbytes)
+{
+	int ret;
+
+	/* reseed needed ? */
+	if (prng_data->prnows.reseed_counter > prng_reseed_limit) {
+		ret = prng_sha512_reseed();
+		if (ret)
+			return ret;
+	}
+
+	/* PRNO generate */
+	cpacf_prno(CPACF_PRNO_SHA512_DRNG_GEN,
+		   &prng_data->prnows, buf, nbytes, NULL, 0);
+
+	/* FIPS 140-2 Conditional Self Test */
+	if (fips_enabled) {
+		if (!memcmp(prng_data->prev, buf, nbytes)) {
+			prng_errorflag = PRNG_GEN_FAILED;
+			return -EILSEQ;
+		}
+		memcpy(prng_data->prev, buf, nbytes);
+	}
+
+	return nbytes;
+}
+
+
+/*** file io functions ***/
+
+static int prng_open(struct inode *inode, struct file *file)
+{
+	return nonseekable_open(inode, file);
+}
+
+
+static ssize_t prng_tdes_read(struct file *file, char __user *ubuf,
+			      size_t nbytes, loff_t *ppos)
+{
+	int chunk, n, ret = 0;
+
+	/* lock prng_data struct */
+	if (mutex_lock_interruptible(&prng_data->mutex))
+		return -ERESTARTSYS;
+
+	while (nbytes) {
+		if (need_resched()) {
+			if (signal_pending(current)) {
+				if (ret == 0)
+					ret = -ERESTARTSYS;
+				break;
+			}
+			/* give mutex free before calling schedule() */
+			mutex_unlock(&prng_data->mutex);
+			schedule();
+			/* occupy mutex again */
+			if (mutex_lock_interruptible(&prng_data->mutex)) {
+				if (ret == 0)
+					ret = -ERESTARTSYS;
+				return ret;
+			}
+		}
+
+		/*
+		 * we lose some random bytes if an attacker issues
+		 * reads < 8 bytes, but we don't care
+		 */
+		chunk = min_t(int, nbytes, prng_chunk_size);
+
+		/* PRNG only likes multiples of 8 bytes */
+		n = (chunk + 7) & -8;
+
+		if (prng_data->prngws.reseed_counter > prng_reseed_limit)
+			prng_tdes_seed(8);
+
+		/* if the CPU supports PRNG stckf is present too */
+		*((unsigned long long *)prng_data->buf) = get_tod_clock_fast();
+
+		/*
+		 * Beside the STCKF the input for the TDES-EDE is the output
+		 * of the last operation. We differ here from X9.17 since we
+		 * only store one timestamp into the buffer. Padding the whole
+		 * buffer with timestamps does not improve security, since
+		 * successive stckf have nearly constant offsets.
+		 * If an attacker knows the first timestamp it would be
+		 * trivial to guess the additional values. One timestamp
+		 * is therefore enough and still guarantees unique input values.
+		 *
+		 * Note: you can still get strict X9.17 conformity by setting
+		 * prng_chunk_size to 8 bytes.
+		 */
+		cpacf_kmc(CPACF_KMC_PRNG, prng_data->prngws.parm_block,
+			  prng_data->buf, prng_data->buf, n);
+
+		prng_data->prngws.byte_counter += n;
+		prng_data->prngws.reseed_counter += n;
+
+		if (copy_to_user(ubuf, prng_data->buf, chunk)) {
+			ret = -EFAULT;
+			break;
+		}
+
+		nbytes -= chunk;
+		ret += chunk;
+		ubuf += chunk;
+	}
+
+	/* unlock prng_data struct */
+	mutex_unlock(&prng_data->mutex);
+
+	return ret;
+}
+
+
+static ssize_t prng_sha512_read(struct file *file, char __user *ubuf,
+				size_t nbytes, loff_t *ppos)
+{
+	int n, ret = 0;
+	u8 *p;
+
+	/* if errorflag is set do nothing and return 'broken pipe' */
+	if (prng_errorflag)
+		return -EPIPE;
+
+	/* lock prng_data struct */
+	if (mutex_lock_interruptible(&prng_data->mutex))
+		return -ERESTARTSYS;
+
+	while (nbytes) {
+		if (need_resched()) {
+			if (signal_pending(current)) {
+				if (ret == 0)
+					ret = -ERESTARTSYS;
+				break;
+			}
+			/* give mutex free before calling schedule() */
+			mutex_unlock(&prng_data->mutex);
+			schedule();
+			/* occopy mutex again */
+			if (mutex_lock_interruptible(&prng_data->mutex)) {
+				if (ret == 0)
+					ret = -ERESTARTSYS;
+				return ret;
+			}
+		}
+		if (prng_data->rest) {
+			/* push left over random bytes from the previous read */
+			p = prng_data->buf + prng_chunk_size - prng_data->rest;
+			n = (nbytes < prng_data->rest) ?
+				nbytes : prng_data->rest;
+			prng_data->rest -= n;
+		} else {
+			/* generate one chunk of random bytes into read buf */
+			p = prng_data->buf;
+			n = prng_sha512_generate(p, prng_chunk_size);
+			if (n < 0) {
+				ret = n;
+				break;
+			}
+			if (nbytes < prng_chunk_size) {
+				n = nbytes;
+				prng_data->rest = prng_chunk_size - n;
+			} else {
+				n = prng_chunk_size;
+				prng_data->rest = 0;
+			}
+		}
+		if (copy_to_user(ubuf, p, n)) {
+			ret = -EFAULT;
+			break;
+		}
+		memzero_explicit(p, n);
+		ubuf += n;
+		nbytes -= n;
+		ret += n;
+	}
+
+	/* unlock prng_data struct */
+	mutex_unlock(&prng_data->mutex);
+
+	return ret;
+}
+
+
+/*** sysfs stuff ***/
+
+static const struct file_operations prng_sha512_fops = {
+	.owner		= THIS_MODULE,
+	.open		= &prng_open,
+	.release	= NULL,
+	.read		= &prng_sha512_read,
+	.llseek		= noop_llseek,
+};
+static const struct file_operations prng_tdes_fops = {
+	.owner		= THIS_MODULE,
+	.open		= &prng_open,
+	.release	= NULL,
+	.read		= &prng_tdes_read,
+	.llseek		= noop_llseek,
+};
+
+/* chunksize attribute (ro) */
+static ssize_t prng_chunksize_show(struct device *dev,
+				   struct device_attribute *attr,
+				   char *buf)
+{
+	return scnprintf(buf, PAGE_SIZE, "%u\n", prng_chunk_size);
+}
+static DEVICE_ATTR(chunksize, 0444, prng_chunksize_show, NULL);
+
+/* counter attribute (ro) */
+static ssize_t prng_counter_show(struct device *dev,
+				 struct device_attribute *attr,
+				 char *buf)
+{
+	u64 counter;
+
+	if (mutex_lock_interruptible(&prng_data->mutex))
+		return -ERESTARTSYS;
+	if (prng_mode == PRNG_MODE_SHA512)
+		counter = prng_data->prnows.stream_bytes;
+	else
+		counter = prng_data->prngws.byte_counter;
+	mutex_unlock(&prng_data->mutex);
+
+	return scnprintf(buf, PAGE_SIZE, "%llu\n", counter);
+}
+static DEVICE_ATTR(byte_counter, 0444, prng_counter_show, NULL);
+
+/* errorflag attribute (ro) */
+static ssize_t prng_errorflag_show(struct device *dev,
+				   struct device_attribute *attr,
+				   char *buf)
+{
+	return scnprintf(buf, PAGE_SIZE, "%d\n", prng_errorflag);
+}
+static DEVICE_ATTR(errorflag, 0444, prng_errorflag_show, NULL);
+
+/* mode attribute (ro) */
+static ssize_t prng_mode_show(struct device *dev,
+			      struct device_attribute *attr,
+			      char *buf)
+{
+	if (prng_mode == PRNG_MODE_TDES)
+		return scnprintf(buf, PAGE_SIZE, "TDES\n");
+	else
+		return scnprintf(buf, PAGE_SIZE, "SHA512\n");
+}
+static DEVICE_ATTR(mode, 0444, prng_mode_show, NULL);
+
+/* reseed attribute (w) */
+static ssize_t prng_reseed_store(struct device *dev,
+				 struct device_attribute *attr,
+				 const char *buf, size_t count)
+{
+	if (mutex_lock_interruptible(&prng_data->mutex))
+		return -ERESTARTSYS;
+	prng_sha512_reseed();
+	mutex_unlock(&prng_data->mutex);
+
+	return count;
+}
+static DEVICE_ATTR(reseed, 0200, NULL, prng_reseed_store);
+
+/* reseed limit attribute (rw) */
+static ssize_t prng_reseed_limit_show(struct device *dev,
+				      struct device_attribute *attr,
+				      char *buf)
+{
+	return scnprintf(buf, PAGE_SIZE, "%u\n", prng_reseed_limit);
+}
+static ssize_t prng_reseed_limit_store(struct device *dev,
+				       struct device_attribute *attr,
+				       const char *buf, size_t count)
+{
+	unsigned limit;
+
+	if (sscanf(buf, "%u\n", &limit) != 1)
+		return -EINVAL;
+
+	if (prng_mode == PRNG_MODE_SHA512) {
+		if (limit < PRNG_RESEED_LIMIT_SHA512_LOWER)
+			return -EINVAL;
+	} else {
+		if (limit < PRNG_RESEED_LIMIT_TDES_LOWER)
+			return -EINVAL;
+	}
+
+	prng_reseed_limit = limit;
+
+	return count;
+}
+static DEVICE_ATTR(reseed_limit, 0644,
+		   prng_reseed_limit_show, prng_reseed_limit_store);
+
+/* strength attribute (ro) */
+static ssize_t prng_strength_show(struct device *dev,
+				  struct device_attribute *attr,
+				  char *buf)
+{
+	return scnprintf(buf, PAGE_SIZE, "256\n");
+}
+static DEVICE_ATTR(strength, 0444, prng_strength_show, NULL);
+
+static struct attribute *prng_sha512_dev_attrs[] = {
+	&dev_attr_errorflag.attr,
+	&dev_attr_chunksize.attr,
+	&dev_attr_byte_counter.attr,
+	&dev_attr_mode.attr,
+	&dev_attr_reseed.attr,
+	&dev_attr_reseed_limit.attr,
+	&dev_attr_strength.attr,
+	NULL
+};
+ATTRIBUTE_GROUPS(prng_sha512_dev);
+
+static struct attribute *prng_tdes_dev_attrs[] = {
+	&dev_attr_chunksize.attr,
+	&dev_attr_byte_counter.attr,
+	&dev_attr_mode.attr,
+	NULL
+};
+ATTRIBUTE_GROUPS(prng_tdes_dev);
+
+static struct miscdevice prng_sha512_dev = {
+	.name	= "prandom",
+	.minor	= MISC_DYNAMIC_MINOR,
+	.mode	= 0644,
+	.fops	= &prng_sha512_fops,
+	.groups = prng_sha512_dev_groups,
+};
+
+static struct miscdevice prng_tdes_dev = {
+	.name	= "prandom",
+	.minor	= MISC_DYNAMIC_MINOR,
+	.mode	= 0644,
+	.fops	= &prng_tdes_fops,
+	.groups = prng_tdes_dev_groups,
+};
+
+
+/*** module init and exit ***/
+
+static int __init prng_init(void)
+{
+	int ret;
+
+	/* check if the CPU has a PRNG */
+	if (!cpacf_query_func(CPACF_KMC, CPACF_KMC_PRNG))
+		return -ENODEV;
+
+	/* check if TRNG subfunction is available */
+	if (cpacf_query_func(CPACF_PRNO, CPACF_PRNO_TRNG))
+		trng_available = true;
+
+	/* choose prng mode */
+	if (prng_mode != PRNG_MODE_TDES) {
+		/* check for MSA5 support for PRNO operations */
+		if (!cpacf_query_func(CPACF_PRNO, CPACF_PRNO_SHA512_DRNG_GEN)) {
+			if (prng_mode == PRNG_MODE_SHA512) {
+				pr_err("The prng module cannot "
+				       "start in SHA-512 mode\n");
+				return -ENODEV;
+			}
+			prng_mode = PRNG_MODE_TDES;
+		} else
+			prng_mode = PRNG_MODE_SHA512;
+	}
+
+	if (prng_mode == PRNG_MODE_SHA512) {
+
+		/* SHA512 mode */
+
+		if (prng_chunk_size < PRNG_CHUNKSIZE_SHA512_MIN
+		    || prng_chunk_size > PRNG_CHUNKSIZE_SHA512_MAX)
+			return -EINVAL;
+		prng_chunk_size = (prng_chunk_size + 0x3f) & ~0x3f;
+
+		if (prng_reseed_limit == 0)
+			prng_reseed_limit = PRNG_RESEED_LIMIT_SHA512;
+		else if (prng_reseed_limit < PRNG_RESEED_LIMIT_SHA512_LOWER)
+			return -EINVAL;
+
+		ret = prng_sha512_instantiate();
+		if (ret)
+			goto out;
+
+		ret = misc_register(&prng_sha512_dev);
+		if (ret) {
+			prng_sha512_deinstantiate();
+			goto out;
+		}
+
+	} else {
+
+		/* TDES mode */
+
+		if (prng_chunk_size < PRNG_CHUNKSIZE_TDES_MIN
+		    || prng_chunk_size > PRNG_CHUNKSIZE_TDES_MAX)
+			return -EINVAL;
+		prng_chunk_size = (prng_chunk_size + 0x07) & ~0x07;
+
+		if (prng_reseed_limit == 0)
+			prng_reseed_limit = PRNG_RESEED_LIMIT_TDES;
+		else if (prng_reseed_limit < PRNG_RESEED_LIMIT_TDES_LOWER)
+			return -EINVAL;
+
+		ret = prng_tdes_instantiate();
+		if (ret)
+			goto out;
+
+		ret = misc_register(&prng_tdes_dev);
+		if (ret) {
+			prng_tdes_deinstantiate();
+			goto out;
+		}
+	}
+
+out:
+	return ret;
+}
+
+
+static void __exit prng_exit(void)
+{
+	if (prng_mode == PRNG_MODE_SHA512) {
+		misc_deregister(&prng_sha512_dev);
+		prng_sha512_deinstantiate();
+	} else {
+		misc_deregister(&prng_tdes_dev);
+		prng_tdes_deinstantiate();
+	}
+}
+
+module_cpu_feature_match(S390_CPU_FEATURE_MSA, prng_init);
+module_exit(prng_exit);