ALSA: hda - Remove duplicated strings from codec name
[linux-2.6/kvm.git] / arch / s390 / crypto / prng.c
blobeca724d229ecd26d7102dfd7c7d4be37af98d19f
1 /*
2 * Copyright IBM Corp. 2006,2007
3 * Author(s): Jan Glauber <jan.glauber@de.ibm.com>
4 * Driver for the s390 pseudo random number generator
5 */
6 #include <linux/fs.h>
7 #include <linux/init.h>
8 #include <linux/kernel.h>
9 #include <linux/smp_lock.h>
10 #include <linux/miscdevice.h>
11 #include <linux/module.h>
12 #include <linux/moduleparam.h>
13 #include <linux/random.h>
14 #include <asm/debug.h>
15 #include <asm/uaccess.h>
17 #include "crypt_s390.h"
19 MODULE_LICENSE("GPL");
20 MODULE_AUTHOR("Jan Glauber <jan.glauber@de.ibm.com>");
21 MODULE_DESCRIPTION("s390 PRNG interface");
23 static int prng_chunk_size = 256;
24 module_param(prng_chunk_size, int, S_IRUSR | S_IRGRP | S_IROTH);
25 MODULE_PARM_DESC(prng_chunk_size, "PRNG read chunk size in bytes");
27 static int prng_entropy_limit = 4096;
28 module_param(prng_entropy_limit, int, S_IRUSR | S_IRGRP | S_IROTH | S_IWUSR);
29 MODULE_PARM_DESC(prng_entropy_limit,
30 "PRNG add entropy after that much bytes were produced");
33 * Any one who considers arithmetical methods of producing random digits is,
34 * of course, in a state of sin. -- John von Neumann
37 struct s390_prng_data {
38 unsigned long count; /* how many bytes were produced */
39 char *buf;
42 static struct s390_prng_data *p;
44 /* copied from libica, use a non-zero initial parameter block */
45 static unsigned char parm_block[32] = {
46 0x0F,0x2B,0x8E,0x63,0x8C,0x8E,0xD2,0x52,0x64,0xB7,0xA0,0x7B,0x75,0x28,0xB8,0xF4,
47 0x75,0x5F,0xD2,0xA6,0x8D,0x97,0x11,0xFF,0x49,0xD8,0x23,0xF3,0x7E,0x21,0xEC,0xA0,
50 static int prng_open(struct inode *inode, struct file *file)
52 cycle_kernel_lock();
53 return nonseekable_open(inode, file);
56 static void prng_add_entropy(void)
58 __u64 entropy[4];
59 unsigned int i;
60 int ret;
62 for (i = 0; i < 16; i++) {
63 ret = crypt_s390_kmc(KMC_PRNG, parm_block, (char *)entropy,
64 (char *)entropy, sizeof(entropy));
65 BUG_ON(ret < 0 || ret != sizeof(entropy));
66 memcpy(parm_block, entropy, sizeof(entropy));
70 static void prng_seed(int nbytes)
72 char buf[16];
73 int i = 0;
75 BUG_ON(nbytes > 16);
76 get_random_bytes(buf, nbytes);
78 /* Add the entropy */
79 while (nbytes >= 8) {
80 *((__u64 *)parm_block) ^= *((__u64 *)buf+i*8);
81 prng_add_entropy();
82 i += 8;
83 nbytes -= 8;
85 prng_add_entropy();
88 static ssize_t prng_read(struct file *file, char __user *ubuf, size_t nbytes,
89 loff_t *ppos)
91 int chunk, n;
92 int ret = 0;
93 int tmp;
95 /* nbytes can be arbitrary length, we split it into chunks */
96 while (nbytes) {
97 /* same as in extract_entropy_user in random.c */
98 if (need_resched()) {
99 if (signal_pending(current)) {
100 if (ret == 0)
101 ret = -ERESTARTSYS;
102 break;
104 schedule();
108 * we lose some random bytes if an attacker issues
109 * reads < 8 bytes, but we don't care
111 chunk = min_t(int, nbytes, prng_chunk_size);
113 /* PRNG only likes multiples of 8 bytes */
114 n = (chunk + 7) & -8;
116 if (p->count > prng_entropy_limit)
117 prng_seed(8);
119 /* if the CPU supports PRNG stckf is present too */
120 asm volatile(".insn s,0xb27c0000,%0"
121 : "=m" (*((unsigned long long *)p->buf)) : : "cc");
124 * Beside the STCKF the input for the TDES-EDE is the output
125 * of the last operation. We differ here from X9.17 since we
126 * only store one timestamp into the buffer. Padding the whole
127 * buffer with timestamps does not improve security, since
128 * successive stckf have nearly constant offsets.
129 * If an attacker knows the first timestamp it would be
130 * trivial to guess the additional values. One timestamp
131 * is therefore enough and still guarantees unique input values.
133 * Note: you can still get strict X9.17 conformity by setting
134 * prng_chunk_size to 8 bytes.
136 tmp = crypt_s390_kmc(KMC_PRNG, parm_block, p->buf, p->buf, n);
137 BUG_ON((tmp < 0) || (tmp != n));
139 p->count += n;
141 if (copy_to_user(ubuf, p->buf, chunk))
142 return -EFAULT;
144 nbytes -= chunk;
145 ret += chunk;
146 ubuf += chunk;
148 return ret;
151 static const struct file_operations prng_fops = {
152 .owner = THIS_MODULE,
153 .open = &prng_open,
154 .release = NULL,
155 .read = &prng_read,
158 static struct miscdevice prng_dev = {
159 .name = "prandom",
160 .minor = MISC_DYNAMIC_MINOR,
161 .fops = &prng_fops,
164 static int __init prng_init(void)
166 int ret;
168 /* check if the CPU has a PRNG */
169 if (!crypt_s390_func_available(KMC_PRNG))
170 return -EOPNOTSUPP;
172 if (prng_chunk_size < 8)
173 return -EINVAL;
175 p = kmalloc(sizeof(struct s390_prng_data), GFP_KERNEL);
176 if (!p)
177 return -ENOMEM;
178 p->count = 0;
180 p->buf = kmalloc(prng_chunk_size, GFP_KERNEL);
181 if (!p->buf) {
182 ret = -ENOMEM;
183 goto out_free;
186 /* initialize the PRNG, add 128 bits of entropy */
187 prng_seed(16);
189 ret = misc_register(&prng_dev);
190 if (ret)
191 goto out_buf;
192 return 0;
194 out_buf:
195 kfree(p->buf);
196 out_free:
197 kfree(p);
198 return ret;
201 static void __exit prng_exit(void)
203 /* wipe me */
204 memset(p->buf, 0, prng_chunk_size);
205 kfree(p->buf);
206 kfree(p);
208 misc_deregister(&prng_dev);
211 module_init(prng_init);
212 module_exit(prng_exit);