1 /* 2 * s390 TRNG device driver 3 * 4 * Driver for the TRNG (true random number generation) command 5 * available via CPACF extension MSA 7 on the s390 arch. 6 7 * Copyright IBM Corp. 2017 8 * Author(s): Harald Freudenberger <freude@de.ibm.com> 9 * 10 * This program is free software; you can redistribute it and/or modify 11 * it under the terms of the GNU General Public License (version 2 only) 12 * as published by the Free Software Foundation. 13 * 14 */ 15 16 #define KMSG_COMPONENT "trng" 17 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt 18 19 #include <linux/hw_random.h> 20 #include <linux/kernel.h> 21 #include <linux/module.h> 22 #include <linux/cpufeature.h> 23 #include <linux/miscdevice.h> 24 #include <linux/debugfs.h> 25 #include <linux/atomic.h> 26 #include <linux/random.h> 27 #include <linux/sched/signal.h> 28 #include <asm/debug.h> 29 #include <asm/cpacf.h> 30 31 MODULE_LICENSE("GPL v2"); 32 MODULE_AUTHOR("IBM Corporation"); 33 MODULE_DESCRIPTION("s390 CPACF TRNG device driver"); 34 35 36 /* trng related debug feature things */ 37 38 static debug_info_t *debug_info; 39 40 #define DEBUG_DBG(...) debug_sprintf_event(debug_info, 6, ##__VA_ARGS__) 41 #define DEBUG_INFO(...) debug_sprintf_event(debug_info, 5, ##__VA_ARGS__) 42 #define DEBUG_WARN(...) debug_sprintf_event(debug_info, 4, ##__VA_ARGS__) 43 #define DEBUG_ERR(...) debug_sprintf_event(debug_info, 3, ##__VA_ARGS__) 44 45 46 /* trng helpers */ 47 48 static atomic64_t trng_dev_counter = ATOMIC64_INIT(0); 49 static atomic64_t trng_hwrng_counter = ATOMIC64_INIT(0); 50 51 52 /* file io functions */ 53 54 static int trng_open(struct inode *inode, struct file *file) 55 { 56 return nonseekable_open(inode, file); 57 } 58 59 static ssize_t trng_read(struct file *file, char __user *ubuf, 60 size_t nbytes, loff_t *ppos) 61 { 62 u8 buf[32]; 63 u8 *p = buf; 64 unsigned int n; 65 ssize_t ret = 0; 66 67 /* 68 * use buf for requests <= sizeof(buf), 69 * otherwise allocate one page and fetch 70 * pagewise. 71 */ 72 73 if (nbytes > sizeof(buf)) { 74 p = (u8 *) __get_free_page(GFP_KERNEL); 75 if (!p) 76 return -ENOMEM; 77 } 78 79 while (nbytes) { 80 if (need_resched()) { 81 if (signal_pending(current)) { 82 if (ret == 0) 83 ret = -ERESTARTSYS; 84 break; 85 } 86 schedule(); 87 } 88 n = nbytes > PAGE_SIZE ? PAGE_SIZE : nbytes; 89 cpacf_trng(NULL, 0, p, n); 90 atomic64_add(n, &trng_dev_counter); 91 if (copy_to_user(ubuf, p, n)) { 92 ret = -EFAULT; 93 break; 94 } 95 nbytes -= n; 96 ubuf += n; 97 ret += n; 98 } 99 100 if (p != buf) 101 free_page((unsigned long) p); 102 103 DEBUG_DBG("trng_read()=%zd\n", ret); 104 return ret; 105 } 106 107 108 /* sysfs */ 109 110 static ssize_t trng_counter_show(struct device *dev, 111 struct device_attribute *attr, char *buf) 112 { 113 u64 dev_counter = atomic64_read(&trng_dev_counter); 114 u64 hwrng_counter = atomic64_read(&trng_hwrng_counter); 115 #if IS_ENABLED(CONFIG_ARCH_RANDOM) 116 u64 arch_counter = atomic64_read(&s390_arch_random_counter); 117 118 return snprintf(buf, PAGE_SIZE, 119 "trng: %llu\n" 120 "hwrng: %llu\n" 121 "arch: %llu\n" 122 "total: %llu\n", 123 dev_counter, hwrng_counter, arch_counter, 124 dev_counter + hwrng_counter + arch_counter); 125 #else 126 return snprintf(buf, PAGE_SIZE, 127 "trng: %llu\n" 128 "hwrng: %llu\n" 129 "total: %llu\n", 130 dev_counter, hwrng_counter, 131 dev_counter + hwrng_counter); 132 #endif 133 } 134 static DEVICE_ATTR(byte_counter, 0444, trng_counter_show, NULL); 135 136 static struct attribute *trng_dev_attrs[] = { 137 &dev_attr_byte_counter.attr, 138 NULL 139 }; 140 141 static const struct attribute_group trng_dev_attr_group = { 142 .attrs = trng_dev_attrs 143 }; 144 145 static const struct attribute_group *trng_dev_attr_groups[] = { 146 &trng_dev_attr_group, 147 NULL 148 }; 149 150 static const struct file_operations trng_fops = { 151 .owner = THIS_MODULE, 152 .open = &trng_open, 153 .release = NULL, 154 .read = &trng_read, 155 .llseek = noop_llseek, 156 }; 157 158 static struct miscdevice trng_dev = { 159 .name = "trng", 160 .minor = MISC_DYNAMIC_MINOR, 161 .mode = 0444, 162 .fops = &trng_fops, 163 .groups = trng_dev_attr_groups, 164 }; 165 166 167 /* hwrng_register */ 168 169 static inline void _trng_hwrng_read(u8 *buf, size_t len) 170 { 171 cpacf_trng(NULL, 0, buf, len); 172 atomic64_add(len, &trng_hwrng_counter); 173 } 174 175 static int trng_hwrng_data_read(struct hwrng *rng, u32 *data) 176 { 177 size_t len = sizeof(*data); 178 179 _trng_hwrng_read((u8 *) data, len); 180 181 DEBUG_DBG("trng_hwrng_data_read()=%zu\n", len); 182 183 return len; 184 } 185 186 static int trng_hwrng_read(struct hwrng *rng, void *data, size_t max, bool wait) 187 { 188 size_t len = max <= PAGE_SIZE ? max : PAGE_SIZE; 189 190 _trng_hwrng_read((u8 *) data, len); 191 192 DEBUG_DBG("trng_hwrng_read()=%zu\n", len); 193 194 return len; 195 } 196 197 /* 198 * hwrng register struct 199 * The trng is suppost to have 100% entropy, and thus 200 * we register with a very high quality value. 201 */ 202 static struct hwrng trng_hwrng_dev = { 203 .name = "s390-trng", 204 .data_read = trng_hwrng_data_read, 205 .read = trng_hwrng_read, 206 .quality = 999, 207 }; 208 209 210 /* init and exit */ 211 212 static void __init trng_debug_init(void) 213 { 214 debug_info = debug_register("trng", 1, 1, 4 * sizeof(long)); 215 debug_register_view(debug_info, &debug_sprintf_view); 216 debug_set_level(debug_info, 3); 217 } 218 219 static void trng_debug_exit(void) 220 { 221 debug_unregister(debug_info); 222 } 223 224 static int __init trng_init(void) 225 { 226 int ret; 227 228 trng_debug_init(); 229 230 /* check if subfunction CPACF_PRNO_TRNG is available */ 231 if (!cpacf_query_func(CPACF_PRNO, CPACF_PRNO_TRNG)) { 232 DEBUG_INFO("trng_init CPACF_PRNO_TRNG not available\n"); 233 ret = -ENODEV; 234 goto out_dbg; 235 } 236 237 ret = misc_register(&trng_dev); 238 if (ret) { 239 DEBUG_WARN("trng_init misc_register() failed rc=%d\n", ret); 240 goto out_dbg; 241 } 242 243 ret = hwrng_register(&trng_hwrng_dev); 244 if (ret) { 245 DEBUG_WARN("trng_init hwrng_register() failed rc=%d\n", ret); 246 goto out_misc; 247 } 248 249 DEBUG_DBG("trng_init successful\n"); 250 251 return 0; 252 253 out_misc: 254 misc_deregister(&trng_dev); 255 out_dbg: 256 trng_debug_exit(); 257 return ret; 258 } 259 260 static void __exit trng_exit(void) 261 { 262 hwrng_unregister(&trng_hwrng_dev); 263 misc_deregister(&trng_dev); 264 trng_debug_exit(); 265 } 266 267 module_cpu_feature_match(MSA, trng_init); 268 module_exit(trng_exit); 269