1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * s390 TRNG device driver 4 * 5 * Driver for the TRNG (true random number generation) command 6 * available via CPACF extension MSA 7 on the s390 arch. 7 8 * Copyright IBM Corp. 2017 9 * Author(s): Harald Freudenberger <freude@de.ibm.com> 10 */ 11 12 #define KMSG_COMPONENT "trng" 13 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt 14 15 #include <linux/hw_random.h> 16 #include <linux/kernel.h> 17 #include <linux/module.h> 18 #include <linux/cpufeature.h> 19 #include <linux/miscdevice.h> 20 #include <linux/debugfs.h> 21 #include <linux/atomic.h> 22 #include <linux/random.h> 23 #include <linux/sched/signal.h> 24 #include <asm/debug.h> 25 #include <asm/cpacf.h> 26 27 MODULE_LICENSE("GPL v2"); 28 MODULE_AUTHOR("IBM Corporation"); 29 MODULE_DESCRIPTION("s390 CPACF TRNG device driver"); 30 31 32 /* trng related debug feature things */ 33 34 static debug_info_t *debug_info; 35 36 #define DEBUG_DBG(...) debug_sprintf_event(debug_info, 6, ##__VA_ARGS__) 37 #define DEBUG_INFO(...) debug_sprintf_event(debug_info, 5, ##__VA_ARGS__) 38 #define DEBUG_WARN(...) debug_sprintf_event(debug_info, 4, ##__VA_ARGS__) 39 #define DEBUG_ERR(...) debug_sprintf_event(debug_info, 3, ##__VA_ARGS__) 40 41 42 /* trng helpers */ 43 44 static atomic64_t trng_dev_counter = ATOMIC64_INIT(0); 45 static atomic64_t trng_hwrng_counter = ATOMIC64_INIT(0); 46 47 48 /* file io functions */ 49 50 static int trng_open(struct inode *inode, struct file *file) 51 { 52 return nonseekable_open(inode, file); 53 } 54 55 static ssize_t trng_read(struct file *file, char __user *ubuf, 56 size_t nbytes, loff_t *ppos) 57 { 58 u8 buf[32]; 59 u8 *p = buf; 60 unsigned int n; 61 ssize_t ret = 0; 62 63 /* 64 * use buf for requests <= sizeof(buf), 65 * otherwise allocate one page and fetch 66 * pagewise. 67 */ 68 69 if (nbytes > sizeof(buf)) { 70 p = (u8 *) __get_free_page(GFP_KERNEL); 71 if (!p) 72 return -ENOMEM; 73 } 74 75 while (nbytes) { 76 if (need_resched()) { 77 if (signal_pending(current)) { 78 if (ret == 0) 79 ret = -ERESTARTSYS; 80 break; 81 } 82 schedule(); 83 } 84 n = nbytes > PAGE_SIZE ? PAGE_SIZE : nbytes; 85 cpacf_trng(NULL, 0, p, n); 86 atomic64_add(n, &trng_dev_counter); 87 if (copy_to_user(ubuf, p, n)) { 88 ret = -EFAULT; 89 break; 90 } 91 nbytes -= n; 92 ubuf += n; 93 ret += n; 94 } 95 96 if (p != buf) 97 free_page((unsigned long) p); 98 99 DEBUG_DBG("trng_read()=%zd\n", ret); 100 return ret; 101 } 102 103 104 /* sysfs */ 105 106 static ssize_t trng_counter_show(struct device *dev, 107 struct device_attribute *attr, char *buf) 108 { 109 u64 dev_counter = atomic64_read(&trng_dev_counter); 110 u64 hwrng_counter = atomic64_read(&trng_hwrng_counter); 111 #if IS_ENABLED(CONFIG_ARCH_RANDOM) 112 u64 arch_counter = atomic64_read(&s390_arch_random_counter); 113 114 return snprintf(buf, PAGE_SIZE, 115 "trng: %llu\n" 116 "hwrng: %llu\n" 117 "arch: %llu\n" 118 "total: %llu\n", 119 dev_counter, hwrng_counter, arch_counter, 120 dev_counter + hwrng_counter + arch_counter); 121 #else 122 return snprintf(buf, PAGE_SIZE, 123 "trng: %llu\n" 124 "hwrng: %llu\n" 125 "total: %llu\n", 126 dev_counter, hwrng_counter, 127 dev_counter + hwrng_counter); 128 #endif 129 } 130 static DEVICE_ATTR(byte_counter, 0444, trng_counter_show, NULL); 131 132 static struct attribute *trng_dev_attrs[] = { 133 &dev_attr_byte_counter.attr, 134 NULL 135 }; 136 137 static const struct attribute_group trng_dev_attr_group = { 138 .attrs = trng_dev_attrs 139 }; 140 141 static const struct attribute_group *trng_dev_attr_groups[] = { 142 &trng_dev_attr_group, 143 NULL 144 }; 145 146 static const struct file_operations trng_fops = { 147 .owner = THIS_MODULE, 148 .open = &trng_open, 149 .release = NULL, 150 .read = &trng_read, 151 .llseek = noop_llseek, 152 }; 153 154 static struct miscdevice trng_dev = { 155 .name = "trng", 156 .minor = MISC_DYNAMIC_MINOR, 157 .mode = 0444, 158 .fops = &trng_fops, 159 .groups = trng_dev_attr_groups, 160 }; 161 162 163 /* hwrng_register */ 164 165 static inline void _trng_hwrng_read(u8 *buf, size_t len) 166 { 167 cpacf_trng(NULL, 0, buf, len); 168 atomic64_add(len, &trng_hwrng_counter); 169 } 170 171 static int trng_hwrng_data_read(struct hwrng *rng, u32 *data) 172 { 173 size_t len = sizeof(*data); 174 175 _trng_hwrng_read((u8 *) data, len); 176 177 DEBUG_DBG("trng_hwrng_data_read()=%zu\n", len); 178 179 return len; 180 } 181 182 static int trng_hwrng_read(struct hwrng *rng, void *data, size_t max, bool wait) 183 { 184 size_t len = max <= PAGE_SIZE ? max : PAGE_SIZE; 185 186 _trng_hwrng_read((u8 *) data, len); 187 188 DEBUG_DBG("trng_hwrng_read()=%zu\n", len); 189 190 return len; 191 } 192 193 /* 194 * hwrng register struct 195 * The trng is suppost to have 100% entropy, and thus 196 * we register with a very high quality value. 197 */ 198 static struct hwrng trng_hwrng_dev = { 199 .name = "s390-trng", 200 .data_read = trng_hwrng_data_read, 201 .read = trng_hwrng_read, 202 .quality = 999, 203 }; 204 205 206 /* init and exit */ 207 208 static void __init trng_debug_init(void) 209 { 210 debug_info = debug_register("trng", 1, 1, 4 * sizeof(long)); 211 debug_register_view(debug_info, &debug_sprintf_view); 212 debug_set_level(debug_info, 3); 213 } 214 215 static void trng_debug_exit(void) 216 { 217 debug_unregister(debug_info); 218 } 219 220 static int __init trng_init(void) 221 { 222 int ret; 223 224 trng_debug_init(); 225 226 /* check if subfunction CPACF_PRNO_TRNG is available */ 227 if (!cpacf_query_func(CPACF_PRNO, CPACF_PRNO_TRNG)) { 228 DEBUG_INFO("trng_init CPACF_PRNO_TRNG not available\n"); 229 ret = -ENODEV; 230 goto out_dbg; 231 } 232 233 ret = misc_register(&trng_dev); 234 if (ret) { 235 DEBUG_WARN("trng_init misc_register() failed rc=%d\n", ret); 236 goto out_dbg; 237 } 238 239 ret = hwrng_register(&trng_hwrng_dev); 240 if (ret) { 241 DEBUG_WARN("trng_init hwrng_register() failed rc=%d\n", ret); 242 goto out_misc; 243 } 244 245 DEBUG_DBG("trng_init successful\n"); 246 247 return 0; 248 249 out_misc: 250 misc_deregister(&trng_dev); 251 out_dbg: 252 trng_debug_exit(); 253 return ret; 254 } 255 256 static void __exit trng_exit(void) 257 { 258 hwrng_unregister(&trng_hwrng_dev); 259 misc_deregister(&trng_dev); 260 trng_debug_exit(); 261 } 262 263 module_cpu_feature_match(MSA, trng_init); 264 module_exit(trng_exit); 265