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 u64 arch_counter = atomic64_read(&s390_arch_random_counter); 112 113 return sysfs_emit(buf, 114 "trng: %llu\n" 115 "hwrng: %llu\n" 116 "arch: %llu\n" 117 "total: %llu\n", 118 dev_counter, hwrng_counter, arch_counter, 119 dev_counter + hwrng_counter + arch_counter); 120 } 121 static DEVICE_ATTR(byte_counter, 0444, trng_counter_show, NULL); 122 123 static struct attribute *trng_dev_attrs[] = { 124 &dev_attr_byte_counter.attr, 125 NULL 126 }; 127 128 static const struct attribute_group trng_dev_attr_group = { 129 .attrs = trng_dev_attrs 130 }; 131 132 static const struct attribute_group *trng_dev_attr_groups[] = { 133 &trng_dev_attr_group, 134 NULL 135 }; 136 137 static const struct file_operations trng_fops = { 138 .owner = THIS_MODULE, 139 .open = &trng_open, 140 .release = NULL, 141 .read = &trng_read, 142 .llseek = noop_llseek, 143 }; 144 145 static struct miscdevice trng_dev = { 146 .name = "trng", 147 .minor = MISC_DYNAMIC_MINOR, 148 .mode = 0444, 149 .fops = &trng_fops, 150 .groups = trng_dev_attr_groups, 151 }; 152 153 154 /* hwrng_register */ 155 156 static inline void _trng_hwrng_read(u8 *buf, size_t len) 157 { 158 cpacf_trng(NULL, 0, buf, len); 159 atomic64_add(len, &trng_hwrng_counter); 160 } 161 162 static int trng_hwrng_data_read(struct hwrng *rng, u32 *data) 163 { 164 size_t len = sizeof(*data); 165 166 _trng_hwrng_read((u8 *) data, len); 167 168 DEBUG_DBG("trng_hwrng_data_read()=%zu\n", len); 169 170 return len; 171 } 172 173 static int trng_hwrng_read(struct hwrng *rng, void *data, size_t max, bool wait) 174 { 175 size_t len = max <= PAGE_SIZE ? max : PAGE_SIZE; 176 177 _trng_hwrng_read((u8 *) data, len); 178 179 DEBUG_DBG("trng_hwrng_read()=%zu\n", len); 180 181 return len; 182 } 183 184 /* 185 * hwrng register struct 186 * The trng is supposed to have 100% entropy, and thus we register with a very 187 * high quality value. If we ever have a better driver in the future, we should 188 * change this value again when we merge this driver. 189 */ 190 static struct hwrng trng_hwrng_dev = { 191 .name = "s390-trng", 192 .data_read = trng_hwrng_data_read, 193 .read = trng_hwrng_read, 194 .quality = 1024, 195 }; 196 197 198 /* init and exit */ 199 200 static void __init trng_debug_init(void) 201 { 202 debug_info = debug_register("trng", 1, 1, 4 * sizeof(long)); 203 debug_register_view(debug_info, &debug_sprintf_view); 204 debug_set_level(debug_info, 3); 205 } 206 207 static void trng_debug_exit(void) 208 { 209 debug_unregister(debug_info); 210 } 211 212 static int __init trng_init(void) 213 { 214 int ret; 215 216 trng_debug_init(); 217 218 /* check if subfunction CPACF_PRNO_TRNG is available */ 219 if (!cpacf_query_func(CPACF_PRNO, CPACF_PRNO_TRNG)) { 220 DEBUG_INFO("trng_init CPACF_PRNO_TRNG not available\n"); 221 ret = -ENODEV; 222 goto out_dbg; 223 } 224 225 ret = misc_register(&trng_dev); 226 if (ret) { 227 DEBUG_WARN("trng_init misc_register() failed rc=%d\n", ret); 228 goto out_dbg; 229 } 230 231 ret = hwrng_register(&trng_hwrng_dev); 232 if (ret) { 233 DEBUG_WARN("trng_init hwrng_register() failed rc=%d\n", ret); 234 goto out_misc; 235 } 236 237 DEBUG_DBG("trng_init successful\n"); 238 239 return 0; 240 241 out_misc: 242 misc_deregister(&trng_dev); 243 out_dbg: 244 trng_debug_exit(); 245 return ret; 246 } 247 248 static void __exit trng_exit(void) 249 { 250 hwrng_unregister(&trng_hwrng_dev); 251 misc_deregister(&trng_dev); 252 trng_debug_exit(); 253 } 254 255 module_cpu_feature_match(S390_CPU_FEATURE_MSA, trng_init); 256 module_exit(trng_exit); 257