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1// SPDX-License-Identifier: GPL-2.0-only2/*3 * s390 TRNG device driver4 *5 * Driver for the TRNG (true random number generation) command6 * available via CPACF extension MSA 7 on the s390 arch.7 8 * Copyright IBM Corp. 20179 * Author(s): Harald Freudenberger <freude@de.ibm.com>10 */11 12#define KMSG_COMPONENT "trng"13#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt14 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#include <asm/archrandom.h>27 28MODULE_LICENSE("GPL v2");29MODULE_AUTHOR("IBM Corporation");30MODULE_DESCRIPTION("s390 CPACF TRNG device driver");31 32 33/* trng related debug feature things */34 35static debug_info_t *debug_info;36 37#define DEBUG_DBG(...) debug_sprintf_event(debug_info, 6, ##__VA_ARGS__)38#define DEBUG_INFO(...) debug_sprintf_event(debug_info, 5, ##__VA_ARGS__)39#define DEBUG_WARN(...) debug_sprintf_event(debug_info, 4, ##__VA_ARGS__)40#define DEBUG_ERR(...) debug_sprintf_event(debug_info, 3, ##__VA_ARGS__)41 42 43/* trng helpers */44 45static atomic64_t trng_dev_counter = ATOMIC64_INIT(0);46static atomic64_t trng_hwrng_counter = ATOMIC64_INIT(0);47 48 49/* file io functions */50 51static int trng_open(struct inode *inode, struct file *file)52{53 return nonseekable_open(inode, file);54}55 56static ssize_t trng_read(struct file *file, char __user *ubuf,57 size_t nbytes, loff_t *ppos)58{59 u8 buf[32];60 u8 *p = buf;61 unsigned int n;62 ssize_t ret = 0;63 64 /*65 * use buf for requests <= sizeof(buf),66 * otherwise allocate one page and fetch67 * pagewise.68 */69 70 if (nbytes > sizeof(buf)) {71 p = (u8 *) __get_free_page(GFP_KERNEL);72 if (!p)73 return -ENOMEM;74 }75 76 while (nbytes) {77 if (need_resched()) {78 if (signal_pending(current)) {79 if (ret == 0)80 ret = -ERESTARTSYS;81 break;82 }83 schedule();84 }85 n = nbytes > PAGE_SIZE ? PAGE_SIZE : nbytes;86 cpacf_trng(NULL, 0, p, n);87 atomic64_add(n, &trng_dev_counter);88 if (copy_to_user(ubuf, p, n)) {89 ret = -EFAULT;90 break;91 }92 nbytes -= n;93 ubuf += n;94 ret += n;95 }96 97 if (p != buf)98 free_page((unsigned long) p);99 100 DEBUG_DBG("trng_read()=%zd\n", ret);101 return ret;102}103 104 105/* sysfs */106 107static ssize_t trng_counter_show(struct device *dev,108 struct device_attribute *attr, char *buf)109{110 u64 dev_counter = atomic64_read(&trng_dev_counter);111 u64 hwrng_counter = atomic64_read(&trng_hwrng_counter);112 u64 arch_counter = atomic64_read(&s390_arch_random_counter);113 114 return sysfs_emit(buf,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}122static DEVICE_ATTR(byte_counter, 0444, trng_counter_show, NULL);123 124static struct attribute *trng_dev_attrs[] = {125 &dev_attr_byte_counter.attr,126 NULL127};128 129static const struct attribute_group trng_dev_attr_group = {130 .attrs = trng_dev_attrs131};132 133static const struct attribute_group *trng_dev_attr_groups[] = {134 &trng_dev_attr_group,135 NULL136};137 138static const struct file_operations trng_fops = {139 .owner = THIS_MODULE,140 .open = &trng_open,141 .release = NULL,142 .read = &trng_read,143 .llseek = noop_llseek,144};145 146static struct miscdevice trng_dev = {147 .name = "trng",148 .minor = MISC_DYNAMIC_MINOR,149 .mode = 0444,150 .fops = &trng_fops,151 .groups = trng_dev_attr_groups,152};153 154 155/* hwrng_register */156 157static inline void _trng_hwrng_read(u8 *buf, size_t len)158{159 cpacf_trng(NULL, 0, buf, len);160 atomic64_add(len, &trng_hwrng_counter);161}162 163static int trng_hwrng_data_read(struct hwrng *rng, u32 *data)164{165 size_t len = sizeof(*data);166 167 _trng_hwrng_read((u8 *) data, len);168 169 DEBUG_DBG("trng_hwrng_data_read()=%zu\n", len);170 171 return len;172}173 174static int trng_hwrng_read(struct hwrng *rng, void *data, size_t max, bool wait)175{176 size_t len = max <= PAGE_SIZE ? max : PAGE_SIZE;177 178 _trng_hwrng_read((u8 *) data, len);179 180 DEBUG_DBG("trng_hwrng_read()=%zu\n", len);181 182 return len;183}184 185/*186 * hwrng register struct187 * The trng is supposed to have 100% entropy, and thus we register with a very188 * high quality value. If we ever have a better driver in the future, we should189 * change this value again when we merge this driver.190 */191static struct hwrng trng_hwrng_dev = {192 .name = "s390-trng",193 .data_read = trng_hwrng_data_read,194 .read = trng_hwrng_read,195};196 197 198/* init and exit */199 200static 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 207static void trng_debug_exit(void)208{209 debug_unregister(debug_info);210}211 212static 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 241out_misc:242 misc_deregister(&trng_dev);243out_dbg:244 trng_debug_exit();245 return ret;246}247 248static void __exit trng_exit(void)249{250 hwrng_unregister(&trng_hwrng_dev);251 misc_deregister(&trng_dev);252 trng_debug_exit();253}254 255module_cpu_feature_match(S390_CPU_FEATURE_MSA, trng_init);256module_exit(trng_exit);257