--- /dev/null
+/*
+ * s390 TRNG device driver
+ *
+ * Driver for the TRNG (true random number generation) command
+ * available via CPACF extension MSA 7 on the s390 arch.
+
+ * Copyright IBM Corp. 2017
+ * Author(s): Harald Freudenberger <freude@de.ibm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License (version 2 only)
+ * as published by the Free Software Foundation.
+ *
+ */
+
+#define KMSG_COMPONENT "trng"
+#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
+
+#include <linux/hw_random.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/cpufeature.h>
+#include <linux/miscdevice.h>
+#include <linux/debugfs.h>
+#include <linux/atomic.h>
+#include <linux/random.h>
+#include <linux/sched/signal.h>
+#include <asm/debug.h>
+#include <asm/cpacf.h>
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("IBM Corporation");
+MODULE_DESCRIPTION("s390 CPACF TRNG device driver");
+
+
+/* trng related debug feature things */
+
+static debug_info_t *debug_info;
+
+#define DEBUG_DBG(...) debug_sprintf_event(debug_info, 6, ##__VA_ARGS__)
+#define DEBUG_INFO(...) debug_sprintf_event(debug_info, 5, ##__VA_ARGS__)
+#define DEBUG_WARN(...) debug_sprintf_event(debug_info, 4, ##__VA_ARGS__)
+#define DEBUG_ERR(...) debug_sprintf_event(debug_info, 3, ##__VA_ARGS__)
+
+
+/* trng helpers */
+
+static atomic64_t trng_dev_counter = ATOMIC64_INIT(0);
+static atomic64_t trng_hwrng_counter = ATOMIC64_INIT(0);
+
+
+/* file io functions */
+
+static int trng_open(struct inode *inode, struct file *file)
+{
+ return nonseekable_open(inode, file);
+}
+
+static ssize_t trng_read(struct file *file, char __user *ubuf,
+ size_t nbytes, loff_t *ppos)
+{
+ u8 buf[32];
+ u8 *p = buf;
+ unsigned int n;
+ ssize_t ret = 0;
+
+ /*
+ * use buf for requests <= sizeof(buf),
+ * otherwise allocate one page and fetch
+ * pagewise.
+ */
+
+ if (nbytes > sizeof(buf)) {
+ p = (u8 *) __get_free_page(GFP_KERNEL);
+ if (!p)
+ return -ENOMEM;
+ }
+
+ while (nbytes) {
+ if (need_resched()) {
+ if (signal_pending(current)) {
+ if (ret == 0)
+ ret = -ERESTARTSYS;
+ break;
+ }
+ schedule();
+ }
+ n = nbytes > PAGE_SIZE ? PAGE_SIZE : nbytes;
+ cpacf_trng(NULL, 0, p, n);
+ atomic64_add(n, &trng_dev_counter);
+ if (copy_to_user(ubuf, p, n)) {
+ ret = -EFAULT;
+ break;
+ }
+ nbytes -= n;
+ ubuf += n;
+ ret += n;
+ }
+
+ if (p != buf)
+ free_page((unsigned long) p);
+
+ DEBUG_DBG("trng_read()=%zd\n", ret);
+ return ret;
+}
+
+
+/* sysfs */
+
+static ssize_t trng_counter_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ u64 dev_counter = atomic64_read(&trng_dev_counter);
+ u64 hwrng_counter = atomic64_read(&trng_hwrng_counter);
+#if IS_ENABLED(CONFIG_ARCH_RANDOM)
+ u64 arch_counter = atomic64_read(&s390_arch_random_counter);
+
+ return snprintf(buf, PAGE_SIZE,
+ "trng: %llu\n"
+ "hwrng: %llu\n"
+ "arch: %llu\n"
+ "total: %llu\n",
+ dev_counter, hwrng_counter, arch_counter,
+ dev_counter + hwrng_counter + arch_counter);
+#else
+ return snprintf(buf, PAGE_SIZE,
+ "trng: %llu\n"
+ "hwrng: %llu\n"
+ "total: %llu\n",
+ dev_counter, hwrng_counter,
+ dev_counter + hwrng_counter);
+#endif
+}
+static DEVICE_ATTR(byte_counter, 0444, trng_counter_show, NULL);
+
+static struct attribute *trng_dev_attrs[] = {
+ &dev_attr_byte_counter.attr,
+ NULL
+};
+
+static const struct attribute_group trng_dev_attr_group = {
+ .attrs = trng_dev_attrs
+};
+
+static const struct attribute_group *trng_dev_attr_groups[] = {
+ &trng_dev_attr_group,
+ NULL
+};
+
+static const struct file_operations trng_fops = {
+ .owner = THIS_MODULE,
+ .open = &trng_open,
+ .release = NULL,
+ .read = &trng_read,
+ .llseek = noop_llseek,
+};
+
+static struct miscdevice trng_dev = {
+ .name = "trng",
+ .minor = MISC_DYNAMIC_MINOR,
+ .mode = 0444,
+ .fops = &trng_fops,
+ .groups = trng_dev_attr_groups,
+};
+
+
+/* hwrng_register */
+
+static inline void _trng_hwrng_read(u8 *buf, size_t len)
+{
+ cpacf_trng(NULL, 0, buf, len);
+ atomic64_add(len, &trng_hwrng_counter);
+}
+
+static int trng_hwrng_data_read(struct hwrng *rng, u32 *data)
+{
+ size_t len = sizeof(*data);
+
+ _trng_hwrng_read((u8 *) data, len);
+
+ DEBUG_DBG("trng_hwrng_data_read()=%zu\n", len);
+
+ return len;
+}
+
+static int trng_hwrng_read(struct hwrng *rng, void *data, size_t max, bool wait)
+{
+ size_t len = max <= PAGE_SIZE ? max : PAGE_SIZE;
+
+ _trng_hwrng_read((u8 *) data, len);
+
+ DEBUG_DBG("trng_hwrng_read()=%zu\n", len);
+
+ return len;
+}
+
+/*
+ * hwrng register struct
+ * The trng is suppost to have 100% entropy, and thus
+ * we register with a very high quality value.
+ */
+static struct hwrng trng_hwrng_dev = {
+ .name = "s390-trng",
+ .data_read = trng_hwrng_data_read,
+ .read = trng_hwrng_read,
+ .quality = 999,
+};
+
+
+/* init and exit */
+
+static void __init trng_debug_init(void)
+{
+ debug_info = debug_register("trng", 1, 1, 4 * sizeof(long));
+ debug_register_view(debug_info, &debug_sprintf_view);
+ debug_set_level(debug_info, 3);
+}
+
+static void trng_debug_exit(void)
+{
+ debug_unregister(debug_info);
+}
+
+static int __init trng_init(void)
+{
+ int ret;
+
+ trng_debug_init();
+
+ /* check if subfunction CPACF_PRNO_TRNG is available */
+ if (!cpacf_query_func(CPACF_PRNO, CPACF_PRNO_TRNG)) {
+ DEBUG_INFO("trng_init CPACF_PRNO_TRNG not available\n");
+ ret = -ENODEV;
+ goto out_dbg;
+ }
+
+ ret = misc_register(&trng_dev);
+ if (ret) {
+ DEBUG_WARN("trng_init misc_register() failed rc=%d\n", ret);
+ goto out_dbg;
+ }
+
+ ret = hwrng_register(&trng_hwrng_dev);
+ if (ret) {
+ DEBUG_WARN("trng_init hwrng_register() failed rc=%d\n", ret);
+ goto out_misc;
+ }
+
+ DEBUG_DBG("trng_init successful\n");
+
+ return 0;
+
+out_misc:
+ misc_deregister(&trng_dev);
+out_dbg:
+ trng_debug_exit();
+ return ret;
+}
+
+static void __exit trng_exit(void)
+{
+ hwrng_unregister(&trng_hwrng_dev);
+ misc_deregister(&trng_dev);
+ trng_debug_exit();
+}
+
+module_cpu_feature_match(MSA, trng_init);
+module_exit(trng_exit);
projects / karo-tx-linux.git / commitdiff