--- /dev/null
+/* SPDX-License-Identifier: GPL-2.0 OR BSD-2-Clause */
+/*
+ * Test interface for Jitter RNG.
+ *
+ * Copyright (C) 2023, Stephan Mueller <smueller@chronox.de>
+ */
+
+#include <linux/debugfs.h>
+#include <linux/module.h>
+#include <linux/uaccess.h>
+
+#include "jitterentropy.h"
+
+#define JENT_TEST_RINGBUFFER_SIZE (1<<10)
+#define JENT_TEST_RINGBUFFER_MASK (JENT_TEST_RINGBUFFER_SIZE - 1)
+
+struct jent_testing {
+ u32 jent_testing_rb[JENT_TEST_RINGBUFFER_SIZE];
+ u32 rb_reader;
+ atomic_t rb_writer;
+ atomic_t jent_testing_enabled;
+ spinlock_t lock;
+ wait_queue_head_t read_wait;
+};
+
+static struct dentry *jent_raw_debugfs_root = NULL;
+
+/*************************** Generic Data Handling ****************************/
+
+/*
+ * boot variable:
+ * 0 ==> No boot test, gathering of runtime data allowed
+ * 1 ==> Boot test enabled and ready for collecting data, gathering runtime
+ * data is disabled
+ * 2 ==> Boot test completed and disabled, gathering of runtime data is
+ * disabled
+ */
+
+static void jent_testing_reset(struct jent_testing *data)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&data->lock, flags);
+ data->rb_reader = 0;
+ atomic_set(&data->rb_writer, 0);
+ spin_unlock_irqrestore(&data->lock, flags);
+}
+
+static void jent_testing_data_init(struct jent_testing *data, u32 boot)
+{
+ /*
+ * The boot time testing implies we have a running test. If the
+ * caller wants to clear it, he has to unset the boot_test flag
+ * at runtime via sysfs to enable regular runtime testing
+ */
+ if (boot)
+ return;
+
+ jent_testing_reset(data);
+ atomic_set(&data->jent_testing_enabled, 1);
+ pr_warn("Enabling data collection\n");
+}
+
+static void jent_testing_fini(struct jent_testing *data, u32 boot)
+{
+ /* If we have boot data, we do not reset yet to allow data to be read */
+ if (boot)
+ return;
+
+ atomic_set(&data->jent_testing_enabled, 0);
+ jent_testing_reset(data);
+ pr_warn("Disabling data collection\n");
+}
+
+static bool jent_testing_store(struct jent_testing *data, u32 value,
+ u32 *boot)
+{
+ unsigned long flags;
+
+ if (!atomic_read(&data->jent_testing_enabled) && (*boot != 1))
+ return false;
+
+ spin_lock_irqsave(&data->lock, flags);
+
+ /*
+ * Disable entropy testing for boot time testing after ring buffer
+ * is filled.
+ */
+ if (*boot) {
+ if (((u32)atomic_read(&data->rb_writer)) >
+ JENT_TEST_RINGBUFFER_SIZE) {
+ *boot = 2;
+ pr_warn_once("One time data collection test disabled\n");
+ spin_unlock_irqrestore(&data->lock, flags);
+ return false;
+ }
+
+ if (atomic_read(&data->rb_writer) == 1)
+ pr_warn("One time data collection test enabled\n");
+ }
+
+ data->jent_testing_rb[((u32)atomic_read(&data->rb_writer)) &
+ JENT_TEST_RINGBUFFER_MASK] = value;
+ atomic_inc(&data->rb_writer);
+
+ spin_unlock_irqrestore(&data->lock, flags);
+
+ if (wq_has_sleeper(&data->read_wait))
+ wake_up_interruptible(&data->read_wait);
+
+ return true;
+}
+
+static bool jent_testing_have_data(struct jent_testing *data)
+{
+ return ((((u32)atomic_read(&data->rb_writer)) &
+ JENT_TEST_RINGBUFFER_MASK) !=
+ (data->rb_reader & JENT_TEST_RINGBUFFER_MASK));
+}
+
+static int jent_testing_reader(struct jent_testing *data, u32 *boot,
+ u8 *outbuf, u32 outbuflen)
+{
+ unsigned long flags;
+ int collected_data = 0;
+
+ jent_testing_data_init(data, *boot);
+
+ while (outbuflen) {
+ u32 writer = (u32)atomic_read(&data->rb_writer);
+
+ spin_lock_irqsave(&data->lock, flags);
+
+ /* We have no data or reached the writer. */
+ if (!writer || (writer == data->rb_reader)) {
+
+ spin_unlock_irqrestore(&data->lock, flags);
+
+ /*
+ * Now we gathered all boot data, enable regular data
+ * collection.
+ */
+ if (*boot) {
+ *boot = 0;
+ goto out;
+ }
+
+ wait_event_interruptible(data->read_wait,
+ jent_testing_have_data(data));
+ if (signal_pending(current)) {
+ collected_data = -ERESTARTSYS;
+ goto out;
+ }
+
+ continue;
+ }
+
+ /* We copy out word-wise */
+ if (outbuflen < sizeof(u32)) {
+ spin_unlock_irqrestore(&data->lock, flags);
+ goto out;
+ }
+
+ memcpy(outbuf, &data->jent_testing_rb[data->rb_reader],
+ sizeof(u32));
+ data->rb_reader++;
+
+ spin_unlock_irqrestore(&data->lock, flags);
+
+ outbuf += sizeof(u32);
+ outbuflen -= sizeof(u32);
+ collected_data += sizeof(u32);
+ }
+
+out:
+ jent_testing_fini(data, *boot);
+ return collected_data;
+}
+
+static int jent_testing_extract_user(struct file *file, char __user *buf,
+ size_t nbytes, loff_t *ppos,
+ int (*reader)(u8 *outbuf, u32 outbuflen))
+{
+ u8 *tmp, *tmp_aligned;
+ int ret = 0, large_request = (nbytes > 256);
+
+ if (!nbytes)
+ return 0;
+
+ /*
+ * The intention of this interface is for collecting at least
+ * 1000 samples due to the SP800-90B requirements. So, we make no
+ * effort in avoiding allocating more memory that actually needed
+ * by the user. Hence, we allocate sufficient memory to always hold
+ * that amount of data.
+ */
+ tmp = kmalloc(JENT_TEST_RINGBUFFER_SIZE + sizeof(u32), GFP_KERNEL);
+ if (!tmp)
+ return -ENOMEM;
+
+ tmp_aligned = PTR_ALIGN(tmp, sizeof(u32));
+
+ while (nbytes) {
+ int i;
+
+ if (large_request && need_resched()) {
+ if (signal_pending(current)) {
+ if (ret == 0)
+ ret = -ERESTARTSYS;
+ break;
+ }
+ schedule();
+ }
+
+ i = min_t(int, nbytes, JENT_TEST_RINGBUFFER_SIZE);
+ i = reader(tmp_aligned, i);
+ if (i <= 0) {
+ if (i < 0)
+ ret = i;
+ break;
+ }
+ if (copy_to_user(buf, tmp_aligned, i)) {
+ ret = -EFAULT;
+ break;
+ }
+
+ nbytes -= i;
+ buf += i;
+ ret += i;
+ }
+
+ kfree_sensitive(tmp);
+
+ if (ret > 0)
+ *ppos += ret;
+
+ return ret;
+}
+
+/************** Raw High-Resolution Timer Entropy Data Handling **************/
+
+static u32 boot_raw_hires_test = 0;
+module_param(boot_raw_hires_test, uint, 0644);
+MODULE_PARM_DESC(boot_raw_hires_test,
+ "Enable gathering boot time high resolution timer entropy of the first Jitter RNG entropy events");
+
+static struct jent_testing jent_raw_hires = {
+ .rb_reader = 0,
+ .rb_writer = ATOMIC_INIT(0),
+ .lock = __SPIN_LOCK_UNLOCKED(jent_raw_hires.lock),
+ .read_wait = __WAIT_QUEUE_HEAD_INITIALIZER(jent_raw_hires.read_wait)
+};
+
+int jent_raw_hires_entropy_store(__u32 value)
+{
+ return jent_testing_store(&jent_raw_hires, value, &boot_raw_hires_test);
+}
+EXPORT_SYMBOL(jent_raw_hires_entropy_store);
+
+static int jent_raw_hires_entropy_reader(u8 *outbuf, u32 outbuflen)
+{
+ return jent_testing_reader(&jent_raw_hires, &boot_raw_hires_test,
+ outbuf, outbuflen);
+}
+
+static ssize_t jent_raw_hires_read(struct file *file, char __user *to,
+ size_t count, loff_t *ppos)
+{
+ return jent_testing_extract_user(file, to, count, ppos,
+ jent_raw_hires_entropy_reader);
+}
+
+static const struct file_operations jent_raw_hires_fops = {
+ .owner = THIS_MODULE,
+ .read = jent_raw_hires_read,
+};
+
+/******************************* Initialization *******************************/
+
+void jent_testing_init(void)
+{
+ jent_raw_debugfs_root = debugfs_create_dir(KBUILD_MODNAME, NULL);
+
+ debugfs_create_file_unsafe("jent_raw_hires", 0400,
+ jent_raw_debugfs_root, NULL,
+ &jent_raw_hires_fops);
+}
+EXPORT_SYMBOL(jent_testing_init);
+
+void jent_testing_exit(void)
+{
+ debugfs_remove_recursive(jent_raw_debugfs_root);
+}
+EXPORT_SYMBOL(jent_testing_exit);
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