Stephan Müller | 69f1c38 | 2023-04-21 08:08:23 +0200 | [diff] [blame] | 1 | /* SPDX-License-Identifier: GPL-2.0 OR BSD-2-Clause */ |
| 2 | /* |
| 3 | * Test interface for Jitter RNG. |
| 4 | * |
| 5 | * Copyright (C) 2023, Stephan Mueller <smueller@chronox.de> |
| 6 | */ |
| 7 | |
| 8 | #include <linux/debugfs.h> |
| 9 | #include <linux/module.h> |
| 10 | #include <linux/uaccess.h> |
| 11 | |
| 12 | #include "jitterentropy.h" |
| 13 | |
| 14 | #define JENT_TEST_RINGBUFFER_SIZE (1<<10) |
| 15 | #define JENT_TEST_RINGBUFFER_MASK (JENT_TEST_RINGBUFFER_SIZE - 1) |
| 16 | |
| 17 | struct jent_testing { |
| 18 | u32 jent_testing_rb[JENT_TEST_RINGBUFFER_SIZE]; |
| 19 | u32 rb_reader; |
| 20 | atomic_t rb_writer; |
| 21 | atomic_t jent_testing_enabled; |
| 22 | spinlock_t lock; |
| 23 | wait_queue_head_t read_wait; |
| 24 | }; |
| 25 | |
| 26 | static struct dentry *jent_raw_debugfs_root = NULL; |
| 27 | |
| 28 | /*************************** Generic Data Handling ****************************/ |
| 29 | |
| 30 | /* |
| 31 | * boot variable: |
| 32 | * 0 ==> No boot test, gathering of runtime data allowed |
| 33 | * 1 ==> Boot test enabled and ready for collecting data, gathering runtime |
| 34 | * data is disabled |
| 35 | * 2 ==> Boot test completed and disabled, gathering of runtime data is |
| 36 | * disabled |
| 37 | */ |
| 38 | |
| 39 | static void jent_testing_reset(struct jent_testing *data) |
| 40 | { |
| 41 | unsigned long flags; |
| 42 | |
| 43 | spin_lock_irqsave(&data->lock, flags); |
| 44 | data->rb_reader = 0; |
| 45 | atomic_set(&data->rb_writer, 0); |
| 46 | spin_unlock_irqrestore(&data->lock, flags); |
| 47 | } |
| 48 | |
| 49 | static void jent_testing_data_init(struct jent_testing *data, u32 boot) |
| 50 | { |
| 51 | /* |
| 52 | * The boot time testing implies we have a running test. If the |
| 53 | * caller wants to clear it, he has to unset the boot_test flag |
| 54 | * at runtime via sysfs to enable regular runtime testing |
| 55 | */ |
| 56 | if (boot) |
| 57 | return; |
| 58 | |
| 59 | jent_testing_reset(data); |
| 60 | atomic_set(&data->jent_testing_enabled, 1); |
| 61 | pr_warn("Enabling data collection\n"); |
| 62 | } |
| 63 | |
| 64 | static void jent_testing_fini(struct jent_testing *data, u32 boot) |
| 65 | { |
| 66 | /* If we have boot data, we do not reset yet to allow data to be read */ |
| 67 | if (boot) |
| 68 | return; |
| 69 | |
| 70 | atomic_set(&data->jent_testing_enabled, 0); |
| 71 | jent_testing_reset(data); |
| 72 | pr_warn("Disabling data collection\n"); |
| 73 | } |
| 74 | |
| 75 | static bool jent_testing_store(struct jent_testing *data, u32 value, |
| 76 | u32 *boot) |
| 77 | { |
| 78 | unsigned long flags; |
| 79 | |
| 80 | if (!atomic_read(&data->jent_testing_enabled) && (*boot != 1)) |
| 81 | return false; |
| 82 | |
| 83 | spin_lock_irqsave(&data->lock, flags); |
| 84 | |
| 85 | /* |
| 86 | * Disable entropy testing for boot time testing after ring buffer |
| 87 | * is filled. |
| 88 | */ |
| 89 | if (*boot) { |
| 90 | if (((u32)atomic_read(&data->rb_writer)) > |
| 91 | JENT_TEST_RINGBUFFER_SIZE) { |
| 92 | *boot = 2; |
| 93 | pr_warn_once("One time data collection test disabled\n"); |
| 94 | spin_unlock_irqrestore(&data->lock, flags); |
| 95 | return false; |
| 96 | } |
| 97 | |
| 98 | if (atomic_read(&data->rb_writer) == 1) |
| 99 | pr_warn("One time data collection test enabled\n"); |
| 100 | } |
| 101 | |
| 102 | data->jent_testing_rb[((u32)atomic_read(&data->rb_writer)) & |
| 103 | JENT_TEST_RINGBUFFER_MASK] = value; |
| 104 | atomic_inc(&data->rb_writer); |
| 105 | |
| 106 | spin_unlock_irqrestore(&data->lock, flags); |
| 107 | |
| 108 | if (wq_has_sleeper(&data->read_wait)) |
| 109 | wake_up_interruptible(&data->read_wait); |
| 110 | |
| 111 | return true; |
| 112 | } |
| 113 | |
| 114 | static bool jent_testing_have_data(struct jent_testing *data) |
| 115 | { |
| 116 | return ((((u32)atomic_read(&data->rb_writer)) & |
| 117 | JENT_TEST_RINGBUFFER_MASK) != |
| 118 | (data->rb_reader & JENT_TEST_RINGBUFFER_MASK)); |
| 119 | } |
| 120 | |
| 121 | static int jent_testing_reader(struct jent_testing *data, u32 *boot, |
| 122 | u8 *outbuf, u32 outbuflen) |
| 123 | { |
| 124 | unsigned long flags; |
| 125 | int collected_data = 0; |
| 126 | |
| 127 | jent_testing_data_init(data, *boot); |
| 128 | |
| 129 | while (outbuflen) { |
| 130 | u32 writer = (u32)atomic_read(&data->rb_writer); |
| 131 | |
| 132 | spin_lock_irqsave(&data->lock, flags); |
| 133 | |
| 134 | /* We have no data or reached the writer. */ |
| 135 | if (!writer || (writer == data->rb_reader)) { |
| 136 | |
| 137 | spin_unlock_irqrestore(&data->lock, flags); |
| 138 | |
| 139 | /* |
| 140 | * Now we gathered all boot data, enable regular data |
| 141 | * collection. |
| 142 | */ |
| 143 | if (*boot) { |
| 144 | *boot = 0; |
| 145 | goto out; |
| 146 | } |
| 147 | |
| 148 | wait_event_interruptible(data->read_wait, |
| 149 | jent_testing_have_data(data)); |
| 150 | if (signal_pending(current)) { |
| 151 | collected_data = -ERESTARTSYS; |
| 152 | goto out; |
| 153 | } |
| 154 | |
| 155 | continue; |
| 156 | } |
| 157 | |
| 158 | /* We copy out word-wise */ |
| 159 | if (outbuflen < sizeof(u32)) { |
| 160 | spin_unlock_irqrestore(&data->lock, flags); |
| 161 | goto out; |
| 162 | } |
| 163 | |
| 164 | memcpy(outbuf, &data->jent_testing_rb[data->rb_reader], |
| 165 | sizeof(u32)); |
| 166 | data->rb_reader++; |
| 167 | |
| 168 | spin_unlock_irqrestore(&data->lock, flags); |
| 169 | |
| 170 | outbuf += sizeof(u32); |
| 171 | outbuflen -= sizeof(u32); |
| 172 | collected_data += sizeof(u32); |
| 173 | } |
| 174 | |
| 175 | out: |
| 176 | jent_testing_fini(data, *boot); |
| 177 | return collected_data; |
| 178 | } |
| 179 | |
| 180 | static int jent_testing_extract_user(struct file *file, char __user *buf, |
| 181 | size_t nbytes, loff_t *ppos, |
| 182 | int (*reader)(u8 *outbuf, u32 outbuflen)) |
| 183 | { |
| 184 | u8 *tmp, *tmp_aligned; |
| 185 | int ret = 0, large_request = (nbytes > 256); |
| 186 | |
| 187 | if (!nbytes) |
| 188 | return 0; |
| 189 | |
| 190 | /* |
| 191 | * The intention of this interface is for collecting at least |
| 192 | * 1000 samples due to the SP800-90B requirements. So, we make no |
| 193 | * effort in avoiding allocating more memory that actually needed |
| 194 | * by the user. Hence, we allocate sufficient memory to always hold |
| 195 | * that amount of data. |
| 196 | */ |
| 197 | tmp = kmalloc(JENT_TEST_RINGBUFFER_SIZE + sizeof(u32), GFP_KERNEL); |
| 198 | if (!tmp) |
| 199 | return -ENOMEM; |
| 200 | |
| 201 | tmp_aligned = PTR_ALIGN(tmp, sizeof(u32)); |
| 202 | |
| 203 | while (nbytes) { |
| 204 | int i; |
| 205 | |
| 206 | if (large_request && need_resched()) { |
| 207 | if (signal_pending(current)) { |
| 208 | if (ret == 0) |
| 209 | ret = -ERESTARTSYS; |
| 210 | break; |
| 211 | } |
| 212 | schedule(); |
| 213 | } |
| 214 | |
| 215 | i = min_t(int, nbytes, JENT_TEST_RINGBUFFER_SIZE); |
| 216 | i = reader(tmp_aligned, i); |
| 217 | if (i <= 0) { |
| 218 | if (i < 0) |
| 219 | ret = i; |
| 220 | break; |
| 221 | } |
| 222 | if (copy_to_user(buf, tmp_aligned, i)) { |
| 223 | ret = -EFAULT; |
| 224 | break; |
| 225 | } |
| 226 | |
| 227 | nbytes -= i; |
| 228 | buf += i; |
| 229 | ret += i; |
| 230 | } |
| 231 | |
| 232 | kfree_sensitive(tmp); |
| 233 | |
| 234 | if (ret > 0) |
| 235 | *ppos += ret; |
| 236 | |
| 237 | return ret; |
| 238 | } |
| 239 | |
| 240 | /************** Raw High-Resolution Timer Entropy Data Handling **************/ |
| 241 | |
| 242 | static u32 boot_raw_hires_test = 0; |
| 243 | module_param(boot_raw_hires_test, uint, 0644); |
| 244 | MODULE_PARM_DESC(boot_raw_hires_test, |
| 245 | "Enable gathering boot time high resolution timer entropy of the first Jitter RNG entropy events"); |
| 246 | |
| 247 | static struct jent_testing jent_raw_hires = { |
| 248 | .rb_reader = 0, |
| 249 | .rb_writer = ATOMIC_INIT(0), |
| 250 | .lock = __SPIN_LOCK_UNLOCKED(jent_raw_hires.lock), |
| 251 | .read_wait = __WAIT_QUEUE_HEAD_INITIALIZER(jent_raw_hires.read_wait) |
| 252 | }; |
| 253 | |
| 254 | int jent_raw_hires_entropy_store(__u32 value) |
| 255 | { |
| 256 | return jent_testing_store(&jent_raw_hires, value, &boot_raw_hires_test); |
| 257 | } |
| 258 | EXPORT_SYMBOL(jent_raw_hires_entropy_store); |
| 259 | |
| 260 | static int jent_raw_hires_entropy_reader(u8 *outbuf, u32 outbuflen) |
| 261 | { |
| 262 | return jent_testing_reader(&jent_raw_hires, &boot_raw_hires_test, |
| 263 | outbuf, outbuflen); |
| 264 | } |
| 265 | |
| 266 | static ssize_t jent_raw_hires_read(struct file *file, char __user *to, |
| 267 | size_t count, loff_t *ppos) |
| 268 | { |
| 269 | return jent_testing_extract_user(file, to, count, ppos, |
| 270 | jent_raw_hires_entropy_reader); |
| 271 | } |
| 272 | |
| 273 | static const struct file_operations jent_raw_hires_fops = { |
| 274 | .owner = THIS_MODULE, |
| 275 | .read = jent_raw_hires_read, |
| 276 | }; |
| 277 | |
| 278 | /******************************* Initialization *******************************/ |
| 279 | |
| 280 | void jent_testing_init(void) |
| 281 | { |
| 282 | jent_raw_debugfs_root = debugfs_create_dir(KBUILD_MODNAME, NULL); |
| 283 | |
| 284 | debugfs_create_file_unsafe("jent_raw_hires", 0400, |
| 285 | jent_raw_debugfs_root, NULL, |
| 286 | &jent_raw_hires_fops); |
| 287 | } |
| 288 | EXPORT_SYMBOL(jent_testing_init); |
| 289 | |
| 290 | void jent_testing_exit(void) |
| 291 | { |
| 292 | debugfs_remove_recursive(jent_raw_debugfs_root); |
| 293 | } |
| 294 | EXPORT_SYMBOL(jent_testing_exit); |