1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * CMOS/NV-RAM driver for Linux 4 * 5 * Copyright (C) 1997 Roman Hodek <Roman.Hodek@informatik.uni-erlangen.de> 6 * idea by and with help from Richard Jelinek <rj@suse.de> 7 * Portions copyright (c) 2001,2002 Sun Microsystems (thockin@sun.com) 8 * 9 * This driver allows you to access the contents of the non-volatile memory in 10 * the mc146818rtc.h real-time clock. This chip is built into all PCs and into 11 * many Atari machines. In the former it's called "CMOS-RAM", in the latter 12 * "NVRAM" (NV stands for non-volatile). 13 * 14 * The data are supplied as a (seekable) character device, /dev/nvram. The 15 * size of this file is dependent on the controller. The usual size is 114, 16 * the number of freely available bytes in the memory (i.e., not used by the 17 * RTC itself). 18 * 19 * Checksums over the NVRAM contents are managed by this driver. In case of a 20 * bad checksum, reads and writes return -EIO. The checksum can be initialized 21 * to a sane state either by ioctl(NVRAM_INIT) (clear whole NVRAM) or 22 * ioctl(NVRAM_SETCKS) (doesn't change contents, just makes checksum valid 23 * again; use with care!) 24 * 25 * 1.1 Cesar Barros: SMP locking fixes 26 * added changelog 27 * 1.2 Erik Gilling: Cobalt Networks support 28 * Tim Hockin: general cleanup, Cobalt support 29 * 1.3 Wim Van Sebroeck: convert PRINT_PROC to seq_file 30 */ 31 32 #define NVRAM_VERSION "1.3" 33 34 #include <linux/module.h> 35 #include <linux/nvram.h> 36 #include <linux/types.h> 37 #include <linux/errno.h> 38 #include <linux/miscdevice.h> 39 #include <linux/ioport.h> 40 #include <linux/fcntl.h> 41 #include <linux/mc146818rtc.h> 42 #include <linux/init.h> 43 #include <linux/proc_fs.h> 44 #include <linux/seq_file.h> 45 #include <linux/slab.h> 46 #include <linux/spinlock.h> 47 #include <linux/io.h> 48 #include <linux/uaccess.h> 49 #include <linux/mutex.h> 50 #include <linux/pagemap.h> 51 52 #ifdef CONFIG_PPC 53 #include <asm/nvram.h> 54 #endif 55 56 static DEFINE_MUTEX(nvram_mutex); 57 static DEFINE_SPINLOCK(nvram_state_lock); 58 static int nvram_open_cnt; /* #times opened */ 59 static int nvram_open_mode; /* special open modes */ 60 static ssize_t nvram_size; 61 #define NVRAM_WRITE 1 /* opened for writing (exclusive) */ 62 #define NVRAM_EXCL 2 /* opened with O_EXCL */ 63 64 #ifdef CONFIG_X86 65 /* 66 * These functions are provided to be called internally or by other parts of 67 * the kernel. It's up to the caller to ensure correct checksum before reading 68 * or after writing (needs to be done only once). 69 * 70 * It is worth noting that these functions all access bytes of general 71 * purpose memory in the NVRAM - that is to say, they all add the 72 * NVRAM_FIRST_BYTE offset. Pass them offsets into NVRAM as if you did not 73 * know about the RTC cruft. 74 */ 75 76 #define NVRAM_BYTES (128 - NVRAM_FIRST_BYTE) 77 78 /* Note that *all* calls to CMOS_READ and CMOS_WRITE must be done with 79 * rtc_lock held. Due to the index-port/data-port design of the RTC, we 80 * don't want two different things trying to get to it at once. (e.g. the 81 * periodic 11 min sync from kernel/time/ntp.c vs. this driver.) 82 */ 83 84 static unsigned char __nvram_read_byte(int i) 85 { 86 return CMOS_READ(NVRAM_FIRST_BYTE + i); 87 } 88 89 static unsigned char pc_nvram_read_byte(int i) 90 { 91 unsigned long flags; 92 unsigned char c; 93 94 spin_lock_irqsave(&rtc_lock, flags); 95 c = __nvram_read_byte(i); 96 spin_unlock_irqrestore(&rtc_lock, flags); 97 return c; 98 } 99 100 /* This races nicely with trying to read with checksum checking (nvram_read) */ 101 static void __nvram_write_byte(unsigned char c, int i) 102 { 103 CMOS_WRITE(c, NVRAM_FIRST_BYTE + i); 104 } 105 106 static void pc_nvram_write_byte(unsigned char c, int i) 107 { 108 unsigned long flags; 109 110 spin_lock_irqsave(&rtc_lock, flags); 111 __nvram_write_byte(c, i); 112 spin_unlock_irqrestore(&rtc_lock, flags); 113 } 114 115 /* On PCs, the checksum is built only over bytes 2..31 */ 116 #define PC_CKS_RANGE_START 2 117 #define PC_CKS_RANGE_END 31 118 #define PC_CKS_LOC 32 119 120 static int __nvram_check_checksum(void) 121 { 122 int i; 123 unsigned short sum = 0; 124 unsigned short expect; 125 126 for (i = PC_CKS_RANGE_START; i <= PC_CKS_RANGE_END; ++i) 127 sum += __nvram_read_byte(i); 128 expect = __nvram_read_byte(PC_CKS_LOC)<<8 | 129 __nvram_read_byte(PC_CKS_LOC+1); 130 return (sum & 0xffff) == expect; 131 } 132 133 static void __nvram_set_checksum(void) 134 { 135 int i; 136 unsigned short sum = 0; 137 138 for (i = PC_CKS_RANGE_START; i <= PC_CKS_RANGE_END; ++i) 139 sum += __nvram_read_byte(i); 140 __nvram_write_byte(sum >> 8, PC_CKS_LOC); 141 __nvram_write_byte(sum & 0xff, PC_CKS_LOC + 1); 142 } 143 144 static long pc_nvram_set_checksum(void) 145 { 146 spin_lock_irq(&rtc_lock); 147 __nvram_set_checksum(); 148 spin_unlock_irq(&rtc_lock); 149 return 0; 150 } 151 152 static long pc_nvram_initialize(void) 153 { 154 ssize_t i; 155 156 spin_lock_irq(&rtc_lock); 157 for (i = 0; i < NVRAM_BYTES; ++i) 158 __nvram_write_byte(0, i); 159 __nvram_set_checksum(); 160 spin_unlock_irq(&rtc_lock); 161 return 0; 162 } 163 164 static ssize_t pc_nvram_get_size(void) 165 { 166 return NVRAM_BYTES; 167 } 168 169 static ssize_t pc_nvram_read(char *buf, size_t count, loff_t *ppos) 170 { 171 char *p = buf; 172 loff_t i; 173 174 spin_lock_irq(&rtc_lock); 175 if (!__nvram_check_checksum()) { 176 spin_unlock_irq(&rtc_lock); 177 return -EIO; 178 } 179 for (i = *ppos; count > 0 && i < NVRAM_BYTES; --count, ++i, ++p) 180 *p = __nvram_read_byte(i); 181 spin_unlock_irq(&rtc_lock); 182 183 *ppos = i; 184 return p - buf; 185 } 186 187 static ssize_t pc_nvram_write(char *buf, size_t count, loff_t *ppos) 188 { 189 char *p = buf; 190 loff_t i; 191 192 spin_lock_irq(&rtc_lock); 193 if (!__nvram_check_checksum()) { 194 spin_unlock_irq(&rtc_lock); 195 return -EIO; 196 } 197 for (i = *ppos; count > 0 && i < NVRAM_BYTES; --count, ++i, ++p) 198 __nvram_write_byte(*p, i); 199 __nvram_set_checksum(); 200 spin_unlock_irq(&rtc_lock); 201 202 *ppos = i; 203 return p - buf; 204 } 205 206 const struct nvram_ops arch_nvram_ops = { 207 .read = pc_nvram_read, 208 .write = pc_nvram_write, 209 .read_byte = pc_nvram_read_byte, 210 .write_byte = pc_nvram_write_byte, 211 .get_size = pc_nvram_get_size, 212 .set_checksum = pc_nvram_set_checksum, 213 .initialize = pc_nvram_initialize, 214 }; 215 EXPORT_SYMBOL(arch_nvram_ops); 216 #endif /* CONFIG_X86 */ 217 218 /* 219 * The are the file operation function for user access to /dev/nvram 220 */ 221 222 static loff_t nvram_misc_llseek(struct file *file, loff_t offset, int origin) 223 { 224 return generic_file_llseek_size(file, offset, origin, MAX_LFS_FILESIZE, 225 nvram_size); 226 } 227 228 static ssize_t nvram_misc_read(struct file *file, char __user *buf, 229 size_t count, loff_t *ppos) 230 { 231 char *tmp; 232 ssize_t ret; 233 234 235 if (*ppos >= nvram_size) 236 return 0; 237 238 count = min_t(size_t, count, nvram_size - *ppos); 239 count = min_t(size_t, count, PAGE_SIZE); 240 241 tmp = kmalloc(count, GFP_KERNEL); 242 if (!tmp) 243 return -ENOMEM; 244 245 ret = nvram_read(tmp, count, ppos); 246 if (ret <= 0) 247 goto out; 248 249 if (copy_to_user(buf, tmp, ret)) { 250 *ppos -= ret; 251 ret = -EFAULT; 252 } 253 254 out: 255 kfree(tmp); 256 return ret; 257 } 258 259 static ssize_t nvram_misc_write(struct file *file, const char __user *buf, 260 size_t count, loff_t *ppos) 261 { 262 char *tmp; 263 ssize_t ret; 264 265 if (*ppos >= nvram_size) 266 return 0; 267 268 count = min_t(size_t, count, nvram_size - *ppos); 269 count = min_t(size_t, count, PAGE_SIZE); 270 271 tmp = memdup_user(buf, count); 272 if (IS_ERR(tmp)) 273 return PTR_ERR(tmp); 274 275 ret = nvram_write(tmp, count, ppos); 276 kfree(tmp); 277 return ret; 278 } 279 280 static long nvram_misc_ioctl(struct file *file, unsigned int cmd, 281 unsigned long arg) 282 { 283 long ret = -ENOTTY; 284 285 switch (cmd) { 286 #ifdef CONFIG_PPC 287 case OBSOLETE_PMAC_NVRAM_GET_OFFSET: 288 pr_warn("nvram: Using obsolete PMAC_NVRAM_GET_OFFSET ioctl\n"); 289 fallthrough; 290 case IOC_NVRAM_GET_OFFSET: 291 ret = -EINVAL; 292 #ifdef CONFIG_PPC_PMAC 293 if (machine_is(powermac)) { 294 int part, offset; 295 296 if (copy_from_user(&part, (void __user *)arg, 297 sizeof(part)) != 0) 298 return -EFAULT; 299 if (part < pmac_nvram_OF || part > pmac_nvram_NR) 300 return -EINVAL; 301 offset = pmac_get_partition(part); 302 if (offset < 0) 303 return -EINVAL; 304 if (copy_to_user((void __user *)arg, 305 &offset, sizeof(offset)) != 0) 306 return -EFAULT; 307 ret = 0; 308 } 309 #endif 310 break; 311 #ifdef CONFIG_PPC32 312 case IOC_NVRAM_SYNC: 313 if (ppc_md.nvram_sync != NULL) { 314 mutex_lock(&nvram_mutex); 315 ppc_md.nvram_sync(); 316 mutex_unlock(&nvram_mutex); 317 } 318 ret = 0; 319 break; 320 #endif 321 #elif defined(CONFIG_X86) || defined(CONFIG_M68K) 322 case NVRAM_INIT: 323 /* initialize NVRAM contents and checksum */ 324 if (!capable(CAP_SYS_ADMIN)) 325 return -EACCES; 326 327 if (arch_nvram_ops.initialize != NULL) { 328 mutex_lock(&nvram_mutex); 329 ret = arch_nvram_ops.initialize(); 330 mutex_unlock(&nvram_mutex); 331 } 332 break; 333 case NVRAM_SETCKS: 334 /* just set checksum, contents unchanged (maybe useful after 335 * checksum garbaged somehow...) */ 336 if (!capable(CAP_SYS_ADMIN)) 337 return -EACCES; 338 339 if (arch_nvram_ops.set_checksum != NULL) { 340 mutex_lock(&nvram_mutex); 341 ret = arch_nvram_ops.set_checksum(); 342 mutex_unlock(&nvram_mutex); 343 } 344 break; 345 #endif /* CONFIG_X86 || CONFIG_M68K */ 346 } 347 return ret; 348 } 349 350 static int nvram_misc_open(struct inode *inode, struct file *file) 351 { 352 spin_lock(&nvram_state_lock); 353 354 /* Prevent multiple readers/writers if desired. */ 355 if ((nvram_open_cnt && (file->f_flags & O_EXCL)) || 356 (nvram_open_mode & NVRAM_EXCL)) { 357 spin_unlock(&nvram_state_lock); 358 return -EBUSY; 359 } 360 361 #if defined(CONFIG_X86) || defined(CONFIG_M68K) 362 /* Prevent multiple writers if the set_checksum ioctl is implemented. */ 363 if ((arch_nvram_ops.set_checksum != NULL) && 364 (file->f_mode & FMODE_WRITE) && (nvram_open_mode & NVRAM_WRITE)) { 365 spin_unlock(&nvram_state_lock); 366 return -EBUSY; 367 } 368 #endif 369 370 if (file->f_flags & O_EXCL) 371 nvram_open_mode |= NVRAM_EXCL; 372 if (file->f_mode & FMODE_WRITE) 373 nvram_open_mode |= NVRAM_WRITE; 374 nvram_open_cnt++; 375 376 spin_unlock(&nvram_state_lock); 377 378 return 0; 379 } 380 381 static int nvram_misc_release(struct inode *inode, struct file *file) 382 { 383 spin_lock(&nvram_state_lock); 384 385 nvram_open_cnt--; 386 387 /* if only one instance is open, clear the EXCL bit */ 388 if (nvram_open_mode & NVRAM_EXCL) 389 nvram_open_mode &= ~NVRAM_EXCL; 390 if (file->f_mode & FMODE_WRITE) 391 nvram_open_mode &= ~NVRAM_WRITE; 392 393 spin_unlock(&nvram_state_lock); 394 395 return 0; 396 } 397 398 #if defined(CONFIG_X86) && defined(CONFIG_PROC_FS) 399 static const char * const floppy_types[] = { 400 "none", "5.25'' 360k", "5.25'' 1.2M", "3.5'' 720k", "3.5'' 1.44M", 401 "3.5'' 2.88M", "3.5'' 2.88M" 402 }; 403 404 static const char * const gfx_types[] = { 405 "EGA, VGA, ... (with BIOS)", 406 "CGA (40 cols)", 407 "CGA (80 cols)", 408 "monochrome", 409 }; 410 411 static void pc_nvram_proc_read(unsigned char *nvram, struct seq_file *seq, 412 void *offset) 413 { 414 int checksum; 415 int type; 416 417 spin_lock_irq(&rtc_lock); 418 checksum = __nvram_check_checksum(); 419 spin_unlock_irq(&rtc_lock); 420 421 seq_printf(seq, "Checksum status: %svalid\n", checksum ? "" : "not "); 422 423 seq_printf(seq, "# floppies : %d\n", 424 (nvram[6] & 1) ? (nvram[6] >> 6) + 1 : 0); 425 seq_printf(seq, "Floppy 0 type : "); 426 type = nvram[2] >> 4; 427 if (type < ARRAY_SIZE(floppy_types)) 428 seq_printf(seq, "%s\n", floppy_types[type]); 429 else 430 seq_printf(seq, "%d (unknown)\n", type); 431 seq_printf(seq, "Floppy 1 type : "); 432 type = nvram[2] & 0x0f; 433 if (type < ARRAY_SIZE(floppy_types)) 434 seq_printf(seq, "%s\n", floppy_types[type]); 435 else 436 seq_printf(seq, "%d (unknown)\n", type); 437 438 seq_printf(seq, "HD 0 type : "); 439 type = nvram[4] >> 4; 440 if (type) 441 seq_printf(seq, "%02x\n", type == 0x0f ? nvram[11] : type); 442 else 443 seq_printf(seq, "none\n"); 444 445 seq_printf(seq, "HD 1 type : "); 446 type = nvram[4] & 0x0f; 447 if (type) 448 seq_printf(seq, "%02x\n", type == 0x0f ? nvram[12] : type); 449 else 450 seq_printf(seq, "none\n"); 451 452 seq_printf(seq, "HD type 48 data: %d/%d/%d C/H/S, precomp %d, lz %d\n", 453 nvram[18] | (nvram[19] << 8), 454 nvram[20], nvram[25], 455 nvram[21] | (nvram[22] << 8), nvram[23] | (nvram[24] << 8)); 456 seq_printf(seq, "HD type 49 data: %d/%d/%d C/H/S, precomp %d, lz %d\n", 457 nvram[39] | (nvram[40] << 8), 458 nvram[41], nvram[46], 459 nvram[42] | (nvram[43] << 8), nvram[44] | (nvram[45] << 8)); 460 461 seq_printf(seq, "DOS base memory: %d kB\n", nvram[7] | (nvram[8] << 8)); 462 seq_printf(seq, "Extended memory: %d kB (configured), %d kB (tested)\n", 463 nvram[9] | (nvram[10] << 8), nvram[34] | (nvram[35] << 8)); 464 465 seq_printf(seq, "Gfx adapter : %s\n", 466 gfx_types[(nvram[6] >> 4) & 3]); 467 468 seq_printf(seq, "FPU : %sinstalled\n", 469 (nvram[6] & 2) ? "" : "not "); 470 471 return; 472 } 473 474 static int nvram_proc_read(struct seq_file *seq, void *offset) 475 { 476 unsigned char contents[NVRAM_BYTES]; 477 int i = 0; 478 479 spin_lock_irq(&rtc_lock); 480 for (i = 0; i < NVRAM_BYTES; ++i) 481 contents[i] = __nvram_read_byte(i); 482 spin_unlock_irq(&rtc_lock); 483 484 pc_nvram_proc_read(contents, seq, offset); 485 486 return 0; 487 } 488 #endif /* CONFIG_X86 && CONFIG_PROC_FS */ 489 490 static const struct file_operations nvram_misc_fops = { 491 .owner = THIS_MODULE, 492 .llseek = nvram_misc_llseek, 493 .read = nvram_misc_read, 494 .write = nvram_misc_write, 495 .unlocked_ioctl = nvram_misc_ioctl, 496 .open = nvram_misc_open, 497 .release = nvram_misc_release, 498 }; 499 500 static struct miscdevice nvram_misc = { 501 NVRAM_MINOR, 502 "nvram", 503 &nvram_misc_fops, 504 }; 505 506 static int __init nvram_module_init(void) 507 { 508 int ret; 509 510 nvram_size = nvram_get_size(); 511 if (nvram_size < 0) 512 return nvram_size; 513 514 ret = misc_register(&nvram_misc); 515 if (ret) { 516 pr_err("nvram: can't misc_register on minor=%d\n", NVRAM_MINOR); 517 return ret; 518 } 519 520 #if defined(CONFIG_X86) && defined(CONFIG_PROC_FS) 521 if (!proc_create_single("driver/nvram", 0, NULL, nvram_proc_read)) { 522 pr_err("nvram: can't create /proc/driver/nvram\n"); 523 misc_deregister(&nvram_misc); 524 return -ENOMEM; 525 } 526 #endif 527 528 pr_info("Non-volatile memory driver v" NVRAM_VERSION "\n"); 529 return 0; 530 } 531 532 static void __exit nvram_module_exit(void) 533 { 534 #if defined(CONFIG_X86) && defined(CONFIG_PROC_FS) 535 remove_proc_entry("driver/nvram", NULL); 536 #endif 537 misc_deregister(&nvram_misc); 538 } 539 540 module_init(nvram_module_init); 541 module_exit(nvram_module_exit); 542 543 MODULE_LICENSE("GPL"); 544 MODULE_ALIAS_MISCDEV(NVRAM_MINOR); 545 MODULE_ALIAS("devname:nvram"); 546