drivers/char/nvram.c

   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");