drivers/char/nvram.c

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This source file includes following definitions.
__nvram_read_byte
pc_nvram_read_byte
__nvram_write_byte
pc_nvram_write_byte
__nvram_check_checksum
__nvram_set_checksum
pc_nvram_set_checksum
pc_nvram_initialize
pc_nvram_get_size
pc_nvram_read
pc_nvram_write
nvram_misc_llseek
nvram_misc_read
nvram_misc_write
nvram_misc_ioctl
nvram_misc_open
nvram_misc_release
pc_nvram_proc_read
nvram_proc_read
nvram_module_init
nvram_module_exit
   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 (!access_ok(buf, count))
 236                 return -EFAULT;
 237         if (*ppos >= nvram_size)
 238                 return 0;
 239 
 240         count = min_t(size_t, count, nvram_size - *ppos);
 241         count = min_t(size_t, count, PAGE_SIZE);
 242 
 243         tmp = kmalloc(count, GFP_KERNEL);
 244         if (!tmp)
 245                 return -ENOMEM;
 246 
 247         ret = nvram_read(tmp, count, ppos);
 248         if (ret <= 0)
 249                 goto out;
 250 
 251         if (copy_to_user(buf, tmp, ret)) {
 252                 *ppos -= ret;
 253                 ret = -EFAULT;
 254         }
 255 
 256 out:
 257         kfree(tmp);
 258         return ret;
 259 }
 260 
 261 static ssize_t nvram_misc_write(struct file *file, const char __user *buf,
 262                                 size_t count, loff_t *ppos)
 263 {
 264         char *tmp;
 265         ssize_t ret;
 266 
 267         if (!access_ok(buf, count))
 268                 return -EFAULT;
 269         if (*ppos >= nvram_size)
 270                 return 0;
 271 
 272         count = min_t(size_t, count, nvram_size - *ppos);
 273         count = min_t(size_t, count, PAGE_SIZE);
 274 
 275         tmp = memdup_user(buf, count);
 276         if (IS_ERR(tmp))
 277                 return PTR_ERR(tmp);
 278 
 279         ret = nvram_write(tmp, count, ppos);
 280         kfree(tmp);
 281         return ret;
 282 }
 283 
 284 static long nvram_misc_ioctl(struct file *file, unsigned int cmd,
 285                              unsigned long arg)
 286 {
 287         long ret = -ENOTTY;
 288 
 289         switch (cmd) {
 290 #ifdef CONFIG_PPC
 291         case OBSOLETE_PMAC_NVRAM_GET_OFFSET:
 292                 pr_warn("nvram: Using obsolete PMAC_NVRAM_GET_OFFSET ioctl\n");
 293                 /* fall through */
 294         case IOC_NVRAM_GET_OFFSET:
 295                 ret = -EINVAL;
 296 #ifdef CONFIG_PPC_PMAC
 297                 if (machine_is(powermac)) {
 298                         int part, offset;
 299 
 300                         if (copy_from_user(&part, (void __user *)arg,
 301                                            sizeof(part)) != 0)
 302                                 return -EFAULT;
 303                         if (part < pmac_nvram_OF || part > pmac_nvram_NR)
 304                                 return -EINVAL;
 305                         offset = pmac_get_partition(part);
 306                         if (offset < 0)
 307                                 return -EINVAL;
 308                         if (copy_to_user((void __user *)arg,
 309                                          &offset, sizeof(offset)) != 0)
 310                                 return -EFAULT;
 311                         ret = 0;
 312                 }
 313 #endif
 314                 break;
 315 #ifdef CONFIG_PPC32
 316         case IOC_NVRAM_SYNC:
 317                 if (ppc_md.nvram_sync != NULL) {
 318                         mutex_lock(&nvram_mutex);
 319                         ppc_md.nvram_sync();
 320                         mutex_unlock(&nvram_mutex);
 321                 }
 322                 ret = 0;
 323                 break;
 324 #endif
 325 #elif defined(CONFIG_X86) || defined(CONFIG_M68K)
 326         case NVRAM_INIT:
 327                 /* initialize NVRAM contents and checksum */
 328                 if (!capable(CAP_SYS_ADMIN))
 329                         return -EACCES;
 330 
 331                 if (arch_nvram_ops.initialize != NULL) {
 332                         mutex_lock(&nvram_mutex);
 333                         ret = arch_nvram_ops.initialize();
 334                         mutex_unlock(&nvram_mutex);
 335                 }
 336                 break;
 337         case NVRAM_SETCKS:
 338                 /* just set checksum, contents unchanged (maybe useful after
 339                  * checksum garbaged somehow...) */
 340                 if (!capable(CAP_SYS_ADMIN))
 341                         return -EACCES;
 342 
 343                 if (arch_nvram_ops.set_checksum != NULL) {
 344                         mutex_lock(&nvram_mutex);
 345                         ret = arch_nvram_ops.set_checksum();
 346                         mutex_unlock(&nvram_mutex);
 347                 }
 348                 break;
 349 #endif /* CONFIG_X86 || CONFIG_M68K */
 350         }
 351         return ret;
 352 }
 353 
 354 static int nvram_misc_open(struct inode *inode, struct file *file)
 355 {
 356         spin_lock(&nvram_state_lock);
 357 
 358         /* Prevent multiple readers/writers if desired. */
 359         if ((nvram_open_cnt && (file->f_flags & O_EXCL)) ||
 360             (nvram_open_mode & NVRAM_EXCL)) {
 361                 spin_unlock(&nvram_state_lock);
 362                 return -EBUSY;
 363         }
 364 
 365 #if defined(CONFIG_X86) || defined(CONFIG_M68K)
 366         /* Prevent multiple writers if the set_checksum ioctl is implemented. */
 367         if ((arch_nvram_ops.set_checksum != NULL) &&
 368             (file->f_mode & FMODE_WRITE) && (nvram_open_mode & NVRAM_WRITE)) {
 369                 spin_unlock(&nvram_state_lock);
 370                 return -EBUSY;
 371         }
 372 #endif
 373 
 374         if (file->f_flags & O_EXCL)
 375                 nvram_open_mode |= NVRAM_EXCL;
 376         if (file->f_mode & FMODE_WRITE)
 377                 nvram_open_mode |= NVRAM_WRITE;
 378         nvram_open_cnt++;
 379 
 380         spin_unlock(&nvram_state_lock);
 381 
 382         return 0;
 383 }
 384 
 385 static int nvram_misc_release(struct inode *inode, struct file *file)
 386 {
 387         spin_lock(&nvram_state_lock);
 388 
 389         nvram_open_cnt--;
 390 
 391         /* if only one instance is open, clear the EXCL bit */
 392         if (nvram_open_mode & NVRAM_EXCL)
 393                 nvram_open_mode &= ~NVRAM_EXCL;
 394         if (file->f_mode & FMODE_WRITE)
 395                 nvram_open_mode &= ~NVRAM_WRITE;
 396 
 397         spin_unlock(&nvram_state_lock);
 398 
 399         return 0;
 400 }
 401 
 402 #if defined(CONFIG_X86) && defined(CONFIG_PROC_FS)
 403 static const char * const floppy_types[] = {
 404         "none", "5.25'' 360k", "5.25'' 1.2M", "3.5'' 720k", "3.5'' 1.44M",
 405         "3.5'' 2.88M", "3.5'' 2.88M"
 406 };
 407 
 408 static const char * const gfx_types[] = {
 409         "EGA, VGA, ... (with BIOS)",
 410         "CGA (40 cols)",
 411         "CGA (80 cols)",
 412         "monochrome",
 413 };
 414 
 415 static void pc_nvram_proc_read(unsigned char *nvram, struct seq_file *seq,
 416                                void *offset)
 417 {
 418         int checksum;
 419         int type;
 420 
 421         spin_lock_irq(&rtc_lock);
 422         checksum = __nvram_check_checksum();
 423         spin_unlock_irq(&rtc_lock);
 424 
 425         seq_printf(seq, "Checksum status: %svalid\n", checksum ? "" : "not ");
 426 
 427         seq_printf(seq, "# floppies     : %d\n",
 428             (nvram[6] & 1) ? (nvram[6] >> 6) + 1 : 0);
 429         seq_printf(seq, "Floppy 0 type  : ");
 430         type = nvram[2] >> 4;
 431         if (type < ARRAY_SIZE(floppy_types))
 432                 seq_printf(seq, "%s\n", floppy_types[type]);
 433         else
 434                 seq_printf(seq, "%d (unknown)\n", type);
 435         seq_printf(seq, "Floppy 1 type  : ");
 436         type = nvram[2] & 0x0f;
 437         if (type < ARRAY_SIZE(floppy_types))
 438                 seq_printf(seq, "%s\n", floppy_types[type]);
 439         else
 440                 seq_printf(seq, "%d (unknown)\n", type);
 441 
 442         seq_printf(seq, "HD 0 type      : ");
 443         type = nvram[4] >> 4;
 444         if (type)
 445                 seq_printf(seq, "%02x\n", type == 0x0f ? nvram[11] : type);
 446         else
 447                 seq_printf(seq, "none\n");
 448 
 449         seq_printf(seq, "HD 1 type      : ");
 450         type = nvram[4] & 0x0f;
 451         if (type)
 452                 seq_printf(seq, "%02x\n", type == 0x0f ? nvram[12] : type);
 453         else
 454                 seq_printf(seq, "none\n");
 455 
 456         seq_printf(seq, "HD type 48 data: %d/%d/%d C/H/S, precomp %d, lz %d\n",
 457             nvram[18] | (nvram[19] << 8),
 458             nvram[20], nvram[25],
 459             nvram[21] | (nvram[22] << 8), nvram[23] | (nvram[24] << 8));
 460         seq_printf(seq, "HD type 49 data: %d/%d/%d C/H/S, precomp %d, lz %d\n",
 461             nvram[39] | (nvram[40] << 8),
 462             nvram[41], nvram[46],
 463             nvram[42] | (nvram[43] << 8), nvram[44] | (nvram[45] << 8));
 464 
 465         seq_printf(seq, "DOS base memory: %d kB\n", nvram[7] | (nvram[8] << 8));
 466         seq_printf(seq, "Extended memory: %d kB (configured), %d kB (tested)\n",
 467             nvram[9] | (nvram[10] << 8), nvram[34] | (nvram[35] << 8));
 468 
 469         seq_printf(seq, "Gfx adapter    : %s\n",
 470             gfx_types[(nvram[6] >> 4) & 3]);
 471 
 472         seq_printf(seq, "FPU            : %sinstalled\n",
 473             (nvram[6] & 2) ? "" : "not ");
 474 
 475         return;
 476 }
 477 
 478 static int nvram_proc_read(struct seq_file *seq, void *offset)
 479 {
 480         unsigned char contents[NVRAM_BYTES];
 481         int i = 0;
 482 
 483         spin_lock_irq(&rtc_lock);
 484         for (i = 0; i < NVRAM_BYTES; ++i)
 485                 contents[i] = __nvram_read_byte(i);
 486         spin_unlock_irq(&rtc_lock);
 487 
 488         pc_nvram_proc_read(contents, seq, offset);
 489 
 490         return 0;
 491 }
 492 #endif /* CONFIG_X86 && CONFIG_PROC_FS */
 493 
 494 static const struct file_operations nvram_misc_fops = {
 495         .owner          = THIS_MODULE,
 496         .llseek         = nvram_misc_llseek,
 497         .read           = nvram_misc_read,
 498         .write          = nvram_misc_write,
 499         .unlocked_ioctl = nvram_misc_ioctl,
 500         .open           = nvram_misc_open,
 501         .release        = nvram_misc_release,
 502 };
 503 
 504 static struct miscdevice nvram_misc = {
 505         NVRAM_MINOR,
 506         "nvram",
 507         &nvram_misc_fops,
 508 };
 509 
 510 static int __init nvram_module_init(void)
 511 {
 512         int ret;
 513 
 514         nvram_size = nvram_get_size();
 515         if (nvram_size < 0)
 516                 return nvram_size;
 517 
 518         ret = misc_register(&nvram_misc);
 519         if (ret) {
 520                 pr_err("nvram: can't misc_register on minor=%d\n", NVRAM_MINOR);
 521                 return ret;
 522         }
 523 
 524 #if defined(CONFIG_X86) && defined(CONFIG_PROC_FS)
 525         if (!proc_create_single("driver/nvram", 0, NULL, nvram_proc_read)) {
 526                 pr_err("nvram: can't create /proc/driver/nvram\n");
 527                 misc_deregister(&nvram_misc);
 528                 return -ENOMEM;
 529         }
 530 #endif
 531 
 532         pr_info("Non-volatile memory driver v" NVRAM_VERSION "\n");
 533         return 0;
 534 }
 535 
 536 static void __exit nvram_module_exit(void)
 537 {
 538 #if defined(CONFIG_X86) && defined(CONFIG_PROC_FS)
 539         remove_proc_entry("driver/nvram", NULL);
 540 #endif
 541         misc_deregister(&nvram_misc);
 542 }
 543 
 544 module_init(nvram_module_init);
 545 module_exit(nvram_module_exit);
 546 
 547 MODULE_LICENSE("GPL");
 548 MODULE_ALIAS_MISCDEV(NVRAM_MINOR);
 549 MODULE_ALIAS("devname:nvram");
/* [<][>][^][v][top][bottom][index][help] */
root/drivers/char/nvram.c

DEFINITIONS
