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
__nvram_read_byte(int i)84 static unsigned char __nvram_read_byte(int i)
85 {
86 return CMOS_READ(NVRAM_FIRST_BYTE + i);
87 }
88
pc_nvram_read_byte(int i)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) */
__nvram_write_byte(unsigned char c,int i)101 static void __nvram_write_byte(unsigned char c, int i)
102 {
103 CMOS_WRITE(c, NVRAM_FIRST_BYTE + i);
104 }
105
pc_nvram_write_byte(unsigned char c,int i)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
__nvram_check_checksum(void)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
__nvram_set_checksum(void)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
pc_nvram_set_checksum(void)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
pc_nvram_initialize(void)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
pc_nvram_get_size(void)164 static ssize_t pc_nvram_get_size(void)
165 {
166 return NVRAM_BYTES;
167 }
168
pc_nvram_read(char * buf,size_t count,loff_t * ppos)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
pc_nvram_write(char * buf,size_t count,loff_t * ppos)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
nvram_misc_llseek(struct file * file,loff_t offset,int origin)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
nvram_misc_read(struct file * file,char __user * buf,size_t count,loff_t * ppos)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
nvram_misc_write(struct file * file,const char __user * buf,size_t count,loff_t * ppos)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
nvram_misc_ioctl(struct file * file,unsigned int cmd,unsigned long arg)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
nvram_misc_open(struct inode * inode,struct file * file)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
nvram_misc_release(struct inode * inode,struct file * file)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
pc_nvram_proc_read(unsigned char * nvram,struct seq_file * seq,void * offset)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
nvram_proc_read(struct seq_file * seq,void * offset)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
nvram_module_init(void)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
nvram_module_exit(void)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