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