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1// SPDX-License-Identifier: GPL-2.0-only2/*3 * CMOS/NV-RAM driver for Linux4 *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 in10 * the mc146818rtc.h real-time clock. This chip is built into all PCs and into11 * many Atari machines. In the former it's called "CMOS-RAM", in the latter12 * "NVRAM" (NV stands for non-volatile).13 *14 * The data are supplied as a (seekable) character device, /dev/nvram. The15 * 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 the17 * RTC itself).18 *19 * Checksums over the NVRAM contents are managed by this driver. In case of a20 * bad checksum, reads and writes return -EIO. The checksum can be initialized21 * to a sane state either by ioctl(NVRAM_INIT) (clear whole NVRAM) or22 * ioctl(NVRAM_SETCKS) (doesn't change contents, just makes checksum valid23 * again; use with care!)24 *25 * 1.1 Cesar Barros: SMP locking fixes26 * added changelog27 * 1.2 Erik Gilling: Cobalt Networks support28 * Tim Hockin: general cleanup, Cobalt support29 * 1.3 Wim Van Sebroeck: convert PRINT_PROC to seq_file30 */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_PPC53#include <asm/nvram.h>54#endif55 56static DEFINE_MUTEX(nvram_mutex);57static DEFINE_SPINLOCK(nvram_state_lock);58static int nvram_open_cnt; /* #times opened */59static int nvram_open_mode; /* special open modes */60static 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_X8665/*66 * These functions are provided to be called internally or by other parts of67 * the kernel. It's up to the caller to ensure correct checksum before reading68 * or after writing (needs to be done only once).69 *70 * It is worth noting that these functions all access bytes of general71 * purpose memory in the NVRAM - that is to say, they all add the72 * NVRAM_FIRST_BYTE offset. Pass them offsets into NVRAM as if you did not73 * 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 with79 * rtc_lock held. Due to the index-port/data-port design of the RTC, we80 * don't want two different things trying to get to it at once. (e.g. the81 * periodic 11 min sync from kernel/time/ntp.c vs. this driver.)82 */83 84static unsigned char __nvram_read_byte(int i)85{86 return CMOS_READ(NVRAM_FIRST_BYTE + i);87}88 89static 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) */101static void __nvram_write_byte(unsigned char c, int i)102{103 CMOS_WRITE(c, NVRAM_FIRST_BYTE + i);104}105 106static 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 2117#define PC_CKS_RANGE_END 31118#define PC_CKS_LOC 32119 120static 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 133static 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 144static 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 152static 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 164static ssize_t pc_nvram_get_size(void)165{166 return NVRAM_BYTES;167}168 169static 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 187static 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 206const 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};215EXPORT_SYMBOL(arch_nvram_ops);216#endif /* CONFIG_X86 */217 218/*219 * The are the file operation function for user access to /dev/nvram220 */221 222static 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 228static 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 254out:255 kfree(tmp);256 return ret;257}258 259static 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 280static 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_PPC287 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_PMAC293 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#endif310 break;311#ifdef CONFIG_PPC32312 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#endif321#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 after335 * 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 350static 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#endif369 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 381static 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)399static 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 404static const char * const gfx_types[] = {405 "EGA, VGA, ... (with BIOS)",406 "CGA (40 cols)",407 "CGA (80 cols)",408 "monochrome",409};410 411static 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 else430 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 else436 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 else443 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 else450 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 474static 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 490static 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 500static struct miscdevice nvram_misc = {501 NVRAM_MINOR,502 "nvram",503 &nvram_misc_fops,504};505 506static 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#endif527 528 pr_info("Non-volatile memory driver v" NVRAM_VERSION "\n");529 return 0;530}531 532static void __exit nvram_module_exit(void)533{534#if defined(CONFIG_X86) && defined(CONFIG_PROC_FS)535 remove_proc_entry("driver/nvram", NULL);536#endif537 misc_deregister(&nvram_misc);538}539 540module_init(nvram_module_init);541module_exit(nvram_module_exit);542 543MODULE_DESCRIPTION("CMOS/NV-RAM driver for Linux");544MODULE_LICENSE("GPL");545MODULE_ALIAS_MISCDEV(NVRAM_MINOR);546MODULE_ALIAS("devname:nvram");547