// SPDX-License-Identifier: GPL-2.0-only
/*
* CMOS/NV-RAM driver for Linux
*
* Copyright (C) 1997 Roman Hodek <[email protected]>
* idea by and with help from Richard Jelinek <[email protected]>
* Portions copyright (c) 2001,2002 Sun Microsystems ([email protected])
*
* This driver allows you to access the contents of the non-volatile memory in
* the mc146818rtc.h real-time clock. This chip is built into all PCs and into
* many Atari machines. In the former it's called "CMOS-RAM", in the latter
* "NVRAM" (NV stands for non-volatile).
*
* The data are supplied as a (seekable) character device, /dev/nvram. The
* size of this file is dependent on the controller. The usual size is 114,
* the number of freely available bytes in the memory (i.e., not used by the
* RTC itself).
*
* Checksums over the NVRAM contents are managed by this driver. In case of a
* bad checksum, reads and writes return -EIO. The checksum can be initialized
* to a sane state either by ioctl(NVRAM_INIT) (clear whole NVRAM) or
* ioctl(NVRAM_SETCKS) (doesn't change contents, just makes checksum valid
* again; use with care!)
*
* 1.1 Cesar Barros: SMP locking fixes
* added changelog
* 1.2 Erik Gilling: Cobalt Networks support
* Tim Hockin: general cleanup, Cobalt support
* 1.3 Wim Van Sebroeck: convert PRINT_PROC to seq_file
*/
#define NVRAM_VERSION "1.3"
#include <linux/module.h>
#include <linux/nvram.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/miscdevice.h>
#include <linux/ioport.h>
#include <linux/fcntl.h>
#include <linux/mc146818rtc.h>
#include <linux/init.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/io.h>
#include <linux/uaccess.h>
#include <linux/mutex.h>
#include <linux/pagemap.h>
#ifdef CONFIG_PPC
#include <asm/nvram.h>
#endif
static DEFINE_MUTEX(nvram_mutex);
static DEFINE_SPINLOCK(nvram_state_lock);
static int nvram_open_cnt; /* #times opened */
static int nvram_open_mode; /* special open modes */
static ssize_t nvram_size;
#define NVRAM_WRITE 1 /* opened for writing (exclusive) */
#define NVRAM_EXCL 2 /* opened with O_EXCL */
#ifdef CONFIG_X86
/*
* These functions are provided to be called internally or by other parts of
* the kernel. It's up to the caller to ensure correct checksum before reading
* or after writing (needs to be done only once).
*
* It is worth noting that these functions all access bytes of general
* purpose memory in the NVRAM - that is to say, they all add the
* NVRAM_FIRST_BYTE offset. Pass them offsets into NVRAM as if you did not
* know about the RTC cruft.
*/
#define NVRAM_BYTES (128 - NVRAM_FIRST_BYTE)
/* Note that *all* calls to CMOS_READ and CMOS_WRITE must be done with
* rtc_lock held. Due to the index-port/data-port design of the RTC, we
* don't want two different things trying to get to it at once. (e.g. the
* periodic 11 min sync from kernel/time/ntp.c vs. this driver.)
*/
static unsigned char __nvram_read_byte(int i)
{
return CMOS_READ(NVRAM_FIRST_BYTE + i);
}
static unsigned char pc_nvram_read_byte(int i)
{
unsigned long flags;
unsigned char c;
spin_lock_irqsave(&rtc_lock, flags);
c = __nvram_read_byte(i);
spin_unlock_irqrestore(&rtc_lock, flags);
return c;
}
/* This races nicely with trying to read with checksum checking (nvram_read) */
static void __nvram_write_byte(unsigned char c, int i)
{
CMOS_WRITE(c, NVRAM_FIRST_BYTE + i);
}
static void pc_nvram_write_byte(unsigned char c, int i)
{
unsigned long flags;
spin_lock_irqsave(&rtc_lock, flags);
__nvram_write_byte(c, i);
spin_unlock_irqrestore(&rtc_lock, flags);
}
/* On PCs, the checksum is built only over bytes 2..31 */
#define PC_CKS_RANGE_START 2
#define PC_CKS_RANGE_END 31
#define PC_CKS_LOC 32
static int __nvram_check_checksum(void)
{
int i;
unsigned short sum = 0;
unsigned short expect;
for (i = PC_CKS_RANGE_START; i <= PC_CKS_RANGE_END; ++i)
sum += __nvram_read_byte(i);
expect = __nvram_read_byte(PC_CKS_LOC)<<8 |
__nvram_read_byte(PC_CKS_LOC+1);
return (sum & 0xffff) == expect;
}
static void __nvram_set_checksum(void)
{
int i;
unsigned short sum = 0;
for (i = PC_CKS_RANGE_START; i <= PC_CKS_RANGE_END; ++i)
sum += __nvram_read_byte(i);
__nvram_write_byte(sum >> 8, PC_CKS_LOC);
__nvram_write_byte(sum & 0xff, PC_CKS_LOC + 1);
}
static long pc_nvram_set_checksum(void)
{
spin_lock_irq(&rtc_lock);
__nvram_set_checksum();
spin_unlock_irq(&rtc_lock);
return 0;
}
static long pc_nvram_initialize(void)
{
ssize_t i;
spin_lock_irq(&rtc_lock);
for (i = 0; i < NVRAM_BYTES; ++i)
__nvram_write_byte(0, i);
__nvram_set_checksum();
spin_unlock_irq(&rtc_lock);
return 0;
}
static ssize_t pc_nvram_get_size(void)
{
return NVRAM_BYTES;
}
static ssize_t pc_nvram_read(char *buf, size_t count, loff_t *ppos)
{
char *p = buf;
loff_t i;
spin_lock_irq(&rtc_lock);
if (!__nvram_check_checksum()) {
spin_unlock_irq(&rtc_lock);
return -EIO;
}
for (i = *ppos; count > 0 && i < NVRAM_BYTES; --count, ++i, ++p)
*p = __nvram_read_byte(i);
spin_unlock_irq(&rtc_lock);
*ppos = i;
return p - buf;
}
static ssize_t pc_nvram_write(char *buf, size_t count, loff_t *ppos)
{
char *p = buf;
loff_t i;
spin_lock_irq(&rtc_lock);
if (!__nvram_check_checksum()) {
spin_unlock_irq(&rtc_lock);
return -EIO;
}
for (i = *ppos; count > 0 && i < NVRAM_BYTES; --count, ++i, ++p)
__nvram_write_byte(*p, i);
__nvram_set_checksum();
spin_unlock_irq(&rtc_lock);
*ppos = i;
return p - buf;
}
const struct nvram_ops arch_nvram_ops = {
.read = pc_nvram_read,
.write = pc_nvram_write,
.read_byte = pc_nvram_read_byte,
.write_byte = pc_nvram_write_byte,
.get_size = pc_nvram_get_size,
.set_checksum = pc_nvram_set_checksum,
.initialize = pc_nvram_initialize,
};
EXPORT_SYMBOL(arch_nvram_ops);
#endif /* CONFIG_X86 */
/*
* The are the file operation function for user access to /dev/nvram
*/
static loff_t nvram_misc_llseek(struct file *file, loff_t offset, int origin)
{
return generic_file_llseek_size(file, offset, origin, MAX_LFS_FILESIZE,
nvram_size);
}
static ssize_t nvram_misc_read(struct file *file, char __user *buf,
size_t count, loff_t *ppos)
{
char *tmp;
ssize_t ret;
if (*ppos >= nvram_size)
return 0;
count = min_t(size_t, count, nvram_size - *ppos);
count = min_t(size_t, count, PAGE_SIZE);
tmp = kmalloc(count, GFP_KERNEL);
if (!tmp)
return -ENOMEM;
ret = nvram_read(tmp, count, ppos);
if (ret <= 0)
goto out;
if (copy_to_user(buf, tmp, ret)) {
*ppos -= ret;
ret = -EFAULT;
}
out:
kfree(tmp);
return ret;
}
static ssize_t nvram_misc_write(struct file *file, const char __user *buf,
size_t count, loff_t *ppos)
{
char *tmp;
ssize_t ret;
if (*ppos >= nvram_size)
return 0;
count = min_t(size_t, count, nvram_size - *ppos);
count = min_t(size_t, count, PAGE_SIZE);
tmp = memdup_user(buf, count);
if (IS_ERR(tmp))
return PTR_ERR(tmp);
ret = nvram_write(tmp, count, ppos);
kfree(tmp);
return ret;
}
static long nvram_misc_ioctl(struct file *file, unsigned int cmd,
unsigned long arg)
{
long ret = -ENOTTY;
switch (cmd) {
#ifdef CONFIG_PPC
case OBSOLETE_PMAC_NVRAM_GET_OFFSET:
pr_warn("nvram: Using obsolete PMAC_NVRAM_GET_OFFSET ioctl\n");
fallthrough;
case IOC_NVRAM_GET_OFFSET:
ret = -EINVAL;
#ifdef CONFIG_PPC_PMAC
if (machine_is(powermac)) {
int part, offset;
if (copy_from_user(&part, (void __user *)arg,
sizeof(part)) != 0)
return -EFAULT;
if (part < pmac_nvram_OF || part > pmac_nvram_NR)
return -EINVAL;
offset = pmac_get_partition(part);
if (offset < 0)
return -EINVAL;
if (copy_to_user((void __user *)arg,
&offset, sizeof(offset)) != 0)
return -EFAULT;
ret = 0;
}
#endif
break;
#ifdef CONFIG_PPC32
case IOC_NVRAM_SYNC:
if (ppc_md.nvram_sync != NULL) {
mutex_lock(&nvram_mutex);
ppc_md.nvram_sync();
mutex_unlock(&nvram_mutex);
}
ret = 0;
break;
#endif
#elif defined(CONFIG_X86) || defined(CONFIG_M68K)
case NVRAM_INIT:
/* initialize NVRAM contents and checksum */
if (!capable(CAP_SYS_ADMIN))
return -EACCES;
if (arch_nvram_ops.initialize != NULL) {
mutex_lock(&nvram_mutex);
ret = arch_nvram_ops.initialize();
mutex_unlock(&nvram_mutex);
}
break;
case NVRAM_SETCKS:
/* just set checksum, contents unchanged (maybe useful after
* checksum garbaged somehow...) */
if (!capable(CAP_SYS_ADMIN))
return -EACCES;
if (arch_nvram_ops.set_checksum != NULL) {
mutex_lock(&nvram_mutex);
ret = arch_nvram_ops.set_checksum();
mutex_unlock(&nvram_mutex);
}
break;
#endif /* CONFIG_X86 || CONFIG_M68K */
}
return ret;
}
static int nvram_misc_open(struct inode *inode, struct file *file)
{
spin_lock(&nvram_state_lock);
/* Prevent multiple readers/writers if desired. */
if ((nvram_open_cnt && (file->f_flags & O_EXCL)) ||
(nvram_open_mode & NVRAM_EXCL)) {
spin_unlock(&nvram_state_lock);
return -EBUSY;
}
#if defined(CONFIG_X86) || defined(CONFIG_M68K)
/* Prevent multiple writers if the set_checksum ioctl is implemented. */
if ((arch_nvram_ops.set_checksum != NULL) &&
(file->f_mode & FMODE_WRITE) && (nvram_open_mode & NVRAM_WRITE)) {
spin_unlock(&nvram_state_lock);
return -EBUSY;
}
#endif
if (file->f_flags & O_EXCL)
nvram_open_mode |= NVRAM_EXCL;
if (file->f_mode & FMODE_WRITE)
nvram_open_mode |= NVRAM_WRITE;
nvram_open_cnt++;
spin_unlock(&nvram_state_lock);
return 0;
}
static int nvram_misc_release(struct inode *inode, struct file *file)
{
spin_lock(&nvram_state_lock);
nvram_open_cnt--;
/* if only one instance is open, clear the EXCL bit */
if (nvram_open_mode & NVRAM_EXCL)
nvram_open_mode &= ~NVRAM_EXCL;
if (file->f_mode & FMODE_WRITE)
nvram_open_mode &= ~NVRAM_WRITE;
spin_unlock(&nvram_state_lock);
return 0;
}
#if defined(CONFIG_X86) && defined(CONFIG_PROC_FS)
static const char * const floppy_types[] = {
"none", "5.25'' 360k", "5.25'' 1.2M", "3.5'' 720k", "3.5'' 1.44M",
"3.5'' 2.88M", "3.5'' 2.88M"
};
static const char * const gfx_types[] = {
"EGA, VGA, ... (with BIOS)",
"CGA (40 cols)",
"CGA (80 cols)",
"monochrome",
};
static void pc_nvram_proc_read(unsigned char *nvram, struct seq_file *seq,
void *offset)
{
int checksum;
int type;
spin_lock_irq(&rtc_lock);
checksum = __nvram_check_checksum();
spin_unlock_irq(&rtc_lock);
seq_printf(seq, "Checksum status: %svalid\n", checksum ? "" : "not ");
seq_printf(seq, "# floppies : %d\n",
(nvram[6] & 1) ? (nvram[6] >> 6) + 1 : 0);
seq_printf(seq, "Floppy 0 type : ");
type = nvram[2] >> 4;
if (type < ARRAY_SIZE(floppy_types))
seq_printf(seq, "%s\n", floppy_types[type]);
else
seq_printf(seq, "%d (unknown)\n", type);
seq_printf(seq, "Floppy 1 type : ");
type = nvram[2] & 0x0f;
if (type < ARRAY_SIZE(floppy_types))
seq_printf(seq, "%s\n", floppy_types[type]);
else
seq_printf(seq, "%d (unknown)\n", type);
seq_printf(seq, "HD 0 type : ");
type = nvram[4] >> 4;
if (type)
seq_printf(seq, "%02x\n", type == 0x0f ? nvram[11] : type);
else
seq_printf(seq, "none\n");
seq_printf(seq, "HD 1 type : ");
type = nvram[4] & 0x0f;
if (type)
seq_printf(seq, "%02x\n", type == 0x0f ? nvram[12] : type);
else
seq_printf(seq, "none\n");
seq_printf(seq, "HD type 48 data: %d/%d/%d C/H/S, precomp %d, lz %d\n",
nvram[18] | (nvram[19] << 8),
nvram[20], nvram[25],
nvram[21] | (nvram[22] << 8), nvram[23] | (nvram[24] << 8));
seq_printf(seq, "HD type 49 data: %d/%d/%d C/H/S, precomp %d, lz %d\n",
nvram[39] | (nvram[40] << 8),
nvram[41], nvram[46],
nvram[42] | (nvram[43] << 8), nvram[44] | (nvram[45] << 8));
seq_printf(seq, "DOS base memory: %d kB\n", nvram[7] | (nvram[8] << 8));
seq_printf(seq, "Extended memory: %d kB (configured), %d kB (tested)\n",
nvram[9] | (nvram[10] << 8), nvram[34] | (nvram[35] << 8));
seq_printf(seq, "Gfx adapter : %s\n",
gfx_types[(nvram[6] >> 4) & 3]);
seq_printf(seq, "FPU : %sinstalled\n",
(nvram[6] & 2) ? "" : "not ");
return;
}
static int nvram_proc_read(struct seq_file *seq, void *offset)
{
unsigned char contents[NVRAM_BYTES];
int i = 0;
spin_lock_irq(&rtc_lock);
for (i = 0; i < NVRAM_BYTES; ++i)
contents[i] = __nvram_read_byte(i);
spin_unlock_irq(&rtc_lock);
pc_nvram_proc_read(contents, seq, offset);
return 0;
}
#endif /* CONFIG_X86 && CONFIG_PROC_FS */
static const struct file_operations nvram_misc_fops = {
.owner = THIS_MODULE,
.llseek = nvram_misc_llseek,
.read = nvram_misc_read,
.write = nvram_misc_write,
.unlocked_ioctl = nvram_misc_ioctl,
.open = nvram_misc_open,
.release = nvram_misc_release,
};
static struct miscdevice nvram_misc = {
NVRAM_MINOR,
"nvram",
&nvram_misc_fops,
};
static int __init nvram_module_init(void)
{
int ret;
nvram_size = nvram_get_size();
if (nvram_size < 0)
return nvram_size;
ret = misc_register(&nvram_misc);
if (ret) {
pr_err("nvram: can't misc_register on minor=%d\n", NVRAM_MINOR);
return ret;
}
#if defined(CONFIG_X86) && defined(CONFIG_PROC_FS)
if (!proc_create_single("driver/nvram", 0, NULL, nvram_proc_read)) {
pr_err("nvram: can't create /proc/driver/nvram\n");
misc_deregister(&nvram_misc);
return -ENOMEM;
}
#endif
pr_info("Non-volatile memory driver v" NVRAM_VERSION "\n");
return 0;
}
static void __exit nvram_module_exit(void)
{
#if defined(CONFIG_X86) && defined(CONFIG_PROC_FS)
remove_proc_entry("driver/nvram", NULL);
#endif
misc_deregister(&nvram_misc);
}
module_init(nvram_module_init);
module_exit(nvram_module_exit);
MODULE_DESCRIPTION("CMOS/NV-RAM driver for Linux");
MODULE_LICENSE("GPL");
MODULE_ALIAS_MISCDEV(NVRAM_MINOR);
MODULE_ALIAS("devname:nvram");
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