// SPDX-License-Identifier: GPL-2.0-only
/*
 * CMOS/NV-RAM driver for Linux
 *
 * Copyright (C) 1997 Roman Hodek <Roman.Hodek@informatik.uni-erlangen.de>
 * idea by and with help from Richard Jelinek <rj@suse.de>
 * Portions copyright (c) 2001,2002 Sun Microsystems (thockin@sun.com)
 *
 * 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");