/* ----------------------------------------------------------------------- *
 *
 *   Copyright 2000-2008 H. Peter Anvin - All Rights Reserved
 *   Copyright 2009 Intel Corporation; author: H. Peter Anvin
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation, Inc., 675 Mass Ave, Cambridge MA 02139,
 *   USA; either version 2 of the License, or (at your option) any later
 *   version; incorporated herein by reference.
 *
 * ----------------------------------------------------------------------- */

/*
 * x86 MSR access device
 *
 * This device is accessed by lseek() to the appropriate register number
 * and then read/write in chunks of 8 bytes.  A larger size means multiple
 * reads or writes of the same register.
 *
 * This driver uses /dev/cpu/%d/msr where %d is the minor number, and on
 * an SMP box will direct the access to CPU %d.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>

#include <linux/types.h>
#include <linux/errno.h>
#include <linux/fcntl.h>
#include <linux/init.h>
#include <linux/poll.h>
#include <linux/smp.h>
#include <linux/major.h>
#include <linux/fs.h>
#include <linux/device.h>
#include <linux/cpu.h>
#include <linux/notifier.h>
#include <linux/uaccess.h>
#include <linux/gfp.h>

#include <asm/cpufeature.h>
#include <asm/msr.h>

static struct class *msr_class;
static enum cpuhp_state cpuhp_msr_state;

static ssize_t msr_read(struct file *file, char __user *buf,
                        size_t count, loff_t *ppos)
{
        u32 __user *tmp = (u32 __user *) buf;
        u32 data[2];
        u32 reg = *ppos;
        int cpu = iminor(file_inode(file));
        int err = 0;
        ssize_t bytes = 0;

        if (count % 8)
                return -EINVAL; /* Invalid chunk size */

        for (; count; count -= 8) {
                err = rdmsr_safe_on_cpu(cpu, reg, &data[0], &data[1]);
                if (err)
                        break;
                if (copy_to_user(tmp, &data, 8)) {
                        err = -EFAULT;
                        break;
                }
                tmp += 2;
                bytes += 8;
        }

        return bytes ? bytes : err;
}

static ssize_t msr_write(struct file *file, const char __user *buf,
                         size_t count, loff_t *ppos)
{
        const u32 __user *tmp = (const u32 __user *)buf;
        u32 data[2];
        u32 reg = *ppos;
        int cpu = iminor(file_inode(file));
        int err = 0;
        ssize_t bytes = 0;

        if (count % 8)
                return -EINVAL; /* Invalid chunk size */

        for (; count; count -= 8) {
                if (copy_from_user(&data, tmp, 8)) {
                        err = -EFAULT;
                        break;
                }
                err = wrmsr_safe_on_cpu(cpu, reg, data[0], data[1]);
                if (err)
                        break;
                tmp += 2;
                bytes += 8;
        }

        return bytes ? bytes : err;
}

static long msr_ioctl(struct file *file, unsigned int ioc, unsigned long arg)
{
        u32 __user *uregs = (u32 __user *)arg;
        u32 regs[8];
        int cpu = iminor(file_inode(file));
        int err;

        switch (ioc) {
        case X86_IOC_RDMSR_REGS:
                if (!(file->f_mode & FMODE_READ)) {
                        err = -EBADF;
                        break;
                }
                if (copy_from_user(&regs, uregs, sizeof regs)) {
                        err = -EFAULT;
                        break;
                }
                err = rdmsr_safe_regs_on_cpu(cpu, regs);
                if (err)
                        break;
                if (copy_to_user(uregs, &regs, sizeof regs))
                        err = -EFAULT;
                break;

        case X86_IOC_WRMSR_REGS:
                if (!(file->f_mode & FMODE_WRITE)) {
                        err = -EBADF;
                        break;
                }
                if (copy_from_user(&regs, uregs, sizeof regs)) {
                        err = -EFAULT;
                        break;
                }
                err = wrmsr_safe_regs_on_cpu(cpu, regs);
                if (err)
                        break;
                if (copy_to_user(uregs, &regs, sizeof regs))
                        err = -EFAULT;
                break;

        default:
                err = -ENOTTY;
                break;
        }

        return err;
}

static int msr_open(struct inode *inode, struct file *file)
{
        unsigned int cpu = iminor(file_inode(file));
        struct cpuinfo_x86 *c;

        if (!capable(CAP_SYS_RAWIO))
                return -EPERM;

        if (cpu >= nr_cpu_ids || !cpu_online(cpu))
                return -ENXIO;  /* No such CPU */

        c = &cpu_data(cpu);
        if (!cpu_has(c, X86_FEATURE_MSR))
                return -EIO;    /* MSR not supported */

        return 0;
}

/*
 * File operations we support
 */
static const struct file_operations msr_fops = {
        .owner = THIS_MODULE,
        .llseek = no_seek_end_llseek,
        .read = msr_read,
        .write = msr_write,
        .open = msr_open,
        .unlocked_ioctl = msr_ioctl,
        .compat_ioctl = msr_ioctl,
};

static int msr_device_create(unsigned int cpu)
{
        struct device *dev;

        dev = device_create(msr_class, NULL, MKDEV(MSR_MAJOR, cpu), NULL,
                            "msr%d", cpu);
        return PTR_ERR_OR_ZERO(dev);
}

static int msr_device_destroy(unsigned int cpu)
{
        device_destroy(msr_class, MKDEV(MSR_MAJOR, cpu));
        return 0;
}

static char *msr_devnode(struct device *dev, umode_t *mode)
{
        return kasprintf(GFP_KERNEL, "cpu/%u/msr", MINOR(dev->devt));
}

static int __init msr_init(void)
{
        int err;

        if (__register_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr", &msr_fops)) {
                pr_err("unable to get major %d for msr\n", MSR_MAJOR);
                return -EBUSY;
        }
        msr_class = class_create(THIS_MODULE, "msr");
        if (IS_ERR(msr_class)) {
                err = PTR_ERR(msr_class);
                goto out_chrdev;
        }
        msr_class->devnode = msr_devnode;

        err  = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "x86/msr:online",
                                 msr_device_create, msr_device_destroy);
        if (err < 0)
                goto out_class;
        cpuhp_msr_state = err;
        return 0;

out_class:
        class_destroy(msr_class);
out_chrdev:
        __unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");
        return err;
}
module_init(msr_init);

static void __exit msr_exit(void)
{
        cpuhp_remove_state(cpuhp_msr_state);
        class_destroy(msr_class);
        __unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");
}
module_exit(msr_exit)

MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
MODULE_DESCRIPTION("x86 generic MSR driver");
MODULE_LICENSE("GPL");