root/arch/x86/kernel/msr.c

DEFINITIONS

1. msr_seek
2. msr_read
3. msr_write
4. msr_open
5. msr_device_create
6. msr_device_destroy
7. msr_class_cpu_callback
8. msr_init
9. msr_exit

/* ----------------------------------------------------------------------- *
 *
 *   Copyright 2000-2008 H. Peter Anvin - All Rights Reserved
 *
 *   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.
 */

#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/smp_lock.h>
#include <linux/major.h>
#include <linux/fs.h>
#include <linux/device.h>
#include <linux/cpu.h>
#include <linux/notifier.h>

#include <asm/processor.h>
#include <asm/msr.h>
#include <asm/uaccess.h>
#include <asm/system.h>

static struct class *msr_class;

static loff_t msr_seek(struct file *file, loff_t offset, int orig)
{
        loff_t ret;
        struct inode *inode = file->f_mapping->host;

        mutex_lock(&inode->i_mutex);
        switch (orig) {
        case 0:
                file->f_pos = offset;
                ret = file->f_pos;
                break;
        case 1:
                file->f_pos += offset;
                ret = file->f_pos;
                break;
        default:
                ret = -EINVAL;
        }
        mutex_unlock(&inode->i_mutex);
        return ret;
}

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->f_path.dentry->d_inode);
        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) {
                        if (err == -EFAULT) /* Fix idiotic error code */
                                err = -EIO;
                        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->f_path.dentry->d_inode);
        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) {
                        if (err == -EFAULT) /* Fix idiotic error code */
                                err = -EIO;
                        break;
                }
                tmp += 2;
                bytes += 8;
        }

        return bytes ? bytes : err;
}

static int msr_open(struct inode *inode, struct file *file)
{
        unsigned int cpu = iminor(file->f_path.dentry->d_inode);
        struct cpuinfo_x86 *c = &cpu_data(cpu);
        int ret = 0;

        lock_kernel();
        cpu = iminor(file->f_path.dentry->d_inode);

        if (cpu >= NR_CPUS || !cpu_online(cpu)) {
                ret = -ENXIO;   /* No such CPU */
                goto out;
        }
        c = &cpu_data(cpu);
        if (!cpu_has(c, X86_FEATURE_MSR))
                ret = -EIO;     /* MSR not supported */
out:
        unlock_kernel();
        return ret;
}

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

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

        dev = device_create_drvdata(msr_class, NULL, MKDEV(MSR_MAJOR, cpu),
                                    NULL, "msr%d", cpu);
        return IS_ERR(dev) ? PTR_ERR(dev) : 0;
}

static void msr_device_destroy(int cpu)
{
        device_destroy(msr_class, MKDEV(MSR_MAJOR, cpu));
}

static int __cpuinit msr_class_cpu_callback(struct notifier_block *nfb,
                                unsigned long action, void *hcpu)
{
        unsigned int cpu = (unsigned long)hcpu;
        int err = 0;

        switch (action) {
        case CPU_UP_PREPARE:
                err = msr_device_create(cpu);
                break;
        case CPU_UP_CANCELED:
        case CPU_UP_CANCELED_FROZEN:
        case CPU_DEAD:
                msr_device_destroy(cpu);
                break;
        }
        return err ? NOTIFY_BAD : NOTIFY_OK;
}

static struct notifier_block __refdata msr_class_cpu_notifier = {
        .notifier_call = msr_class_cpu_callback,
};

static int __init msr_init(void)
{
        int i, err = 0;
        i = 0;

        if (register_chrdev(MSR_MAJOR, "cpu/msr", &msr_fops)) {
                printk(KERN_ERR "msr: unable to get major %d for msr\n",
                       MSR_MAJOR);
                err = -EBUSY;
                goto out;
        }
        msr_class = class_create(THIS_MODULE, "msr");
        if (IS_ERR(msr_class)) {
                err = PTR_ERR(msr_class);
                goto out_chrdev;
        }
        for_each_online_cpu(i) {
                err = msr_device_create(i);
                if (err != 0)
                        goto out_class;
        }
        register_hotcpu_notifier(&msr_class_cpu_notifier);

        err = 0;
        goto out;

out_class:
        i = 0;
        for_each_online_cpu(i)
                msr_device_destroy(i);
        class_destroy(msr_class);
out_chrdev:
        unregister_chrdev(MSR_MAJOR, "cpu/msr");
out:
        return err;
}

static void __exit msr_exit(void)
{
        int cpu = 0;
        for_each_online_cpu(cpu)
                msr_device_destroy(cpu);
        class_destroy(msr_class);
        unregister_chrdev(MSR_MAJOR, "cpu/msr");
        unregister_hotcpu_notifier(&msr_class_cpu_notifier);
}

module_init(msr_init);
module_exit(msr_exit)

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