arch/x86/kernel/msr.c

   1 /* ----------------------------------------------------------------------- *
   2  *
   3  *   Copyright 2000-2008 H. Peter Anvin - All Rights Reserved
   4  *   Copyright 2009 Intel Corporation; author: H. Peter Anvin
   5  *
   6  *   This program is free software; you can redistribute it and/or modify
   7  *   it under the terms of the GNU General Public License as published by
   8  *   the Free Software Foundation, Inc., 675 Mass Ave, Cambridge MA 02139,
   9  *   USA; either version 2 of the License, or (at your option) any later
  10  *   version; incorporated herein by reference.
  11  *
  12  * ----------------------------------------------------------------------- */
  13
  14 /*
  15  * x86 MSR access device
  16  *
  17  * This device is accessed by lseek() to the appropriate register number
  18  * and then read/write in chunks of 8 bytes.  A larger size means multiple
  19  * reads or writes of the same register.
  20  *
  21  * This driver uses /dev/cpu/%d/msr where %d is the minor number, and on
  22  * an SMP box will direct the access to CPU %d.
  23  */
  24
  25 #include <linux/module.h>
  26
  27 #include <linux/types.h>
  28 #include <linux/errno.h>
  29 #include <linux/fcntl.h>
  30 #include <linux/init.h>
  31 #include <linux/poll.h>
  32 #include <linux/smp.h>
  33 #include <linux/major.h>
  34 #include <linux/fs.h>
  35 #include <linux/device.h>
  36 #include <linux/cpu.h>
  37 #include <linux/notifier.h>
  38 #include <linux/uaccess.h>
  39 #include <linux/gfp.h>
  40
  41 #include <asm/processor.h>
  42 #include <asm/msr.h>
  43 #include <asm/system.h>
  44
  45 static struct class *msr_class;
  46
  47 static loff_t msr_seek(struct file *file, loff_t offset, int orig)
  48 {
  49         loff_t ret;
  50         struct inode *inode = file->f_mapping->host;
  51
  52         mutex_lock(&inode->i_mutex);
  53         switch (orig) {
  54         case 0:
  55                 file->f_pos = offset;
  56                 ret = file->f_pos;
  57                 break;
  58         case 1:
  59                 file->f_pos += offset;
  60                 ret = file->f_pos;
  61                 break;
  62         default:
  63                 ret = -EINVAL;
  64         }
  65         mutex_unlock(&inode->i_mutex);
  66         return ret;
  67 }
  68
  69 static ssize_t msr_read(struct file *file, char __user *buf,
  70                         size_t count, loff_t *ppos)
  71 {
  72         u32 __user *tmp = (u32 __user *) buf;
  73         u32 data[2];
  74         u32 reg = *ppos;
  75         int cpu = iminor(file->f_path.dentry->d_inode);
  76         int err = 0;
  77         ssize_t bytes = 0;
  78
  79         if (count % 8)
  80                 return -EINVAL; /* Invalid chunk size */
  81
  82         for (; count; count -= 8) {
  83                 err = rdmsr_safe_on_cpu(cpu, reg, &data[0], &data[1]);
  84                 if (err)
  85                         break;
  86                 if (copy_to_user(tmp, &data, 8)) {
  87                         err = -EFAULT;
  88                         break;
  89                 }
  90                 tmp += 2;
  91                 bytes += 8;
  92         }
  93
  94         return bytes ? bytes : err;
  95 }
  96
  97 static ssize_t msr_write(struct file *file, const char __user *buf,
  98                          size_t count, loff_t *ppos)
  99 {
 100         const u32 __user *tmp = (const u32 __user *)buf;
 101         u32 data[2];
 102         u32 reg = *ppos;
 103         int cpu = iminor(file->f_path.dentry->d_inode);
 104         int err = 0;
 105         ssize_t bytes = 0;
 106
 107         if (count % 8)
 108                 return -EINVAL; /* Invalid chunk size */
 109
 110         for (; count; count -= 8) {
 111                 if (copy_from_user(&data, tmp, 8)) {
 112                         err = -EFAULT;
 113                         break;
 114                 }
 115                 err = wrmsr_safe_on_cpu(cpu, reg, data[0], data[1]);
 116                 if (err)
 117                         break;
 118                 tmp += 2;
 119                 bytes += 8;
 120         }
 121
 122         return bytes ? bytes : err;
 123 }
 124
 125 static long msr_ioctl(struct file *file, unsigned int ioc, unsigned long arg)
 126 {
 127         u32 __user *uregs = (u32 __user *)arg;
 128         u32 regs[8];
 129         int cpu = iminor(file->f_path.dentry->d_inode);
 130         int err;
 131
 132         switch (ioc) {
 133         case X86_IOC_RDMSR_REGS:
 134                 if (!(file->f_mode & FMODE_READ)) {
 135                         err = -EBADF;
 136                         break;
 137                 }
 138                 if (copy_from_user(&regs, uregs, sizeof regs)) {
 139                         err = -EFAULT;
 140                         break;
 141                 }
 142                 err = rdmsr_safe_regs_on_cpu(cpu, regs);
 143                 if (err)
 144                         break;
 145                 if (copy_to_user(uregs, &regs, sizeof regs))
 146                         err = -EFAULT;
 147                 break;
 148
 149         case X86_IOC_WRMSR_REGS:
 150                 if (!(file->f_mode & FMODE_WRITE)) {
 151                         err = -EBADF;
 152                         break;
 153                 }
 154                 if (copy_from_user(&regs, uregs, sizeof regs)) {
 155                         err = -EFAULT;
 156                         break;
 157                 }
 158                 err = wrmsr_safe_regs_on_cpu(cpu, regs);
 159                 if (err)
 160                         break;
 161                 if (copy_to_user(uregs, &regs, sizeof regs))
 162                         err = -EFAULT;
 163                 break;
 164
 165         default:
 166                 err = -ENOTTY;
 167                 break;
 168         }
 169
 170         return err;
 171 }
 172
 173 static int msr_open(struct inode *inode, struct file *file)
 174 {
 175         unsigned int cpu;
 176         struct cpuinfo_x86 *c;
 177
 178         cpu = iminor(file->f_path.dentry->d_inode);
 179         if (cpu >= nr_cpu_ids || !cpu_online(cpu))
 180                 return -ENXIO;  /* No such CPU */
 181
 182         c = &cpu_data(cpu);
 183         if (!cpu_has(c, X86_FEATURE_MSR))
 184                 return -EIO;    /* MSR not supported */
 185
 186         return 0;
 187 }
 188
 189 /*
 190  * File operations we support
 191  */
 192 static const struct file_operations msr_fops = {
 193         .owner = THIS_MODULE,
 194         .llseek = msr_seek,
 195         .read = msr_read,
 196         .write = msr_write,
 197         .open = msr_open,
 198         .unlocked_ioctl = msr_ioctl,
 199         .compat_ioctl = msr_ioctl,
 200 };
 201
 202 static int __cpuinit msr_device_create(int cpu)
 203 {
 204         struct device *dev;
 205
 206         dev = device_create(msr_class, NULL, MKDEV(MSR_MAJOR, cpu), NULL,
 207                             "msr%d", cpu);
 208         return IS_ERR(dev) ? PTR_ERR(dev) : 0;
 209 }
 210
 211 static void msr_device_destroy(int cpu)
 212 {
 213         device_destroy(msr_class, MKDEV(MSR_MAJOR, cpu));
 214 }
 215
 216 static int __cpuinit msr_class_cpu_callback(struct notifier_block *nfb,
 217                                 unsigned long action, void *hcpu)
 218 {
 219         unsigned int cpu = (unsigned long)hcpu;
 220         int err = 0;
 221
 222         switch (action) {
 223         case CPU_UP_PREPARE:
 224                 err = msr_device_create(cpu);
 225                 break;
 226         case CPU_UP_CANCELED:
 227         case CPU_UP_CANCELED_FROZEN:
 228         case CPU_DEAD:
 229                 msr_device_destroy(cpu);
 230                 break;
 231         }
 232         return notifier_from_errno(err);
 233 }
 234
 235 static struct notifier_block __refdata msr_class_cpu_notifier = {
 236         .notifier_call = msr_class_cpu_callback,
 237 };
 238
 239 static char *msr_devnode(struct device *dev, mode_t *mode)
 240 {
 241         return kasprintf(GFP_KERNEL, "cpu/%u/msr", MINOR(dev->devt));
 242 }
 243
 244 static int __init msr_init(void)
 245 {
 246         int i, err = 0;
 247         i = 0;
 248
 249         if (__register_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr", &msr_fops)) {
 250                 printk(KERN_ERR "msr: unable to get major %d for msr\n",
 251                        MSR_MAJOR);
 252                 err = -EBUSY;
 253                 goto out;
 254         }
 255         msr_class = class_create(THIS_MODULE, "msr");
 256         if (IS_ERR(msr_class)) {
 257                 err = PTR_ERR(msr_class);
 258                 goto out_chrdev;
 259         }
 260         msr_class->devnode = msr_devnode;
 261         for_each_online_cpu(i) {
 262                 err = msr_device_create(i);
 263                 if (err != 0)
 264                         goto out_class;
 265         }
 266         register_hotcpu_notifier(&msr_class_cpu_notifier);
 267
 268         err = 0;
 269         goto out;
 270
 271 out_class:
 272         i = 0;
 273         for_each_online_cpu(i)
 274                 msr_device_destroy(i);
 275         class_destroy(msr_class);
 276 out_chrdev:
 277         __unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");
 278 out:
 279         return err;
 280 }
 281
 282 static void __exit msr_exit(void)
 283 {
 284         int cpu = 0;
 285         for_each_online_cpu(cpu)
 286                 msr_device_destroy(cpu);
 287         class_destroy(msr_class);
 288         __unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");
 289         unregister_hotcpu_notifier(&msr_class_cpu_notifier);
 290 }
 291
 292 module_init(msr_init);
 293 module_exit(msr_exit)
 294
 295 MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
 296 MODULE_DESCRIPTION("x86 generic MSR driver");
 297 MODULE_LICENSE("GPL");