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
  44 static struct class *msr_class;
  45
  46 static loff_t msr_seek(struct file *file, loff_t offset, int orig)
  47 {
  48         loff_t ret;
  49         struct inode *inode = file_inode(file);
  50
  51         mutex_lock(&inode->i_mutex);
  52         switch (orig) {
  53         case 0:
  54                 file->f_pos = offset;
  55                 ret = file->f_pos;
  56                 break;
  57         case 1:
  58                 file->f_pos += offset;
  59                 ret = file->f_pos;
  60                 break;
  61         default:
  62                 ret = -EINVAL;
  63         }
  64         mutex_unlock(&inode->i_mutex);
  65         return ret;
  66 }
  67
  68 static ssize_t msr_read(struct file *file, char __user *buf,
  69                         size_t count, loff_t *ppos)
  70 {
  71         u32 __user *tmp = (u32 __user *) buf;
  72         u32 data[2];
  73         u32 reg = *ppos;
  74         int cpu = iminor(file_inode(file));
  75         int err = 0;
  76         ssize_t bytes = 0;
  77
  78         if (count % 8)
  79                 return -EINVAL; /* Invalid chunk size */
  80
  81         for (; count; count -= 8) {
  82                 err = rdmsr_safe_on_cpu(cpu, reg, &data[0], &data[1]);
  83                 if (err)
  84                         break;
  85                 if (copy_to_user(tmp, &data, 8)) {
  86                         err = -EFAULT;
  87                         break;
  88                 }
  89                 tmp += 2;
  90                 bytes += 8;
  91         }
  92
  93         return bytes ? bytes : err;
  94 }
  95
  96 static ssize_t msr_write(struct file *file, const char __user *buf,
  97                          size_t count, loff_t *ppos)
  98 {
  99         const u32 __user *tmp = (const u32 __user *)buf;
 100         u32 data[2];
 101         u32 reg = *ppos;
 102         int cpu = iminor(file_inode(file));
 103         int err = 0;
 104         ssize_t bytes = 0;
 105
 106         if (count % 8)
 107                 return -EINVAL; /* Invalid chunk size */
 108
 109         for (; count; count -= 8) {
 110                 if (copy_from_user(&data, tmp, 8)) {
 111                         err = -EFAULT;
 112                         break;
 113                 }
 114                 err = wrmsr_safe_on_cpu(cpu, reg, data[0], data[1]);
 115                 if (err)
 116                         break;
 117                 tmp += 2;
 118                 bytes += 8;
 119         }
 120
 121         return bytes ? bytes : err;
 122 }
 123
 124 static long msr_ioctl(struct file *file, unsigned int ioc, unsigned long arg)
 125 {
 126         u32 __user *uregs = (u32 __user *)arg;
 127         u32 regs[8];
 128         int cpu = iminor(file_inode(file));
 129         int err;
 130
 131         switch (ioc) {
 132         case X86_IOC_RDMSR_REGS:
 133                 if (!(file->f_mode & FMODE_READ)) {
 134                         err = -EBADF;
 135                         break;
 136                 }
 137                 if (copy_from_user(&regs, uregs, sizeof regs)) {
 138                         err = -EFAULT;
 139                         break;
 140                 }
 141                 err = rdmsr_safe_regs_on_cpu(cpu, regs);
 142                 if (err)
 143                         break;
 144                 if (copy_to_user(uregs, &regs, sizeof regs))
 145                         err = -EFAULT;
 146                 break;
 147
 148         case X86_IOC_WRMSR_REGS:
 149                 if (!(file->f_mode & FMODE_WRITE)) {
 150                         err = -EBADF;
 151                         break;
 152                 }
 153                 if (copy_from_user(&regs, uregs, sizeof regs)) {
 154                         err = -EFAULT;
 155                         break;
 156                 }
 157                 err = wrmsr_safe_regs_on_cpu(cpu, regs);
 158                 if (err)
 159                         break;
 160                 if (copy_to_user(uregs, &regs, sizeof regs))
 161                         err = -EFAULT;
 162                 break;
 163
 164         default:
 165                 err = -ENOTTY;
 166                 break;
 167         }
 168
 169         return err;
 170 }
 171
 172 static int msr_open(struct inode *inode, struct file *file)
 173 {
 174         unsigned int cpu = iminor(file_inode(file));
 175         struct cpuinfo_x86 *c;
 176
 177         if (!capable(CAP_SYS_RAWIO))
 178                 return -EPERM;
 179
 180         if (cpu >= nr_cpu_ids || !cpu_online(cpu))
 181                 return -ENXIO;  /* No such CPU */
 182
 183         c = &cpu_data(cpu);
 184         if (!cpu_has(c, X86_FEATURE_MSR))
 185                 return -EIO;    /* MSR not supported */
 186
 187         return 0;
 188 }
 189
 190 /*
 191  * File operations we support
 192  */
 193 static const struct file_operations msr_fops = {
 194         .owner = THIS_MODULE,
 195         .llseek = msr_seek,
 196         .read = msr_read,
 197         .write = msr_write,
 198         .open = msr_open,
 199         .unlocked_ioctl = msr_ioctl,
 200         .compat_ioctl = msr_ioctl,
 201 };
 202
 203 static int msr_device_create(int cpu)
 204 {
 205         struct device *dev;
 206
 207         dev = device_create(msr_class, NULL, MKDEV(MSR_MAJOR, cpu), NULL,
 208                             "msr%d", cpu);
 209         return IS_ERR(dev) ? PTR_ERR(dev) : 0;
 210 }
 211
 212 static void msr_device_destroy(int cpu)
 213 {
 214         device_destroy(msr_class, MKDEV(MSR_MAJOR, cpu));
 215 }
 216
 217 static int msr_class_cpu_callback(struct notifier_block *nfb,
 218                                   unsigned long action, void *hcpu)
 219 {
 220         unsigned int cpu = (unsigned long)hcpu;
 221         int err = 0;
 222
 223         switch (action) {
 224         case CPU_UP_PREPARE:
 225                 err = msr_device_create(cpu);
 226                 break;
 227         case CPU_UP_CANCELED:
 228         case CPU_UP_CANCELED_FROZEN:
 229         case CPU_DEAD:
 230                 msr_device_destroy(cpu);
 231                 break;
 232         }
 233         return notifier_from_errno(err);
 234 }
 235
 236 static struct notifier_block __refdata msr_class_cpu_notifier = {
 237         .notifier_call = msr_class_cpu_callback,
 238 };
 239
 240 static char *msr_devnode(struct device *dev, umode_t *mode)
 241 {
 242         return kasprintf(GFP_KERNEL, "cpu/%u/msr", MINOR(dev->devt));
 243 }
 244
 245 static int __init msr_init(void)
 246 {
 247         int i, err = 0;
 248         i = 0;
 249
 250         if (__register_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr", &msr_fops)) {
 251                 printk(KERN_ERR "msr: unable to get major %d for msr\n",
 252                        MSR_MAJOR);
 253                 err = -EBUSY;
 254                 goto out;
 255         }
 256         msr_class = class_create(THIS_MODULE, "msr");
 257         if (IS_ERR(msr_class)) {
 258                 err = PTR_ERR(msr_class);
 259                 goto out_chrdev;
 260         }
 261         msr_class->devnode = msr_devnode;
 262
 263         cpu_notifier_register_begin();
 264         for_each_online_cpu(i) {
 265                 err = msr_device_create(i);
 266                 if (err != 0)
 267                         goto out_class;
 268         }
 269         __register_hotcpu_notifier(&msr_class_cpu_notifier);
 270         cpu_notifier_register_done();
 271
 272         err = 0;
 273         goto out;
 274
 275 out_class:
 276         i = 0;
 277         for_each_online_cpu(i)
 278                 msr_device_destroy(i);
 279         cpu_notifier_register_done();
 280         class_destroy(msr_class);
 281 out_chrdev:
 282         __unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");
 283 out:
 284         return err;
 285 }
 286
 287 static void __exit msr_exit(void)
 288 {
 289         int cpu = 0;
 290
 291         cpu_notifier_register_begin();
 292         for_each_online_cpu(cpu)
 293                 msr_device_destroy(cpu);
 294         class_destroy(msr_class);
 295         __unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");
 296         __unregister_hotcpu_notifier(&msr_class_cpu_notifier);
 297         cpu_notifier_register_done();
 298 }
 299
 300 module_init(msr_init);
 301 module_exit(msr_exit)
 302
 303 MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
 304 MODULE_DESCRIPTION("x86 generic MSR driver");
 305 MODULE_LICENSE("GPL");