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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  26
  27 #include <linux/module.h>
  28
  29 #include <linux/types.h>
  30 #include <linux/errno.h>
  31 #include <linux/fcntl.h>
  32 #include <linux/init.h>
  33 #include <linux/poll.h>
  34 #include <linux/smp.h>
  35 #include <linux/major.h>
  36 #include <linux/fs.h>
  37 #include <linux/device.h>
  38 #include <linux/cpu.h>
  39 #include <linux/notifier.h>
  40 #include <linux/uaccess.h>
  41 #include <linux/gfp.h>
  42
  43 #include <asm/processor.h>
  44 #include <asm/msr.h>
  45
  46 static struct class *msr_class;
  47
  48 static loff_t msr_seek(struct file *file, loff_t offset, int orig)
  49 {
  50         loff_t ret;
  51         struct inode *inode = file_inode(file);
  52
  53         mutex_lock(&inode->i_mutex);
  54         switch (orig) {
  55         case SEEK_SET:
  56                 file->f_pos = offset;
  57                 ret = file->f_pos;
  58                 break;
  59         case SEEK_CUR:
  60                 file->f_pos += offset;
  61                 ret = file->f_pos;
  62                 break;
  63         default:
  64                 ret = -EINVAL;
  65         }
  66         mutex_unlock(&inode->i_mutex);
  67         return ret;
  68 }
  69
  70 static ssize_t msr_read(struct file *file, char __user *buf,
  71                         size_t count, loff_t *ppos)
  72 {
  73         u32 __user *tmp = (u32 __user *) buf;
  74         u32 data[2];
  75         u32 reg = *ppos;
  76         int cpu = iminor(file_inode(file));
  77         int err = 0;
  78         ssize_t bytes = 0;
  79
  80         if (count % 8)
  81                 return -EINVAL; /* Invalid chunk size */
  82
  83         for (; count; count -= 8) {
  84                 err = rdmsr_safe_on_cpu(cpu, reg, &data[0], &data[1]);
  85                 if (err)
  86                         break;
  87                 if (copy_to_user(tmp, &data, 8)) {
  88                         err = -EFAULT;
  89                         break;
  90                 }
  91                 tmp += 2;
  92                 bytes += 8;
  93         }
  94
  95         return bytes ? bytes : err;
  96 }
  97
  98 static ssize_t msr_write(struct file *file, const char __user *buf,
  99                          size_t count, loff_t *ppos)
 100 {
 101         const u32 __user *tmp = (const u32 __user *)buf;
 102         u32 data[2];
 103         u32 reg = *ppos;
 104         int cpu = iminor(file_inode(file));
 105         int err = 0;
 106         ssize_t bytes = 0;
 107
 108         if (count % 8)
 109                 return -EINVAL; /* Invalid chunk size */
 110
 111         for (; count; count -= 8) {
 112                 if (copy_from_user(&data, tmp, 8)) {
 113                         err = -EFAULT;
 114                         break;
 115                 }
 116                 err = wrmsr_safe_on_cpu(cpu, reg, data[0], data[1]);
 117                 if (err)
 118                         break;
 119                 tmp += 2;
 120                 bytes += 8;
 121         }
 122
 123         return bytes ? bytes : err;
 124 }
 125
 126 static long msr_ioctl(struct file *file, unsigned int ioc, unsigned long arg)
 127 {
 128         u32 __user *uregs = (u32 __user *)arg;
 129         u32 regs[8];
 130         int cpu = iminor(file_inode(file));
 131         int err;
 132
 133         switch (ioc) {
 134         case X86_IOC_RDMSR_REGS:
 135                 if (!(file->f_mode & FMODE_READ)) {
 136                         err = -EBADF;
 137                         break;
 138                 }
 139                 if (copy_from_user(&regs, uregs, sizeof regs)) {
 140                         err = -EFAULT;
 141                         break;
 142                 }
 143                 err = rdmsr_safe_regs_on_cpu(cpu, regs);
 144                 if (err)
 145                         break;
 146                 if (copy_to_user(uregs, &regs, sizeof regs))
 147                         err = -EFAULT;
 148                 break;
 149
 150         case X86_IOC_WRMSR_REGS:
 151                 if (!(file->f_mode & FMODE_WRITE)) {
 152                         err = -EBADF;
 153                         break;
 154                 }
 155                 if (copy_from_user(&regs, uregs, sizeof regs)) {
 156                         err = -EFAULT;
 157                         break;
 158                 }
 159                 err = wrmsr_safe_regs_on_cpu(cpu, regs);
 160                 if (err)
 161                         break;
 162                 if (copy_to_user(uregs, &regs, sizeof regs))
 163                         err = -EFAULT;
 164                 break;
 165
 166         default:
 167                 err = -ENOTTY;
 168                 break;
 169         }
 170
 171         return err;
 172 }
 173
 174 static int msr_open(struct inode *inode, struct file *file)
 175 {
 176         unsigned int cpu = iminor(file_inode(file));
 177         struct cpuinfo_x86 *c;
 178
 179         if (!capable(CAP_SYS_RAWIO))
 180                 return -EPERM;
 181
 182         if (cpu >= nr_cpu_ids || !cpu_online(cpu))
 183                 return -ENXIO;  /* No such CPU */
 184
 185         c = &cpu_data(cpu);
 186         if (!cpu_has(c, X86_FEATURE_MSR))
 187                 return -EIO;    /* MSR not supported */
 188
 189         return 0;
 190 }
 191
 192 /*
 193  * File operations we support
 194  */
 195 static const struct file_operations msr_fops = {
 196         .owner = THIS_MODULE,
 197         .llseek = msr_seek,
 198         .read = msr_read,
 199         .write = msr_write,
 200         .open = msr_open,
 201         .unlocked_ioctl = msr_ioctl,
 202         .compat_ioctl = msr_ioctl,
 203 };
 204
 205 static int msr_device_create(int cpu)
 206 {
 207         struct device *dev;
 208
 209         dev = device_create(msr_class, NULL, MKDEV(MSR_MAJOR, cpu), NULL,
 210                             "msr%d", cpu);
 211         return PTR_ERR_OR_ZERO(dev);
 212 }
 213
 214 static void msr_device_destroy(int cpu)
 215 {
 216         device_destroy(msr_class, MKDEV(MSR_MAJOR, cpu));
 217 }
 218
 219 static int msr_class_cpu_callback(struct notifier_block *nfb,
 220                                   unsigned long action, void *hcpu)
 221 {
 222         unsigned int cpu = (unsigned long)hcpu;
 223         int err = 0;
 224
 225         switch (action) {
 226         case CPU_UP_PREPARE:
 227                 err = msr_device_create(cpu);
 228                 break;
 229         case CPU_UP_CANCELED:
 230         case CPU_UP_CANCELED_FROZEN:
 231         case CPU_DEAD:
 232                 msr_device_destroy(cpu);
 233                 break;
 234         }
 235         return notifier_from_errno(err);
 236 }
 237
 238 static struct notifier_block __refdata msr_class_cpu_notifier = {
 239         .notifier_call = msr_class_cpu_callback,
 240 };
 241
 242 static char *msr_devnode(struct device *dev, umode_t *mode)
 243 {
 244         return kasprintf(GFP_KERNEL, "cpu/%u/msr", MINOR(dev->devt));
 245 }
 246
 247 static int __init msr_init(void)
 248 {
 249         int i, err = 0;
 250         i = 0;
 251
 252         if (__register_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr", &msr_fops)) {
 253                 pr_err("unable to get major %d for msr\n", MSR_MAJOR);
 254                 err = -EBUSY;
 255                 goto out;
 256         }
 257         msr_class = class_create(THIS_MODULE, "msr");
 258         if (IS_ERR(msr_class)) {
 259                 err = PTR_ERR(msr_class);
 260                 goto out_chrdev;
 261         }
 262         msr_class->devnode = msr_devnode;
 263
 264         cpu_notifier_register_begin();
 265         for_each_online_cpu(i) {
 266                 err = msr_device_create(i);
 267                 if (err != 0)
 268                         goto out_class;
 269         }
 270         __register_hotcpu_notifier(&msr_class_cpu_notifier);
 271         cpu_notifier_register_done();
 272
 273         err = 0;
 274         goto out;
 275
 276 out_class:
 277         i = 0;
 278         for_each_online_cpu(i)
 279                 msr_device_destroy(i);
 280         cpu_notifier_register_done();
 281         class_destroy(msr_class);
 282 out_chrdev:
 283         __unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");
 284 out:
 285         return err;
 286 }
 287
 288 static void __exit msr_exit(void)
 289 {
 290         int cpu = 0;
 291
 292         cpu_notifier_register_begin();
 293         for_each_online_cpu(cpu)
 294                 msr_device_destroy(cpu);
 295         class_destroy(msr_class);
 296         __unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");
 297         __unregister_hotcpu_notifier(&msr_class_cpu_notifier);
 298         cpu_notifier_register_done();
 299 }
 300
 301 module_init(msr_init);
 302 module_exit(msr_exit)
 303
 304 MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
 305 MODULE_DESCRIPTION("x86 generic MSR driver");
 306 MODULE_LICENSE("GPL");