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