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/smp_lock.h> 34#include <linux/major.h> 35#include <linux/fs.h> 36#include <linux/device.h> 37#include <linux/cpu.h> 38#include <linux/notifier.h> 39#include <linux/uaccess.h> 40#include <linux/gfp.h> 41 42#include <asm/processor.h> 43#include <asm/msr.h> 44#include <asm/system.h> 45 46static struct class *msr_class; 47 48static loff_t msr_seek(struct file *file, loff_t offset, int orig) 49{ 50 loff_t ret; 51 struct inode *inode = file->f_mapping->host; 52 53 mutex_lock(&inode->i_mutex); 54 switch (orig) { 55 case 0: 56 file->f_pos = offset; 57 ret = file->f_pos; 58 break; 59 case 1: 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 70static 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->f_path.dentry->d_inode); 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 98static 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->f_path.dentry->d_inode); 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 126static 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->f_path.dentry->d_inode); 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(®s, 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, ®s, 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(®s, 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, ®s, sizeof regs)) 163 err = -EFAULT; 164 break; 165 166 default: 167 err = -ENOTTY; 168 break; 169 } 170 171 return err; 172} 173 174static int msr_open(struct inode *inode, struct file *file) 175{ 176 unsigned int cpu; 177 struct cpuinfo_x86 *c; 178 179 cpu = iminor(file->f_path.dentry->d_inode); 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 */ 193static 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 203static int __cpuinit 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 212static void msr_device_destroy(int cpu) 213{ 214 device_destroy(msr_class, MKDEV(MSR_MAJOR, cpu)); 215} 216 217static int __cpuinit 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 236static struct notifier_block __refdata msr_class_cpu_notifier = { 237 .notifier_call = msr_class_cpu_callback, 238}; 239 240static char *msr_devnode(struct device *dev, mode_t *mode) 241{ 242 return kasprintf(GFP_KERNEL, "cpu/%u/msr", MINOR(dev->devt)); 243} 244 245static 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 for_each_online_cpu(i) { 263 err = msr_device_create(i); 264 if (err != 0) 265 goto out_class; 266 } 267 register_hotcpu_notifier(&msr_class_cpu_notifier); 268 269 err = 0; 270 goto out; 271 272out_class: 273 i = 0; 274 for_each_online_cpu(i) 275 msr_device_destroy(i); 276 class_destroy(msr_class); 277out_chrdev: 278 __unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr"); 279out: 280 return err; 281} 282 283static void __exit msr_exit(void) 284{ 285 int cpu = 0; 286 for_each_online_cpu(cpu) 287 msr_device_destroy(cpu); 288 class_destroy(msr_class); 289 __unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr"); 290 unregister_hotcpu_notifier(&msr_class_cpu_notifier); 291} 292 293module_init(msr_init); 294module_exit(msr_exit) 295 296MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>"); 297MODULE_DESCRIPTION("x86 generic MSR driver"); 298MODULE_LICENSE("GPL"); 299