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->f_mapping->host; 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(®s, 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, ®s, 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(®s, 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, ®s, 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 get_online_cpus(); 263 for_each_online_cpu(i) { 264 err = msr_device_create(i); 265 if (err != 0) 266 goto out_class; 267 } 268 register_hotcpu_notifier(&msr_class_cpu_notifier); 269 put_online_cpus(); 270 271 err = 0; 272 goto out; 273 274 out_class: 275 i = 0; 276 for_each_online_cpu(i) 277 msr_device_destroy(i); 278 put_online_cpus(); 279 class_destroy(msr_class); 280 out_chrdev: 281 __unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr"); 282 out: 283 return err; 284 } 285 286 static void __exit msr_exit(void) 287 { 288 int cpu = 0; 289 get_online_cpus(); 290 for_each_online_cpu(cpu) 291 msr_device_destroy(cpu); 292 class_destroy(msr_class); 293 __unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr"); 294 unregister_hotcpu_notifier(&msr_class_cpu_notifier); 295 put_online_cpus(); 296 } 297 298 module_init(msr_init); 299 module_exit(msr_exit) 300 301 MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>"); 302 MODULE_DESCRIPTION("x86 generic MSR driver"); 303 MODULE_LICENSE("GPL"); 304