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