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 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(®s, 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, ®s, 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(®s, 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, ®s, 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"); 285