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