| 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 | cpuhp_remove_state(cpuhp_msr_state); |
| 228 | class_destroy(msr_class); |
| 229 | out_chrdev: |
| 230 | __unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr"); |
| 231 | return err; |
| 232 | } |
| 233 | module_init(msr_init); |
| 234 | |
| 235 | static void __exit msr_exit(void) |
| 236 | { |
| 237 | cpuhp_remove_state(cpuhp_msr_state); |
| 238 | class_destroy(msr_class); |
| 239 | __unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr"); |
| 240 | } |
| 241 | module_exit(msr_exit) |
| 242 | |
| 243 | MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>"); |
| 244 | MODULE_DESCRIPTION("x86 generic MSR driver"); |
| 245 | MODULE_LICENSE("GPL"); |