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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
46static struct class *msr_class;
47static enum cpuhp_state cpuhp_msr_state;
48
49static 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
77static 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
105static 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
153static 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 */
174static 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
184static 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
193static int msr_device_destroy(unsigned int cpu)
194{
195 device_destroy(msr_class, MKDEV(MSR_MAJOR, cpu));
196 return 0;
197}
198
199static char *msr_devnode(struct device *dev, umode_t *mode)
200{
201 return kasprintf(GFP_KERNEL, "cpu/%u/msr", MINOR(dev->devt));
202}
203
204static 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
226out_class:
227 class_destroy(msr_class);
228out_chrdev:
229 __unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");
230 return err;
231}
232module_init(msr_init);
233
234static 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}
240module_exit(msr_exit)
241
242MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
243MODULE_DESCRIPTION("x86 generic MSR driver");
244MODULE_LICENSE("GPL");
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
44static struct class *msr_class;
45
46static 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
68static 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->f_path.dentry->d_inode);
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
96static 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->f_path.dentry->d_inode);
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
124static 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->f_path.dentry->d_inode);
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
172static int msr_open(struct inode *inode, struct file *file)
173{
174 unsigned int cpu;
175 struct cpuinfo_x86 *c;
176
177 cpu = iminor(file->f_path.dentry->d_inode);
178 if (cpu >= nr_cpu_ids || !cpu_online(cpu))
179 return -ENXIO; /* No such CPU */
180
181 c = &cpu_data(cpu);
182 if (!cpu_has(c, X86_FEATURE_MSR))
183 return -EIO; /* MSR not supported */
184
185 return 0;
186}
187
188/*
189 * File operations we support
190 */
191static const struct file_operations msr_fops = {
192 .owner = THIS_MODULE,
193 .llseek = msr_seek,
194 .read = msr_read,
195 .write = msr_write,
196 .open = msr_open,
197 .unlocked_ioctl = msr_ioctl,
198 .compat_ioctl = msr_ioctl,
199};
200
201static int __cpuinit msr_device_create(int cpu)
202{
203 struct device *dev;
204
205 dev = device_create(msr_class, NULL, MKDEV(MSR_MAJOR, cpu), NULL,
206 "msr%d", cpu);
207 return IS_ERR(dev) ? PTR_ERR(dev) : 0;
208}
209
210static void msr_device_destroy(int cpu)
211{
212 device_destroy(msr_class, MKDEV(MSR_MAJOR, cpu));
213}
214
215static int __cpuinit msr_class_cpu_callback(struct notifier_block *nfb,
216 unsigned long action, void *hcpu)
217{
218 unsigned int cpu = (unsigned long)hcpu;
219 int err = 0;
220
221 switch (action) {
222 case CPU_UP_PREPARE:
223 err = msr_device_create(cpu);
224 break;
225 case CPU_UP_CANCELED:
226 case CPU_UP_CANCELED_FROZEN:
227 case CPU_DEAD:
228 msr_device_destroy(cpu);
229 break;
230 }
231 return notifier_from_errno(err);
232}
233
234static struct notifier_block __refdata msr_class_cpu_notifier = {
235 .notifier_call = msr_class_cpu_callback,
236};
237
238static char *msr_devnode(struct device *dev, umode_t *mode)
239{
240 return kasprintf(GFP_KERNEL, "cpu/%u/msr", MINOR(dev->devt));
241}
242
243static int __init msr_init(void)
244{
245 int i, err = 0;
246 i = 0;
247
248 if (__register_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr", &msr_fops)) {
249 printk(KERN_ERR "msr: unable to get major %d for msr\n",
250 MSR_MAJOR);
251 err = -EBUSY;
252 goto out;
253 }
254 msr_class = class_create(THIS_MODULE, "msr");
255 if (IS_ERR(msr_class)) {
256 err = PTR_ERR(msr_class);
257 goto out_chrdev;
258 }
259 msr_class->devnode = msr_devnode;
260 for_each_online_cpu(i) {
261 err = msr_device_create(i);
262 if (err != 0)
263 goto out_class;
264 }
265 register_hotcpu_notifier(&msr_class_cpu_notifier);
266
267 err = 0;
268 goto out;
269
270out_class:
271 i = 0;
272 for_each_online_cpu(i)
273 msr_device_destroy(i);
274 class_destroy(msr_class);
275out_chrdev:
276 __unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");
277out:
278 return err;
279}
280
281static void __exit msr_exit(void)
282{
283 int cpu = 0;
284 for_each_online_cpu(cpu)
285 msr_device_destroy(cpu);
286 class_destroy(msr_class);
287 __unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");
288 unregister_hotcpu_notifier(&msr_class_cpu_notifier);
289}
290
291module_init(msr_init);
292module_exit(msr_exit)
293
294MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
295MODULE_DESCRIPTION("x86 generic MSR driver");
296MODULE_LICENSE("GPL");