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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#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;
47
48static 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
76static 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
104static 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
152static 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 */
173static 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
183static 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
192static void msr_device_destroy(int cpu)
193{
194 device_destroy(msr_class, MKDEV(MSR_MAJOR, cpu));
195}
196
197static 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
216static struct notifier_block __refdata msr_class_cpu_notifier = {
217 .notifier_call = msr_class_cpu_callback,
218};
219
220static char *msr_devnode(struct device *dev, umode_t *mode)
221{
222 return kasprintf(GFP_KERNEL, "cpu/%u/msr", MINOR(dev->devt));
223}
224
225static 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
254out_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);
260out_chrdev:
261 __unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");
262out:
263 return err;
264}
265
266static 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
279module_init(msr_init);
280module_exit(msr_exit)
281
282MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
283MODULE_DESCRIPTION("x86 generic MSR driver");
284MODULE_LICENSE("GPL");