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1// SPDX-License-Identifier: GPL-2.0-or-later
2/* ----------------------------------------------------------------------- *
3 *
4 * Copyright 2000-2008 H. Peter Anvin - All Rights Reserved
5 * Copyright 2009 Intel Corporation; author: H. Peter Anvin
6 *
7 * ----------------------------------------------------------------------- */
8
9/*
10 * x86 MSR access device
11 *
12 * This device is accessed by lseek() to the appropriate register number
13 * and then read/write in chunks of 8 bytes. A larger size means multiple
14 * reads or writes of the same register.
15 *
16 * This driver uses /dev/cpu/%d/msr where %d is the minor number, and on
17 * an SMP box will direct the access to CPU %d.
18 */
19
20#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
21
22#include <linux/module.h>
23
24#include <linux/types.h>
25#include <linux/errno.h>
26#include <linux/fcntl.h>
27#include <linux/init.h>
28#include <linux/poll.h>
29#include <linux/smp.h>
30#include <linux/major.h>
31#include <linux/fs.h>
32#include <linux/device.h>
33#include <linux/cpu.h>
34#include <linux/notifier.h>
35#include <linux/uaccess.h>
36#include <linux/gfp.h>
37#include <linux/security.h>
38
39#include <asm/cpufeature.h>
40#include <asm/msr.h>
41
42static struct class *msr_class;
43static enum cpuhp_state cpuhp_msr_state;
44
45static ssize_t msr_read(struct file *file, char __user *buf,
46 size_t count, loff_t *ppos)
47{
48 u32 __user *tmp = (u32 __user *) buf;
49 u32 data[2];
50 u32 reg = *ppos;
51 int cpu = iminor(file_inode(file));
52 int err = 0;
53 ssize_t bytes = 0;
54
55 if (count % 8)
56 return -EINVAL; /* Invalid chunk size */
57
58 for (; count; count -= 8) {
59 err = rdmsr_safe_on_cpu(cpu, reg, &data[0], &data[1]);
60 if (err)
61 break;
62 if (copy_to_user(tmp, &data, 8)) {
63 err = -EFAULT;
64 break;
65 }
66 tmp += 2;
67 bytes += 8;
68 }
69
70 return bytes ? bytes : err;
71}
72
73static ssize_t msr_write(struct file *file, const char __user *buf,
74 size_t count, loff_t *ppos)
75{
76 const u32 __user *tmp = (const u32 __user *)buf;
77 u32 data[2];
78 u32 reg = *ppos;
79 int cpu = iminor(file_inode(file));
80 int err = 0;
81 ssize_t bytes = 0;
82
83 err = security_locked_down(LOCKDOWN_MSR);
84 if (err)
85 return err;
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 = security_locked_down(LOCKDOWN_MSR);
139 if (err)
140 break;
141 err = wrmsr_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 default:
149 err = -ENOTTY;
150 break;
151 }
152
153 return err;
154}
155
156static int msr_open(struct inode *inode, struct file *file)
157{
158 unsigned int cpu = iminor(file_inode(file));
159 struct cpuinfo_x86 *c;
160
161 if (!capable(CAP_SYS_RAWIO))
162 return -EPERM;
163
164 if (cpu >= nr_cpu_ids || !cpu_online(cpu))
165 return -ENXIO; /* No such CPU */
166
167 c = &cpu_data(cpu);
168 if (!cpu_has(c, X86_FEATURE_MSR))
169 return -EIO; /* MSR not supported */
170
171 return 0;
172}
173
174/*
175 * File operations we support
176 */
177static const struct file_operations msr_fops = {
178 .owner = THIS_MODULE,
179 .llseek = no_seek_end_llseek,
180 .read = msr_read,
181 .write = msr_write,
182 .open = msr_open,
183 .unlocked_ioctl = msr_ioctl,
184 .compat_ioctl = msr_ioctl,
185};
186
187static int msr_device_create(unsigned int cpu)
188{
189 struct device *dev;
190
191 dev = device_create(msr_class, NULL, MKDEV(MSR_MAJOR, cpu), NULL,
192 "msr%d", cpu);
193 return PTR_ERR_OR_ZERO(dev);
194}
195
196static int msr_device_destroy(unsigned int cpu)
197{
198 device_destroy(msr_class, MKDEV(MSR_MAJOR, cpu));
199 return 0;
200}
201
202static char *msr_devnode(struct device *dev, umode_t *mode)
203{
204 return kasprintf(GFP_KERNEL, "cpu/%u/msr", MINOR(dev->devt));
205}
206
207static int __init msr_init(void)
208{
209 int err;
210
211 if (__register_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr", &msr_fops)) {
212 pr_err("unable to get major %d for msr\n", MSR_MAJOR);
213 return -EBUSY;
214 }
215 msr_class = class_create(THIS_MODULE, "msr");
216 if (IS_ERR(msr_class)) {
217 err = PTR_ERR(msr_class);
218 goto out_chrdev;
219 }
220 msr_class->devnode = msr_devnode;
221
222 err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "x86/msr:online",
223 msr_device_create, msr_device_destroy);
224 if (err < 0)
225 goto out_class;
226 cpuhp_msr_state = err;
227 return 0;
228
229out_class:
230 class_destroy(msr_class);
231out_chrdev:
232 __unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");
233 return err;
234}
235module_init(msr_init);
236
237static void __exit msr_exit(void)
238{
239 cpuhp_remove_state(cpuhp_msr_state);
240 class_destroy(msr_class);
241 __unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");
242}
243module_exit(msr_exit)
244
245MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
246MODULE_DESCRIPTION("x86 generic MSR driver");
247MODULE_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_inode(file);
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_inode(file));
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_inode(file));
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_inode(file));
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 = iminor(file_inode(file));
175 struct cpuinfo_x86 *c;
176
177 if (!capable(CAP_SYS_RAWIO))
178 return -EPERM;
179
180 if (cpu >= nr_cpu_ids || !cpu_online(cpu))
181 return -ENXIO; /* No such CPU */
182
183 c = &cpu_data(cpu);
184 if (!cpu_has(c, X86_FEATURE_MSR))
185 return -EIO; /* MSR not supported */
186
187 return 0;
188}
189
190/*
191 * File operations we support
192 */
193static const struct file_operations msr_fops = {
194 .owner = THIS_MODULE,
195 .llseek = msr_seek,
196 .read = msr_read,
197 .write = msr_write,
198 .open = msr_open,
199 .unlocked_ioctl = msr_ioctl,
200 .compat_ioctl = msr_ioctl,
201};
202
203static int msr_device_create(int cpu)
204{
205 struct device *dev;
206
207 dev = device_create(msr_class, NULL, MKDEV(MSR_MAJOR, cpu), NULL,
208 "msr%d", cpu);
209 return IS_ERR(dev) ? PTR_ERR(dev) : 0;
210}
211
212static void msr_device_destroy(int cpu)
213{
214 device_destroy(msr_class, MKDEV(MSR_MAJOR, cpu));
215}
216
217static int msr_class_cpu_callback(struct notifier_block *nfb,
218 unsigned long action, void *hcpu)
219{
220 unsigned int cpu = (unsigned long)hcpu;
221 int err = 0;
222
223 switch (action) {
224 case CPU_UP_PREPARE:
225 err = msr_device_create(cpu);
226 break;
227 case CPU_UP_CANCELED:
228 case CPU_UP_CANCELED_FROZEN:
229 case CPU_DEAD:
230 msr_device_destroy(cpu);
231 break;
232 }
233 return notifier_from_errno(err);
234}
235
236static struct notifier_block __refdata msr_class_cpu_notifier = {
237 .notifier_call = msr_class_cpu_callback,
238};
239
240static char *msr_devnode(struct device *dev, umode_t *mode)
241{
242 return kasprintf(GFP_KERNEL, "cpu/%u/msr", MINOR(dev->devt));
243}
244
245static int __init msr_init(void)
246{
247 int i, err = 0;
248 i = 0;
249
250 if (__register_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr", &msr_fops)) {
251 printk(KERN_ERR "msr: unable to get major %d for msr\n",
252 MSR_MAJOR);
253 err = -EBUSY;
254 goto out;
255 }
256 msr_class = class_create(THIS_MODULE, "msr");
257 if (IS_ERR(msr_class)) {
258 err = PTR_ERR(msr_class);
259 goto out_chrdev;
260 }
261 msr_class->devnode = msr_devnode;
262
263 cpu_notifier_register_begin();
264 for_each_online_cpu(i) {
265 err = msr_device_create(i);
266 if (err != 0)
267 goto out_class;
268 }
269 __register_hotcpu_notifier(&msr_class_cpu_notifier);
270 cpu_notifier_register_done();
271
272 err = 0;
273 goto out;
274
275out_class:
276 i = 0;
277 for_each_online_cpu(i)
278 msr_device_destroy(i);
279 cpu_notifier_register_done();
280 class_destroy(msr_class);
281out_chrdev:
282 __unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");
283out:
284 return err;
285}
286
287static void __exit msr_exit(void)
288{
289 int cpu = 0;
290
291 cpu_notifier_register_begin();
292 for_each_online_cpu(cpu)
293 msr_device_destroy(cpu);
294 class_destroy(msr_class);
295 __unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");
296 __unregister_hotcpu_notifier(&msr_class_cpu_notifier);
297 cpu_notifier_register_done();
298}
299
300module_init(msr_init);
301module_exit(msr_exit)
302
303MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
304MODULE_DESCRIPTION("x86 generic MSR driver");
305MODULE_LICENSE("GPL");