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/processor.h>
44#include <asm/msr.h>
45
46static struct class *msr_class;
47
48static loff_t msr_seek(struct file *file, loff_t offset, int orig)
49{
50	loff_t ret;
51	struct inode *inode = file_inode(file);
52
53	mutex_lock(&inode->i_mutex);
54	switch (orig) {
55	case SEEK_SET:
56		file->f_pos = offset;
57		ret = file->f_pos;
58		break;
59	case SEEK_CUR:
60		file->f_pos += offset;
61		ret = file->f_pos;
62		break;
63	default:
64		ret = -EINVAL;
65	}
66	mutex_unlock(&inode->i_mutex);
67	return ret;
68}
69
70static ssize_t msr_read(struct file *file, char __user *buf,
71			size_t count, loff_t *ppos)
72{
73	u32 __user *tmp = (u32 __user *) buf;
74	u32 data[2];
75	u32 reg = *ppos;
76	int cpu = iminor(file_inode(file));
77	int err = 0;
78	ssize_t bytes = 0;
79
80	if (count % 8)
81		return -EINVAL;	/* Invalid chunk size */
82
83	for (; count; count -= 8) {
84		err = rdmsr_safe_on_cpu(cpu, reg, &data[0], &data[1]);
85		if (err)
86			break;
87		if (copy_to_user(tmp, &data, 8)) {
88			err = -EFAULT;
89			break;
90		}
91		tmp += 2;
92		bytes += 8;
93	}
94
95	return bytes ? bytes : err;
96}
97
98static ssize_t msr_write(struct file *file, const char __user *buf,
99			 size_t count, loff_t *ppos)
100{
101	const u32 __user *tmp = (const u32 __user *)buf;
102	u32 data[2];
103	u32 reg = *ppos;
104	int cpu = iminor(file_inode(file));
105	int err = 0;
106	ssize_t bytes = 0;
107
108	if (count % 8)
109		return -EINVAL;	/* Invalid chunk size */
110
111	for (; count; count -= 8) {
112		if (copy_from_user(&data, tmp, 8)) {
113			err = -EFAULT;
114			break;
115		}
116		err = wrmsr_safe_on_cpu(cpu, reg, data[0], data[1]);
117		if (err)
118			break;
119		tmp += 2;
120		bytes += 8;
121	}
122
123	return bytes ? bytes : err;
124}
125
126static long msr_ioctl(struct file *file, unsigned int ioc, unsigned long arg)
127{
128	u32 __user *uregs = (u32 __user *)arg;
129	u32 regs[8];
130	int cpu = iminor(file_inode(file));
131	int err;
132
133	switch (ioc) {
134	case X86_IOC_RDMSR_REGS:
135		if (!(file->f_mode & FMODE_READ)) {
136			err = -EBADF;
137			break;
138		}
139		if (copy_from_user(&regs, uregs, sizeof regs)) {
140			err = -EFAULT;
141			break;
142		}
143		err = rdmsr_safe_regs_on_cpu(cpu, regs);
144		if (err)
145			break;
146		if (copy_to_user(uregs, &regs, sizeof regs))
147			err = -EFAULT;
148		break;
149
150	case X86_IOC_WRMSR_REGS:
151		if (!(file->f_mode & FMODE_WRITE)) {
152			err = -EBADF;
153			break;
154		}
155		if (copy_from_user(&regs, uregs, sizeof regs)) {
156			err = -EFAULT;
157			break;
158		}
159		err = wrmsr_safe_regs_on_cpu(cpu, regs);
160		if (err)
161			break;
162		if (copy_to_user(uregs, &regs, sizeof regs))
163			err = -EFAULT;
164		break;
165
166	default:
167		err = -ENOTTY;
168		break;
169	}
170
171	return err;
172}
173
174static int msr_open(struct inode *inode, struct file *file)
175{
176	unsigned int cpu = iminor(file_inode(file));
177	struct cpuinfo_x86 *c;
178
179	if (!capable(CAP_SYS_RAWIO))
180		return -EPERM;
181
182	if (cpu >= nr_cpu_ids || !cpu_online(cpu))
183		return -ENXIO;	/* No such CPU */
184
185	c = &cpu_data(cpu);
186	if (!cpu_has(c, X86_FEATURE_MSR))
187		return -EIO;	/* MSR not supported */
188
189	return 0;
190}
191
192/*
193 * File operations we support
194 */
195static const struct file_operations msr_fops = {
196	.owner = THIS_MODULE,
197	.llseek = msr_seek,
198	.read = msr_read,
199	.write = msr_write,
200	.open = msr_open,
201	.unlocked_ioctl = msr_ioctl,
202	.compat_ioctl = msr_ioctl,
203};
204
205static int msr_device_create(int cpu)
206{
207	struct device *dev;
208
209	dev = device_create(msr_class, NULL, MKDEV(MSR_MAJOR, cpu), NULL,
210			    "msr%d", cpu);
211	return PTR_ERR_OR_ZERO(dev);
212}
213
214static void msr_device_destroy(int cpu)
215{
216	device_destroy(msr_class, MKDEV(MSR_MAJOR, cpu));
217}
218
219static int msr_class_cpu_callback(struct notifier_block *nfb,
220				  unsigned long action, void *hcpu)
221{
222	unsigned int cpu = (unsigned long)hcpu;
223	int err = 0;
224
225	switch (action) {
226	case CPU_UP_PREPARE:
227		err = msr_device_create(cpu);
228		break;
229	case CPU_UP_CANCELED:
230	case CPU_UP_CANCELED_FROZEN:
231	case CPU_DEAD:
232		msr_device_destroy(cpu);
233		break;
234	}
235	return notifier_from_errno(err);
236}
237
238static struct notifier_block __refdata msr_class_cpu_notifier = {
239	.notifier_call = msr_class_cpu_callback,
240};
241
242static char *msr_devnode(struct device *dev, umode_t *mode)
243{
244	return kasprintf(GFP_KERNEL, "cpu/%u/msr", MINOR(dev->devt));
245}
246
247static int __init msr_init(void)
248{
249	int i, err = 0;
250	i = 0;
251
252	if (__register_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr", &msr_fops)) {
253		pr_err("unable to get major %d for msr\n", MSR_MAJOR);
254		err = -EBUSY;
255		goto out;
256	}
257	msr_class = class_create(THIS_MODULE, "msr");
258	if (IS_ERR(msr_class)) {
259		err = PTR_ERR(msr_class);
260		goto out_chrdev;
261	}
262	msr_class->devnode = msr_devnode;
263
264	cpu_notifier_register_begin();
265	for_each_online_cpu(i) {
266		err = msr_device_create(i);
267		if (err != 0)
268			goto out_class;
269	}
270	__register_hotcpu_notifier(&msr_class_cpu_notifier);
271	cpu_notifier_register_done();
272
273	err = 0;
274	goto out;
275
276out_class:
277	i = 0;
278	for_each_online_cpu(i)
279		msr_device_destroy(i);
280	cpu_notifier_register_done();
281	class_destroy(msr_class);
282out_chrdev:
283	__unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");
284out:
285	return err;
286}
287
288static void __exit msr_exit(void)
289{
290	int cpu = 0;
291
292	cpu_notifier_register_begin();
293	for_each_online_cpu(cpu)
294		msr_device_destroy(cpu);
295	class_destroy(msr_class);
296	__unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");
297	__unregister_hotcpu_notifier(&msr_class_cpu_notifier);
298	cpu_notifier_register_done();
299}
300
301module_init(msr_init);
302module_exit(msr_exit)
303
304MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
305MODULE_DESCRIPTION("x86 generic MSR driver");
306MODULE_LICENSE("GPL");
307