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(&regs, 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, &regs, 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(&regs, 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, &regs, 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");
306