xref: /openbmc/linux/arch/x86/kernel/msr.c (revision a09d2831)
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/smp_lock.h>
34 #include <linux/major.h>
35 #include <linux/fs.h>
36 #include <linux/device.h>
37 #include <linux/cpu.h>
38 #include <linux/notifier.h>
39 #include <linux/uaccess.h>
40 
41 #include <asm/processor.h>
42 #include <asm/msr.h>
43 #include <asm/system.h>
44 
45 static struct class *msr_class;
46 
47 static loff_t msr_seek(struct file *file, loff_t offset, int orig)
48 {
49 	loff_t ret;
50 	struct inode *inode = file->f_mapping->host;
51 
52 	mutex_lock(&inode->i_mutex);
53 	switch (orig) {
54 	case 0:
55 		file->f_pos = offset;
56 		ret = file->f_pos;
57 		break;
58 	case 1:
59 		file->f_pos += offset;
60 		ret = file->f_pos;
61 		break;
62 	default:
63 		ret = -EINVAL;
64 	}
65 	mutex_unlock(&inode->i_mutex);
66 	return ret;
67 }
68 
69 static ssize_t msr_read(struct file *file, char __user *buf,
70 			size_t count, loff_t *ppos)
71 {
72 	u32 __user *tmp = (u32 __user *) buf;
73 	u32 data[2];
74 	u32 reg = *ppos;
75 	int cpu = iminor(file->f_path.dentry->d_inode);
76 	int err = 0;
77 	ssize_t bytes = 0;
78 
79 	if (count % 8)
80 		return -EINVAL;	/* Invalid chunk size */
81 
82 	for (; count; count -= 8) {
83 		err = rdmsr_safe_on_cpu(cpu, reg, &data[0], &data[1]);
84 		if (err)
85 			break;
86 		if (copy_to_user(tmp, &data, 8)) {
87 			err = -EFAULT;
88 			break;
89 		}
90 		tmp += 2;
91 		bytes += 8;
92 	}
93 
94 	return bytes ? bytes : err;
95 }
96 
97 static ssize_t msr_write(struct file *file, const char __user *buf,
98 			 size_t count, loff_t *ppos)
99 {
100 	const u32 __user *tmp = (const u32 __user *)buf;
101 	u32 data[2];
102 	u32 reg = *ppos;
103 	int cpu = iminor(file->f_path.dentry->d_inode);
104 	int err = 0;
105 	ssize_t bytes = 0;
106 
107 	if (count % 8)
108 		return -EINVAL;	/* Invalid chunk size */
109 
110 	for (; count; count -= 8) {
111 		if (copy_from_user(&data, tmp, 8)) {
112 			err = -EFAULT;
113 			break;
114 		}
115 		err = wrmsr_safe_on_cpu(cpu, reg, data[0], data[1]);
116 		if (err)
117 			break;
118 		tmp += 2;
119 		bytes += 8;
120 	}
121 
122 	return bytes ? bytes : err;
123 }
124 
125 static long msr_ioctl(struct file *file, unsigned int ioc, unsigned long arg)
126 {
127 	u32 __user *uregs = (u32 __user *)arg;
128 	u32 regs[8];
129 	int cpu = iminor(file->f_path.dentry->d_inode);
130 	int err;
131 
132 	switch (ioc) {
133 	case X86_IOC_RDMSR_REGS:
134 		if (!(file->f_mode & FMODE_READ)) {
135 			err = -EBADF;
136 			break;
137 		}
138 		if (copy_from_user(&regs, uregs, sizeof regs)) {
139 			err = -EFAULT;
140 			break;
141 		}
142 		err = rdmsr_safe_regs_on_cpu(cpu, regs);
143 		if (err)
144 			break;
145 		if (copy_to_user(uregs, &regs, sizeof regs))
146 			err = -EFAULT;
147 		break;
148 
149 	case X86_IOC_WRMSR_REGS:
150 		if (!(file->f_mode & FMODE_WRITE)) {
151 			err = -EBADF;
152 			break;
153 		}
154 		if (copy_from_user(&regs, uregs, sizeof regs)) {
155 			err = -EFAULT;
156 			break;
157 		}
158 		err = wrmsr_safe_regs_on_cpu(cpu, regs);
159 		if (err)
160 			break;
161 		if (copy_to_user(uregs, &regs, sizeof regs))
162 			err = -EFAULT;
163 		break;
164 
165 	default:
166 		err = -ENOTTY;
167 		break;
168 	}
169 
170 	return err;
171 }
172 
173 static int msr_open(struct inode *inode, struct file *file)
174 {
175 	unsigned int cpu;
176 	struct cpuinfo_x86 *c;
177 
178 	cpu = iminor(file->f_path.dentry->d_inode);
179 	if (cpu >= nr_cpu_ids || !cpu_online(cpu))
180 		return -ENXIO;	/* No such CPU */
181 
182 	c = &cpu_data(cpu);
183 	if (!cpu_has(c, X86_FEATURE_MSR))
184 		return -EIO;	/* MSR not supported */
185 
186 	return 0;
187 }
188 
189 /*
190  * File operations we support
191  */
192 static const struct file_operations msr_fops = {
193 	.owner = THIS_MODULE,
194 	.llseek = msr_seek,
195 	.read = msr_read,
196 	.write = msr_write,
197 	.open = msr_open,
198 	.unlocked_ioctl = msr_ioctl,
199 	.compat_ioctl = msr_ioctl,
200 };
201 
202 static int __cpuinit msr_device_create(int cpu)
203 {
204 	struct device *dev;
205 
206 	dev = device_create(msr_class, NULL, MKDEV(MSR_MAJOR, cpu), NULL,
207 			    "msr%d", cpu);
208 	return IS_ERR(dev) ? PTR_ERR(dev) : 0;
209 }
210 
211 static void msr_device_destroy(int cpu)
212 {
213 	device_destroy(msr_class, MKDEV(MSR_MAJOR, cpu));
214 }
215 
216 static int __cpuinit msr_class_cpu_callback(struct notifier_block *nfb,
217 				unsigned long action, void *hcpu)
218 {
219 	unsigned int cpu = (unsigned long)hcpu;
220 	int err = 0;
221 
222 	switch (action) {
223 	case CPU_UP_PREPARE:
224 		err = msr_device_create(cpu);
225 		break;
226 	case CPU_UP_CANCELED:
227 	case CPU_UP_CANCELED_FROZEN:
228 	case CPU_DEAD:
229 		msr_device_destroy(cpu);
230 		break;
231 	}
232 	return err ? NOTIFY_BAD : NOTIFY_OK;
233 }
234 
235 static struct notifier_block __refdata msr_class_cpu_notifier = {
236 	.notifier_call = msr_class_cpu_callback,
237 };
238 
239 static char *msr_devnode(struct device *dev, mode_t *mode)
240 {
241 	return kasprintf(GFP_KERNEL, "cpu/%u/msr", MINOR(dev->devt));
242 }
243 
244 static int __init msr_init(void)
245 {
246 	int i, err = 0;
247 	i = 0;
248 
249 	if (__register_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr", &msr_fops)) {
250 		printk(KERN_ERR "msr: unable to get major %d for msr\n",
251 		       MSR_MAJOR);
252 		err = -EBUSY;
253 		goto out;
254 	}
255 	msr_class = class_create(THIS_MODULE, "msr");
256 	if (IS_ERR(msr_class)) {
257 		err = PTR_ERR(msr_class);
258 		goto out_chrdev;
259 	}
260 	msr_class->devnode = msr_devnode;
261 	for_each_online_cpu(i) {
262 		err = msr_device_create(i);
263 		if (err != 0)
264 			goto out_class;
265 	}
266 	register_hotcpu_notifier(&msr_class_cpu_notifier);
267 
268 	err = 0;
269 	goto out;
270 
271 out_class:
272 	i = 0;
273 	for_each_online_cpu(i)
274 		msr_device_destroy(i);
275 	class_destroy(msr_class);
276 out_chrdev:
277 	__unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");
278 out:
279 	return err;
280 }
281 
282 static void __exit msr_exit(void)
283 {
284 	int cpu = 0;
285 	for_each_online_cpu(cpu)
286 		msr_device_destroy(cpu);
287 	class_destroy(msr_class);
288 	unregister_chrdev(MSR_MAJOR, "cpu/msr");
289 	unregister_hotcpu_notifier(&msr_class_cpu_notifier);
290 }
291 
292 module_init(msr_init);
293 module_exit(msr_exit)
294 
295 MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
296 MODULE_DESCRIPTION("x86 generic MSR driver");
297 MODULE_LICENSE("GPL");
298