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Linux/arch/x86/kernel/msr.c

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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 #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 
 44 static struct class *msr_class;
 45 
 46 static loff_t msr_seek(struct file *file, loff_t offset, int orig)
 47 {
 48         loff_t ret;
 49         struct inode *inode = file->f_mapping->host;
 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 
 68 static 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->f_path.dentry->d_inode);
 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 
 96 static 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->f_path.dentry->d_inode);
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 
124 static 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->f_path.dentry->d_inode);
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 
172 static int msr_open(struct inode *inode, struct file *file)
173 {
174         unsigned int cpu;
175         struct cpuinfo_x86 *c;
176 
177         if (!capable(CAP_SYS_RAWIO))
178                 return -EPERM;
179 
180         cpu = iminor(file->f_path.dentry->d_inode);
181         if (cpu >= nr_cpu_ids || !cpu_online(cpu))
182                 return -ENXIO;  /* No such CPU */
183 
184         c = &cpu_data(cpu);
185         if (!cpu_has(c, X86_FEATURE_MSR))
186                 return -EIO;    /* MSR not supported */
187 
188         return 0;
189 }
190 
191 /*
192  * File operations we support
193  */
194 static const struct file_operations msr_fops = {
195         .owner = THIS_MODULE,
196         .llseek = msr_seek,
197         .read = msr_read,
198         .write = msr_write,
199         .open = msr_open,
200         .unlocked_ioctl = msr_ioctl,
201         .compat_ioctl = msr_ioctl,
202 };
203 
204 static int __cpuinit msr_device_create(int cpu)
205 {
206         struct device *dev;
207 
208         dev = device_create(msr_class, NULL, MKDEV(MSR_MAJOR, cpu), NULL,
209                             "msr%d", cpu);
210         return IS_ERR(dev) ? PTR_ERR(dev) : 0;
211 }
212 
213 static void msr_device_destroy(int cpu)
214 {
215         device_destroy(msr_class, MKDEV(MSR_MAJOR, cpu));
216 }
217 
218 static int __cpuinit msr_class_cpu_callback(struct notifier_block *nfb,
219                                 unsigned long action, void *hcpu)
220 {
221         unsigned int cpu = (unsigned long)hcpu;
222         int err = 0;
223 
224         switch (action) {
225         case CPU_UP_PREPARE:
226                 err = msr_device_create(cpu);
227                 break;
228         case CPU_UP_CANCELED:
229         case CPU_UP_CANCELED_FROZEN:
230         case CPU_DEAD:
231                 msr_device_destroy(cpu);
232                 break;
233         }
234         return notifier_from_errno(err);
235 }
236 
237 static struct notifier_block __refdata msr_class_cpu_notifier = {
238         .notifier_call = msr_class_cpu_callback,
239 };
240 
241 static char *msr_devnode(struct device *dev, umode_t *mode)
242 {
243         return kasprintf(GFP_KERNEL, "cpu/%u/msr", MINOR(dev->devt));
244 }
245 
246 static int __init msr_init(void)
247 {
248         int i, err = 0;
249         i = 0;
250 
251         if (__register_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr", &msr_fops)) {
252                 printk(KERN_ERR "msr: unable to get major %d for msr\n",
253                        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         get_online_cpus();
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         put_online_cpus();
271 
272         err = 0;
273         goto out;
274 
275 out_class:
276         i = 0;
277         for_each_online_cpu(i)
278                 msr_device_destroy(i);
279         put_online_cpus();
280         class_destroy(msr_class);
281 out_chrdev:
282         __unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");
283 out:
284         return err;
285 }
286 
287 static void __exit msr_exit(void)
288 {
289         int cpu = 0;
290         get_online_cpus();
291         for_each_online_cpu(cpu)
292                 msr_device_destroy(cpu);
293         class_destroy(msr_class);
294         __unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");
295         unregister_hotcpu_notifier(&msr_class_cpu_notifier);
296         put_online_cpus();
297 }
298 
299 module_init(msr_init);
300 module_exit(msr_exit)
301 
302 MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
303 MODULE_DESCRIPTION("x86 generic MSR driver");
304 MODULE_LICENSE("GPL");
305 

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