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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 #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         if (!capable(CAP_SYS_RAWIO))
179                 return -EPERM;
180 
181         cpu = iminor(file->f_path.dentry->d_inode);
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  */
195 static 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 
205 static int __cpuinit 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 IS_ERR(dev) ? PTR_ERR(dev) : 0;
212 }
213 
214 static void msr_device_destroy(int cpu)
215 {
216         device_destroy(msr_class, MKDEV(MSR_MAJOR, cpu));
217 }
218 
219 static int __cpuinit 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 
238 static struct notifier_block __refdata msr_class_cpu_notifier = {
239         .notifier_call = msr_class_cpu_callback,
240 };
241 
242 static char *msr_devnode(struct device *dev, mode_t *mode)
243 {
244         return kasprintf(GFP_KERNEL, "cpu/%u/msr", MINOR(dev->devt));
245 }
246 
247 static 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                 printk(KERN_ERR "msr: unable to get major %d for msr\n",
254                        MSR_MAJOR);
255                 err = -EBUSY;
256                 goto out;
257         }
258         msr_class = class_create(THIS_MODULE, "msr");
259         if (IS_ERR(msr_class)) {
260                 err = PTR_ERR(msr_class);
261                 goto out_chrdev;
262         }
263         msr_class->devnode = msr_devnode;
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 
271         err = 0;
272         goto out;
273 
274 out_class:
275         i = 0;
276         for_each_online_cpu(i)
277                 msr_device_destroy(i);
278         class_destroy(msr_class);
279 out_chrdev:
280         __unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");
281 out:
282         return err;
283 }
284 
285 static void __exit msr_exit(void)
286 {
287         int cpu = 0;
288         for_each_online_cpu(cpu)
289                 msr_device_destroy(cpu);
290         class_destroy(msr_class);
291         __unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");
292         unregister_hotcpu_notifier(&msr_class_cpu_notifier);
293 }
294 
295 module_init(msr_init);
296 module_exit(msr_exit)
297 
298 MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
299 MODULE_DESCRIPTION("x86 generic MSR driver");
300 MODULE_LICENSE("GPL");
301 

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