arch/x86/kernel/cpuid.c

   1 /* ----------------------------------------------------------------------- *
   2  *
   3  *   Copyright 2000-2008 H. Peter Anvin - All Rights Reserved
   4  *
   5  *   This program is free software; you can redistribute it and/or modify
   6  *   it under the terms of the GNU General Public License as published by
   7  *   the Free Software Foundation, Inc., 675 Mass Ave, Cambridge MA 02139,
   8  *   USA; either version 2 of the License, or (at your option) any later
   9  *   version; incorporated herein by reference.
  10  *
  11  * ----------------------------------------------------------------------- */
  12
  13 /*
  14  * x86 CPUID access device
  15  *
  16  * This device is accessed by lseek() to the appropriate CPUID level
  17  * and then read in chunks of 16 bytes.  A larger size means multiple
  18  * reads of consecutive levels.
  19  *
  20  * The lower 32 bits of the file position is used as the incoming %eax,
  21  * and the upper 32 bits of the file position as the incoming %ecx,
  22  * the latter intended for "counting" eax levels like eax=4.
  23  *
  24  * This driver uses /dev/cpu/%d/cpuid where %d is the minor number, and on
  25  * an SMP box will direct the access to CPU %d.
  26  */
  27
  28 #include <linux/module.h>
  29
  30 #include <linux/types.h>
  31 #include <linux/errno.h>
  32 #include <linux/fcntl.h>
  33 #include <linux/init.h>
  34 #include <linux/poll.h>
  35 #include <linux/smp.h>
  36 #include <linux/major.h>
  37 #include <linux/fs.h>
  38 #include <linux/device.h>
  39 #include <linux/cpu.h>
  40 #include <linux/notifier.h>
  41 #include <linux/uaccess.h>
  42 #include <linux/gfp.h>
  43
  44 #include <asm/processor.h>
  45 #include <asm/msr.h>
  46
  47 static struct class *cpuid_class;
  48
  49 struct cpuid_regs {
  50         u32 eax, ebx, ecx, edx;
  51 };
  52
  53 static void cpuid_smp_cpuid(void *cmd_block)
  54 {
  55         struct cpuid_regs *cmd = (struct cpuid_regs *)cmd_block;
  56
  57         cpuid_count(cmd->eax, cmd->ecx,
  58                     &cmd->eax, &cmd->ebx, &cmd->ecx, &cmd->edx);
  59 }
  60
  61 static loff_t cpuid_seek(struct file *file, loff_t offset, int orig)
  62 {
  63         loff_t ret;
  64         struct inode *inode = file->f_mapping->host;
  65
  66         mutex_lock(&inode->i_mutex);
  67         switch (orig) {
  68         case 0:
  69                 file->f_pos = offset;
  70                 ret = file->f_pos;
  71                 break;
  72         case 1:
  73                 file->f_pos += offset;
  74                 ret = file->f_pos;
  75                 break;
  76         default:
  77                 ret = -EINVAL;
  78         }
  79         mutex_unlock(&inode->i_mutex);
  80         return ret;
  81 }
  82
  83 static ssize_t cpuid_read(struct file *file, char __user *buf,
  84                           size_t count, loff_t *ppos)
  85 {
  86         char __user *tmp = buf;
  87         struct cpuid_regs cmd;
  88         int cpu = iminor(file_inode(file));
  89         u64 pos = *ppos;
  90         ssize_t bytes = 0;
  91         int err = 0;
  92
  93         if (count % 16)
  94                 return -EINVAL; /* Invalid chunk size */
  95
  96         for (; count; count -= 16) {
  97                 cmd.eax = pos;
  98                 cmd.ecx = pos >> 32;
  99                 err = smp_call_function_single(cpu, cpuid_smp_cpuid, &cmd, 1);
 100                 if (err)
 101                         break;
 102                 if (copy_to_user(tmp, &cmd, 16)) {
 103                         err = -EFAULT;
 104                         break;
 105                 }
 106                 tmp += 16;
 107                 bytes += 16;
 108                 *ppos = ++pos;
 109         }
 110
 111         return bytes ? bytes : err;
 112 }
 113
 114 static int cpuid_open(struct inode *inode, struct file *file)
 115 {
 116         unsigned int cpu;
 117         struct cpuinfo_x86 *c;
 118
 119         cpu = iminor(file_inode(file));
 120         if (cpu >= nr_cpu_ids || !cpu_online(cpu))
 121                 return -ENXIO;  /* No such CPU */
 122
 123         c = &cpu_data(cpu);
 124         if (c->cpuid_level < 0)
 125                 return -EIO;    /* CPUID not supported */
 126
 127         return 0;
 128 }
 129
 130 /*
 131  * File operations we support
 132  */
 133 static const struct file_operations cpuid_fops = {
 134         .owner = THIS_MODULE,
 135         .llseek = cpuid_seek,
 136         .read = cpuid_read,
 137         .open = cpuid_open,
 138 };
 139
 140 static int cpuid_device_create(int cpu)
 141 {
 142         struct device *dev;
 143
 144         dev = device_create(cpuid_class, NULL, MKDEV(CPUID_MAJOR, cpu), NULL,
 145                             "cpu%d", cpu);
 146         return IS_ERR(dev) ? PTR_ERR(dev) : 0;
 147 }
 148
 149 static void cpuid_device_destroy(int cpu)
 150 {
 151         device_destroy(cpuid_class, MKDEV(CPUID_MAJOR, cpu));
 152 }
 153
 154 static int cpuid_class_cpu_callback(struct notifier_block *nfb,
 155                                     unsigned long action, void *hcpu)
 156 {
 157         unsigned int cpu = (unsigned long)hcpu;
 158         int err = 0;
 159
 160         switch (action) {
 161         case CPU_UP_PREPARE:
 162                 err = cpuid_device_create(cpu);
 163                 break;
 164         case CPU_UP_CANCELED:
 165         case CPU_UP_CANCELED_FROZEN:
 166         case CPU_DEAD:
 167                 cpuid_device_destroy(cpu);
 168                 break;
 169         }
 170         return notifier_from_errno(err);
 171 }
 172
 173 static struct notifier_block __refdata cpuid_class_cpu_notifier =
 174 {
 175         .notifier_call = cpuid_class_cpu_callback,
 176 };
 177
 178 static char *cpuid_devnode(struct device *dev, umode_t *mode)
 179 {
 180         return kasprintf(GFP_KERNEL, "cpu/%u/cpuid", MINOR(dev->devt));
 181 }
 182
 183 static int __init cpuid_init(void)
 184 {
 185         int i, err = 0;
 186         i = 0;
 187
 188         if (__register_chrdev(CPUID_MAJOR, 0, NR_CPUS,
 189                               "cpu/cpuid", &cpuid_fops)) {
 190                 printk(KERN_ERR "cpuid: unable to get major %d for cpuid\n",
 191                        CPUID_MAJOR);
 192                 err = -EBUSY;
 193                 goto out;
 194         }
 195         cpuid_class = class_create(THIS_MODULE, "cpuid");
 196         if (IS_ERR(cpuid_class)) {
 197                 err = PTR_ERR(cpuid_class);
 198                 goto out_chrdev;
 199         }
 200         cpuid_class->devnode = cpuid_devnode;
 201         get_online_cpus();
 202         for_each_online_cpu(i) {
 203                 err = cpuid_device_create(i);
 204                 if (err != 0)
 205                         goto out_class;
 206         }
 207         register_hotcpu_notifier(&cpuid_class_cpu_notifier);
 208         put_online_cpus();
 209
 210         err = 0;
 211         goto out;
 212
 213 out_class:
 214         i = 0;
 215         for_each_online_cpu(i) {
 216                 cpuid_device_destroy(i);
 217         }
 218         put_online_cpus();
 219         class_destroy(cpuid_class);
 220 out_chrdev:
 221         __unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid");
 222 out:
 223         return err;
 224 }
 225
 226 static void __exit cpuid_exit(void)
 227 {
 228         int cpu = 0;
 229
 230         get_online_cpus();
 231         for_each_online_cpu(cpu)
 232                 cpuid_device_destroy(cpu);
 233         class_destroy(cpuid_class);
 234         __unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid");
 235         unregister_hotcpu_notifier(&cpuid_class_cpu_notifier);
 236         put_online_cpus();
 237 }
 238
 239 module_init(cpuid_init);
 240 module_exit(cpuid_exit);
 241
 242 MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
 243 MODULE_DESCRIPTION("x86 generic CPUID driver");
 244 MODULE_LICENSE("GPL");