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 static void cpuid_smp_cpuid(void *cmd_block)
  50 {
  51         struct cpuid_regs *cmd = (struct cpuid_regs *)cmd_block;
  52
  53         cpuid_count(cmd->eax, cmd->ecx,
  54                     &cmd->eax, &cmd->ebx, &cmd->ecx, &cmd->edx);
  55 }
  56
  57 static ssize_t cpuid_read(struct file *file, char __user *buf,
  58                           size_t count, loff_t *ppos)
  59 {
  60         char __user *tmp = buf;
  61         struct cpuid_regs cmd;
  62         int cpu = iminor(file_inode(file));
  63         u64 pos = *ppos;
  64         ssize_t bytes = 0;
  65         int err = 0;
  66
  67         if (count % 16)
  68                 return -EINVAL; /* Invalid chunk size */
  69
  70         for (; count; count -= 16) {
  71                 cmd.eax = pos;
  72                 cmd.ecx = pos >> 32;
  73                 err = smp_call_function_single(cpu, cpuid_smp_cpuid, &cmd, 1);
  74                 if (err)
  75                         break;
  76                 if (copy_to_user(tmp, &cmd, 16)) {
  77                         err = -EFAULT;
  78                         break;
  79                 }
  80                 tmp += 16;
  81                 bytes += 16;
  82                 *ppos = ++pos;
  83         }
  84
  85         return bytes ? bytes : err;
  86 }
  87
  88 static int cpuid_open(struct inode *inode, struct file *file)
  89 {
  90         unsigned int cpu;
  91         struct cpuinfo_x86 *c;
  92
  93         cpu = iminor(file_inode(file));
  94         if (cpu >= nr_cpu_ids || !cpu_online(cpu))
  95                 return -ENXIO;  /* No such CPU */
  96
  97         c = &cpu_data(cpu);
  98         if (c->cpuid_level < 0)
  99                 return -EIO;    /* CPUID not supported */
 100
 101         return 0;
 102 }
 103
 104 /*
 105  * File operations we support
 106  */
 107 static const struct file_operations cpuid_fops = {
 108         .owner = THIS_MODULE,
 109         .llseek = no_seek_end_llseek,
 110         .read = cpuid_read,
 111         .open = cpuid_open,
 112 };
 113
 114 static int cpuid_device_create(int cpu)
 115 {
 116         struct device *dev;
 117
 118         dev = device_create(cpuid_class, NULL, MKDEV(CPUID_MAJOR, cpu), NULL,
 119                             "cpu%d", cpu);
 120         return PTR_ERR_OR_ZERO(dev);
 121 }
 122
 123 static void cpuid_device_destroy(int cpu)
 124 {
 125         device_destroy(cpuid_class, MKDEV(CPUID_MAJOR, cpu));
 126 }
 127
 128 static int cpuid_class_cpu_callback(struct notifier_block *nfb,
 129                                     unsigned long action, void *hcpu)
 130 {
 131         unsigned int cpu = (unsigned long)hcpu;
 132         int err = 0;
 133
 134         switch (action) {
 135         case CPU_UP_PREPARE:
 136                 err = cpuid_device_create(cpu);
 137                 break;
 138         case CPU_UP_CANCELED:
 139         case CPU_UP_CANCELED_FROZEN:
 140         case CPU_DEAD:
 141                 cpuid_device_destroy(cpu);
 142                 break;
 143         }
 144         return notifier_from_errno(err);
 145 }
 146
 147 static struct notifier_block cpuid_class_cpu_notifier =
 148 {
 149         .notifier_call = cpuid_class_cpu_callback,
 150 };
 151
 152 static char *cpuid_devnode(struct device *dev, umode_t *mode)
 153 {
 154         return kasprintf(GFP_KERNEL, "cpu/%u/cpuid", MINOR(dev->devt));
 155 }
 156
 157 static int __init cpuid_init(void)
 158 {
 159         int i, err = 0;
 160         i = 0;
 161
 162         if (__register_chrdev(CPUID_MAJOR, 0, NR_CPUS,
 163                               "cpu/cpuid", &cpuid_fops)) {
 164                 printk(KERN_ERR "cpuid: unable to get major %d for cpuid\n",
 165                        CPUID_MAJOR);
 166                 err = -EBUSY;
 167                 goto out;
 168         }
 169         cpuid_class = class_create(THIS_MODULE, "cpuid");
 170         if (IS_ERR(cpuid_class)) {
 171                 err = PTR_ERR(cpuid_class);
 172                 goto out_chrdev;
 173         }
 174         cpuid_class->devnode = cpuid_devnode;
 175
 176         cpu_notifier_register_begin();
 177         for_each_online_cpu(i) {
 178                 err = cpuid_device_create(i);
 179                 if (err != 0)
 180                         goto out_class;
 181         }
 182         __register_hotcpu_notifier(&cpuid_class_cpu_notifier);
 183         cpu_notifier_register_done();
 184
 185         err = 0;
 186         goto out;
 187
 188 out_class:
 189         i = 0;
 190         for_each_online_cpu(i) {
 191                 cpuid_device_destroy(i);
 192         }
 193         cpu_notifier_register_done();
 194         class_destroy(cpuid_class);
 195 out_chrdev:
 196         __unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid");
 197 out:
 198         return err;
 199 }
 200
 201 static void __exit cpuid_exit(void)
 202 {
 203         int cpu = 0;
 204
 205         cpu_notifier_register_begin();
 206         for_each_online_cpu(cpu)
 207                 cpuid_device_destroy(cpu);
 208         class_destroy(cpuid_class);
 209         __unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid");
 210         __unregister_hotcpu_notifier(&cpuid_class_cpu_notifier);
 211         cpu_notifier_register_done();
 212 }
 213
 214 module_init(cpuid_init);
 215 module_exit(cpuid_exit);
 216
 217 MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
 218 MODULE_DESCRIPTION("x86 generic CPUID driver");
 219 MODULE_LICENSE("GPL");