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 ssize_t cpuid_read(struct file *file, char __user *buf,
  62                           size_t count, loff_t *ppos)
  63 {
  64         char __user *tmp = buf;
  65         struct cpuid_regs cmd;
  66         int cpu = iminor(file_inode(file));
  67         u64 pos = *ppos;
  68         ssize_t bytes = 0;
  69         int err = 0;
  70
  71         if (count % 16)
  72                 return -EINVAL; /* Invalid chunk size */
  73
  74         for (; count; count -= 16) {
  75                 cmd.eax = pos;
  76                 cmd.ecx = pos >> 32;
  77                 err = smp_call_function_single(cpu, cpuid_smp_cpuid, &cmd, 1);
  78                 if (err)
  79                         break;
  80                 if (copy_to_user(tmp, &cmd, 16)) {
  81                         err = -EFAULT;
  82                         break;
  83                 }
  84                 tmp += 16;
  85                 bytes += 16;
  86                 *ppos = ++pos;
  87         }
  88
  89         return bytes ? bytes : err;
  90 }
  91
  92 static int cpuid_open(struct inode *inode, struct file *file)
  93 {
  94         unsigned int cpu;
  95         struct cpuinfo_x86 *c;
  96
  97         cpu = iminor(file_inode(file));
  98         if (cpu >= nr_cpu_ids || !cpu_online(cpu))
  99                 return -ENXIO;  /* No such CPU */
 100
 101         c = &cpu_data(cpu);
 102         if (c->cpuid_level < 0)
 103                 return -EIO;    /* CPUID not supported */
 104
 105         return 0;
 106 }
 107
 108 /*
 109  * File operations we support
 110  */
 111 static const struct file_operations cpuid_fops = {
 112         .owner = THIS_MODULE,
 113         .llseek = no_seek_end_llseek,
 114         .read = cpuid_read,
 115         .open = cpuid_open,
 116 };
 117
 118 static int cpuid_device_create(int cpu)
 119 {
 120         struct device *dev;
 121
 122         dev = device_create(cpuid_class, NULL, MKDEV(CPUID_MAJOR, cpu), NULL,
 123                             "cpu%d", cpu);
 124         return PTR_ERR_OR_ZERO(dev);
 125 }
 126
 127 static void cpuid_device_destroy(int cpu)
 128 {
 129         device_destroy(cpuid_class, MKDEV(CPUID_MAJOR, cpu));
 130 }
 131
 132 static int cpuid_class_cpu_callback(struct notifier_block *nfb,
 133                                     unsigned long action, void *hcpu)
 134 {
 135         unsigned int cpu = (unsigned long)hcpu;
 136         int err = 0;
 137
 138         switch (action) {
 139         case CPU_UP_PREPARE:
 140                 err = cpuid_device_create(cpu);
 141                 break;
 142         case CPU_UP_CANCELED:
 143         case CPU_UP_CANCELED_FROZEN:
 144         case CPU_DEAD:
 145                 cpuid_device_destroy(cpu);
 146                 break;
 147         }
 148         return notifier_from_errno(err);
 149 }
 150
 151 static struct notifier_block cpuid_class_cpu_notifier =
 152 {
 153         .notifier_call = cpuid_class_cpu_callback,
 154 };
 155
 156 static char *cpuid_devnode(struct device *dev, umode_t *mode)
 157 {
 158         return kasprintf(GFP_KERNEL, "cpu/%u/cpuid", MINOR(dev->devt));
 159 }
 160
 161 static int __init cpuid_init(void)
 162 {
 163         int i, err = 0;
 164         i = 0;
 165
 166         if (__register_chrdev(CPUID_MAJOR, 0, NR_CPUS,
 167                               "cpu/cpuid", &cpuid_fops)) {
 168                 printk(KERN_ERR "cpuid: unable to get major %d for cpuid\n",
 169                        CPUID_MAJOR);
 170                 err = -EBUSY;
 171                 goto out;
 172         }
 173         cpuid_class = class_create(THIS_MODULE, "cpuid");
 174         if (IS_ERR(cpuid_class)) {
 175                 err = PTR_ERR(cpuid_class);
 176                 goto out_chrdev;
 177         }
 178         cpuid_class->devnode = cpuid_devnode;
 179
 180         cpu_notifier_register_begin();
 181         for_each_online_cpu(i) {
 182                 err = cpuid_device_create(i);
 183                 if (err != 0)
 184                         goto out_class;
 185         }
 186         __register_hotcpu_notifier(&cpuid_class_cpu_notifier);
 187         cpu_notifier_register_done();
 188
 189         err = 0;
 190         goto out;
 191
 192 out_class:
 193         i = 0;
 194         for_each_online_cpu(i) {
 195                 cpuid_device_destroy(i);
 196         }
 197         cpu_notifier_register_done();
 198         class_destroy(cpuid_class);
 199 out_chrdev:
 200         __unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid");
 201 out:
 202         return err;
 203 }
 204
 205 static void __exit cpuid_exit(void)
 206 {
 207         int cpu = 0;
 208
 209         cpu_notifier_register_begin();
 210         for_each_online_cpu(cpu)
 211                 cpuid_device_destroy(cpu);
 212         class_destroy(cpuid_class);
 213         __unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid");
 214         __unregister_hotcpu_notifier(&cpuid_class_cpu_notifier);
 215         cpu_notifier_register_done();
 216 }
 217
 218 module_init(cpuid_init);
 219 module_exit(cpuid_exit);
 220
 221 MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
 222 MODULE_DESCRIPTION("x86 generic CPUID driver");
 223 MODULE_LICENSE("GPL");