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 #include <asm/system.h>
  47
  48 static struct class *cpuid_class;
  49
  50 struct cpuid_regs {
  51         u32 eax, ebx, ecx, edx;
  52 };
  53
  54 static void cpuid_smp_cpuid(void *cmd_block)
  55 {
  56         struct cpuid_regs *cmd = (struct cpuid_regs *)cmd_block;
  57
  58         cpuid_count(cmd->eax, cmd->ecx,
  59                     &cmd->eax, &cmd->ebx, &cmd->ecx, &cmd->edx);
  60 }
  61
  62 static loff_t cpuid_seek(struct file *file, loff_t offset, int orig)
  63 {
  64         loff_t ret;
  65         struct inode *inode = file->f_mapping->host;
  66
  67         mutex_lock(&inode->i_mutex);
  68         switch (orig) {
  69         case 0:
  70                 file->f_pos = offset;
  71                 ret = file->f_pos;
  72                 break;
  73         case 1:
  74                 file->f_pos += offset;
  75                 ret = file->f_pos;
  76                 break;
  77         default:
  78                 ret = -EINVAL;
  79         }
  80         mutex_unlock(&inode->i_mutex);
  81         return ret;
  82 }
  83
  84 static ssize_t cpuid_read(struct file *file, char __user *buf,
  85                           size_t count, loff_t *ppos)
  86 {
  87         char __user *tmp = buf;
  88         struct cpuid_regs cmd;
  89         int cpu = iminor(file->f_path.dentry->d_inode);
  90         u64 pos = *ppos;
  91         ssize_t bytes = 0;
  92         int err = 0;
  93
  94         if (count % 16)
  95                 return -EINVAL; /* Invalid chunk size */
  96
  97         for (; count; count -= 16) {
  98                 cmd.eax = pos;
  99                 cmd.ecx = pos >> 32;
 100                 err = smp_call_function_single(cpu, cpuid_smp_cpuid, &cmd, 1);
 101                 if (err)
 102                         break;
 103                 if (copy_to_user(tmp, &cmd, 16)) {
 104                         err = -EFAULT;
 105                         break;
 106                 }
 107                 tmp += 16;
 108                 bytes += 16;
 109                 *ppos = ++pos;
 110         }
 111
 112         return bytes ? bytes : err;
 113 }
 114
 115 static int cpuid_open(struct inode *inode, struct file *file)
 116 {
 117         unsigned int cpu;
 118         struct cpuinfo_x86 *c;
 119
 120         cpu = iminor(file->f_path.dentry->d_inode);
 121         if (cpu >= nr_cpu_ids || !cpu_online(cpu))
 122                 return -ENXIO;  /* No such CPU */
 123
 124         c = &cpu_data(cpu);
 125         if (c->cpuid_level < 0)
 126                 return -EIO;    /* CPUID not supported */
 127
 128         return 0;
 129 }
 130
 131 /*
 132  * File operations we support
 133  */
 134 static const struct file_operations cpuid_fops = {
 135         .owner = THIS_MODULE,
 136         .llseek = cpuid_seek,
 137         .read = cpuid_read,
 138         .open = cpuid_open,
 139 };
 140
 141 static __cpuinit int cpuid_device_create(int cpu)
 142 {
 143         struct device *dev;
 144
 145         dev = device_create(cpuid_class, NULL, MKDEV(CPUID_MAJOR, cpu), NULL,
 146                             "cpu%d", cpu);
 147         return IS_ERR(dev) ? PTR_ERR(dev) : 0;
 148 }
 149
 150 static void cpuid_device_destroy(int cpu)
 151 {
 152         device_destroy(cpuid_class, MKDEV(CPUID_MAJOR, cpu));
 153 }
 154
 155 static int __cpuinit cpuid_class_cpu_callback(struct notifier_block *nfb,
 156                                               unsigned long action,
 157                                               void *hcpu)
 158 {
 159         unsigned int cpu = (unsigned long)hcpu;
 160         int err = 0;
 161
 162         switch (action) {
 163         case CPU_UP_PREPARE:
 164                 err = cpuid_device_create(cpu);
 165                 break;
 166         case CPU_UP_CANCELED:
 167         case CPU_UP_CANCELED_FROZEN:
 168         case CPU_DEAD:
 169                 cpuid_device_destroy(cpu);
 170                 break;
 171         }
 172         return notifier_from_errno(err);
 173 }
 174
 175 static struct notifier_block __refdata cpuid_class_cpu_notifier =
 176 {
 177         .notifier_call = cpuid_class_cpu_callback,
 178 };
 179
 180 static char *cpuid_devnode(struct device *dev, mode_t *mode)
 181 {
 182         return kasprintf(GFP_KERNEL, "cpu/%u/cpuid", MINOR(dev->devt));
 183 }
 184
 185 static int __init cpuid_init(void)
 186 {
 187         int i, err = 0;
 188         i = 0;
 189
 190         if (__register_chrdev(CPUID_MAJOR, 0, NR_CPUS,
 191                               "cpu/cpuid", &cpuid_fops)) {
 192                 printk(KERN_ERR "cpuid: unable to get major %d for cpuid\n",
 193                        CPUID_MAJOR);
 194                 err = -EBUSY;
 195                 goto out;
 196         }
 197         cpuid_class = class_create(THIS_MODULE, "cpuid");
 198         if (IS_ERR(cpuid_class)) {
 199                 err = PTR_ERR(cpuid_class);
 200                 goto out_chrdev;
 201         }
 202         cpuid_class->devnode = cpuid_devnode;
 203         for_each_online_cpu(i) {
 204                 err = cpuid_device_create(i);
 205                 if (err != 0)
 206                         goto out_class;
 207         }
 208         register_hotcpu_notifier(&cpuid_class_cpu_notifier);
 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         class_destroy(cpuid_class);
 219 out_chrdev:
 220         __unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid");
 221 out:
 222         return err;
 223 }
 224
 225 static void __exit cpuid_exit(void)
 226 {
 227         int cpu = 0;
 228
 229         for_each_online_cpu(cpu)
 230                 cpuid_device_destroy(cpu);
 231         class_destroy(cpuid_class);
 232         __unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid");
 233         unregister_hotcpu_notifier(&cpuid_class_cpu_notifier);
 234 }
 235
 236 module_init(cpuid_init);
 237 module_exit(cpuid_exit);
 238
 239 MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
 240 MODULE_DESCRIPTION("x86 generic CPUID driver");
 241 MODULE_LICENSE("GPL");