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/smp_lock.h>
  39 #include <linux/device.h>
  40 #include <linux/cpu.h>
  41 #include <linux/notifier.h>
  42
  43 #include <asm/processor.h>
  44 #include <asm/msr.h>
  45 #include <asm/uaccess.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
  92         if (count % 16)
  93                 return -EINVAL; /* Invalid chunk size */
  94
  95         for (; count; count -= 16) {
  96                 cmd.eax = pos;
  97                 cmd.ecx = pos >> 32;
  98                 smp_call_function_single(cpu, cpuid_smp_cpuid, &cmd, 1, 1);
  99                 if (copy_to_user(tmp, &cmd, 16))
 100                         return -EFAULT;
 101                 tmp += 16;
 102                 *ppos = ++pos;
 103         }
 104
 105         return tmp - buf;
 106 }
 107
 108 static int cpuid_open(struct inode *inode, struct file *file)
 109 {
 110         unsigned int cpu = iminor(file->f_path.dentry->d_inode);
 111         struct cpuinfo_x86 *c = &cpu_data(cpu);
 112
 113         if (cpu >= NR_CPUS || !cpu_online(cpu))
 114                 return -ENXIO;  /* No such CPU */
 115         if (c->cpuid_level < 0)
 116                 return -EIO;    /* CPUID not supported */
 117
 118         return 0;
 119 }
 120
 121 /*
 122  * File operations we support
 123  */
 124 static const struct file_operations cpuid_fops = {
 125         .owner = THIS_MODULE,
 126         .llseek = cpuid_seek,
 127         .read = cpuid_read,
 128         .open = cpuid_open,
 129 };
 130
 131 static __cpuinit int cpuid_device_create(int cpu)
 132 {
 133         struct device *dev;
 134
 135         dev = device_create(cpuid_class, NULL, MKDEV(CPUID_MAJOR, cpu),
 136                             "cpu%d", cpu);
 137         return IS_ERR(dev) ? PTR_ERR(dev) : 0;
 138 }
 139
 140 static void cpuid_device_destroy(int cpu)
 141 {
 142         device_destroy(cpuid_class, MKDEV(CPUID_MAJOR, cpu));
 143 }
 144
 145 static int __cpuinit cpuid_class_cpu_callback(struct notifier_block *nfb,
 146                                               unsigned long action,
 147                                               void *hcpu)
 148 {
 149         unsigned int cpu = (unsigned long)hcpu;
 150         int err = 0;
 151
 152         switch (action) {
 153         case CPU_UP_PREPARE:
 154                 err = cpuid_device_create(cpu);
 155                 break;
 156         case CPU_UP_CANCELED:
 157         case CPU_UP_CANCELED_FROZEN:
 158         case CPU_DEAD:
 159                 cpuid_device_destroy(cpu);
 160                 break;
 161         }
 162         return err ? NOTIFY_BAD : NOTIFY_OK;
 163 }
 164
 165 static struct notifier_block __refdata cpuid_class_cpu_notifier =
 166 {
 167         .notifier_call = cpuid_class_cpu_callback,
 168 };
 169
 170 static int __init cpuid_init(void)
 171 {
 172         int i, err = 0;
 173         i = 0;
 174
 175         if (register_chrdev(CPUID_MAJOR, "cpu/cpuid", &cpuid_fops)) {
 176                 printk(KERN_ERR "cpuid: unable to get major %d for cpuid\n",
 177                        CPUID_MAJOR);
 178                 err = -EBUSY;
 179                 goto out;
 180         }
 181         cpuid_class = class_create(THIS_MODULE, "cpuid");
 182         if (IS_ERR(cpuid_class)) {
 183                 err = PTR_ERR(cpuid_class);
 184                 goto out_chrdev;
 185         }
 186         for_each_online_cpu(i) {
 187                 err = cpuid_device_create(i);
 188                 if (err != 0)
 189                         goto out_class;
 190         }
 191         register_hotcpu_notifier(&cpuid_class_cpu_notifier);
 192
 193         err = 0;
 194         goto out;
 195
 196 out_class:
 197         i = 0;
 198         for_each_online_cpu(i) {
 199                 cpuid_device_destroy(i);
 200         }
 201         class_destroy(cpuid_class);
 202 out_chrdev:
 203         unregister_chrdev(CPUID_MAJOR, "cpu/cpuid");
 204 out:
 205         return err;
 206 }
 207
 208 static void __exit cpuid_exit(void)
 209 {
 210         int cpu = 0;
 211
 212         for_each_online_cpu(cpu)
 213                 cpuid_device_destroy(cpu);
 214         class_destroy(cpuid_class);
 215         unregister_chrdev(CPUID_MAJOR, "cpu/cpuid");
 216         unregister_hotcpu_notifier(&cpuid_class_cpu_notifier);
 217 }
 218
 219 module_init(cpuid_init);
 220 module_exit(cpuid_exit);
 221
 222 MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
 223 MODULE_DESCRIPTION("x86 generic CPUID driver");
 224 MODULE_LICENSE("GPL");