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/smp_lock.h>
  37 #include <linux/major.h>
  38 #include <linux/fs.h>
  39 #include <linux/device.h>
  40 #include <linux/cpu.h>
  41 #include <linux/notifier.h>
  42 #include <linux/uaccess.h>
  43 #include <linux/gfp.h>
  44
  45 #include <asm/processor.h>
  46 #include <asm/msr.h>
  47 #include <asm/system.h>
  48
  49 static struct class *cpuid_class;
  50
  51 struct cpuid_regs {
  52         u32 eax, ebx, ecx, edx;
  53 };
  54
  55 static void cpuid_smp_cpuid(void *cmd_block)
  56 {
  57         struct cpuid_regs *cmd = (struct cpuid_regs *)cmd_block;
  58
  59         cpuid_count(cmd->eax, cmd->ecx,
  60                     &cmd->eax, &cmd->ebx, &cmd->ecx, &cmd->edx);
  61 }
  62
  63 static loff_t cpuid_seek(struct file *file, loff_t offset, int orig)
  64 {
  65         loff_t ret;
  66         struct inode *inode = file->f_mapping->host;
  67
  68         mutex_lock(&inode->i_mutex);
  69         switch (orig) {
  70         case 0:
  71                 file->f_pos = offset;
  72                 ret = file->f_pos;
  73                 break;
  74         case 1:
  75                 file->f_pos += offset;
  76                 ret = file->f_pos;
  77                 break;
  78         default:
  79                 ret = -EINVAL;
  80         }
  81         mutex_unlock(&inode->i_mutex);
  82         return ret;
  83 }
  84
  85 static ssize_t cpuid_read(struct file *file, char __user *buf,
  86                           size_t count, loff_t *ppos)
  87 {
  88         char __user *tmp = buf;
  89         struct cpuid_regs cmd;
  90         int cpu = iminor(file->f_path.dentry->d_inode);
  91         u64 pos = *ppos;
  92         ssize_t bytes = 0;
  93         int err = 0;
  94
  95         if (count % 16)
  96                 return -EINVAL; /* Invalid chunk size */
  97
  98         for (; count; count -= 16) {
  99                 cmd.eax = pos;
 100                 cmd.ecx = pos >> 32;
 101                 err = smp_call_function_single(cpu, cpuid_smp_cpuid, &cmd, 1);
 102                 if (err)
 103                         break;
 104                 if (copy_to_user(tmp, &cmd, 16)) {
 105                         err = -EFAULT;
 106                         break;
 107                 }
 108                 tmp += 16;
 109                 bytes += 16;
 110                 *ppos = ++pos;
 111         }
 112
 113         return bytes ? bytes : err;
 114 }
 115
 116 static int cpuid_open(struct inode *inode, struct file *file)
 117 {
 118         unsigned int cpu;
 119         struct cpuinfo_x86 *c;
 120
 121         cpu = iminor(file->f_path.dentry->d_inode);
 122         if (cpu >= nr_cpu_ids || !cpu_online(cpu))
 123                 return -ENXIO;  /* No such CPU */
 124
 125         c = &cpu_data(cpu);
 126         if (c->cpuid_level < 0)
 127                 return -EIO;    /* CPUID not supported */
 128
 129         return 0;
 130 }
 131
 132 /*
 133  * File operations we support
 134  */
 135 static const struct file_operations cpuid_fops = {
 136         .owner = THIS_MODULE,
 137         .llseek = cpuid_seek,
 138         .read = cpuid_read,
 139         .open = cpuid_open,
 140 };
 141
 142 static __cpuinit int cpuid_device_create(int cpu)
 143 {
 144         struct device *dev;
 145
 146         dev = device_create(cpuid_class, NULL, MKDEV(CPUID_MAJOR, cpu), NULL,
 147                             "cpu%d", cpu);
 148         return IS_ERR(dev) ? PTR_ERR(dev) : 0;
 149 }
 150
 151 static void cpuid_device_destroy(int cpu)
 152 {
 153         device_destroy(cpuid_class, MKDEV(CPUID_MAJOR, cpu));
 154 }
 155
 156 static int __cpuinit cpuid_class_cpu_callback(struct notifier_block *nfb,
 157                                               unsigned long action,
 158                                               void *hcpu)
 159 {
 160         unsigned int cpu = (unsigned long)hcpu;
 161         int err = 0;
 162
 163         switch (action) {
 164         case CPU_UP_PREPARE:
 165                 err = cpuid_device_create(cpu);
 166                 break;
 167         case CPU_UP_CANCELED:
 168         case CPU_UP_CANCELED_FROZEN:
 169         case CPU_DEAD:
 170                 cpuid_device_destroy(cpu);
 171                 break;
 172         }
 173         return err ? NOTIFY_BAD : NOTIFY_OK;
 174 }
 175
 176 static struct notifier_block __refdata cpuid_class_cpu_notifier =
 177 {
 178         .notifier_call = cpuid_class_cpu_callback,
 179 };
 180
 181 static char *cpuid_devnode(struct device *dev, mode_t *mode)
 182 {
 183         return kasprintf(GFP_KERNEL, "cpu/%u/cpuid", MINOR(dev->devt));
 184 }
 185
 186 static int __init cpuid_init(void)
 187 {
 188         int i, err = 0;
 189         i = 0;
 190
 191         if (__register_chrdev(CPUID_MAJOR, 0, NR_CPUS,
 192                               "cpu/cpuid", &cpuid_fops)) {
 193                 printk(KERN_ERR "cpuid: unable to get major %d for cpuid\n",
 194                        CPUID_MAJOR);
 195                 err = -EBUSY;
 196                 goto out;
 197         }
 198         cpuid_class = class_create(THIS_MODULE, "cpuid");
 199         if (IS_ERR(cpuid_class)) {
 200                 err = PTR_ERR(cpuid_class);
 201                 goto out_chrdev;
 202         }
 203         cpuid_class->devnode = cpuid_devnode;
 204         for_each_online_cpu(i) {
 205                 err = cpuid_device_create(i);
 206                 if (err != 0)
 207                         goto out_class;
 208         }
 209         register_hotcpu_notifier(&cpuid_class_cpu_notifier);
 210
 211         err = 0;
 212         goto out;
 213
 214 out_class:
 215         i = 0;
 216         for_each_online_cpu(i) {
 217                 cpuid_device_destroy(i);
 218         }
 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         for_each_online_cpu(cpu)
 231                 cpuid_device_destroy(cpu);
 232         class_destroy(cpuid_class);
 233         __unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid");
 234         unregister_hotcpu_notifier(&cpuid_class_cpu_notifier);
 235 }
 236
 237 module_init(cpuid_init);
 238 module_exit(cpuid_exit);
 239
 240 MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
 241 MODULE_DESCRIPTION("x86 generic CPUID driver");
 242 MODULE_LICENSE("GPL");