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/smp_lock.h>
  40 #include <linux/device.h>
  41 #include <linux/cpu.h>
  42 #include <linux/notifier.h>
  43
  44 #include <asm/processor.h>
  45 #include <asm/msr.h>
  46 #include <asm/uaccess.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         int err;
  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                         return err;
 103                 if (copy_to_user(tmp, &cmd, 16))
 104                         return -EFAULT;
 105                 tmp += 16;
 106                 *ppos = ++pos;
 107         }
 108
 109         return tmp - buf;
 110 }
 111
 112 static int cpuid_open(struct inode *inode, struct file *file)
 113 {
 114         unsigned int cpu;
 115         struct cpuinfo_x86 *c;
 116         int ret = 0;
 117
 118         lock_kernel();
 119
 120         cpu = iminor(file->f_path.dentry->d_inode);
 121         if (cpu >= NR_CPUS || !cpu_online(cpu)) {
 122                 ret = -ENXIO;   /* No such CPU */
 123                 goto out;
 124         }
 125         c = &cpu_data(cpu);
 126         if (c->cpuid_level < 0)
 127                 ret = -EIO;     /* CPUID not supported */
 128 out:
 129         unlock_kernel();
 130         return ret;
 131 }
 132
 133 /*
 134  * File operations we support
 135  */
 136 static const struct file_operations cpuid_fops = {
 137         .owner = THIS_MODULE,
 138         .llseek = cpuid_seek,
 139         .read = cpuid_read,
 140         .open = cpuid_open,
 141 };
 142
 143 static __cpuinit int cpuid_device_create(int cpu)
 144 {
 145         struct device *dev;
 146
 147         dev = device_create_drvdata(cpuid_class, NULL, MKDEV(CPUID_MAJOR, cpu),
 148                                     NULL, "cpu%d", cpu);
 149         return IS_ERR(dev) ? PTR_ERR(dev) : 0;
 150 }
 151
 152 static void cpuid_device_destroy(int cpu)
 153 {
 154         device_destroy(cpuid_class, MKDEV(CPUID_MAJOR, cpu));
 155 }
 156
 157 static int __cpuinit cpuid_class_cpu_callback(struct notifier_block *nfb,
 158                                               unsigned long action,
 159                                               void *hcpu)
 160 {
 161         unsigned int cpu = (unsigned long)hcpu;
 162         int err = 0;
 163
 164         switch (action) {
 165         case CPU_UP_PREPARE:
 166                 err = cpuid_device_create(cpu);
 167                 break;
 168         case CPU_UP_CANCELED:
 169         case CPU_UP_CANCELED_FROZEN:
 170         case CPU_DEAD:
 171                 cpuid_device_destroy(cpu);
 172                 break;
 173         }
 174         return err ? NOTIFY_BAD : NOTIFY_OK;
 175 }
 176
 177 static struct notifier_block __refdata cpuid_class_cpu_notifier =
 178 {
 179         .notifier_call = cpuid_class_cpu_callback,
 180 };
 181
 182 static int __init cpuid_init(void)
 183 {
 184         int i, err = 0;
 185         i = 0;
 186
 187         if (register_chrdev(CPUID_MAJOR, "cpu/cpuid", &cpuid_fops)) {
 188                 printk(KERN_ERR "cpuid: unable to get major %d for cpuid\n",
 189                        CPUID_MAJOR);
 190                 err = -EBUSY;
 191                 goto out;
 192         }
 193         cpuid_class = class_create(THIS_MODULE, "cpuid");
 194         if (IS_ERR(cpuid_class)) {
 195                 err = PTR_ERR(cpuid_class);
 196                 goto out_chrdev;
 197         }
 198         for_each_online_cpu(i) {
 199                 err = cpuid_device_create(i);
 200                 if (err != 0)
 201                         goto out_class;
 202         }
 203         register_hotcpu_notifier(&cpuid_class_cpu_notifier);
 204
 205         err = 0;
 206         goto out;
 207
 208 out_class:
 209         i = 0;
 210         for_each_online_cpu(i) {
 211                 cpuid_device_destroy(i);
 212         }
 213         class_destroy(cpuid_class);
 214 out_chrdev:
 215         unregister_chrdev(CPUID_MAJOR, "cpu/cpuid");
 216 out:
 217         return err;
 218 }
 219
 220 static void __exit cpuid_exit(void)
 221 {
 222         int cpu = 0;
 223
 224         for_each_online_cpu(cpu)
 225                 cpuid_device_destroy(cpu);
 226         class_destroy(cpuid_class);
 227         unregister_chrdev(CPUID_MAJOR, "cpu/cpuid");
 228         unregister_hotcpu_notifier(&cpuid_class_cpu_notifier);
 229 }
 230
 231 module_init(cpuid_init);
 232 module_exit(cpuid_exit);
 233
 234 MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
 235 MODULE_DESCRIPTION("x86 generic CPUID driver");
 236 MODULE_LICENSE("GPL");