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
  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         int ret = 0;
 120
 121         lock_kernel();
 122
 123         cpu = iminor(file->f_path.dentry->d_inode);
 124         if (cpu >= nr_cpu_ids || !cpu_online(cpu)) {
 125                 ret = -ENXIO;   /* No such CPU */
 126                 goto out;
 127         }
 128         c = &cpu_data(cpu);
 129         if (c->cpuid_level < 0)
 130                 ret = -EIO;     /* CPUID not supported */
 131 out:
 132         unlock_kernel();
 133         return ret;
 134 }
 135
 136 /*
 137  * File operations we support
 138  */
 139 static const struct file_operations cpuid_fops = {
 140         .owner = THIS_MODULE,
 141         .llseek = cpuid_seek,
 142         .read = cpuid_read,
 143         .open = cpuid_open,
 144 };
 145
 146 static __cpuinit int cpuid_device_create(int cpu)
 147 {
 148         struct device *dev;
 149
 150         dev = device_create(cpuid_class, NULL, MKDEV(CPUID_MAJOR, cpu), NULL,
 151                             "cpu%d", cpu);
 152         return IS_ERR(dev) ? PTR_ERR(dev) : 0;
 153 }
 154
 155 static void cpuid_device_destroy(int cpu)
 156 {
 157         device_destroy(cpuid_class, MKDEV(CPUID_MAJOR, cpu));
 158 }
 159
 160 static int __cpuinit cpuid_class_cpu_callback(struct notifier_block *nfb,
 161                                               unsigned long action,
 162                                               void *hcpu)
 163 {
 164         unsigned int cpu = (unsigned long)hcpu;
 165         int err = 0;
 166
 167         switch (action) {
 168         case CPU_UP_PREPARE:
 169                 err = cpuid_device_create(cpu);
 170                 break;
 171         case CPU_UP_CANCELED:
 172         case CPU_UP_CANCELED_FROZEN:
 173         case CPU_DEAD:
 174                 cpuid_device_destroy(cpu);
 175                 break;
 176         }
 177         return err ? NOTIFY_BAD : NOTIFY_OK;
 178 }
 179
 180 static struct notifier_block __refdata cpuid_class_cpu_notifier =
 181 {
 182         .notifier_call = cpuid_class_cpu_callback,
 183 };
 184
 185 static char *cpuid_nodename(struct device *dev)
 186 {
 187         return kasprintf(GFP_KERNEL, "cpu/%u/cpuid", MINOR(dev->devt));
 188 }
 189
 190 static int __init cpuid_init(void)
 191 {
 192         int i, err = 0;
 193         i = 0;
 194
 195         if (register_chrdev(CPUID_MAJOR, "cpu/cpuid", &cpuid_fops)) {
 196                 printk(KERN_ERR "cpuid: unable to get major %d for cpuid\n",
 197                        CPUID_MAJOR);
 198                 err = -EBUSY;
 199                 goto out;
 200         }
 201         cpuid_class = class_create(THIS_MODULE, "cpuid");
 202         if (IS_ERR(cpuid_class)) {
 203                 err = PTR_ERR(cpuid_class);
 204                 goto out_chrdev;
 205         }
 206         cpuid_class->nodename = cpuid_nodename;
 207         for_each_online_cpu(i) {
 208                 err = cpuid_device_create(i);
 209                 if (err != 0)
 210                         goto out_class;
 211         }
 212         register_hotcpu_notifier(&cpuid_class_cpu_notifier);
 213
 214         err = 0;
 215         goto out;
 216
 217 out_class:
 218         i = 0;
 219         for_each_online_cpu(i) {
 220                 cpuid_device_destroy(i);
 221         }
 222         class_destroy(cpuid_class);
 223 out_chrdev:
 224         unregister_chrdev(CPUID_MAJOR, "cpu/cpuid");
 225 out:
 226         return err;
 227 }
 228
 229 static void __exit cpuid_exit(void)
 230 {
 231         int cpu = 0;
 232
 233         for_each_online_cpu(cpu)
 234                 cpuid_device_destroy(cpu);
 235         class_destroy(cpuid_class);
 236         unregister_chrdev(CPUID_MAJOR, "cpu/cpuid");
 237         unregister_hotcpu_notifier(&cpuid_class_cpu_notifier);
 238 }
 239
 240 module_init(cpuid_init);
 241 module_exit(cpuid_exit);
 242
 243 MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
 244 MODULE_DESCRIPTION("x86 generic CPUID driver");
 245 MODULE_LICENSE("GPL");