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
  47 static struct class *cpuid_class;
  48 static enum cpuhp_state cpuhp_cpuid_state;
  49
  50 static void cpuid_smp_cpuid(void *cmd_block)
  51 {
  52         struct cpuid_regs *cmd = (struct cpuid_regs *)cmd_block;
  53
  54         cpuid_count(cmd->eax, cmd->ecx,
  55                     &cmd->eax, &cmd->ebx, &cmd->ecx, &cmd->edx);
  56 }
  57
  58 static ssize_t cpuid_read(struct file *file, char __user *buf,
  59                           size_t count, loff_t *ppos)
  60 {
  61         char __user *tmp = buf;
  62         struct cpuid_regs cmd;
  63         int cpu = iminor(file_inode(file));
  64         u64 pos = *ppos;
  65         ssize_t bytes = 0;
  66         int err = 0;
  67
  68         if (count % 16)
  69                 return -EINVAL; /* Invalid chunk size */
  70
  71         for (; count; count -= 16) {
  72                 cmd.eax = pos;
  73                 cmd.ecx = pos >> 32;
  74                 err = smp_call_function_single(cpu, cpuid_smp_cpuid, &cmd, 1);
  75                 if (err)
  76                         break;
  77                 if (copy_to_user(tmp, &cmd, 16)) {
  78                         err = -EFAULT;
  79                         break;
  80                 }
  81                 tmp += 16;
  82                 bytes += 16;
  83                 *ppos = ++pos;
  84         }
  85
  86         return bytes ? bytes : err;
  87 }
  88
  89 static int cpuid_open(struct inode *inode, struct file *file)
  90 {
  91         unsigned int cpu;
  92         struct cpuinfo_x86 *c;
  93
  94         cpu = iminor(file_inode(file));
  95         if (cpu >= nr_cpu_ids || !cpu_online(cpu))
  96                 return -ENXIO;  /* No such CPU */
  97
  98         c = &cpu_data(cpu);
  99         if (c->cpuid_level < 0)
 100                 return -EIO;    /* CPUID not supported */
 101
 102         return 0;
 103 }
 104
 105 /*
 106  * File operations we support
 107  */
 108 static const struct file_operations cpuid_fops = {
 109         .owner = THIS_MODULE,
 110         .llseek = no_seek_end_llseek,
 111         .read = cpuid_read,
 112         .open = cpuid_open,
 113 };
 114
 115 static int cpuid_device_create(unsigned int cpu)
 116 {
 117         struct device *dev;
 118
 119         dev = device_create(cpuid_class, NULL, MKDEV(CPUID_MAJOR, cpu), NULL,
 120                             "cpu%d", cpu);
 121         return PTR_ERR_OR_ZERO(dev);
 122 }
 123
 124 static int cpuid_device_destroy(unsigned int cpu)
 125 {
 126         device_destroy(cpuid_class, MKDEV(CPUID_MAJOR, cpu));
 127         return 0;
 128 }
 129
 130 static char *cpuid_devnode(struct device *dev, umode_t *mode)
 131 {
 132         return kasprintf(GFP_KERNEL, "cpu/%u/cpuid", MINOR(dev->devt));
 133 }
 134
 135 static int __init cpuid_init(void)
 136 {
 137         int err;
 138
 139         if (__register_chrdev(CPUID_MAJOR, 0, NR_CPUS,
 140                               "cpu/cpuid", &cpuid_fops)) {
 141                 printk(KERN_ERR "cpuid: unable to get major %d for cpuid\n",
 142                        CPUID_MAJOR);
 143                 return -EBUSY;
 144         }
 145         cpuid_class = class_create(THIS_MODULE, "cpuid");
 146         if (IS_ERR(cpuid_class)) {
 147                 err = PTR_ERR(cpuid_class);
 148                 goto out_chrdev;
 149         }
 150         cpuid_class->devnode = cpuid_devnode;
 151
 152         err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "x86/cpuid:online",
 153                                 cpuid_device_create, cpuid_device_destroy);
 154         if (err < 0)
 155                 goto out_class;
 156
 157         cpuhp_cpuid_state = err;
 158         return 0;
 159
 160 out_class:
 161         class_destroy(cpuid_class);
 162 out_chrdev:
 163         __unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid");
 164         return err;
 165 }
 166 module_init(cpuid_init);
 167
 168 static void __exit cpuid_exit(void)
 169 {
 170         cpuhp_remove_state(cpuhp_cpuid_state);
 171         class_destroy(cpuid_class);
 172         __unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid");
 173 }
 174 module_exit(cpuid_exit);
 175
 176 MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
 177 MODULE_DESCRIPTION("x86 generic CPUID driver");
 178 MODULE_LICENSE("GPL");