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 #include <linux/completion.h>
  44
  45 #include <asm/processor.h>
  46 #include <asm/msr.h>
  47
  48 static struct class *cpuid_class;
  49 static enum cpuhp_state cpuhp_cpuid_state;
  50
  51 struct cpuid_regs_done {
  52         struct cpuid_regs regs;
  53         struct completion done;
  54 };
  55
  56 static void cpuid_smp_cpuid(void *cmd_block)
  57 {
  58         struct cpuid_regs_done *cmd = cmd_block;
  59
  60         cpuid_count(cmd->regs.eax, cmd->regs.ecx,
  61                     &cmd->regs.eax, &cmd->regs.ebx,
  62                     &cmd->regs.ecx, &cmd->regs.edx);
  63
  64         complete(&cmd->done);
  65 }
  66
  67 static ssize_t cpuid_read(struct file *file, char __user *buf,
  68                           size_t count, loff_t *ppos)
  69 {
  70         char __user *tmp = buf;
  71         struct cpuid_regs_done cmd;
  72         int cpu = iminor(file_inode(file));
  73         u64 pos = *ppos;
  74         ssize_t bytes = 0;
  75         int err = 0;
  76
  77         if (count % 16)
  78                 return -EINVAL; /* Invalid chunk size */
  79
  80         init_completion(&cmd.done);
  81         for (; count; count -= 16) {
  82                 call_single_data_t csd = {
  83                         .func = cpuid_smp_cpuid,
  84                         .info = &cmd,
  85                 };
  86
  87                 cmd.regs.eax = pos;
  88                 cmd.regs.ecx = pos >> 32;
  89
  90                 err = smp_call_function_single_async(cpu, &csd);
  91                 if (err)
  92                         break;
  93                 wait_for_completion(&cmd.done);
  94                 if (copy_to_user(tmp, &cmd.regs, 16)) {
  95                         err = -EFAULT;
  96                         break;
  97                 }
  98                 tmp += 16;
  99                 bytes += 16;
 100                 *ppos = ++pos;
 101                 reinit_completion(&cmd.done);
 102         }
 103
 104         return bytes ? bytes : err;
 105 }
 106
 107 static int cpuid_open(struct inode *inode, struct file *file)
 108 {
 109         unsigned int cpu;
 110         struct cpuinfo_x86 *c;
 111
 112         cpu = iminor(file_inode(file));
 113         if (cpu >= nr_cpu_ids || !cpu_online(cpu))
 114                 return -ENXIO;  /* No such CPU */
 115
 116         c = &cpu_data(cpu);
 117         if (c->cpuid_level < 0)
 118                 return -EIO;    /* CPUID not supported */
 119
 120         return 0;
 121 }
 122
 123 /*
 124  * File operations we support
 125  */
 126 static const struct file_operations cpuid_fops = {
 127         .owner = THIS_MODULE,
 128         .llseek = no_seek_end_llseek,
 129         .read = cpuid_read,
 130         .open = cpuid_open,
 131 };
 132
 133 static int cpuid_device_create(unsigned int cpu)
 134 {
 135         struct device *dev;
 136
 137         dev = device_create(cpuid_class, NULL, MKDEV(CPUID_MAJOR, cpu), NULL,
 138                             "cpu%d", cpu);
 139         return PTR_ERR_OR_ZERO(dev);
 140 }
 141
 142 static int cpuid_device_destroy(unsigned int cpu)
 143 {
 144         device_destroy(cpuid_class, MKDEV(CPUID_MAJOR, cpu));
 145         return 0;
 146 }
 147
 148 static char *cpuid_devnode(struct device *dev, umode_t *mode)
 149 {
 150         return kasprintf(GFP_KERNEL, "cpu/%u/cpuid", MINOR(dev->devt));
 151 }
 152
 153 static int __init cpuid_init(void)
 154 {
 155         int err;
 156
 157         if (__register_chrdev(CPUID_MAJOR, 0, NR_CPUS,
 158                               "cpu/cpuid", &cpuid_fops)) {
 159                 printk(KERN_ERR "cpuid: unable to get major %d for cpuid\n",
 160                        CPUID_MAJOR);
 161                 return -EBUSY;
 162         }
 163         cpuid_class = class_create(THIS_MODULE, "cpuid");
 164         if (IS_ERR(cpuid_class)) {
 165                 err = PTR_ERR(cpuid_class);
 166                 goto out_chrdev;
 167         }
 168         cpuid_class->devnode = cpuid_devnode;
 169
 170         err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "x86/cpuid:online",
 171                                 cpuid_device_create, cpuid_device_destroy);
 172         if (err < 0)
 173                 goto out_class;
 174
 175         cpuhp_cpuid_state = err;
 176         return 0;
 177
 178 out_class:
 179         class_destroy(cpuid_class);
 180 out_chrdev:
 181         __unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid");
 182         return err;
 183 }
 184 module_init(cpuid_init);
 185
 186 static void __exit cpuid_exit(void)
 187 {
 188         cpuhp_remove_state(cpuhp_cpuid_state);
 189         class_destroy(cpuid_class);
 190         __unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid");
 191 }
 192 module_exit(cpuid_exit);
 193
 194 MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
 195 MODULE_DESCRIPTION("x86 generic CPUID driver");
 196 MODULE_LICENSE("GPL");