arch/i386/kernel/cpuid.c

   1 /* ----------------------------------------------------------------------- *
   2  *
   3  *   Copyright 2000 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  * cpuid.c
  15  *
  16  * x86 CPUID access device
  17  *
  18  * This device is accessed by lseek() to the appropriate CPUID level
  19  * and then read in chunks of 16 bytes.  A larger size means multiple
  20  * reads of consecutive levels.
  21  *
  22  * This driver uses /dev/cpu/%d/cpuid where %d is the minor number, and on
  23  * an SMP box will direct the access to CPU %d.
  24  */
  25
  26 #include <linux/module.h>
  27
  28 #include <linux/types.h>
  29 #include <linux/errno.h>
  30 #include <linux/fcntl.h>
  31 #include <linux/init.h>
  32 #include <linux/poll.h>
  33 #include <linux/smp.h>
  34 #include <linux/major.h>
  35 #include <linux/fs.h>
  36 #include <linux/smp_lock.h>
  37 #include <linux/device.h>
  38 #include <linux/cpu.h>
  39 #include <linux/notifier.h>
  40
  41 #include <asm/processor.h>
  42 #include <asm/msr.h>
  43 #include <asm/uaccess.h>
  44 #include <asm/system.h>
  45
  46 static struct class *cpuid_class;
  47
  48 #ifdef CONFIG_SMP
  49
  50 struct cpuid_command {
  51         u32 reg;
  52         u32 *data;
  53 };
  54
  55 static void cpuid_smp_cpuid(void *cmd_block)
  56 {
  57         struct cpuid_command *cmd = (struct cpuid_command *)cmd_block;
  58
  59         cpuid(cmd->reg, &cmd->data[0], &cmd->data[1], &cmd->data[2],
  60                       &cmd->data[3]);
  61 }
  62
  63 static inline void do_cpuid(int cpu, u32 reg, u32 * data)
  64 {
  65         struct cpuid_command cmd;
  66
  67         preempt_disable();
  68         if (cpu == smp_processor_id()) {
  69                 cpuid(reg, &data[0], &data[1], &data[2], &data[3]);
  70         } else {
  71                 cmd.reg = reg;
  72                 cmd.data = data;
  73
  74                 smp_call_function_single(cpu, cpuid_smp_cpuid, &cmd, 1, 1);
  75         }
  76         preempt_enable();
  77 }
  78 #else                           /* ! CONFIG_SMP */
  79
  80 static inline void do_cpuid(int cpu, u32 reg, u32 * data)
  81 {
  82         cpuid(reg, &data[0], &data[1], &data[2], &data[3]);
  83 }
  84
  85 #endif                          /* ! CONFIG_SMP */
  86
  87 static loff_t cpuid_seek(struct file *file, loff_t offset, int orig)
  88 {
  89         loff_t ret;
  90
  91         lock_kernel();
  92
  93         switch (orig) {
  94         case 0:
  95                 file->f_pos = offset;
  96                 ret = file->f_pos;
  97                 break;
  98         case 1:
  99                 file->f_pos += offset;
 100                 ret = file->f_pos;
 101                 break;
 102         default:
 103                 ret = -EINVAL;
 104         }
 105
 106         unlock_kernel();
 107         return ret;
 108 }
 109
 110 static ssize_t cpuid_read(struct file *file, char __user *buf,
 111                           size_t count, loff_t * ppos)
 112 {
 113         char __user *tmp = buf;
 114         u32 data[4];
 115         u32 reg = *ppos;
 116         int cpu = iminor(file->f_path.dentry->d_inode);
 117
 118         if (count % 16)
 119                 return -EINVAL; /* Invalid chunk size */
 120
 121         for (; count; count -= 16) {
 122                 do_cpuid(cpu, reg, data);
 123                 if (copy_to_user(tmp, &data, 16))
 124                         return -EFAULT;
 125                 tmp += 16;
 126                 *ppos = reg++;
 127         }
 128
 129         return tmp - buf;
 130 }
 131
 132 static int cpuid_open(struct inode *inode, struct file *file)
 133 {
 134         unsigned int cpu = iminor(file->f_path.dentry->d_inode);
 135         struct cpuinfo_x86 *c = &(cpu_data)[cpu];
 136
 137         if (cpu >= NR_CPUS || !cpu_online(cpu))
 138                 return -ENXIO;  /* No such CPU */
 139         if (c->cpuid_level < 0)
 140                 return -EIO;    /* CPUID not supported */
 141
 142         return 0;
 143 }
 144
 145 /*
 146  * File operations we support
 147  */
 148 static const struct file_operations cpuid_fops = {
 149         .owner = THIS_MODULE,
 150         .llseek = cpuid_seek,
 151         .read = cpuid_read,
 152         .open = cpuid_open,
 153 };
 154
 155 static int cpuid_device_create(int i)
 156 {
 157         int err = 0;
 158         struct device *dev;
 159
 160         dev = device_create(cpuid_class, NULL, MKDEV(CPUID_MAJOR, i), "cpu%d",i);
 161         if (IS_ERR(dev))
 162                 err = PTR_ERR(dev);
 163         return err;
 164 }
 165
 166 static int cpuid_class_cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
 167 {
 168         unsigned int cpu = (unsigned long)hcpu;
 169
 170         switch (action) {
 171         case CPU_ONLINE:
 172                 cpuid_device_create(cpu);
 173                 break;
 174         case CPU_DEAD:
 175                 device_destroy(cpuid_class, MKDEV(CPUID_MAJOR, cpu));
 176                 break;
 177         }
 178         return NOTIFY_OK;
 179 }
 180
 181 static struct notifier_block __cpuinitdata cpuid_class_cpu_notifier =
 182 {
 183         .notifier_call = cpuid_class_cpu_callback,
 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, "cpu/cpuid", &cpuid_fops)) {
 192                 printk(KERN_ERR "cpuid: unable to get major %d for cpuid\n",
 193                        CPUID_MAJOR);
 194                 err = -EBUSY;
 195                 goto out;
 196         }
 197         cpuid_class = class_create(THIS_MODULE, "cpuid");
 198         if (IS_ERR(cpuid_class)) {
 199                 err = PTR_ERR(cpuid_class);
 200                 goto out_chrdev;
 201         }
 202         for_each_online_cpu(i) {
 203                 err = cpuid_device_create(i);
 204                 if (err != 0)
 205                         goto out_class;
 206         }
 207         register_hotcpu_notifier(&cpuid_class_cpu_notifier);
 208
 209         err = 0;
 210         goto out;
 211
 212 out_class:
 213         i = 0;
 214         for_each_online_cpu(i) {
 215                 device_destroy(cpuid_class, MKDEV(CPUID_MAJOR, i));
 216         }
 217         class_destroy(cpuid_class);
 218 out_chrdev:
 219         unregister_chrdev(CPUID_MAJOR, "cpu/cpuid");
 220 out:
 221         return err;
 222 }
 223
 224 static void __exit cpuid_exit(void)
 225 {
 226         int cpu = 0;
 227
 228         for_each_online_cpu(cpu)
 229                 device_destroy(cpuid_class, MKDEV(CPUID_MAJOR, cpu));
 230         class_destroy(cpuid_class);
 231         unregister_chrdev(CPUID_MAJOR, "cpu/cpuid");
 232         unregister_hotcpu_notifier(&cpuid_class_cpu_notifier);
 233 }
 234
 235 module_init(cpuid_init);
 236 module_exit(cpuid_exit);
 237
 238 MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
 239 MODULE_DESCRIPTION("x86 generic CPUID driver");
 240 MODULE_LICENSE("GPL");