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/* ----------------------------------------------------------------------- *
*
* Copyright 2000-2008 H. Peter Anvin - All Rights Reserved
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, Inc., 675 Mass Ave, Cambridge MA 02139,
* USA; either version 2 of the License, or (at your option) any later
* version; incorporated herein by reference.
*
* ----------------------------------------------------------------------- */
/*
* x86 CPUID access device
*
* This device is accessed by lseek() to the appropriate CPUID level
* and then read in chunks of 16 bytes. A larger size means multiple
* reads of consecutive levels.
*
* The lower 32 bits of the file position is used as the incoming %eax,
* and the upper 32 bits of the file position as the incoming %ecx,
* the latter intended for "counting" eax levels like eax=4.
*
* This driver uses /dev/cpu/%d/cpuid where %d is the minor number, and on
* an SMP box will direct the access to CPU %d.
*/
#include <linux/module.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/fcntl.h>
#include <linux/init.h>
#include <linux/poll.h>
#include <linux/smp.h>
#include <linux/major.h>
#include <linux/fs.h>
#include <linux/device.h>
#include <linux/cpu.h>
#include <linux/notifier.h>
#include <linux/uaccess.h>
#include <linux/gfp.h>
#include <asm/processor.h>
#include <asm/msr.h>
#include <asm/system.h>
static struct class *cpuid_class;
struct cpuid_regs {
u32 eax, ebx, ecx, edx;
};
static void cpuid_smp_cpuid(void *cmd_block)
{
struct cpuid_regs *cmd = (struct cpuid_regs *)cmd_block;
cpuid_count(cmd->eax, cmd->ecx,
&cmd->eax, &cmd->ebx, &cmd->ecx, &cmd->edx);
}
static loff_t cpuid_seek(struct file *file, loff_t offset, int orig)
{
loff_t ret;
struct inode *inode = file->f_mapping->host;
mutex_lock(&inode->i_mutex);
switch (orig) {
case 0:
file->f_pos = offset;
ret = file->f_pos;
break;
case 1:
file->f_pos += offset;
ret = file->f_pos;
break;
default:
ret = -EINVAL;
}
mutex_unlock(&inode->i_mutex);
return ret;
}
static ssize_t cpuid_read(struct file *file, char __user *buf,
size_t count, loff_t *ppos)
{
char __user *tmp = buf;
struct cpuid_regs cmd;
int cpu = iminor(file->f_path.dentry->d_inode);
u64 pos = *ppos;
ssize_t bytes = 0;
int err = 0;
if (count % 16)
return -EINVAL; /* Invalid chunk size */
for (; count; count -= 16) {
cmd.eax = pos;
cmd.ecx = pos >> 32;
err = smp_call_function_single(cpu, cpuid_smp_cpuid, &cmd, 1);
if (err)
break;
if (copy_to_user(tmp, &cmd, 16)) {
err = -EFAULT;
break;
}
tmp += 16;
bytes += 16;
*ppos = ++pos;
}
return bytes ? bytes : err;
}
static int cpuid_open(struct inode *inode, struct file *file)
{
unsigned int cpu;
struct cpuinfo_x86 *c;
cpu = iminor(file->f_path.dentry->d_inode);
if (cpu >= nr_cpu_ids || !cpu_online(cpu))
return -ENXIO; /* No such CPU */
c = &cpu_data(cpu);
if (c->cpuid_level < 0)
return -EIO; /* CPUID not supported */
return 0;
}
/*
* File operations we support
*/
static const struct file_operations cpuid_fops = {
.owner = THIS_MODULE,
.llseek = cpuid_seek,
.read = cpuid_read,
.open = cpuid_open,
};
static __cpuinit int cpuid_device_create(int cpu)
{
struct device *dev;
dev = device_create(cpuid_class, NULL, MKDEV(CPUID_MAJOR, cpu), NULL,
"cpu%d", cpu);
return IS_ERR(dev) ? PTR_ERR(dev) : 0;
}
static void cpuid_device_destroy(int cpu)
{
device_destroy(cpuid_class, MKDEV(CPUID_MAJOR, cpu));
}
static int __cpuinit cpuid_class_cpu_callback(struct notifier_block *nfb,
unsigned long action,
void *hcpu)
{
unsigned int cpu = (unsigned long)hcpu;
int err = 0;
switch (action) {
case CPU_UP_PREPARE:
err = cpuid_device_create(cpu);
break;
case CPU_UP_CANCELED:
case CPU_UP_CANCELED_FROZEN:
case CPU_DEAD:
cpuid_device_destroy(cpu);
break;
}
return notifier_from_errno(err);
}
static struct notifier_block __refdata cpuid_class_cpu_notifier =
{
.notifier_call = cpuid_class_cpu_callback,
};
static char *cpuid_devnode(struct device *dev, umode_t *mode)
{
return kasprintf(GFP_KERNEL, "cpu/%u/cpuid", MINOR(dev->devt));
}
static int __init cpuid_init(void)
{
int i, err = 0;
i = 0;
if (__register_chrdev(CPUID_MAJOR, 0, NR_CPUS,
"cpu/cpuid", &cpuid_fops)) {
printk(KERN_ERR "cpuid: unable to get major %d for cpuid\n",
CPUID_MAJOR);
err = -EBUSY;
goto out;
}
cpuid_class = class_create(THIS_MODULE, "cpuid");
if (IS_ERR(cpuid_class)) {
err = PTR_ERR(cpuid_class);
goto out_chrdev;
}
cpuid_class->devnode = cpuid_devnode;
for_each_online_cpu(i) {
err = cpuid_device_create(i);
if (err != 0)
goto out_class;
}
register_hotcpu_notifier(&cpuid_class_cpu_notifier);
err = 0;
goto out;
out_class:
i = 0;
for_each_online_cpu(i) {
cpuid_device_destroy(i);
}
class_destroy(cpuid_class);
out_chrdev:
__unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid");
out:
return err;
}
static void __exit cpuid_exit(void)
{
int cpu = 0;
for_each_online_cpu(cpu)
cpuid_device_destroy(cpu);
class_destroy(cpuid_class);
__unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid");
unregister_hotcpu_notifier(&cpuid_class_cpu_notifier);
}
module_init(cpuid_init);
module_exit(cpuid_exit);
MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
MODULE_DESCRIPTION("x86 generic CPUID driver");
MODULE_LICENSE("GPL");
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