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
47static struct class *cpuid_class;
48
49struct cpuid_regs {
50	u32 eax, ebx, ecx, edx;
51};
52
53static void cpuid_smp_cpuid(void *cmd_block)
54{
55	struct cpuid_regs *cmd = (struct cpuid_regs *)cmd_block;
56
57	cpuid_count(cmd->eax, cmd->ecx,
58		    &cmd->eax, &cmd->ebx, &cmd->ecx, &cmd->edx);
59}
60
61static loff_t cpuid_seek(struct file *file, loff_t offset, int orig)
62{
63	loff_t ret;
64	struct inode *inode = file->f_mapping->host;
65
66	mutex_lock(&inode->i_mutex);
67	switch (orig) {
68	case 0:
69		file->f_pos = offset;
70		ret = file->f_pos;
71		break;
72	case 1:
73		file->f_pos += offset;
74		ret = file->f_pos;
75		break;
76	default:
77		ret = -EINVAL;
78	}
79	mutex_unlock(&inode->i_mutex);
80	return ret;
81}
82
83static ssize_t cpuid_read(struct file *file, char __user *buf,
84			  size_t count, loff_t *ppos)
85{
86	char __user *tmp = buf;
87	struct cpuid_regs cmd;
88	int cpu = iminor(file_inode(file));
89	u64 pos = *ppos;
90	ssize_t bytes = 0;
91	int err = 0;
92
93	if (count % 16)
94		return -EINVAL;	/* Invalid chunk size */
95
96	for (; count; count -= 16) {
97		cmd.eax = pos;
98		cmd.ecx = pos >> 32;
99		err = smp_call_function_single(cpu, cpuid_smp_cpuid, &cmd, 1);
100		if (err)
101			break;
102		if (copy_to_user(tmp, &cmd, 16)) {
103			err = -EFAULT;
104			break;
105		}
106		tmp += 16;
107		bytes += 16;
108		*ppos = ++pos;
109	}
110
111	return bytes ? bytes : err;
112}
113
114static int cpuid_open(struct inode *inode, struct file *file)
115{
116	unsigned int cpu;
117	struct cpuinfo_x86 *c;
118
119	cpu = iminor(file_inode(file));
120	if (cpu >= nr_cpu_ids || !cpu_online(cpu))
121		return -ENXIO;	/* No such CPU */
122
123	c = &cpu_data(cpu);
124	if (c->cpuid_level < 0)
125		return -EIO;	/* CPUID not supported */
126
127	return 0;
128}
129
130/*
131 * File operations we support
132 */
133static const struct file_operations cpuid_fops = {
134	.owner = THIS_MODULE,
135	.llseek = cpuid_seek,
136	.read = cpuid_read,
137	.open = cpuid_open,
138};
139
140static int cpuid_device_create(int cpu)
141{
142	struct device *dev;
143
144	dev = device_create(cpuid_class, NULL, MKDEV(CPUID_MAJOR, cpu), NULL,
145			    "cpu%d", cpu);
146	return PTR_ERR_OR_ZERO(dev);
147}
148
149static void cpuid_device_destroy(int cpu)
150{
151	device_destroy(cpuid_class, MKDEV(CPUID_MAJOR, cpu));
152}
153
154static int cpuid_class_cpu_callback(struct notifier_block *nfb,
155				    unsigned long action, void *hcpu)
156{
157	unsigned int cpu = (unsigned long)hcpu;
158	int err = 0;
159
160	switch (action) {
161	case CPU_UP_PREPARE:
162		err = cpuid_device_create(cpu);
163		break;
164	case CPU_UP_CANCELED:
165	case CPU_UP_CANCELED_FROZEN:
166	case CPU_DEAD:
167		cpuid_device_destroy(cpu);
168		break;
169	}
170	return notifier_from_errno(err);
171}
172
173static struct notifier_block cpuid_class_cpu_notifier =
174{
175	.notifier_call = cpuid_class_cpu_callback,
176};
177
178static char *cpuid_devnode(struct device *dev, umode_t *mode)
179{
180	return kasprintf(GFP_KERNEL, "cpu/%u/cpuid", MINOR(dev->devt));
181}
182
183static int __init cpuid_init(void)
184{
185	int i, err = 0;
186	i = 0;
187
188	if (__register_chrdev(CPUID_MAJOR, 0, NR_CPUS,
189			      "cpu/cpuid", &cpuid_fops)) {
190		printk(KERN_ERR "cpuid: unable to get major %d for cpuid\n",
191		       CPUID_MAJOR);
192		err = -EBUSY;
193		goto out;
194	}
195	cpuid_class = class_create(THIS_MODULE, "cpuid");
196	if (IS_ERR(cpuid_class)) {
197		err = PTR_ERR(cpuid_class);
198		goto out_chrdev;
199	}
200	cpuid_class->devnode = cpuid_devnode;
201
202	cpu_notifier_register_begin();
203	for_each_online_cpu(i) {
204		err = cpuid_device_create(i);
205		if (err != 0)
206			goto out_class;
207	}
208	__register_hotcpu_notifier(&cpuid_class_cpu_notifier);
209	cpu_notifier_register_done();
210
211	err = 0;
212	goto out;
213
214out_class:
215	i = 0;
216	for_each_online_cpu(i) {
217		cpuid_device_destroy(i);
218	}
219	cpu_notifier_register_done();
220	class_destroy(cpuid_class);
221out_chrdev:
222	__unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid");
223out:
224	return err;
225}
226
227static void __exit cpuid_exit(void)
228{
229	int cpu = 0;
230
231	cpu_notifier_register_begin();
232	for_each_online_cpu(cpu)
233		cpuid_device_destroy(cpu);
234	class_destroy(cpuid_class);
235	__unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid");
236	__unregister_hotcpu_notifier(&cpuid_class_cpu_notifier);
237	cpu_notifier_register_done();
238}
239
240module_init(cpuid_init);
241module_exit(cpuid_exit);
242
243MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
244MODULE_DESCRIPTION("x86 generic CPUID driver");
245MODULE_LICENSE("GPL");
246