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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->f_path.dentry->d_inode);
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->f_path.dentry->d_inode);
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 __cpuinit 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 IS_ERR(dev) ? PTR_ERR(dev) : 0;
147}
148
149static void cpuid_device_destroy(int cpu)
150{
151 device_destroy(cpuid_class, MKDEV(CPUID_MAJOR, cpu));
152}
153
154static int __cpuinit cpuid_class_cpu_callback(struct notifier_block *nfb,
155 unsigned long action,
156 void *hcpu)
157{
158 unsigned int cpu = (unsigned long)hcpu;
159 int err = 0;
160
161 switch (action) {
162 case CPU_UP_PREPARE:
163 err = cpuid_device_create(cpu);
164 break;
165 case CPU_UP_CANCELED:
166 case CPU_UP_CANCELED_FROZEN:
167 case CPU_DEAD:
168 cpuid_device_destroy(cpu);
169 break;
170 }
171 return notifier_from_errno(err);
172}
173
174static struct notifier_block __refdata cpuid_class_cpu_notifier =
175{
176 .notifier_call = cpuid_class_cpu_callback,
177};
178
179static char *cpuid_devnode(struct device *dev, umode_t *mode)
180{
181 return kasprintf(GFP_KERNEL, "cpu/%u/cpuid", MINOR(dev->devt));
182}
183
184static int __init cpuid_init(void)
185{
186 int i, err = 0;
187 i = 0;
188
189 if (__register_chrdev(CPUID_MAJOR, 0, NR_CPUS,
190 "cpu/cpuid", &cpuid_fops)) {
191 printk(KERN_ERR "cpuid: unable to get major %d for cpuid\n",
192 CPUID_MAJOR);
193 err = -EBUSY;
194 goto out;
195 }
196 cpuid_class = class_create(THIS_MODULE, "cpuid");
197 if (IS_ERR(cpuid_class)) {
198 err = PTR_ERR(cpuid_class);
199 goto out_chrdev;
200 }
201 cpuid_class->devnode = cpuid_devnode;
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
212out_class:
213 i = 0;
214 for_each_online_cpu(i) {
215 cpuid_device_destroy(i);
216 }
217 class_destroy(cpuid_class);
218out_chrdev:
219 __unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid");
220out:
221 return err;
222}
223
224static void __exit cpuid_exit(void)
225{
226 int cpu = 0;
227
228 for_each_online_cpu(cpu)
229 cpuid_device_destroy(cpu);
230 class_destroy(cpuid_class);
231 __unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid");
232 unregister_hotcpu_notifier(&cpuid_class_cpu_notifier);
233}
234
235module_init(cpuid_init);
236module_exit(cpuid_exit);
237
238MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
239MODULE_DESCRIPTION("x86 generic CPUID driver");
240MODULE_LICENSE("GPL");
1// SPDX-License-Identifier: GPL-2.0-or-later
2/* ----------------------------------------------------------------------- *
3 *
4 * Copyright 2000-2008 H. Peter Anvin - All Rights Reserved
5 *
6 * ----------------------------------------------------------------------- */
7
8/*
9 * x86 CPUID access device
10 *
11 * This device is accessed by lseek() to the appropriate CPUID level
12 * and then read in chunks of 16 bytes. A larger size means multiple
13 * reads of consecutive levels.
14 *
15 * The lower 32 bits of the file position is used as the incoming %eax,
16 * and the upper 32 bits of the file position as the incoming %ecx,
17 * the latter intended for "counting" eax levels like eax=4.
18 *
19 * This driver uses /dev/cpu/%d/cpuid where %d is the minor number, and on
20 * an SMP box will direct the access to CPU %d.
21 */
22
23#include <linux/module.h>
24
25#include <linux/types.h>
26#include <linux/errno.h>
27#include <linux/fcntl.h>
28#include <linux/init.h>
29#include <linux/poll.h>
30#include <linux/smp.h>
31#include <linux/major.h>
32#include <linux/fs.h>
33#include <linux/device.h>
34#include <linux/cpu.h>
35#include <linux/notifier.h>
36#include <linux/uaccess.h>
37#include <linux/gfp.h>
38#include <linux/completion.h>
39
40#include <asm/processor.h>
41#include <asm/msr.h>
42
43static struct class *cpuid_class;
44static enum cpuhp_state cpuhp_cpuid_state;
45
46struct cpuid_regs_done {
47 struct cpuid_regs regs;
48 struct completion done;
49};
50
51static void cpuid_smp_cpuid(void *cmd_block)
52{
53 struct cpuid_regs_done *cmd = cmd_block;
54
55 cpuid_count(cmd->regs.eax, cmd->regs.ecx,
56 &cmd->regs.eax, &cmd->regs.ebx,
57 &cmd->regs.ecx, &cmd->regs.edx);
58
59 complete(&cmd->done);
60}
61
62static ssize_t cpuid_read(struct file *file, char __user *buf,
63 size_t count, loff_t *ppos)
64{
65 char __user *tmp = buf;
66 struct cpuid_regs_done cmd;
67 int cpu = iminor(file_inode(file));
68 u64 pos = *ppos;
69 ssize_t bytes = 0;
70 int err = 0;
71
72 if (count % 16)
73 return -EINVAL; /* Invalid chunk size */
74
75 init_completion(&cmd.done);
76 for (; count; count -= 16) {
77 call_single_data_t csd;
78
79 INIT_CSD(&csd, cpuid_smp_cpuid, &cmd);
80
81 cmd.regs.eax = pos;
82 cmd.regs.ecx = pos >> 32;
83
84 err = smp_call_function_single_async(cpu, &csd);
85 if (err)
86 break;
87 wait_for_completion(&cmd.done);
88 if (copy_to_user(tmp, &cmd.regs, 16)) {
89 err = -EFAULT;
90 break;
91 }
92 tmp += 16;
93 bytes += 16;
94 *ppos = ++pos;
95 reinit_completion(&cmd.done);
96 }
97
98 return bytes ? bytes : err;
99}
100
101static int cpuid_open(struct inode *inode, struct file *file)
102{
103 unsigned int cpu;
104 struct cpuinfo_x86 *c;
105
106 cpu = iminor(file_inode(file));
107 if (cpu >= nr_cpu_ids || !cpu_online(cpu))
108 return -ENXIO; /* No such CPU */
109
110 c = &cpu_data(cpu);
111 if (c->cpuid_level < 0)
112 return -EIO; /* CPUID not supported */
113
114 return 0;
115}
116
117/*
118 * File operations we support
119 */
120static const struct file_operations cpuid_fops = {
121 .owner = THIS_MODULE,
122 .llseek = no_seek_end_llseek,
123 .read = cpuid_read,
124 .open = cpuid_open,
125};
126
127static int cpuid_device_create(unsigned int cpu)
128{
129 struct device *dev;
130
131 dev = device_create(cpuid_class, NULL, MKDEV(CPUID_MAJOR, cpu), NULL,
132 "cpu%d", cpu);
133 return PTR_ERR_OR_ZERO(dev);
134}
135
136static int cpuid_device_destroy(unsigned int cpu)
137{
138 device_destroy(cpuid_class, MKDEV(CPUID_MAJOR, cpu));
139 return 0;
140}
141
142static char *cpuid_devnode(struct device *dev, umode_t *mode)
143{
144 return kasprintf(GFP_KERNEL, "cpu/%u/cpuid", MINOR(dev->devt));
145}
146
147static int __init cpuid_init(void)
148{
149 int err;
150
151 if (__register_chrdev(CPUID_MAJOR, 0, NR_CPUS,
152 "cpu/cpuid", &cpuid_fops)) {
153 printk(KERN_ERR "cpuid: unable to get major %d for cpuid\n",
154 CPUID_MAJOR);
155 return -EBUSY;
156 }
157 cpuid_class = class_create(THIS_MODULE, "cpuid");
158 if (IS_ERR(cpuid_class)) {
159 err = PTR_ERR(cpuid_class);
160 goto out_chrdev;
161 }
162 cpuid_class->devnode = cpuid_devnode;
163
164 err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "x86/cpuid:online",
165 cpuid_device_create, cpuid_device_destroy);
166 if (err < 0)
167 goto out_class;
168
169 cpuhp_cpuid_state = err;
170 return 0;
171
172out_class:
173 class_destroy(cpuid_class);
174out_chrdev:
175 __unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid");
176 return err;
177}
178module_init(cpuid_init);
179
180static void __exit cpuid_exit(void)
181{
182 cpuhp_remove_state(cpuhp_cpuid_state);
183 class_destroy(cpuid_class);
184 __unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid");
185}
186module_exit(cpuid_exit);
187
188MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
189MODULE_DESCRIPTION("x86 generic CPUID driver");
190MODULE_LICENSE("GPL");