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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 .func = cpuid_smp_cpuid,
79 .info = &cmd,
80 };
81
82 cmd.regs.eax = pos;
83 cmd.regs.ecx = pos >> 32;
84
85 err = smp_call_function_single_async(cpu, &csd);
86 if (err)
87 break;
88 wait_for_completion(&cmd.done);
89 if (copy_to_user(tmp, &cmd.regs, 16)) {
90 err = -EFAULT;
91 break;
92 }
93 tmp += 16;
94 bytes += 16;
95 *ppos = ++pos;
96 reinit_completion(&cmd.done);
97 }
98
99 return bytes ? bytes : err;
100}
101
102static int cpuid_open(struct inode *inode, struct file *file)
103{
104 unsigned int cpu;
105 struct cpuinfo_x86 *c;
106
107 cpu = iminor(file_inode(file));
108 if (cpu >= nr_cpu_ids || !cpu_online(cpu))
109 return -ENXIO; /* No such CPU */
110
111 c = &cpu_data(cpu);
112 if (c->cpuid_level < 0)
113 return -EIO; /* CPUID not supported */
114
115 return 0;
116}
117
118/*
119 * File operations we support
120 */
121static const struct file_operations cpuid_fops = {
122 .owner = THIS_MODULE,
123 .llseek = no_seek_end_llseek,
124 .read = cpuid_read,
125 .open = cpuid_open,
126};
127
128static int cpuid_device_create(unsigned int cpu)
129{
130 struct device *dev;
131
132 dev = device_create(cpuid_class, NULL, MKDEV(CPUID_MAJOR, cpu), NULL,
133 "cpu%d", cpu);
134 return PTR_ERR_OR_ZERO(dev);
135}
136
137static int cpuid_device_destroy(unsigned int cpu)
138{
139 device_destroy(cpuid_class, MKDEV(CPUID_MAJOR, cpu));
140 return 0;
141}
142
143static char *cpuid_devnode(struct device *dev, umode_t *mode)
144{
145 return kasprintf(GFP_KERNEL, "cpu/%u/cpuid", MINOR(dev->devt));
146}
147
148static int __init cpuid_init(void)
149{
150 int err;
151
152 if (__register_chrdev(CPUID_MAJOR, 0, NR_CPUS,
153 "cpu/cpuid", &cpuid_fops)) {
154 printk(KERN_ERR "cpuid: unable to get major %d for cpuid\n",
155 CPUID_MAJOR);
156 return -EBUSY;
157 }
158 cpuid_class = class_create(THIS_MODULE, "cpuid");
159 if (IS_ERR(cpuid_class)) {
160 err = PTR_ERR(cpuid_class);
161 goto out_chrdev;
162 }
163 cpuid_class->devnode = cpuid_devnode;
164
165 err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "x86/cpuid:online",
166 cpuid_device_create, cpuid_device_destroy);
167 if (err < 0)
168 goto out_class;
169
170 cpuhp_cpuid_state = err;
171 return 0;
172
173out_class:
174 class_destroy(cpuid_class);
175out_chrdev:
176 __unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid");
177 return err;
178}
179module_init(cpuid_init);
180
181static void __exit cpuid_exit(void)
182{
183 cpuhp_remove_state(cpuhp_cpuid_state);
184 class_destroy(cpuid_class);
185 __unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid");
186}
187module_exit(cpuid_exit);
188
189MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
190MODULE_DESCRIPTION("x86 generic CPUID driver");
191MODULE_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(const 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");