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 #include <linux/completion.h>
44
45 #include <asm/processor.h>
46 #include <asm/msr.h>
47
48 static struct class *cpuid_class;
49 static enum cpuhp_state cpuhp_cpuid_state;
50
51 struct cpuid_regs_done {
52 struct cpuid_regs regs;
53 struct completion done;
54 };
55
cpuid_smp_cpuid(void * cmd_block)56 static void cpuid_smp_cpuid(void *cmd_block)
57 {
58 struct cpuid_regs_done *cmd = cmd_block;
59
60 cpuid_count(cmd->regs.eax, cmd->regs.ecx,
61 &cmd->regs.eax, &cmd->regs.ebx,
62 &cmd->regs.ecx, &cmd->regs.edx);
63
64 complete(&cmd->done);
65 }
66
cpuid_read(struct file * file,char __user * buf,size_t count,loff_t * ppos)67 static ssize_t cpuid_read(struct file *file, char __user *buf,
68 size_t count, loff_t *ppos)
69 {
70 char __user *tmp = buf;
71 struct cpuid_regs_done cmd;
72 int cpu = iminor(file_inode(file));
73 u64 pos = *ppos;
74 ssize_t bytes = 0;
75 int err = 0;
76
77 if (count % 16)
78 return -EINVAL; /* Invalid chunk size */
79
80 init_completion(&cmd.done);
81 for (; count; count -= 16) {
82 call_single_data_t csd = {
83 .func = cpuid_smp_cpuid,
84 .info = &cmd,
85 };
86
87 cmd.regs.eax = pos;
88 cmd.regs.ecx = pos >> 32;
89
90 err = smp_call_function_single_async(cpu, &csd);
91 if (err)
92 break;
93 wait_for_completion(&cmd.done);
94 if (copy_to_user(tmp, &cmd.regs, 16)) {
95 err = -EFAULT;
96 break;
97 }
98 tmp += 16;
99 bytes += 16;
100 *ppos = ++pos;
101 reinit_completion(&cmd.done);
102 }
103
104 return bytes ? bytes : err;
105 }
106
cpuid_open(struct inode * inode,struct file * file)107 static int cpuid_open(struct inode *inode, struct file *file)
108 {
109 unsigned int cpu;
110 struct cpuinfo_x86 *c;
111
112 cpu = iminor(file_inode(file));
113 if (cpu >= nr_cpu_ids || !cpu_online(cpu))
114 return -ENXIO; /* No such CPU */
115
116 c = &cpu_data(cpu);
117 if (c->cpuid_level < 0)
118 return -EIO; /* CPUID not supported */
119
120 return 0;
121 }
122
123 /*
124 * File operations we support
125 */
126 static const struct file_operations cpuid_fops = {
127 .owner = THIS_MODULE,
128 .llseek = no_seek_end_llseek,
129 .read = cpuid_read,
130 .open = cpuid_open,
131 };
132
cpuid_device_create(unsigned int cpu)133 static int cpuid_device_create(unsigned int cpu)
134 {
135 struct device *dev;
136
137 dev = device_create(cpuid_class, NULL, MKDEV(CPUID_MAJOR, cpu), NULL,
138 "cpu%d", cpu);
139 return PTR_ERR_OR_ZERO(dev);
140 }
141
cpuid_device_destroy(unsigned int cpu)142 static int cpuid_device_destroy(unsigned int cpu)
143 {
144 device_destroy(cpuid_class, MKDEV(CPUID_MAJOR, cpu));
145 return 0;
146 }
147
cpuid_devnode(struct device * dev,umode_t * mode)148 static char *cpuid_devnode(struct device *dev, umode_t *mode)
149 {
150 return kasprintf(GFP_KERNEL, "cpu/%u/cpuid", MINOR(dev->devt));
151 }
152
cpuid_init(void)153 static int __init cpuid_init(void)
154 {
155 int err;
156
157 if (__register_chrdev(CPUID_MAJOR, 0, NR_CPUS,
158 "cpu/cpuid", &cpuid_fops)) {
159 printk(KERN_ERR "cpuid: unable to get major %d for cpuid\n",
160 CPUID_MAJOR);
161 return -EBUSY;
162 }
163 cpuid_class = class_create(THIS_MODULE, "cpuid");
164 if (IS_ERR(cpuid_class)) {
165 err = PTR_ERR(cpuid_class);
166 goto out_chrdev;
167 }
168 cpuid_class->devnode = cpuid_devnode;
169
170 err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "x86/cpuid:online",
171 cpuid_device_create, cpuid_device_destroy);
172 if (err < 0)
173 goto out_class;
174
175 cpuhp_cpuid_state = err;
176 return 0;
177
178 out_class:
179 class_destroy(cpuid_class);
180 out_chrdev:
181 __unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid");
182 return err;
183 }
184 module_init(cpuid_init);
185
cpuid_exit(void)186 static void __exit cpuid_exit(void)
187 {
188 cpuhp_remove_state(cpuhp_cpuid_state);
189 class_destroy(cpuid_class);
190 __unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid");
191 }
192 module_exit(cpuid_exit);
193
194 MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
195 MODULE_DESCRIPTION("x86 generic CPUID driver");
196 MODULE_LICENSE("GPL");
197
