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Linux/arch/x86/kernel/cpuid.c

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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 #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 
 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 
 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 
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 
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 
142 static int cpuid_device_destroy(unsigned int cpu)
143 {
144         device_destroy(cpuid_class, MKDEV(CPUID_MAJOR, cpu));
145         return 0;
146 }
147 
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 
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 
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 

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