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/smp_lock.h> 37#include <linux/major.h> 38#include <linux/fs.h> 39#include <linux/device.h> 40#include <linux/cpu.h> 41#include <linux/notifier.h> 42#include <linux/uaccess.h> 43#include <linux/gfp.h> 44 45#include <asm/processor.h> 46#include <asm/msr.h> 47#include <asm/system.h> 48 49static struct class *cpuid_class; 50 51struct cpuid_regs { 52 u32 eax, ebx, ecx, edx; 53}; 54 55static void cpuid_smp_cpuid(void *cmd_block) 56{ 57 struct cpuid_regs *cmd = (struct cpuid_regs *)cmd_block; 58 59 cpuid_count(cmd->eax, cmd->ecx, 60 &cmd->eax, &cmd->ebx, &cmd->ecx, &cmd->edx); 61} 62 63static loff_t cpuid_seek(struct file *file, loff_t offset, int orig) 64{ 65 loff_t ret; 66 struct inode *inode = file->f_mapping->host; 67 68 mutex_lock(&inode->i_mutex); 69 switch (orig) { 70 case 0: 71 file->f_pos = offset; 72 ret = file->f_pos; 73 break; 74 case 1: 75 file->f_pos += offset; 76 ret = file->f_pos; 77 break; 78 default: 79 ret = -EINVAL; 80 } 81 mutex_unlock(&inode->i_mutex); 82 return ret; 83} 84 85static ssize_t cpuid_read(struct file *file, char __user *buf, 86 size_t count, loff_t *ppos) 87{ 88 char __user *tmp = buf; 89 struct cpuid_regs cmd; 90 int cpu = iminor(file->f_path.dentry->d_inode); 91 u64 pos = *ppos; 92 ssize_t bytes = 0; 93 int err = 0; 94 95 if (count % 16) 96 return -EINVAL; /* Invalid chunk size */ 97 98 for (; count; count -= 16) { 99 cmd.eax = pos; 100 cmd.ecx = pos >> 32; 101 err = smp_call_function_single(cpu, cpuid_smp_cpuid, &cmd, 1); 102 if (err) 103 break; 104 if (copy_to_user(tmp, &cmd, 16)) { 105 err = -EFAULT; 106 break; 107 } 108 tmp += 16; 109 bytes += 16; 110 *ppos = ++pos; 111 } 112 113 return bytes ? bytes : err; 114} 115 116static int cpuid_open(struct inode *inode, struct file *file) 117{ 118 unsigned int cpu; 119 struct cpuinfo_x86 *c; 120 121 cpu = iminor(file->f_path.dentry->d_inode); 122 if (cpu >= nr_cpu_ids || !cpu_online(cpu)) 123 return -ENXIO; /* No such CPU */ 124 125 c = &cpu_data(cpu); 126 if (c->cpuid_level < 0) 127 return -EIO; /* CPUID not supported */ 128 129 return 0; 130} 131 132/* 133 * File operations we support 134 */ 135static const struct file_operations cpuid_fops = { 136 .owner = THIS_MODULE, 137 .llseek = cpuid_seek, 138 .read = cpuid_read, 139 .open = cpuid_open, 140}; 141 142static __cpuinit int cpuid_device_create(int cpu) 143{ 144 struct device *dev; 145 146 dev = device_create(cpuid_class, NULL, MKDEV(CPUID_MAJOR, cpu), NULL, 147 "cpu%d", cpu); 148 return IS_ERR(dev) ? PTR_ERR(dev) : 0; 149} 150 151static void cpuid_device_destroy(int cpu) 152{ 153 device_destroy(cpuid_class, MKDEV(CPUID_MAJOR, cpu)); 154} 155 156static int __cpuinit cpuid_class_cpu_callback(struct notifier_block *nfb, 157 unsigned long action, 158 void *hcpu) 159{ 160 unsigned int cpu = (unsigned long)hcpu; 161 int err = 0; 162 163 switch (action) { 164 case CPU_UP_PREPARE: 165 err = cpuid_device_create(cpu); 166 break; 167 case CPU_UP_CANCELED: 168 case CPU_UP_CANCELED_FROZEN: 169 case CPU_DEAD: 170 cpuid_device_destroy(cpu); 171 break; 172 } 173 return notifier_from_errno(err); 174} 175 176static struct notifier_block __refdata cpuid_class_cpu_notifier = 177{ 178 .notifier_call = cpuid_class_cpu_callback, 179}; 180 181static char *cpuid_devnode(struct device *dev, mode_t *mode) 182{ 183 return kasprintf(GFP_KERNEL, "cpu/%u/cpuid", MINOR(dev->devt)); 184} 185 186static int __init cpuid_init(void) 187{ 188 int i, err = 0; 189 i = 0; 190 191 if (__register_chrdev(CPUID_MAJOR, 0, NR_CPUS, 192 "cpu/cpuid", &cpuid_fops)) { 193 printk(KERN_ERR "cpuid: unable to get major %d for cpuid\n", 194 CPUID_MAJOR); 195 err = -EBUSY; 196 goto out; 197 } 198 cpuid_class = class_create(THIS_MODULE, "cpuid"); 199 if (IS_ERR(cpuid_class)) { 200 err = PTR_ERR(cpuid_class); 201 goto out_chrdev; 202 } 203 cpuid_class->devnode = cpuid_devnode; 204 for_each_online_cpu(i) { 205 err = cpuid_device_create(i); 206 if (err != 0) 207 goto out_class; 208 } 209 register_hotcpu_notifier(&cpuid_class_cpu_notifier); 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 class_destroy(cpuid_class); 220out_chrdev: 221 __unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid"); 222out: 223 return err; 224} 225 226static void __exit cpuid_exit(void) 227{ 228 int cpu = 0; 229 230 for_each_online_cpu(cpu) 231 cpuid_device_destroy(cpu); 232 class_destroy(cpuid_class); 233 __unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid"); 234 unregister_hotcpu_notifier(&cpuid_class_cpu_notifier); 235} 236 237module_init(cpuid_init); 238module_exit(cpuid_exit); 239 240MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>"); 241MODULE_DESCRIPTION("x86 generic CPUID driver"); 242MODULE_LICENSE("GPL"); 243