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 47 static struct class *cpuid_class; 48 49 struct cpuid_regs { 50 u32 eax, ebx, ecx, edx; 51 }; 52 53 static 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 61 static 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 83 static 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_inode(file)); 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 } 113 114 static int cpuid_open(struct inode *inode, struct file *file) 115 { 116 unsigned int cpu; 117 struct cpuinfo_x86 *c; 118 119 cpu = iminor(file_inode(file)); 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 */ 133 static const struct file_operations cpuid_fops = { 134 .owner = THIS_MODULE, 135 .llseek = cpuid_seek, 136 .read = cpuid_read, 137 .open = cpuid_open, 138 }; 139 140 static 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 PTR_ERR_OR_ZERO(dev); 147 } 148 149 static void cpuid_device_destroy(int cpu) 150 { 151 device_destroy(cpuid_class, MKDEV(CPUID_MAJOR, cpu)); 152 } 153 154 static int cpuid_class_cpu_callback(struct notifier_block *nfb, 155 unsigned long action, void *hcpu) 156 { 157 unsigned int cpu = (unsigned long)hcpu; 158 int err = 0; 159 160 switch (action) { 161 case CPU_UP_PREPARE: 162 err = cpuid_device_create(cpu); 163 break; 164 case CPU_UP_CANCELED: 165 case CPU_UP_CANCELED_FROZEN: 166 case CPU_DEAD: 167 cpuid_device_destroy(cpu); 168 break; 169 } 170 return notifier_from_errno(err); 171 } 172 173 static struct notifier_block __refdata cpuid_class_cpu_notifier = 174 { 175 .notifier_call = cpuid_class_cpu_callback, 176 }; 177 178 static char *cpuid_devnode(struct device *dev, umode_t *mode) 179 { 180 return kasprintf(GFP_KERNEL, "cpu/%u/cpuid", MINOR(dev->devt)); 181 } 182 183 static int __init cpuid_init(void) 184 { 185 int i, err = 0; 186 i = 0; 187 188 if (__register_chrdev(CPUID_MAJOR, 0, NR_CPUS, 189 "cpu/cpuid", &cpuid_fops)) { 190 printk(KERN_ERR "cpuid: unable to get major %d for cpuid\n", 191 CPUID_MAJOR); 192 err = -EBUSY; 193 goto out; 194 } 195 cpuid_class = class_create(THIS_MODULE, "cpuid"); 196 if (IS_ERR(cpuid_class)) { 197 err = PTR_ERR(cpuid_class); 198 goto out_chrdev; 199 } 200 cpuid_class->devnode = cpuid_devnode; 201 202 cpu_notifier_register_begin(); 203 for_each_online_cpu(i) { 204 err = cpuid_device_create(i); 205 if (err != 0) 206 goto out_class; 207 } 208 __register_hotcpu_notifier(&cpuid_class_cpu_notifier); 209 cpu_notifier_register_done(); 210 211 err = 0; 212 goto out; 213 214 out_class: 215 i = 0; 216 for_each_online_cpu(i) { 217 cpuid_device_destroy(i); 218 } 219 cpu_notifier_register_done(); 220 class_destroy(cpuid_class); 221 out_chrdev: 222 __unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid"); 223 out: 224 return err; 225 } 226 227 static void __exit cpuid_exit(void) 228 { 229 int cpu = 0; 230 231 cpu_notifier_register_begin(); 232 for_each_online_cpu(cpu) 233 cpuid_device_destroy(cpu); 234 class_destroy(cpuid_class); 235 __unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid"); 236 __unregister_hotcpu_notifier(&cpuid_class_cpu_notifier); 237 cpu_notifier_register_done(); 238 } 239 240 module_init(cpuid_init); 241 module_exit(cpuid_exit); 242 243 MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>"); 244 MODULE_DESCRIPTION("x86 generic CPUID driver"); 245 MODULE_LICENSE("GPL"); 246