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 #include <asm/system.h> 47 48 static struct class *cpuid_class; 49 50 struct cpuid_regs { 51 u32 eax, ebx, ecx, edx; 52 }; 53 54 static void cpuid_smp_cpuid(void *cmd_block) 55 { 56 struct cpuid_regs *cmd = (struct cpuid_regs *)cmd_block; 57 58 cpuid_count(cmd->eax, cmd->ecx, 59 &cmd->eax, &cmd->ebx, &cmd->ecx, &cmd->edx); 60 } 61 62 static loff_t cpuid_seek(struct file *file, loff_t offset, int orig) 63 { 64 loff_t ret; 65 struct inode *inode = file->f_mapping->host; 66 67 mutex_lock(&inode->i_mutex); 68 switch (orig) { 69 case 0: 70 file->f_pos = offset; 71 ret = file->f_pos; 72 break; 73 case 1: 74 file->f_pos += offset; 75 ret = file->f_pos; 76 break; 77 default: 78 ret = -EINVAL; 79 } 80 mutex_unlock(&inode->i_mutex); 81 return ret; 82 } 83 84 static ssize_t cpuid_read(struct file *file, char __user *buf, 85 size_t count, loff_t *ppos) 86 { 87 char __user *tmp = buf; 88 struct cpuid_regs cmd; 89 int cpu = iminor(file->f_path.dentry->d_inode); 90 u64 pos = *ppos; 91 ssize_t bytes = 0; 92 int err = 0; 93 94 if (count % 16) 95 return -EINVAL; /* Invalid chunk size */ 96 97 for (; count; count -= 16) { 98 cmd.eax = pos; 99 cmd.ecx = pos >> 32; 100 err = smp_call_function_single(cpu, cpuid_smp_cpuid, &cmd, 1); 101 if (err) 102 break; 103 if (copy_to_user(tmp, &cmd, 16)) { 104 err = -EFAULT; 105 break; 106 } 107 tmp += 16; 108 bytes += 16; 109 *ppos = ++pos; 110 } 111 112 return bytes ? bytes : err; 113 } 114 115 static int cpuid_open(struct inode *inode, struct file *file) 116 { 117 unsigned int cpu; 118 struct cpuinfo_x86 *c; 119 120 cpu = iminor(file->f_path.dentry->d_inode); 121 if (cpu >= nr_cpu_ids || !cpu_online(cpu)) 122 return -ENXIO; /* No such CPU */ 123 124 c = &cpu_data(cpu); 125 if (c->cpuid_level < 0) 126 return -EIO; /* CPUID not supported */ 127 128 return 0; 129 } 130 131 /* 132 * File operations we support 133 */ 134 static const struct file_operations cpuid_fops = { 135 .owner = THIS_MODULE, 136 .llseek = cpuid_seek, 137 .read = cpuid_read, 138 .open = cpuid_open, 139 }; 140 141 static __cpuinit int cpuid_device_create(int cpu) 142 { 143 struct device *dev; 144 145 dev = device_create(cpuid_class, NULL, MKDEV(CPUID_MAJOR, cpu), NULL, 146 "cpu%d", cpu); 147 return IS_ERR(dev) ? PTR_ERR(dev) : 0; 148 } 149 150 static void cpuid_device_destroy(int cpu) 151 { 152 device_destroy(cpuid_class, MKDEV(CPUID_MAJOR, cpu)); 153 } 154 155 static int __cpuinit cpuid_class_cpu_callback(struct notifier_block *nfb, 156 unsigned long action, 157 void *hcpu) 158 { 159 unsigned int cpu = (unsigned long)hcpu; 160 int err = 0; 161 162 switch (action) { 163 case CPU_UP_PREPARE: 164 err = cpuid_device_create(cpu); 165 break; 166 case CPU_UP_CANCELED: 167 case CPU_UP_CANCELED_FROZEN: 168 case CPU_DEAD: 169 cpuid_device_destroy(cpu); 170 break; 171 } 172 return notifier_from_errno(err); 173 } 174 175 static struct notifier_block __refdata cpuid_class_cpu_notifier = 176 { 177 .notifier_call = cpuid_class_cpu_callback, 178 }; 179 180 static char *cpuid_devnode(struct device *dev, umode_t *mode) 181 { 182 return kasprintf(GFP_KERNEL, "cpu/%u/cpuid", MINOR(dev->devt)); 183 } 184 185 static int __init cpuid_init(void) 186 { 187 int i, err = 0; 188 i = 0; 189 190 if (__register_chrdev(CPUID_MAJOR, 0, NR_CPUS, 191 "cpu/cpuid", &cpuid_fops)) { 192 printk(KERN_ERR "cpuid: unable to get major %d for cpuid\n", 193 CPUID_MAJOR); 194 err = -EBUSY; 195 goto out; 196 } 197 cpuid_class = class_create(THIS_MODULE, "cpuid"); 198 if (IS_ERR(cpuid_class)) { 199 err = PTR_ERR(cpuid_class); 200 goto out_chrdev; 201 } 202 cpuid_class->devnode = cpuid_devnode; 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); 209 210 err = 0; 211 goto out; 212 213 out_class: 214 i = 0; 215 for_each_online_cpu(i) { 216 cpuid_device_destroy(i); 217 } 218 class_destroy(cpuid_class); 219 out_chrdev: 220 __unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid"); 221 out: 222 return err; 223 } 224 225 static void __exit cpuid_exit(void) 226 { 227 int cpu = 0; 228 229 for_each_online_cpu(cpu) 230 cpuid_device_destroy(cpu); 231 class_destroy(cpuid_class); 232 __unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid"); 233 unregister_hotcpu_notifier(&cpuid_class_cpu_notifier); 234 } 235 236 module_init(cpuid_init); 237 module_exit(cpuid_exit); 238 239 MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>"); 240 MODULE_DESCRIPTION("x86 generic CPUID driver"); 241 MODULE_LICENSE("GPL"); 242