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 ssize_t cpuid_read(struct file *file, char __user *buf, 62 size_t count, loff_t *ppos) 63 { 64 char __user *tmp = buf; 65 struct cpuid_regs cmd; 66 int cpu = iminor(file_inode(file)); 67 u64 pos = *ppos; 68 ssize_t bytes = 0; 69 int err = 0; 70 71 if (count % 16) 72 return -EINVAL; /* Invalid chunk size */ 73 74 for (; count; count -= 16) { 75 cmd.eax = pos; 76 cmd.ecx = pos >> 32; 77 err = smp_call_function_single(cpu, cpuid_smp_cpuid, &cmd, 1); 78 if (err) 79 break; 80 if (copy_to_user(tmp, &cmd, 16)) { 81 err = -EFAULT; 82 break; 83 } 84 tmp += 16; 85 bytes += 16; 86 *ppos = ++pos; 87 } 88 89 return bytes ? bytes : err; 90 } 91 92 static int cpuid_open(struct inode *inode, struct file *file) 93 { 94 unsigned int cpu; 95 struct cpuinfo_x86 *c; 96 97 cpu = iminor(file_inode(file)); 98 if (cpu >= nr_cpu_ids || !cpu_online(cpu)) 99 return -ENXIO; /* No such CPU */ 100 101 c = &cpu_data(cpu); 102 if (c->cpuid_level < 0) 103 return -EIO; /* CPUID not supported */ 104 105 return 0; 106 } 107 108 /* 109 * File operations we support 110 */ 111 static const struct file_operations cpuid_fops = { 112 .owner = THIS_MODULE, 113 .llseek = no_seek_end_llseek, 114 .read = cpuid_read, 115 .open = cpuid_open, 116 }; 117 118 static int cpuid_device_create(int cpu) 119 { 120 struct device *dev; 121 122 dev = device_create(cpuid_class, NULL, MKDEV(CPUID_MAJOR, cpu), NULL, 123 "cpu%d", cpu); 124 return PTR_ERR_OR_ZERO(dev); 125 } 126 127 static void cpuid_device_destroy(int cpu) 128 { 129 device_destroy(cpuid_class, MKDEV(CPUID_MAJOR, cpu)); 130 } 131 132 static int cpuid_class_cpu_callback(struct notifier_block *nfb, 133 unsigned long action, void *hcpu) 134 { 135 unsigned int cpu = (unsigned long)hcpu; 136 int err = 0; 137 138 switch (action) { 139 case CPU_UP_PREPARE: 140 err = cpuid_device_create(cpu); 141 break; 142 case CPU_UP_CANCELED: 143 case CPU_UP_CANCELED_FROZEN: 144 case CPU_DEAD: 145 cpuid_device_destroy(cpu); 146 break; 147 } 148 return notifier_from_errno(err); 149 } 150 151 static struct notifier_block cpuid_class_cpu_notifier = 152 { 153 .notifier_call = cpuid_class_cpu_callback, 154 }; 155 156 static char *cpuid_devnode(struct device *dev, umode_t *mode) 157 { 158 return kasprintf(GFP_KERNEL, "cpu/%u/cpuid", MINOR(dev->devt)); 159 } 160 161 static int __init cpuid_init(void) 162 { 163 int i, err = 0; 164 i = 0; 165 166 if (__register_chrdev(CPUID_MAJOR, 0, NR_CPUS, 167 "cpu/cpuid", &cpuid_fops)) { 168 printk(KERN_ERR "cpuid: unable to get major %d for cpuid\n", 169 CPUID_MAJOR); 170 err = -EBUSY; 171 goto out; 172 } 173 cpuid_class = class_create(THIS_MODULE, "cpuid"); 174 if (IS_ERR(cpuid_class)) { 175 err = PTR_ERR(cpuid_class); 176 goto out_chrdev; 177 } 178 cpuid_class->devnode = cpuid_devnode; 179 180 cpu_notifier_register_begin(); 181 for_each_online_cpu(i) { 182 err = cpuid_device_create(i); 183 if (err != 0) 184 goto out_class; 185 } 186 __register_hotcpu_notifier(&cpuid_class_cpu_notifier); 187 cpu_notifier_register_done(); 188 189 err = 0; 190 goto out; 191 192 out_class: 193 i = 0; 194 for_each_online_cpu(i) { 195 cpuid_device_destroy(i); 196 } 197 cpu_notifier_register_done(); 198 class_destroy(cpuid_class); 199 out_chrdev: 200 __unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid"); 201 out: 202 return err; 203 } 204 205 static void __exit cpuid_exit(void) 206 { 207 int cpu = 0; 208 209 cpu_notifier_register_begin(); 210 for_each_online_cpu(cpu) 211 cpuid_device_destroy(cpu); 212 class_destroy(cpuid_class); 213 __unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid"); 214 __unregister_hotcpu_notifier(&cpuid_class_cpu_notifier); 215 cpu_notifier_register_done(); 216 } 217 218 module_init(cpuid_init); 219 module_exit(cpuid_exit); 220 221 MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>"); 222 MODULE_DESCRIPTION("x86 generic CPUID driver"); 223 MODULE_LICENSE("GPL"); 224