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/smp_lock.h> 40 #include <linux/device.h> 41 #include <linux/cpu.h> 42 #include <linux/notifier.h> 43 44 #include <asm/processor.h> 45 #include <asm/msr.h> 46 #include <asm/uaccess.h> 47 #include <asm/system.h> 48 49 static struct class *cpuid_class; 50 51 struct cpuid_regs { 52 u32 eax, ebx, ecx, edx; 53 }; 54 55 static 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 63 static 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 85 static 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 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 smp_call_function_single(cpu, cpuid_smp_cpuid, &cmd, 1); 100 if (copy_to_user(tmp, &cmd, 16)) 101 return -EFAULT; 102 tmp += 16; 103 *ppos = ++pos; 104 } 105 106 return tmp - buf; 107 } 108 109 static int cpuid_open(struct inode *inode, struct file *file) 110 { 111 unsigned int cpu; 112 struct cpuinfo_x86 *c; 113 int ret = 0; 114 115 lock_kernel(); 116 117 cpu = iminor(file->f_path.dentry->d_inode); 118 if (cpu >= NR_CPUS || !cpu_online(cpu)) { 119 ret = -ENXIO; /* No such CPU */ 120 goto out; 121 } 122 c = &cpu_data(cpu); 123 if (c->cpuid_level < 0) 124 ret = -EIO; /* CPUID not supported */ 125 out: 126 unlock_kernel(); 127 return ret; 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 __cpuinit int cpuid_device_create(int cpu) 141 { 142 struct device *dev; 143 144 dev = device_create_drvdata(cpuid_class, NULL, MKDEV(CPUID_MAJOR, cpu), 145 NULL, "cpu%d", cpu); 146 return IS_ERR(dev) ? PTR_ERR(dev) : 0; 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 __cpuinit cpuid_class_cpu_callback(struct notifier_block *nfb, 155 unsigned long action, 156 void *hcpu) 157 { 158 unsigned int cpu = (unsigned long)hcpu; 159 int err = 0; 160 161 switch (action) { 162 case CPU_UP_PREPARE: 163 err = cpuid_device_create(cpu); 164 break; 165 case CPU_UP_CANCELED: 166 case CPU_UP_CANCELED_FROZEN: 167 case CPU_DEAD: 168 cpuid_device_destroy(cpu); 169 break; 170 } 171 return err ? NOTIFY_BAD : NOTIFY_OK; 172 } 173 174 static struct notifier_block __refdata cpuid_class_cpu_notifier = 175 { 176 .notifier_call = cpuid_class_cpu_callback, 177 }; 178 179 static int __init cpuid_init(void) 180 { 181 int i, err = 0; 182 i = 0; 183 184 if (register_chrdev(CPUID_MAJOR, "cpu/cpuid", &cpuid_fops)) { 185 printk(KERN_ERR "cpuid: unable to get major %d for cpuid\n", 186 CPUID_MAJOR); 187 err = -EBUSY; 188 goto out; 189 } 190 cpuid_class = class_create(THIS_MODULE, "cpuid"); 191 if (IS_ERR(cpuid_class)) { 192 err = PTR_ERR(cpuid_class); 193 goto out_chrdev; 194 } 195 for_each_online_cpu(i) { 196 err = cpuid_device_create(i); 197 if (err != 0) 198 goto out_class; 199 } 200 register_hotcpu_notifier(&cpuid_class_cpu_notifier); 201 202 err = 0; 203 goto out; 204 205 out_class: 206 i = 0; 207 for_each_online_cpu(i) { 208 cpuid_device_destroy(i); 209 } 210 class_destroy(cpuid_class); 211 out_chrdev: 212 unregister_chrdev(CPUID_MAJOR, "cpu/cpuid"); 213 out: 214 return err; 215 } 216 217 static void __exit cpuid_exit(void) 218 { 219 int cpu = 0; 220 221 for_each_online_cpu(cpu) 222 cpuid_device_destroy(cpu); 223 class_destroy(cpuid_class); 224 unregister_chrdev(CPUID_MAJOR, "cpu/cpuid"); 225 unregister_hotcpu_notifier(&cpuid_class_cpu_notifier); 226 } 227 228 module_init(cpuid_init); 229 module_exit(cpuid_exit); 230 231 MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>"); 232 MODULE_DESCRIPTION("x86 generic CPUID driver"); 233 MODULE_LICENSE("GPL"); 234