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 static enum cpuhp_state cpuhp_cpuid_state; 49 50 static void cpuid_smp_cpuid(void *cmd_block) 51 { 52 struct cpuid_regs *cmd = (struct cpuid_regs *)cmd_block; 53 54 cpuid_count(cmd->eax, cmd->ecx, 55 &cmd->eax, &cmd->ebx, &cmd->ecx, &cmd->edx); 56 } 57 58 static ssize_t cpuid_read(struct file *file, char __user *buf, 59 size_t count, loff_t *ppos) 60 { 61 char __user *tmp = buf; 62 struct cpuid_regs cmd; 63 int cpu = iminor(file_inode(file)); 64 u64 pos = *ppos; 65 ssize_t bytes = 0; 66 int err = 0; 67 68 if (count % 16) 69 return -EINVAL; /* Invalid chunk size */ 70 71 for (; count; count -= 16) { 72 cmd.eax = pos; 73 cmd.ecx = pos >> 32; 74 err = smp_call_function_single(cpu, cpuid_smp_cpuid, &cmd, 1); 75 if (err) 76 break; 77 if (copy_to_user(tmp, &cmd, 16)) { 78 err = -EFAULT; 79 break; 80 } 81 tmp += 16; 82 bytes += 16; 83 *ppos = ++pos; 84 } 85 86 return bytes ? bytes : err; 87 } 88 89 static int cpuid_open(struct inode *inode, struct file *file) 90 { 91 unsigned int cpu; 92 struct cpuinfo_x86 *c; 93 94 cpu = iminor(file_inode(file)); 95 if (cpu >= nr_cpu_ids || !cpu_online(cpu)) 96 return -ENXIO; /* No such CPU */ 97 98 c = &cpu_data(cpu); 99 if (c->cpuid_level < 0) 100 return -EIO; /* CPUID not supported */ 101 102 return 0; 103 } 104 105 /* 106 * File operations we support 107 */ 108 static const struct file_operations cpuid_fops = { 109 .owner = THIS_MODULE, 110 .llseek = no_seek_end_llseek, 111 .read = cpuid_read, 112 .open = cpuid_open, 113 }; 114 115 static int cpuid_device_create(unsigned int cpu) 116 { 117 struct device *dev; 118 119 dev = device_create(cpuid_class, NULL, MKDEV(CPUID_MAJOR, cpu), NULL, 120 "cpu%d", cpu); 121 return PTR_ERR_OR_ZERO(dev); 122 } 123 124 static int cpuid_device_destroy(unsigned int cpu) 125 { 126 device_destroy(cpuid_class, MKDEV(CPUID_MAJOR, cpu)); 127 return 0; 128 } 129 130 static char *cpuid_devnode(struct device *dev, umode_t *mode) 131 { 132 return kasprintf(GFP_KERNEL, "cpu/%u/cpuid", MINOR(dev->devt)); 133 } 134 135 static int __init cpuid_init(void) 136 { 137 int err; 138 139 if (__register_chrdev(CPUID_MAJOR, 0, NR_CPUS, 140 "cpu/cpuid", &cpuid_fops)) { 141 printk(KERN_ERR "cpuid: unable to get major %d for cpuid\n", 142 CPUID_MAJOR); 143 return -EBUSY; 144 } 145 cpuid_class = class_create(THIS_MODULE, "cpuid"); 146 if (IS_ERR(cpuid_class)) { 147 err = PTR_ERR(cpuid_class); 148 goto out_chrdev; 149 } 150 cpuid_class->devnode = cpuid_devnode; 151 152 err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "x86/cpuid:online", 153 cpuid_device_create, cpuid_device_destroy); 154 if (err < 0) 155 goto out_class; 156 157 cpuhp_cpuid_state = err; 158 return 0; 159 160 out_class: 161 class_destroy(cpuid_class); 162 out_chrdev: 163 __unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid"); 164 return err; 165 } 166 module_init(cpuid_init); 167 168 static void __exit cpuid_exit(void) 169 { 170 cpuhp_remove_state(cpuhp_cpuid_state); 171 class_destroy(cpuid_class); 172 __unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid"); 173 } 174 module_exit(cpuid_exit); 175 176 MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>"); 177 MODULE_DESCRIPTION("x86 generic CPUID driver"); 178 MODULE_LICENSE("GPL"); 179