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 #include <linux/completion.h> 44 45 #include <asm/processor.h> 46 #include <asm/msr.h> 47 48 static struct class *cpuid_class; 49 static enum cpuhp_state cpuhp_cpuid_state; 50 51 struct cpuid_regs_done { 52 struct cpuid_regs regs; 53 struct completion done; 54 }; 55 56 static void cpuid_smp_cpuid(void *cmd_block) 57 { 58 struct cpuid_regs_done *cmd = cmd_block; 59 60 cpuid_count(cmd->regs.eax, cmd->regs.ecx, 61 &cmd->regs.eax, &cmd->regs.ebx, 62 &cmd->regs.ecx, &cmd->regs.edx); 63 64 complete(&cmd->done); 65 } 66 67 static ssize_t cpuid_read(struct file *file, char __user *buf, 68 size_t count, loff_t *ppos) 69 { 70 char __user *tmp = buf; 71 struct cpuid_regs_done cmd; 72 int cpu = iminor(file_inode(file)); 73 u64 pos = *ppos; 74 ssize_t bytes = 0; 75 int err = 0; 76 77 if (count % 16) 78 return -EINVAL; /* Invalid chunk size */ 79 80 init_completion(&cmd.done); 81 for (; count; count -= 16) { 82 call_single_data_t csd = { 83 .func = cpuid_smp_cpuid, 84 .info = &cmd, 85 }; 86 87 cmd.regs.eax = pos; 88 cmd.regs.ecx = pos >> 32; 89 90 err = smp_call_function_single_async(cpu, &csd); 91 if (err) 92 break; 93 wait_for_completion(&cmd.done); 94 if (copy_to_user(tmp, &cmd.regs, 16)) { 95 err = -EFAULT; 96 break; 97 } 98 tmp += 16; 99 bytes += 16; 100 *ppos = ++pos; 101 reinit_completion(&cmd.done); 102 } 103 104 return bytes ? bytes : err; 105 } 106 107 static int cpuid_open(struct inode *inode, struct file *file) 108 { 109 unsigned int cpu; 110 struct cpuinfo_x86 *c; 111 112 cpu = iminor(file_inode(file)); 113 if (cpu >= nr_cpu_ids || !cpu_online(cpu)) 114 return -ENXIO; /* No such CPU */ 115 116 c = &cpu_data(cpu); 117 if (c->cpuid_level < 0) 118 return -EIO; /* CPUID not supported */ 119 120 return 0; 121 } 122 123 /* 124 * File operations we support 125 */ 126 static const struct file_operations cpuid_fops = { 127 .owner = THIS_MODULE, 128 .llseek = no_seek_end_llseek, 129 .read = cpuid_read, 130 .open = cpuid_open, 131 }; 132 133 static int cpuid_device_create(unsigned int cpu) 134 { 135 struct device *dev; 136 137 dev = device_create(cpuid_class, NULL, MKDEV(CPUID_MAJOR, cpu), NULL, 138 "cpu%d", cpu); 139 return PTR_ERR_OR_ZERO(dev); 140 } 141 142 static int cpuid_device_destroy(unsigned int cpu) 143 { 144 device_destroy(cpuid_class, MKDEV(CPUID_MAJOR, cpu)); 145 return 0; 146 } 147 148 static char *cpuid_devnode(struct device *dev, umode_t *mode) 149 { 150 return kasprintf(GFP_KERNEL, "cpu/%u/cpuid", MINOR(dev->devt)); 151 } 152 153 static int __init cpuid_init(void) 154 { 155 int err; 156 157 if (__register_chrdev(CPUID_MAJOR, 0, NR_CPUS, 158 "cpu/cpuid", &cpuid_fops)) { 159 printk(KERN_ERR "cpuid: unable to get major %d for cpuid\n", 160 CPUID_MAJOR); 161 return -EBUSY; 162 } 163 cpuid_class = class_create(THIS_MODULE, "cpuid"); 164 if (IS_ERR(cpuid_class)) { 165 err = PTR_ERR(cpuid_class); 166 goto out_chrdev; 167 } 168 cpuid_class->devnode = cpuid_devnode; 169 170 err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "x86/cpuid:online", 171 cpuid_device_create, cpuid_device_destroy); 172 if (err < 0) 173 goto out_class; 174 175 cpuhp_cpuid_state = err; 176 return 0; 177 178 out_class: 179 class_destroy(cpuid_class); 180 out_chrdev: 181 __unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid"); 182 return err; 183 } 184 module_init(cpuid_init); 185 186 static void __exit cpuid_exit(void) 187 { 188 cpuhp_remove_state(cpuhp_cpuid_state); 189 class_destroy(cpuid_class); 190 __unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid"); 191 } 192 module_exit(cpuid_exit); 193 194 MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>"); 195 MODULE_DESCRIPTION("x86 generic CPUID driver"); 196 MODULE_LICENSE("GPL"); 197