| 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 loff_t cpuid_seek(struct file *file, loff_t offset, int orig) |
| 62 | { |
| 63 | loff_t ret; |
| 64 | struct inode *inode = file->f_mapping->host; |
| 65 | |
| 66 | mutex_lock(&inode->i_mutex); |
| 67 | switch (orig) { |
| 68 | case 0: |
| 69 | file->f_pos = offset; |
| 70 | ret = file->f_pos; |
| 71 | break; |
| 72 | case 1: |
| 73 | file->f_pos += offset; |
| 74 | ret = file->f_pos; |
| 75 | break; |
| 76 | default: |
| 77 | ret = -EINVAL; |
| 78 | } |
| 79 | mutex_unlock(&inode->i_mutex); |
| 80 | return ret; |
| 81 | } |
| 82 | |
| 83 | static ssize_t cpuid_read(struct file *file, char __user *buf, |
| 84 | size_t count, loff_t *ppos) |
| 85 | { |
| 86 | char __user *tmp = buf; |
| 87 | struct cpuid_regs cmd; |
| 88 | int cpu = iminor(file_inode(file)); |
| 89 | u64 pos = *ppos; |
| 90 | ssize_t bytes = 0; |
| 91 | int err = 0; |
| 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 | err = smp_call_function_single(cpu, cpuid_smp_cpuid, &cmd, 1); |
| 100 | if (err) |
| 101 | break; |
| 102 | if (copy_to_user(tmp, &cmd, 16)) { |
| 103 | err = -EFAULT; |
| 104 | break; |
| 105 | } |
| 106 | tmp += 16; |
| 107 | bytes += 16; |
| 108 | *ppos = ++pos; |
| 109 | } |
| 110 | |
| 111 | return bytes ? bytes : err; |
| 112 | } |
| 113 | |
| 114 | static int cpuid_open(struct inode *inode, struct file *file) |
| 115 | { |
| 116 | unsigned int cpu; |
| 117 | struct cpuinfo_x86 *c; |
| 118 | |
| 119 | cpu = iminor(file_inode(file)); |
| 120 | if (cpu >= nr_cpu_ids || !cpu_online(cpu)) |
| 121 | return -ENXIO; /* No such CPU */ |
| 122 | |
| 123 | c = &cpu_data(cpu); |
| 124 | if (c->cpuid_level < 0) |
| 125 | return -EIO; /* CPUID not supported */ |
| 126 | |
| 127 | return 0; |
| 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 int cpuid_device_create(int cpu) |
| 141 | { |
| 142 | struct device *dev; |
| 143 | |
| 144 | dev = device_create(cpuid_class, NULL, MKDEV(CPUID_MAJOR, cpu), NULL, |
| 145 | "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 cpuid_class_cpu_callback(struct notifier_block *nfb, |
| 155 | unsigned long action, void *hcpu) |
| 156 | { |
| 157 | unsigned int cpu = (unsigned long)hcpu; |
| 158 | int err = 0; |
| 159 | |
| 160 | switch (action) { |
| 161 | case CPU_UP_PREPARE: |
| 162 | err = cpuid_device_create(cpu); |
| 163 | break; |
| 164 | case CPU_UP_CANCELED: |
| 165 | case CPU_UP_CANCELED_FROZEN: |
| 166 | case CPU_DEAD: |
| 167 | cpuid_device_destroy(cpu); |
| 168 | break; |
| 169 | } |
| 170 | return notifier_from_errno(err); |
| 171 | } |
| 172 | |
| 173 | static struct notifier_block __refdata cpuid_class_cpu_notifier = |
| 174 | { |
| 175 | .notifier_call = cpuid_class_cpu_callback, |
| 176 | }; |
| 177 | |
| 178 | static char *cpuid_devnode(struct device *dev, umode_t *mode) |
| 179 | { |
| 180 | return kasprintf(GFP_KERNEL, "cpu/%u/cpuid", MINOR(dev->devt)); |
| 181 | } |
| 182 | |
| 183 | static int __init cpuid_init(void) |
| 184 | { |
| 185 | int i, err = 0; |
| 186 | i = 0; |
| 187 | |
| 188 | if (__register_chrdev(CPUID_MAJOR, 0, NR_CPUS, |
| 189 | "cpu/cpuid", &cpuid_fops)) { |
| 190 | printk(KERN_ERR "cpuid: unable to get major %d for cpuid\n", |
| 191 | CPUID_MAJOR); |
| 192 | err = -EBUSY; |
| 193 | goto out; |
| 194 | } |
| 195 | cpuid_class = class_create(THIS_MODULE, "cpuid"); |
| 196 | if (IS_ERR(cpuid_class)) { |
| 197 | err = PTR_ERR(cpuid_class); |
| 198 | goto out_chrdev; |
| 199 | } |
| 200 | cpuid_class->devnode = cpuid_devnode; |
| 201 | |
| 202 | cpu_notifier_register_begin(); |
| 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 | cpu_notifier_register_done(); |
| 210 | |
| 211 | err = 0; |
| 212 | goto out; |
| 213 | |
| 214 | out_class: |
| 215 | i = 0; |
| 216 | for_each_online_cpu(i) { |
| 217 | cpuid_device_destroy(i); |
| 218 | } |
| 219 | cpu_notifier_register_done(); |
| 220 | class_destroy(cpuid_class); |
| 221 | out_chrdev: |
| 222 | __unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid"); |
| 223 | out: |
| 224 | return err; |
| 225 | } |
| 226 | |
| 227 | static void __exit cpuid_exit(void) |
| 228 | { |
| 229 | int cpu = 0; |
| 230 | |
| 231 | cpu_notifier_register_begin(); |
| 232 | for_each_online_cpu(cpu) |
| 233 | cpuid_device_destroy(cpu); |
| 234 | class_destroy(cpuid_class); |
| 235 | __unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid"); |
| 236 | __unregister_hotcpu_notifier(&cpuid_class_cpu_notifier); |
| 237 | cpu_notifier_register_done(); |
| 238 | } |
| 239 | |
| 240 | module_init(cpuid_init); |
| 241 | module_exit(cpuid_exit); |
| 242 | |
| 243 | MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>"); |
| 244 | MODULE_DESCRIPTION("x86 generic CPUID driver"); |
| 245 | MODULE_LICENSE("GPL"); |