/* ----------------------------------------------------------------------- * * * Copyright 2000-2008 H. Peter Anvin - All Rights Reserved * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation, Inc., 675 Mass Ave, Cambridge MA 02139, * USA; either version 2 of the License, or (at your option) any later * version; incorporated herein by reference. * * ----------------------------------------------------------------------- */ /* * x86 CPUID access device * * This device is accessed by lseek() to the appropriate CPUID level * and then read in chunks of 16 bytes. A larger size means multiple * reads of consecutive levels. * * The lower 32 bits of the file position is used as the incoming %eax, * and the upper 32 bits of the file position as the incoming %ecx, * the latter intended for "counting" eax levels like eax=4. * * This driver uses /dev/cpu/%d/cpuid where %d is the minor number, and on * an SMP box will direct the access to CPU %d. */ #include <linux/module.h> #include <linux/types.h> #include <linux/errno.h> #include <linux/fcntl.h> #include <linux/init.h> #include <linux/poll.h> #include <linux/smp.h> #include <linux/smp_lock.h> #include <linux/major.h> #include <linux/fs.h> #include <linux/device.h> #include <linux/cpu.h> #include <linux/notifier.h> #include <asm/processor.h> #include <asm/msr.h> #include <asm/uaccess.h> #include <asm/system.h> static struct class *cpuid_class; struct cpuid_regs { u32 eax, ebx, ecx, edx; }; static void cpuid_smp_cpuid(void *cmd_block) { struct cpuid_regs *cmd = (struct cpuid_regs *)cmd_block; cpuid_count(cmd->eax, cmd->ecx, &cmd->eax, &cmd->ebx, &cmd->ecx, &cmd->edx); } static loff_t cpuid_seek(struct file *file, loff_t offset, int orig) { loff_t ret; struct inode *inode = file->f_mapping->host; mutex_lock(&inode->i_mutex); switch (orig) { case 0: file->f_pos = offset; ret = file->f_pos; break; case 1: file->f_pos += offset; ret = file->f_pos; break; default: ret = -EINVAL; } mutex_unlock(&inode->i_mutex); return ret; } static ssize_t cpuid_read(struct file *file, char __user *buf, size_t count, loff_t * ppos) { char __user *tmp = buf; struct cpuid_regs cmd; int cpu = iminor(file->f_path.dentry->d_inode); u64 pos = *ppos; ssize_t bytes = 0; int err = 0; if (count % 16) return -EINVAL; /* Invalid chunk size */ for (; count; count -= 16) { cmd.eax = pos; cmd.ecx = pos >> 32; err = smp_call_function_single(cpu, cpuid_smp_cpuid, &cmd, 1); if (err) break; if (copy_to_user(tmp, &cmd, 16)) { err = -EFAULT; break; } tmp += 16; bytes += 16; *ppos = ++pos; } return bytes ? bytes : err; } static int cpuid_open(struct inode *inode, struct file *file) { unsigned int cpu; struct cpuinfo_x86 *c; int ret = 0; lock_kernel(); cpu = iminor(file->f_path.dentry->d_inode); if (cpu >= NR_CPUS || !cpu_online(cpu)) { ret = -ENXIO; /* No such CPU */ goto out; } c = &cpu_data(cpu); if (c->cpuid_level < 0) ret = -EIO; /* CPUID not supported */ out: unlock_kernel(); return ret; } /* * File operations we support */ static const struct file_operations cpuid_fops = { .owner = THIS_MODULE, .llseek = cpuid_seek, .read = cpuid_read, .open = cpuid_open, }; static __cpuinit int cpuid_device_create(int cpu) { struct device *dev; dev = device_create_drvdata(cpuid_class, NULL, MKDEV(CPUID_MAJOR, cpu), NULL, "cpu%d", cpu); return IS_ERR(dev) ? PTR_ERR(dev) : 0; } static void cpuid_device_destroy(int cpu) { device_destroy(cpuid_class, MKDEV(CPUID_MAJOR, cpu)); } static int __cpuinit cpuid_class_cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu) { unsigned int cpu = (unsigned long)hcpu; int err = 0; switch (action) { case CPU_UP_PREPARE: err = cpuid_device_create(cpu); break; case CPU_UP_CANCELED: case CPU_UP_CANCELED_FROZEN: case CPU_DEAD: cpuid_device_destroy(cpu); break; } return err ? NOTIFY_BAD : NOTIFY_OK; } static struct notifier_block __refdata cpuid_class_cpu_notifier = { .notifier_call = cpuid_class_cpu_callback, }; static int __init cpuid_init(void) { int i, err = 0; i = 0; if (register_chrdev(CPUID_MAJOR, "cpu/cpuid", &cpuid_fops)) { printk(KERN_ERR "cpuid: unable to get major %d for cpuid\n", CPUID_MAJOR); err = -EBUSY; goto out; } cpuid_class = class_create(THIS_MODULE, "cpuid"); if (IS_ERR(cpuid_class)) { err = PTR_ERR(cpuid_class); goto out_chrdev; } for_each_online_cpu(i) { err = cpuid_device_create(i); if (err != 0) goto out_class; } register_hotcpu_notifier(&cpuid_class_cpu_notifier); err = 0; goto out; out_class: i = 0; for_each_online_cpu(i) { cpuid_device_destroy(i); } class_destroy(cpuid_class); out_chrdev: unregister_chrdev(CPUID_MAJOR, "cpu/cpuid"); out: return err; } static void __exit cpuid_exit(void) { int cpu = 0; for_each_online_cpu(cpu) cpuid_device_destroy(cpu); class_destroy(cpuid_class); unregister_chrdev(CPUID_MAJOR, "cpu/cpuid"); unregister_hotcpu_notifier(&cpuid_class_cpu_notifier); } module_init(cpuid_init); module_exit(cpuid_exit); MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>"); MODULE_DESCRIPTION("x86 generic CPUID driver"); MODULE_LICENSE("GPL");