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190 lines
4.3 KiB
190 lines
4.3 KiB
// SPDX-License-Identifier: GPL-2.0-or-later |
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/* ----------------------------------------------------------------------- * |
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* |
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* Copyright 2000-2008 H. Peter Anvin - All Rights Reserved |
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* |
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* ----------------------------------------------------------------------- */ |
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|
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/* |
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* x86 CPUID access device |
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* |
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* This device is accessed by lseek() to the appropriate CPUID level |
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* and then read in chunks of 16 bytes. A larger size means multiple |
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* reads of consecutive levels. |
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* |
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* The lower 32 bits of the file position is used as the incoming %eax, |
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* and the upper 32 bits of the file position as the incoming %ecx, |
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* the latter intended for "counting" eax levels like eax=4. |
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* |
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* This driver uses /dev/cpu/%d/cpuid where %d is the minor number, and on |
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* an SMP box will direct the access to CPU %d. |
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*/ |
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#include <linux/module.h> |
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#include <linux/types.h> |
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#include <linux/errno.h> |
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#include <linux/fcntl.h> |
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#include <linux/init.h> |
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#include <linux/poll.h> |
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#include <linux/smp.h> |
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#include <linux/major.h> |
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#include <linux/fs.h> |
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#include <linux/device.h> |
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#include <linux/cpu.h> |
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#include <linux/notifier.h> |
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#include <linux/uaccess.h> |
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#include <linux/gfp.h> |
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#include <linux/completion.h> |
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#include <asm/processor.h> |
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#include <asm/msr.h> |
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static struct class *cpuid_class; |
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static enum cpuhp_state cpuhp_cpuid_state; |
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struct cpuid_regs_done { |
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struct cpuid_regs regs; |
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struct completion done; |
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}; |
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static void cpuid_smp_cpuid(void *cmd_block) |
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{ |
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struct cpuid_regs_done *cmd = cmd_block; |
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cpuid_count(cmd->regs.eax, cmd->regs.ecx, |
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&cmd->regs.eax, &cmd->regs.ebx, |
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&cmd->regs.ecx, &cmd->regs.edx); |
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complete(&cmd->done); |
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} |
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static ssize_t cpuid_read(struct file *file, char __user *buf, |
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size_t count, loff_t *ppos) |
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{ |
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char __user *tmp = buf; |
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struct cpuid_regs_done cmd; |
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int cpu = iminor(file_inode(file)); |
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u64 pos = *ppos; |
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ssize_t bytes = 0; |
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int err = 0; |
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if (count % 16) |
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return -EINVAL; /* Invalid chunk size */ |
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init_completion(&cmd.done); |
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for (; count; count -= 16) { |
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call_single_data_t csd; |
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INIT_CSD(&csd, cpuid_smp_cpuid, &cmd); |
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cmd.regs.eax = pos; |
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cmd.regs.ecx = pos >> 32; |
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err = smp_call_function_single_async(cpu, &csd); |
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if (err) |
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break; |
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wait_for_completion(&cmd.done); |
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if (copy_to_user(tmp, &cmd.regs, 16)) { |
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err = -EFAULT; |
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break; |
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} |
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tmp += 16; |
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bytes += 16; |
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*ppos = ++pos; |
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reinit_completion(&cmd.done); |
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} |
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return bytes ? bytes : err; |
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} |
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static int cpuid_open(struct inode *inode, struct file *file) |
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{ |
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unsigned int cpu; |
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struct cpuinfo_x86 *c; |
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cpu = iminor(file_inode(file)); |
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if (cpu >= nr_cpu_ids || !cpu_online(cpu)) |
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return -ENXIO; /* No such CPU */ |
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c = &cpu_data(cpu); |
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if (c->cpuid_level < 0) |
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return -EIO; /* CPUID not supported */ |
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return 0; |
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} |
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/* |
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* File operations we support |
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*/ |
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static const struct file_operations cpuid_fops = { |
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.owner = THIS_MODULE, |
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.llseek = no_seek_end_llseek, |
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.read = cpuid_read, |
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.open = cpuid_open, |
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}; |
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static int cpuid_device_create(unsigned int cpu) |
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{ |
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struct device *dev; |
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dev = device_create(cpuid_class, NULL, MKDEV(CPUID_MAJOR, cpu), NULL, |
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"cpu%d", cpu); |
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return PTR_ERR_OR_ZERO(dev); |
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} |
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static int cpuid_device_destroy(unsigned int cpu) |
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{ |
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device_destroy(cpuid_class, MKDEV(CPUID_MAJOR, cpu)); |
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return 0; |
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} |
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static char *cpuid_devnode(struct device *dev, umode_t *mode) |
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{ |
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return kasprintf(GFP_KERNEL, "cpu/%u/cpuid", MINOR(dev->devt)); |
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} |
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static int __init cpuid_init(void) |
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{ |
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int err; |
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if (__register_chrdev(CPUID_MAJOR, 0, NR_CPUS, |
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"cpu/cpuid", &cpuid_fops)) { |
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printk(KERN_ERR "cpuid: unable to get major %d for cpuid\n", |
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CPUID_MAJOR); |
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return -EBUSY; |
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} |
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cpuid_class = class_create(THIS_MODULE, "cpuid"); |
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if (IS_ERR(cpuid_class)) { |
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err = PTR_ERR(cpuid_class); |
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goto out_chrdev; |
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} |
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cpuid_class->devnode = cpuid_devnode; |
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err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "x86/cpuid:online", |
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cpuid_device_create, cpuid_device_destroy); |
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if (err < 0) |
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goto out_class; |
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cpuhp_cpuid_state = err; |
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return 0; |
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out_class: |
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class_destroy(cpuid_class); |
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out_chrdev: |
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__unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid"); |
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return err; |
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} |
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module_init(cpuid_init); |
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static void __exit cpuid_exit(void) |
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{ |
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cpuhp_remove_state(cpuhp_cpuid_state); |
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class_destroy(cpuid_class); |
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__unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid"); |
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} |
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module_exit(cpuid_exit); |
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MODULE_AUTHOR("H. Peter Anvin <[email protected]>"); |
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MODULE_DESCRIPTION("x86 generic CPUID driver"); |
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MODULE_LICENSE("GPL");
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