1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* ----------------------------------------------------------------------- *
4  *   Copyright 2000-2008 H. Peter Anvin - All Rights Reserved
7  * ----------------------------------------------------------------------- */
13  * and then read/write in chunks of 8 bytes.  A larger size means multiple
16  * This driver uses /dev/cpu/%d/msr where %d is the minor number, and on
17  * an SMP box will direct the access to CPU %d.
33 #include <linux/cpu.h>
58 	int cpu = iminor(file_inode(file));  in msr_read()  local
62 	if (count % 8)  in msr_read()
63 		return -EINVAL;	/* Invalid chunk size */  in msr_read()
65 	for (; count; count -= 8) {  in msr_read()
66 		err = rdmsr_safe_on_cpu(cpu, reg, &data[0], &data[1]);  in msr_read()
69 		if (copy_to_user(tmp, &data, 8)) {  in msr_read()
70 			err = -EFAULT;  in msr_read()
74 		bytes += 8;  in msr_read()
86 	 * It's possible to be smarter here and do it (for example) per-MSR, but  in filter_write()
94 	case MSR_WRITES_OFF: return -EPERM;  in filter_write()
102 	        reg, current->comm, current->pid);  in filter_write()
114 	int cpu = iminor(file_inode(file));  in msr_write()  local
126 	if (count % 8)  in msr_write()
127 		return -EINVAL;	/* Invalid chunk size */  in msr_write()
129 	for (; count; count -= 8) {  in msr_write()
130 		if (copy_from_user(&data, tmp, 8)) {  in msr_write()
131 			err = -EFAULT;  in msr_write()
137 		err = wrmsr_safe_on_cpu(cpu, reg, data[0], data[1]);  in msr_write()
142 		bytes += 8;  in msr_write()
151 	u32 regs[8];  in msr_ioctl()
152 	int cpu = iminor(file_inode(file));  in msr_ioctl()  local
157 		if (!(file->f_mode & FMODE_READ)) {  in msr_ioctl()
158 			err = -EBADF;  in msr_ioctl()
162 			err = -EFAULT;  in msr_ioctl()
165 		err = rdmsr_safe_regs_on_cpu(cpu, regs);  in msr_ioctl()
169 			err = -EFAULT;  in msr_ioctl()
173 		if (!(file->f_mode & FMODE_WRITE)) {  in msr_ioctl()
174 			err = -EBADF;  in msr_ioctl()
178 			err = -EFAULT;  in msr_ioctl()
191 		err = wrmsr_safe_regs_on_cpu(cpu, regs);  in msr_ioctl()
195 			err = -EFAULT;  in msr_ioctl()
199 		err = -ENOTTY;  in msr_ioctl()
208 	unsigned int cpu = iminor(file_inode(file));  in msr_open()  local
212 		return -EPERM;  in msr_open()
214 	if (cpu >= nr_cpu_ids || !cpu_online(cpu))  in msr_open()
215 		return -ENXIO;	/* No such CPU */  in msr_open()
217 	c = &cpu_data(cpu);  in msr_open()
219 		return -EIO;	/* MSR not supported */  in msr_open()
239 	return kasprintf(GFP_KERNEL, "cpu/%u/msr", MINOR(dev->devt));  in msr_devnode()
247 static int msr_device_create(unsigned int cpu)  in msr_device_create()  argument
251 	dev = device_create(&msr_class, NULL, MKDEV(MSR_MAJOR, cpu), NULL,  in msr_device_create()
252 			    "msr%d", cpu);  in msr_device_create()
256 static int msr_device_destroy(unsigned int cpu)  in msr_device_destroy()  argument
258 	device_destroy(&msr_class, MKDEV(MSR_MAJOR, cpu));  in msr_device_destroy()
266 	if (__register_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr", &msr_fops)) {  in msr_init()
268 		return -EBUSY;  in msr_init()
284 	__unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");  in msr_init()
293 	__unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");  in msr_exit()
299 	/* val is NUL-terminated, see kernfs_fop_write() */  in module_exit()