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>
59 	int cpu = iminor(file_inode(file));  in msr_read()  local
63 	if (count % 8)  in msr_read()
64 		return -EINVAL;	/* Invalid chunk size */  in msr_read()
66 	for (; count; count -= 8) {  in msr_read()
67 		err = rdmsr_safe_on_cpu(cpu, reg, &data[0], &data[1]);  in msr_read()
70 		if (copy_to_user(tmp, &data, 8)) {  in msr_read()
71 			err = -EFAULT;  in msr_read()
75 		bytes += 8;  in msr_read()
87 	 * It's possible to be smarter here and do it (for example) per-MSR, but  in filter_write()
95 	case MSR_WRITES_OFF: return -EPERM;  in filter_write()
106 	       reg, current->comm, current->pid);  in filter_write()
117 	int cpu = iminor(file_inode(file));  in msr_write()  local
129 	if (count % 8)  in msr_write()
130 		return -EINVAL;	/* Invalid chunk size */  in msr_write()
132 	for (; count; count -= 8) {  in msr_write()
133 		if (copy_from_user(&data, tmp, 8)) {  in msr_write()
134 			err = -EFAULT;  in msr_write()
140 		err = wrmsr_safe_on_cpu(cpu, reg, data[0], data[1]);  in msr_write()
145 		bytes += 8;  in msr_write()
154 	u32 regs[8];  in msr_ioctl()
155 	int cpu = iminor(file_inode(file));  in msr_ioctl()  local
160 		if (!(file->f_mode & FMODE_READ)) {  in msr_ioctl()
161 			err = -EBADF;  in msr_ioctl()
165 			err = -EFAULT;  in msr_ioctl()
168 		err = rdmsr_safe_regs_on_cpu(cpu, regs);  in msr_ioctl()
172 			err = -EFAULT;  in msr_ioctl()
176 		if (!(file->f_mode & FMODE_WRITE)) {  in msr_ioctl()
177 			err = -EBADF;  in msr_ioctl()
181 			err = -EFAULT;  in msr_ioctl()
187 		err = wrmsr_safe_regs_on_cpu(cpu, regs);  in msr_ioctl()
191 			err = -EFAULT;  in msr_ioctl()
195 		err = -ENOTTY;  in msr_ioctl()
204 	unsigned int cpu = iminor(file_inode(file));  in msr_open()  local
208 		return -EPERM;  in msr_open()
210 	if (cpu >= nr_cpu_ids || !cpu_online(cpu))  in msr_open()
211 		return -ENXIO;	/* No such CPU */  in msr_open()
213 	c = &cpu_data(cpu);  in msr_open()
215 		return -EIO;	/* MSR not supported */  in msr_open()
233 static int msr_device_create(unsigned int cpu)  in msr_device_create()  argument
237 	dev = device_create(msr_class, NULL, MKDEV(MSR_MAJOR, cpu), NULL,  in msr_device_create()
238 			    "msr%d", cpu);  in msr_device_create()
242 static int msr_device_destroy(unsigned int cpu)  in msr_device_destroy()  argument
244 	device_destroy(msr_class, MKDEV(MSR_MAJOR, cpu));  in msr_device_destroy()
250 	return kasprintf(GFP_KERNEL, "cpu/%u/msr", MINOR(dev->devt));  in msr_devnode()
257 	if (__register_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr", &msr_fops)) {  in msr_init()
259 		return -EBUSY;  in msr_init()
266 	msr_class->devnode = msr_devnode;  in msr_init()
278 	__unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");  in msr_init()
287 	__unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");  in msr_exit()
293 	/* val is NUL-terminated, see kernfs_fop_write() */  in module_exit()