Commit | Line | Data |
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a94da204 | 1 | // SPDX-License-Identifier: GPL-2.0-or-later |
1da177e4 | 2 | /* ----------------------------------------------------------------------- * |
2b06ac86 PA |
3 | * |
4 | * Copyright 2000-2008 H. Peter Anvin - All Rights Reserved | |
ff55df53 | 5 | * Copyright 2009 Intel Corporation; author: H. Peter Anvin |
1da177e4 | 6 | * |
1da177e4 LT |
7 | * ----------------------------------------------------------------------- */ |
8 | ||
9 | /* | |
1da177e4 LT |
10 | * x86 MSR access device |
11 | * | |
12 | * This device is accessed by lseek() to the appropriate register number | |
13 | * and then read/write in chunks of 8 bytes. A larger size means multiple | |
14 | * reads or writes of the same register. | |
15 | * | |
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. | |
18 | */ | |
19 | ||
951a18c6 FF |
20 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
21 | ||
1da177e4 | 22 | #include <linux/module.h> |
1da177e4 LT |
23 | |
24 | #include <linux/types.h> | |
25 | #include <linux/errno.h> | |
26 | #include <linux/fcntl.h> | |
27 | #include <linux/init.h> | |
28 | #include <linux/poll.h> | |
29 | #include <linux/smp.h> | |
1da177e4 LT |
30 | #include <linux/major.h> |
31 | #include <linux/fs.h> | |
32 | #include <linux/device.h> | |
33 | #include <linux/cpu.h> | |
34 | #include <linux/notifier.h> | |
448dd2fa | 35 | #include <linux/uaccess.h> |
5a0e3ad6 | 36 | #include <linux/gfp.h> |
95f5e95f | 37 | #include <linux/security.h> |
1da177e4 | 38 | |
cd4d09ec | 39 | #include <asm/cpufeature.h> |
1da177e4 | 40 | #include <asm/msr.h> |
1da177e4 | 41 | |
8874b414 | 42 | static struct class *msr_class; |
8fba38c9 | 43 | static enum cpuhp_state cpuhp_msr_state; |
1da177e4 | 44 | |
94a9fa41 PC |
45 | static ssize_t msr_read(struct file *file, char __user *buf, |
46 | size_t count, loff_t *ppos) | |
1da177e4 LT |
47 | { |
48 | u32 __user *tmp = (u32 __user *) buf; | |
49 | u32 data[2]; | |
1da177e4 | 50 | u32 reg = *ppos; |
6131ffaa | 51 | int cpu = iminor(file_inode(file)); |
85f1cb60 PA |
52 | int err = 0; |
53 | ssize_t bytes = 0; | |
1da177e4 LT |
54 | |
55 | if (count % 8) | |
56 | return -EINVAL; /* Invalid chunk size */ | |
57 | ||
6926d570 | 58 | for (; count; count -= 8) { |
78a62d2c | 59 | err = rdmsr_safe_on_cpu(cpu, reg, &data[0], &data[1]); |
0cc0213e | 60 | if (err) |
85f1cb60 | 61 | break; |
85f1cb60 PA |
62 | if (copy_to_user(tmp, &data, 8)) { |
63 | err = -EFAULT; | |
64 | break; | |
c6f31932 | 65 | } |
1da177e4 | 66 | tmp += 2; |
85f1cb60 | 67 | bytes += 8; |
1da177e4 LT |
68 | } |
69 | ||
85f1cb60 | 70 | return bytes ? bytes : err; |
1da177e4 LT |
71 | } |
72 | ||
73 | static ssize_t msr_write(struct file *file, const char __user *buf, | |
74 | size_t count, loff_t *ppos) | |
75 | { | |
76 | const u32 __user *tmp = (const u32 __user *)buf; | |
77 | u32 data[2]; | |
1da177e4 | 78 | u32 reg = *ppos; |
6131ffaa | 79 | int cpu = iminor(file_inode(file)); |
85f1cb60 PA |
80 | int err = 0; |
81 | ssize_t bytes = 0; | |
1da177e4 | 82 | |
95f5e95f MG |
83 | err = security_locked_down(LOCKDOWN_MSR); |
84 | if (err) | |
85 | return err; | |
86 | ||
1da177e4 LT |
87 | if (count % 8) |
88 | return -EINVAL; /* Invalid chunk size */ | |
89 | ||
f475ff35 | 90 | for (; count; count -= 8) { |
85f1cb60 PA |
91 | if (copy_from_user(&data, tmp, 8)) { |
92 | err = -EFAULT; | |
93 | break; | |
94 | } | |
78a62d2c | 95 | err = wrmsr_safe_on_cpu(cpu, reg, data[0], data[1]); |
0cc0213e | 96 | if (err) |
85f1cb60 | 97 | break; |
1da177e4 | 98 | tmp += 2; |
85f1cb60 | 99 | bytes += 8; |
1da177e4 LT |
100 | } |
101 | ||
85f1cb60 | 102 | return bytes ? bytes : err; |
1da177e4 LT |
103 | } |
104 | ||
ff55df53 PA |
105 | static long msr_ioctl(struct file *file, unsigned int ioc, unsigned long arg) |
106 | { | |
107 | u32 __user *uregs = (u32 __user *)arg; | |
108 | u32 regs[8]; | |
6131ffaa | 109 | int cpu = iminor(file_inode(file)); |
ff55df53 PA |
110 | int err; |
111 | ||
112 | switch (ioc) { | |
113 | case X86_IOC_RDMSR_REGS: | |
114 | if (!(file->f_mode & FMODE_READ)) { | |
115 | err = -EBADF; | |
116 | break; | |
117 | } | |
0e96f31e | 118 | if (copy_from_user(®s, uregs, sizeof(regs))) { |
ff55df53 PA |
119 | err = -EFAULT; |
120 | break; | |
121 | } | |
122 | err = rdmsr_safe_regs_on_cpu(cpu, regs); | |
123 | if (err) | |
124 | break; | |
0e96f31e | 125 | if (copy_to_user(uregs, ®s, sizeof(regs))) |
ff55df53 PA |
126 | err = -EFAULT; |
127 | break; | |
128 | ||
129 | case X86_IOC_WRMSR_REGS: | |
130 | if (!(file->f_mode & FMODE_WRITE)) { | |
131 | err = -EBADF; | |
132 | break; | |
133 | } | |
0e96f31e | 134 | if (copy_from_user(®s, uregs, sizeof(regs))) { |
ff55df53 PA |
135 | err = -EFAULT; |
136 | break; | |
137 | } | |
95f5e95f MG |
138 | err = security_locked_down(LOCKDOWN_MSR); |
139 | if (err) | |
140 | break; | |
ff55df53 PA |
141 | err = wrmsr_safe_regs_on_cpu(cpu, regs); |
142 | if (err) | |
143 | break; | |
0e96f31e | 144 | if (copy_to_user(uregs, ®s, sizeof(regs))) |
ff55df53 PA |
145 | err = -EFAULT; |
146 | break; | |
147 | ||
148 | default: | |
149 | err = -ENOTTY; | |
150 | break; | |
151 | } | |
152 | ||
153 | return err; | |
154 | } | |
155 | ||
1da177e4 LT |
156 | static int msr_open(struct inode *inode, struct file *file) |
157 | { | |
6131ffaa | 158 | unsigned int cpu = iminor(file_inode(file)); |
494c2ebf | 159 | struct cpuinfo_x86 *c; |
1da177e4 | 160 | |
c903f045 AC |
161 | if (!capable(CAP_SYS_RAWIO)) |
162 | return -EPERM; | |
163 | ||
d6c30405 FW |
164 | if (cpu >= nr_cpu_ids || !cpu_online(cpu)) |
165 | return -ENXIO; /* No such CPU */ | |
166 | ||
5119e92e JC |
167 | c = &cpu_data(cpu); |
168 | if (!cpu_has(c, X86_FEATURE_MSR)) | |
d6c30405 FW |
169 | return -EIO; /* MSR not supported */ |
170 | ||
171 | return 0; | |
1da177e4 LT |
172 | } |
173 | ||
174 | /* | |
175 | * File operations we support | |
176 | */ | |
5dfe4c96 | 177 | static const struct file_operations msr_fops = { |
1da177e4 | 178 | .owner = THIS_MODULE, |
b25472f9 | 179 | .llseek = no_seek_end_llseek, |
1da177e4 LT |
180 | .read = msr_read, |
181 | .write = msr_write, | |
182 | .open = msr_open, | |
ff55df53 PA |
183 | .unlocked_ioctl = msr_ioctl, |
184 | .compat_ioctl = msr_ioctl, | |
1da177e4 LT |
185 | }; |
186 | ||
8fba38c9 | 187 | static int msr_device_create(unsigned int cpu) |
1da177e4 | 188 | { |
a271aaf1 | 189 | struct device *dev; |
1da177e4 | 190 | |
a9b12619 GKH |
191 | dev = device_create(msr_class, NULL, MKDEV(MSR_MAJOR, cpu), NULL, |
192 | "msr%d", cpu); | |
cba0fdbc | 193 | return PTR_ERR_OR_ZERO(dev); |
881a841f AM |
194 | } |
195 | ||
8fba38c9 | 196 | static int msr_device_destroy(unsigned int cpu) |
881a841f AM |
197 | { |
198 | device_destroy(msr_class, MKDEV(MSR_MAJOR, cpu)); | |
8fba38c9 | 199 | return 0; |
1da177e4 LT |
200 | } |
201 | ||
2c9ede55 | 202 | static char *msr_devnode(struct device *dev, umode_t *mode) |
07e9bb8e KS |
203 | { |
204 | return kasprintf(GFP_KERNEL, "cpu/%u/msr", MINOR(dev->devt)); | |
205 | } | |
206 | ||
1da177e4 LT |
207 | static int __init msr_init(void) |
208 | { | |
8fba38c9 | 209 | int err; |
1da177e4 | 210 | |
0b962d47 | 211 | if (__register_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr", &msr_fops)) { |
951a18c6 | 212 | pr_err("unable to get major %d for msr\n", MSR_MAJOR); |
8fba38c9 | 213 | return -EBUSY; |
1da177e4 | 214 | } |
8874b414 | 215 | msr_class = class_create(THIS_MODULE, "msr"); |
1da177e4 LT |
216 | if (IS_ERR(msr_class)) { |
217 | err = PTR_ERR(msr_class); | |
218 | goto out_chrdev; | |
219 | } | |
e454cea2 | 220 | msr_class->devnode = msr_devnode; |
de82a01b | 221 | |
8fba38c9 SAS |
222 | err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "x86/msr:online", |
223 | msr_device_create, msr_device_destroy); | |
224 | if (err < 0) | |
225 | goto out_class; | |
226 | cpuhp_msr_state = err; | |
227 | return 0; | |
1da177e4 LT |
228 | |
229 | out_class: | |
8874b414 | 230 | class_destroy(msr_class); |
1da177e4 | 231 | out_chrdev: |
0b962d47 | 232 | __unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr"); |
1da177e4 LT |
233 | return err; |
234 | } | |
8fba38c9 | 235 | module_init(msr_init); |
1da177e4 LT |
236 | |
237 | static void __exit msr_exit(void) | |
238 | { | |
8fba38c9 | 239 | cpuhp_remove_state(cpuhp_msr_state); |
8874b414 | 240 | class_destroy(msr_class); |
da482474 | 241 | __unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr"); |
1da177e4 | 242 | } |
1da177e4 LT |
243 | module_exit(msr_exit) |
244 | ||
245 | MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>"); | |
246 | MODULE_DESCRIPTION("x86 generic MSR driver"); | |
247 | MODULE_LICENSE("GPL"); |