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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * kernel/ksysfs.c - sysfs attributes in /sys/kernel, which
4 * are not related to any other subsystem
5 *
6 * Copyright (C) 2004 Kay Sievers <[email protected]>
7 */
8
9#include <asm/byteorder.h>
10#include <linux/kobject.h>
11#include <linux/ksysfs.h>
12#include <linux/string.h>
13#include <linux/sysfs.h>
14#include <linux/export.h>
15#include <linux/init.h>
16#include <linux/vmcore_info.h>
17#include <linux/profile.h>
18#include <linux/stat.h>
19#include <linux/sched.h>
20#include <linux/capability.h>
21#include <linux/compiler.h>
22
23#include <linux/rcupdate.h> /* rcu_expedited and rcu_normal */
24
25#if defined(__LITTLE_ENDIAN)
26#define CPU_BYTEORDER_STRING "little"
27#elif defined(__BIG_ENDIAN)
28#define CPU_BYTEORDER_STRING "big"
29#else
30#error Unknown byteorder
31#endif
32
33#define KERNEL_ATTR_RO(_name) \
34static struct kobj_attribute _name##_attr = __ATTR_RO(_name)
35
36#define KERNEL_ATTR_RW(_name) \
37static struct kobj_attribute _name##_attr = __ATTR_RW(_name)
38
39/* current uevent sequence number */
40static ssize_t uevent_seqnum_show(struct kobject *kobj,
41 struct kobj_attribute *attr, char *buf)
42{
43 return sysfs_emit(buf, "%llu\n", (u64)atomic64_read(&uevent_seqnum));
44}
45KERNEL_ATTR_RO(uevent_seqnum);
46
47/* cpu byteorder */
48static ssize_t cpu_byteorder_show(struct kobject *kobj,
49 struct kobj_attribute *attr, char *buf)
50{
51 return sysfs_emit(buf, "%s\n", CPU_BYTEORDER_STRING);
52}
53KERNEL_ATTR_RO(cpu_byteorder);
54
55/* address bits */
56static ssize_t address_bits_show(struct kobject *kobj,
57 struct kobj_attribute *attr, char *buf)
58{
59 return sysfs_emit(buf, "%zu\n", sizeof(void *) * 8 /* CHAR_BIT */);
60}
61KERNEL_ATTR_RO(address_bits);
62
63#ifdef CONFIG_UEVENT_HELPER
64/* uevent helper program, used during early boot */
65static ssize_t uevent_helper_show(struct kobject *kobj,
66 struct kobj_attribute *attr, char *buf)
67{
68 return sysfs_emit(buf, "%s\n", uevent_helper);
69}
70static ssize_t uevent_helper_store(struct kobject *kobj,
71 struct kobj_attribute *attr,
72 const char *buf, size_t count)
73{
74 if (count+1 > UEVENT_HELPER_PATH_LEN)
75 return -ENOENT;
76 memcpy(uevent_helper, buf, count);
77 uevent_helper[count] = '\0';
78 if (count && uevent_helper[count-1] == '\n')
79 uevent_helper[count-1] = '\0';
80 return count;
81}
82KERNEL_ATTR_RW(uevent_helper);
83#endif
84
85#ifdef CONFIG_PROFILING
86static ssize_t profiling_show(struct kobject *kobj,
87 struct kobj_attribute *attr, char *buf)
88{
89 return sysfs_emit(buf, "%d\n", prof_on);
90}
91static ssize_t profiling_store(struct kobject *kobj,
92 struct kobj_attribute *attr,
93 const char *buf, size_t count)
94{
95 int ret;
96 static DEFINE_MUTEX(lock);
97
98 /*
99 * We need serialization, for profile_setup() initializes prof_on
100 * value and profile_init() must not reallocate prof_buffer after
101 * once allocated.
102 */
103 guard(mutex)(&lock);
104 if (prof_on)
105 return -EEXIST;
106 /*
107 * This eventually calls into get_option() which
108 * has a ton of callers and is not const. It is
109 * easiest to cast it away here.
110 */
111 profile_setup((char *)buf);
112 ret = profile_init();
113 if (ret)
114 return ret;
115 ret = create_proc_profile();
116 if (ret)
117 return ret;
118 return count;
119}
120KERNEL_ATTR_RW(profiling);
121#endif
122
123#ifdef CONFIG_VMCORE_INFO
124
125static ssize_t vmcoreinfo_show(struct kobject *kobj,
126 struct kobj_attribute *attr, char *buf)
127{
128 phys_addr_t vmcore_base = paddr_vmcoreinfo_note();
129 return sysfs_emit(buf, "%pa %x\n", &vmcore_base,
130 (unsigned int)VMCOREINFO_NOTE_SIZE);
131}
132KERNEL_ATTR_RO(vmcoreinfo);
133
134#endif /* CONFIG_VMCORE_INFO */
135
136/* whether file capabilities are enabled */
137static ssize_t fscaps_show(struct kobject *kobj,
138 struct kobj_attribute *attr, char *buf)
139{
140 return sysfs_emit(buf, "%d\n", file_caps_enabled);
141}
142KERNEL_ATTR_RO(fscaps);
143
144#ifndef CONFIG_TINY_RCU
145int rcu_expedited;
146static ssize_t rcu_expedited_show(struct kobject *kobj,
147 struct kobj_attribute *attr, char *buf)
148{
149 return sysfs_emit(buf, "%d\n", READ_ONCE(rcu_expedited));
150}
151static ssize_t rcu_expedited_store(struct kobject *kobj,
152 struct kobj_attribute *attr,
153 const char *buf, size_t count)
154{
155 if (kstrtoint(buf, 0, &rcu_expedited))
156 return -EINVAL;
157
158 return count;
159}
160KERNEL_ATTR_RW(rcu_expedited);
161
162int rcu_normal;
163static ssize_t rcu_normal_show(struct kobject *kobj,
164 struct kobj_attribute *attr, char *buf)
165{
166 return sysfs_emit(buf, "%d\n", READ_ONCE(rcu_normal));
167}
168static ssize_t rcu_normal_store(struct kobject *kobj,
169 struct kobj_attribute *attr,
170 const char *buf, size_t count)
171{
172 if (kstrtoint(buf, 0, &rcu_normal))
173 return -EINVAL;
174
175 return count;
176}
177KERNEL_ATTR_RW(rcu_normal);
178#endif /* #ifndef CONFIG_TINY_RCU */
179
180/*
181 * Make /sys/kernel/notes give the raw contents of our kernel .notes section.
182 */
183extern const void __start_notes;
184extern const void __stop_notes;
185#define notes_size (&__stop_notes - &__start_notes)
186
187static __ro_after_init BIN_ATTR_SIMPLE_RO(notes);
188
189struct kobject *kernel_kobj;
190EXPORT_SYMBOL_GPL(kernel_kobj);
191
192static struct attribute * kernel_attrs[] = {
193 &fscaps_attr.attr,
194 &uevent_seqnum_attr.attr,
195 &cpu_byteorder_attr.attr,
196 &address_bits_attr.attr,
197#ifdef CONFIG_UEVENT_HELPER
198 &uevent_helper_attr.attr,
199#endif
200#ifdef CONFIG_PROFILING
201 &profiling_attr.attr,
202#endif
203#ifdef CONFIG_VMCORE_INFO
204 &vmcoreinfo_attr.attr,
205#endif
206#ifndef CONFIG_TINY_RCU
207 &rcu_expedited_attr.attr,
208 &rcu_normal_attr.attr,
209#endif
210 NULL
211};
212
213static const struct attribute_group kernel_attr_group = {
214 .attrs = kernel_attrs,
215};
216
217void __init ksysfs_init(void)
218{
219 int error;
220
221 kernel_kobj = kobject_create_and_add("kernel", NULL);
222 if (!kernel_kobj) {
223 error = -ENOMEM;
224 goto exit;
225 }
226 error = sysfs_create_group(kernel_kobj, &kernel_attr_group);
227 if (error)
228 goto kset_exit;
229
230 if (notes_size > 0) {
231 bin_attr_notes.private = (void *)&__start_notes;
232 bin_attr_notes.size = notes_size;
233 error = sysfs_create_bin_file(kernel_kobj, &bin_attr_notes);
234 if (error)
235 goto group_exit;
236 }
237
238 return;
239
240group_exit:
241 sysfs_remove_group(kernel_kobj, &kernel_attr_group);
242kset_exit:
243 kobject_put(kernel_kobj);
244exit:
245 pr_err("failed to initialize the kernel kobject: %d\n", error);
246}