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 <kay.sievers@vrfy.org>
7 */
8
9#include <asm/byteorder.h>
10#include <linux/kobject.h>
11#include <linux/string.h>
12#include <linux/sysfs.h>
13#include <linux/export.h>
14#include <linux/init.h>
15#include <linux/vmcore_info.h>
16#include <linux/profile.h>
17#include <linux/stat.h>
18#include <linux/sched.h>
19#include <linux/capability.h>
20#include <linux/compiler.h>
21
22#include <linux/rcupdate.h> /* rcu_expedited and rcu_normal */
23
24#if defined(__LITTLE_ENDIAN)
25#define CPU_BYTEORDER_STRING "little"
26#elif defined(__BIG_ENDIAN)
27#define CPU_BYTEORDER_STRING "big"
28#else
29#error Unknown byteorder
30#endif
31
32#define KERNEL_ATTR_RO(_name) \
33static struct kobj_attribute _name##_attr = __ATTR_RO(_name)
34
35#define KERNEL_ATTR_RW(_name) \
36static struct kobj_attribute _name##_attr = __ATTR_RW(_name)
37
38/* current uevent sequence number */
39static ssize_t uevent_seqnum_show(struct kobject *kobj,
40 struct kobj_attribute *attr, char *buf)
41{
42 return sysfs_emit(buf, fmt: "%llu\n", (u64)atomic64_read(v: &uevent_seqnum));
43}
44KERNEL_ATTR_RO(uevent_seqnum);
45
46/* cpu byteorder */
47static ssize_t cpu_byteorder_show(struct kobject *kobj,
48 struct kobj_attribute *attr, char *buf)
49{
50 return sysfs_emit(buf, fmt: "%s\n", CPU_BYTEORDER_STRING);
51}
52KERNEL_ATTR_RO(cpu_byteorder);
53
54/* address bits */
55static ssize_t address_bits_show(struct kobject *kobj,
56 struct kobj_attribute *attr, char *buf)
57{
58 return sysfs_emit(buf, fmt: "%zu\n", sizeof(void *) * 8 /* CHAR_BIT */);
59}
60KERNEL_ATTR_RO(address_bits);
61
62#ifdef CONFIG_UEVENT_HELPER
63/* uevent helper program, used during early boot */
64static ssize_t uevent_helper_show(struct kobject *kobj,
65 struct kobj_attribute *attr, char *buf)
66{
67 return sysfs_emit(buf, fmt: "%s\n", uevent_helper);
68}
69static ssize_t uevent_helper_store(struct kobject *kobj,
70 struct kobj_attribute *attr,
71 const char *buf, size_t count)
72{
73 if (count+1 > UEVENT_HELPER_PATH_LEN)
74 return -ENOENT;
75 memcpy(uevent_helper, buf, count);
76 uevent_helper[count] = '\0';
77 if (count && uevent_helper[count-1] == '\n')
78 uevent_helper[count-1] = '\0';
79 return count;
80}
81KERNEL_ATTR_RW(uevent_helper);
82#endif
83
84#ifdef CONFIG_PROFILING
85static ssize_t profiling_show(struct kobject *kobj,
86 struct kobj_attribute *attr, char *buf)
87{
88 return sysfs_emit(buf, fmt: "%d\n", prof_on);
89}
90static ssize_t profiling_store(struct kobject *kobj,
91 struct kobj_attribute *attr,
92 const char *buf, size_t count)
93{
94 int ret;
95 static DEFINE_MUTEX(lock);
96
97 /*
98 * We need serialization, for profile_setup() initializes prof_on
99 * value and profile_init() must not reallocate prof_buffer after
100 * once allocated.
101 */
102 guard(mutex)(T: &lock);
103 if (prof_on)
104 return -EEXIST;
105 /*
106 * This eventually calls into get_option() which
107 * has a ton of callers and is not const. It is
108 * easiest to cast it away here.
109 */
110 profile_setup(str: (char *)buf);
111 ret = profile_init();
112 if (ret)
113 return ret;
114 ret = create_proc_profile();
115 if (ret)
116 return ret;
117 return count;
118}
119KERNEL_ATTR_RW(profiling);
120#endif
121
122#ifdef CONFIG_VMCORE_INFO
123
124static ssize_t vmcoreinfo_show(struct kobject *kobj,
125 struct kobj_attribute *attr, char *buf)
126{
127 phys_addr_t vmcore_base = paddr_vmcoreinfo_note();
128 return sysfs_emit(buf, fmt: "%pa %x\n", &vmcore_base,
129 (unsigned int)VMCOREINFO_NOTE_SIZE);
130}
131KERNEL_ATTR_RO(vmcoreinfo);
132
133#endif /* CONFIG_VMCORE_INFO */
134
135/* whether file capabilities are enabled */
136static ssize_t fscaps_show(struct kobject *kobj,
137 struct kobj_attribute *attr, char *buf)
138{
139 return sysfs_emit(buf, fmt: "%d\n", file_caps_enabled);
140}
141KERNEL_ATTR_RO(fscaps);
142
143#ifndef CONFIG_TINY_RCU
144int rcu_expedited;
145static ssize_t rcu_expedited_show(struct kobject *kobj,
146 struct kobj_attribute *attr, char *buf)
147{
148 return sysfs_emit(buf, fmt: "%d\n", READ_ONCE(rcu_expedited));
149}
150static ssize_t rcu_expedited_store(struct kobject *kobj,
151 struct kobj_attribute *attr,
152 const char *buf, size_t count)
153{
154 if (kstrtoint(s: buf, base: 0, res: &rcu_expedited))
155 return -EINVAL;
156
157 return count;
158}
159KERNEL_ATTR_RW(rcu_expedited);
160
161int rcu_normal;
162static ssize_t rcu_normal_show(struct kobject *kobj,
163 struct kobj_attribute *attr, char *buf)
164{
165 return sysfs_emit(buf, fmt: "%d\n", READ_ONCE(rcu_normal));
166}
167static ssize_t rcu_normal_store(struct kobject *kobj,
168 struct kobj_attribute *attr,
169 const char *buf, size_t count)
170{
171 if (kstrtoint(s: buf, base: 0, res: &rcu_normal))
172 return -EINVAL;
173
174 return count;
175}
176KERNEL_ATTR_RW(rcu_normal);
177#endif /* #ifndef CONFIG_TINY_RCU */
178
179/*
180 * Make /sys/kernel/notes give the raw contents of our kernel .notes section.
181 */
182extern const void __start_notes;
183extern const void __stop_notes;
184#define notes_size (&__stop_notes - &__start_notes)
185
186static __ro_after_init BIN_ATTR_SIMPLE_RO(notes);
187
188struct kobject *kernel_kobj;
189EXPORT_SYMBOL_GPL(kernel_kobj);
190
191static struct attribute * kernel_attrs[] = {
192 &fscaps_attr.attr,
193 &uevent_seqnum_attr.attr,
194 &cpu_byteorder_attr.attr,
195 &address_bits_attr.attr,
196#ifdef CONFIG_UEVENT_HELPER
197 &uevent_helper_attr.attr,
198#endif
199#ifdef CONFIG_PROFILING
200 &profiling_attr.attr,
201#endif
202#ifdef CONFIG_VMCORE_INFO
203 &vmcoreinfo_attr.attr,
204#endif
205#ifndef CONFIG_TINY_RCU
206 &rcu_expedited_attr.attr,
207 &rcu_normal_attr.attr,
208#endif
209 NULL
210};
211
212static const struct attribute_group kernel_attr_group = {
213 .attrs = kernel_attrs,
214};
215
216static int __init ksysfs_init(void)
217{
218 int error;
219
220 kernel_kobj = kobject_create_and_add(name: "kernel", NULL);
221 if (!kernel_kobj) {
222 error = -ENOMEM;
223 goto exit;
224 }
225 error = sysfs_create_group(kobj: kernel_kobj, grp: &kernel_attr_group);
226 if (error)
227 goto kset_exit;
228
229 if (notes_size > 0) {
230 bin_attr_notes.private = (void *)&__start_notes;
231 bin_attr_notes.size = notes_size;
232 error = sysfs_create_bin_file(kobj: kernel_kobj, attr: &bin_attr_notes);
233 if (error)
234 goto group_exit;
235 }
236
237 return 0;
238
239group_exit:
240 sysfs_remove_group(kobj: kernel_kobj, grp: &kernel_attr_group);
241kset_exit:
242 kobject_put(kobj: kernel_kobj);
243exit:
244 return error;
245}
246
247core_initcall(ksysfs_init);
248

source code of linux/kernel/ksysfs.c