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/kexec.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_KEXEC_CORE
123static ssize_t kexec_loaded_show(struct kobject *kobj,
124 struct kobj_attribute *attr, char *buf)
125{
126 return sysfs_emit(buf, fmt: "%d\n", !!kexec_image);
127}
128KERNEL_ATTR_RO(kexec_loaded);
129
130#ifdef CONFIG_CRASH_DUMP
131static ssize_t kexec_crash_loaded_show(struct kobject *kobj,
132 struct kobj_attribute *attr, char *buf)
133{
134 return sysfs_emit(buf, fmt: "%d\n", kexec_crash_loaded());
135}
136KERNEL_ATTR_RO(kexec_crash_loaded);
137
138static ssize_t kexec_crash_size_show(struct kobject *kobj,
139 struct kobj_attribute *attr, char *buf)
140{
141 ssize_t size = crash_get_memory_size();
142
143 if (size < 0)
144 return size;
145
146 return sysfs_emit(buf, fmt: "%zd\n", size);
147}
148static ssize_t kexec_crash_size_store(struct kobject *kobj,
149 struct kobj_attribute *attr,
150 const char *buf, size_t count)
151{
152 unsigned long cnt;
153 int ret;
154
155 if (kstrtoul(s: buf, base: 0, res: &cnt))
156 return -EINVAL;
157
158 ret = crash_shrink_memory(new_size: cnt);
159 return ret < 0 ? ret : count;
160}
161KERNEL_ATTR_RW(kexec_crash_size);
162
163#endif /* CONFIG_CRASH_DUMP*/
164#endif /* CONFIG_KEXEC_CORE */
165
166#ifdef CONFIG_VMCORE_INFO
167
168static ssize_t vmcoreinfo_show(struct kobject *kobj,
169 struct kobj_attribute *attr, char *buf)
170{
171 phys_addr_t vmcore_base = paddr_vmcoreinfo_note();
172 return sysfs_emit(buf, fmt: "%pa %x\n", &vmcore_base,
173 (unsigned int)VMCOREINFO_NOTE_SIZE);
174}
175KERNEL_ATTR_RO(vmcoreinfo);
176
177#ifdef CONFIG_CRASH_HOTPLUG
178static ssize_t crash_elfcorehdr_size_show(struct kobject *kobj,
179 struct kobj_attribute *attr, char *buf)
180{
181 unsigned int sz = crash_get_elfcorehdr_size();
182
183 return sysfs_emit(buf, fmt: "%u\n", sz);
184}
185KERNEL_ATTR_RO(crash_elfcorehdr_size);
186
187#endif
188
189#endif /* CONFIG_VMCORE_INFO */
190
191/* whether file capabilities are enabled */
192static ssize_t fscaps_show(struct kobject *kobj,
193 struct kobj_attribute *attr, char *buf)
194{
195 return sysfs_emit(buf, fmt: "%d\n", file_caps_enabled);
196}
197KERNEL_ATTR_RO(fscaps);
198
199#ifndef CONFIG_TINY_RCU
200int rcu_expedited;
201static ssize_t rcu_expedited_show(struct kobject *kobj,
202 struct kobj_attribute *attr, char *buf)
203{
204 return sysfs_emit(buf, fmt: "%d\n", READ_ONCE(rcu_expedited));
205}
206static ssize_t rcu_expedited_store(struct kobject *kobj,
207 struct kobj_attribute *attr,
208 const char *buf, size_t count)
209{
210 if (kstrtoint(s: buf, base: 0, res: &rcu_expedited))
211 return -EINVAL;
212
213 return count;
214}
215KERNEL_ATTR_RW(rcu_expedited);
216
217int rcu_normal;
218static ssize_t rcu_normal_show(struct kobject *kobj,
219 struct kobj_attribute *attr, char *buf)
220{
221 return sysfs_emit(buf, fmt: "%d\n", READ_ONCE(rcu_normal));
222}
223static ssize_t rcu_normal_store(struct kobject *kobj,
224 struct kobj_attribute *attr,
225 const char *buf, size_t count)
226{
227 if (kstrtoint(s: buf, base: 0, res: &rcu_normal))
228 return -EINVAL;
229
230 return count;
231}
232KERNEL_ATTR_RW(rcu_normal);
233#endif /* #ifndef CONFIG_TINY_RCU */
234
235/*
236 * Make /sys/kernel/notes give the raw contents of our kernel .notes section.
237 */
238extern const void __start_notes;
239extern const void __stop_notes;
240#define notes_size (&__stop_notes - &__start_notes)
241
242static __ro_after_init BIN_ATTR_SIMPLE_RO(notes);
243
244struct kobject *kernel_kobj;
245EXPORT_SYMBOL_GPL(kernel_kobj);
246
247static struct attribute * kernel_attrs[] = {
248 &fscaps_attr.attr,
249 &uevent_seqnum_attr.attr,
250 &cpu_byteorder_attr.attr,
251 &address_bits_attr.attr,
252#ifdef CONFIG_UEVENT_HELPER
253 &uevent_helper_attr.attr,
254#endif
255#ifdef CONFIG_PROFILING
256 &profiling_attr.attr,
257#endif
258#ifdef CONFIG_KEXEC_CORE
259 &kexec_loaded_attr.attr,
260#ifdef CONFIG_CRASH_DUMP
261 &kexec_crash_loaded_attr.attr,
262 &kexec_crash_size_attr.attr,
263#endif
264#endif
265#ifdef CONFIG_VMCORE_INFO
266 &vmcoreinfo_attr.attr,
267#ifdef CONFIG_CRASH_HOTPLUG
268 &crash_elfcorehdr_size_attr.attr,
269#endif
270#endif
271#ifndef CONFIG_TINY_RCU
272 &rcu_expedited_attr.attr,
273 &rcu_normal_attr.attr,
274#endif
275 NULL
276};
277
278static const struct attribute_group kernel_attr_group = {
279 .attrs = kernel_attrs,
280};
281
282static int __init ksysfs_init(void)
283{
284 int error;
285
286 kernel_kobj = kobject_create_and_add(name: "kernel", NULL);
287 if (!kernel_kobj) {
288 error = -ENOMEM;
289 goto exit;
290 }
291 error = sysfs_create_group(kobj: kernel_kobj, grp: &kernel_attr_group);
292 if (error)
293 goto kset_exit;
294
295 if (notes_size > 0) {
296 bin_attr_notes.private = (void *)&__start_notes;
297 bin_attr_notes.size = notes_size;
298 error = sysfs_create_bin_file(kobj: kernel_kobj, attr: &bin_attr_notes);
299 if (error)
300 goto group_exit;
301 }
302
303 return 0;
304
305group_exit:
306 sysfs_remove_group(kobj: kernel_kobj, grp: &kernel_attr_group);
307kset_exit:
308 kobject_put(kobj: kernel_kobj);
309exit:
310 return error;
311}
312
313core_initcall(ksysfs_init);
314

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source code of linux/kernel/ksysfs.c