ksysfs.c

  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, "%llu\n", (u64)atomic64_read(&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, "%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, "%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, "%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, "%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)(&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((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, "%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, "%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, "%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(buf, 0, &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, "%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(buf, 0, &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("kernel", NULL);
221	if (!kernel_kobj) {
222		error = -ENOMEM;
223		goto exit;
224	}
225	error = sysfs_create_group(kernel_kobj, &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(kernel_kobj, &bin_attr_notes);
233		if (error)
234			goto group_exit;
235	}
236
237	return 0;
238
239group_exit:
240	sysfs_remove_group(kernel_kobj, &kernel_attr_group);
241kset_exit:
242	kobject_put(kernel_kobj);
243exit:
244	return error;
245}
246
247core_initcall(ksysfs_init);