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) \
33 static struct kobj_attribute _name##_attr = __ATTR_RO(_name)
34 
35 #define KERNEL_ATTR_RW(_name) \
36 static struct kobj_attribute _name##_attr = __ATTR_RW(_name)
37 
38 /* current uevent sequence number */
uevent_seqnum_show(struct kobject * kobj,struct kobj_attribute * attr,char * buf)39 static ssize_t uevent_seqnum_show(struct kobject *kobj,
40 				  struct kobj_attribute *attr, char *buf)
41 {
42 	return sysfs_emit(buf, "%llu\n", (unsigned long long)uevent_seqnum);
43 }
44 KERNEL_ATTR_RO(uevent_seqnum);
45 
46 /* cpu byteorder */
cpu_byteorder_show(struct kobject * kobj,struct kobj_attribute * attr,char * buf)47 static 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 }
52 KERNEL_ATTR_RO(cpu_byteorder);
53 
54 /* address bits */
address_bits_show(struct kobject * kobj,struct kobj_attribute * attr,char * buf)55 static 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 }
60 KERNEL_ATTR_RO(address_bits);
61 
62 #ifdef CONFIG_UEVENT_HELPER
63 /* uevent helper program, used during early boot */
uevent_helper_show(struct kobject * kobj,struct kobj_attribute * attr,char * buf)64 static 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 }
uevent_helper_store(struct kobject * kobj,struct kobj_attribute * attr,const char * buf,size_t count)69 static 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 }
81 KERNEL_ATTR_RW(uevent_helper);
82 #endif
83 
84 #ifdef CONFIG_PROFILING
profiling_show(struct kobject * kobj,struct kobj_attribute * attr,char * buf)85 static 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 }
profiling_store(struct kobject * kobj,struct kobj_attribute * attr,const char * buf,size_t count)90 static ssize_t profiling_store(struct kobject *kobj,
91 				   struct kobj_attribute *attr,
92 				   const char *buf, size_t count)
93 {
94 	int ret;
95 
96 	if (prof_on)
97 		return -EEXIST;
98 	/*
99 	 * This eventually calls into get_option() which
100 	 * has a ton of callers and is not const.  It is
101 	 * easiest to cast it away here.
102 	 */
103 	profile_setup((char *)buf);
104 	ret = profile_init();
105 	if (ret)
106 		return ret;
107 	ret = create_proc_profile();
108 	if (ret)
109 		return ret;
110 	return count;
111 }
112 KERNEL_ATTR_RW(profiling);
113 #endif
114 
115 #ifdef CONFIG_KEXEC_CORE
kexec_loaded_show(struct kobject * kobj,struct kobj_attribute * attr,char * buf)116 static ssize_t kexec_loaded_show(struct kobject *kobj,
117 				 struct kobj_attribute *attr, char *buf)
118 {
119 	return sysfs_emit(buf, "%d\n", !!kexec_image);
120 }
121 KERNEL_ATTR_RO(kexec_loaded);
122 
kexec_crash_loaded_show(struct kobject * kobj,struct kobj_attribute * attr,char * buf)123 static ssize_t kexec_crash_loaded_show(struct kobject *kobj,
124 				       struct kobj_attribute *attr, char *buf)
125 {
126 	return sysfs_emit(buf, "%d\n", kexec_crash_loaded());
127 }
128 KERNEL_ATTR_RO(kexec_crash_loaded);
129 
kexec_crash_size_show(struct kobject * kobj,struct kobj_attribute * attr,char * buf)130 static ssize_t kexec_crash_size_show(struct kobject *kobj,
131 				       struct kobj_attribute *attr, char *buf)
132 {
133 	ssize_t size = crash_get_memory_size();
134 
135 	if (size < 0)
136 		return size;
137 
138 	return sysfs_emit(buf, "%zd\n", size);
139 }
kexec_crash_size_store(struct kobject * kobj,struct kobj_attribute * attr,const char * buf,size_t count)140 static ssize_t kexec_crash_size_store(struct kobject *kobj,
141 				   struct kobj_attribute *attr,
142 				   const char *buf, size_t count)
143 {
144 	unsigned long cnt;
145 	int ret;
146 
147 	if (kstrtoul(buf, 0, &cnt))
148 		return -EINVAL;
149 
150 	ret = crash_shrink_memory(cnt);
151 	return ret < 0 ? ret : count;
152 }
153 KERNEL_ATTR_RW(kexec_crash_size);
154 
155 #endif /* CONFIG_KEXEC_CORE */
156 
157 #ifdef CONFIG_CRASH_CORE
158 
vmcoreinfo_show(struct kobject * kobj,struct kobj_attribute * attr,char * buf)159 static ssize_t vmcoreinfo_show(struct kobject *kobj,
160 			       struct kobj_attribute *attr, char *buf)
161 {
162 	phys_addr_t vmcore_base = paddr_vmcoreinfo_note();
163 	return sysfs_emit(buf, "%pa %x\n", &vmcore_base,
164 			  (unsigned int)VMCOREINFO_NOTE_SIZE);
165 }
166 KERNEL_ATTR_RO(vmcoreinfo);
167 
168 #ifdef CONFIG_CRASH_HOTPLUG
crash_elfcorehdr_size_show(struct kobject * kobj,struct kobj_attribute * attr,char * buf)169 static ssize_t crash_elfcorehdr_size_show(struct kobject *kobj,
170 			       struct kobj_attribute *attr, char *buf)
171 {
172 	unsigned int sz = crash_get_elfcorehdr_size();
173 
174 	return sysfs_emit(buf, "%u\n", sz);
175 }
176 KERNEL_ATTR_RO(crash_elfcorehdr_size);
177 
178 #endif
179 
180 #endif /* CONFIG_CRASH_CORE */
181 
182 /* whether file capabilities are enabled */
fscaps_show(struct kobject * kobj,struct kobj_attribute * attr,char * buf)183 static ssize_t fscaps_show(struct kobject *kobj,
184 				  struct kobj_attribute *attr, char *buf)
185 {
186 	return sysfs_emit(buf, "%d\n", file_caps_enabled);
187 }
188 KERNEL_ATTR_RO(fscaps);
189 
190 #ifndef CONFIG_TINY_RCU
191 int rcu_expedited;
rcu_expedited_show(struct kobject * kobj,struct kobj_attribute * attr,char * buf)192 static ssize_t rcu_expedited_show(struct kobject *kobj,
193 				  struct kobj_attribute *attr, char *buf)
194 {
195 	return sysfs_emit(buf, "%d\n", READ_ONCE(rcu_expedited));
196 }
rcu_expedited_store(struct kobject * kobj,struct kobj_attribute * attr,const char * buf,size_t count)197 static ssize_t rcu_expedited_store(struct kobject *kobj,
198 				   struct kobj_attribute *attr,
199 				   const char *buf, size_t count)
200 {
201 	if (kstrtoint(buf, 0, &rcu_expedited))
202 		return -EINVAL;
203 
204 	return count;
205 }
206 KERNEL_ATTR_RW(rcu_expedited);
207 
208 int rcu_normal;
rcu_normal_show(struct kobject * kobj,struct kobj_attribute * attr,char * buf)209 static ssize_t rcu_normal_show(struct kobject *kobj,
210 			       struct kobj_attribute *attr, char *buf)
211 {
212 	return sysfs_emit(buf, "%d\n", READ_ONCE(rcu_normal));
213 }
rcu_normal_store(struct kobject * kobj,struct kobj_attribute * attr,const char * buf,size_t count)214 static ssize_t rcu_normal_store(struct kobject *kobj,
215 				struct kobj_attribute *attr,
216 				const char *buf, size_t count)
217 {
218 	if (kstrtoint(buf, 0, &rcu_normal))
219 		return -EINVAL;
220 
221 	return count;
222 }
223 KERNEL_ATTR_RW(rcu_normal);
224 #endif /* #ifndef CONFIG_TINY_RCU */
225 
226 /*
227  * Make /sys/kernel/notes give the raw contents of our kernel .notes section.
228  */
229 extern const void __start_notes __weak;
230 extern const void __stop_notes __weak;
231 #define	notes_size (&__stop_notes - &__start_notes)
232 
notes_read(struct file * filp,struct kobject * kobj,struct bin_attribute * bin_attr,char * buf,loff_t off,size_t count)233 static ssize_t notes_read(struct file *filp, struct kobject *kobj,
234 			  struct bin_attribute *bin_attr,
235 			  char *buf, loff_t off, size_t count)
236 {
237 	memcpy(buf, &__start_notes + off, count);
238 	return count;
239 }
240 
241 static struct bin_attribute notes_attr __ro_after_init  = {
242 	.attr = {
243 		.name = "notes",
244 		.mode = S_IRUGO,
245 	},
246 	.read = &notes_read,
247 };
248 
249 struct kobject *kernel_kobj;
250 EXPORT_SYMBOL_GPL(kernel_kobj);
251 
252 static struct attribute * kernel_attrs[] = {
253 	&fscaps_attr.attr,
254 	&uevent_seqnum_attr.attr,
255 	&cpu_byteorder_attr.attr,
256 	&address_bits_attr.attr,
257 #ifdef CONFIG_UEVENT_HELPER
258 	&uevent_helper_attr.attr,
259 #endif
260 #ifdef CONFIG_PROFILING
261 	&profiling_attr.attr,
262 #endif
263 #ifdef CONFIG_KEXEC_CORE
264 	&kexec_loaded_attr.attr,
265 	&kexec_crash_loaded_attr.attr,
266 	&kexec_crash_size_attr.attr,
267 #endif
268 #ifdef CONFIG_CRASH_CORE
269 	&vmcoreinfo_attr.attr,
270 #ifdef CONFIG_CRASH_HOTPLUG
271 	&crash_elfcorehdr_size_attr.attr,
272 #endif
273 #endif
274 #ifndef CONFIG_TINY_RCU
275 	&rcu_expedited_attr.attr,
276 	&rcu_normal_attr.attr,
277 #endif
278 	NULL
279 };
280 
281 static const struct attribute_group kernel_attr_group = {
282 	.attrs = kernel_attrs,
283 };
284 
ksysfs_init(void)285 static int __init ksysfs_init(void)
286 {
287 	int error;
288 
289 	kernel_kobj = kobject_create_and_add("kernel", NULL);
290 	if (!kernel_kobj) {
291 		error = -ENOMEM;
292 		goto exit;
293 	}
294 	error = sysfs_create_group(kernel_kobj, &kernel_attr_group);
295 	if (error)
296 		goto kset_exit;
297 
298 	if (notes_size > 0) {
299 		notes_attr.size = notes_size;
300 		error = sysfs_create_bin_file(kernel_kobj, &notes_attr);
301 		if (error)
302 			goto group_exit;
303 	}
304 
305 	return 0;
306 
307 group_exit:
308 	sysfs_remove_group(kernel_kobj, &kernel_attr_group);
309 kset_exit:
310 	kobject_put(kernel_kobj);
311 exit:
312 	return error;
313 }
314 
315 core_initcall(ksysfs_init);
316