kernel/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/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 */
  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", (u64)atomic64_read(&uevent_seqnum));
  43 }
  44 KERNEL_ATTR_RO(uevent_seqnum);
  45
  46 /* cpu byteorder */
  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 */
  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 */
  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 }
  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
  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 }
  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         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 }
 119 KERNEL_ATTR_RW(profiling);
 120 #endif
 121
 122 #ifdef CONFIG_KEXEC_CORE
 123 static ssize_t kexec_loaded_show(struct kobject *kobj,
 124                                  struct kobj_attribute *attr, char *buf)
 125 {
 126         return sysfs_emit(buf, "%d\n", !!kexec_image);
 127 }
 128 KERNEL_ATTR_RO(kexec_loaded);
 129
 130 #ifdef CONFIG_CRASH_DUMP
 131 static ssize_t kexec_crash_loaded_show(struct kobject *kobj,
 132                                        struct kobj_attribute *attr, char *buf)
 133 {
 134         return sysfs_emit(buf, "%d\n", kexec_crash_loaded());
 135 }
 136 KERNEL_ATTR_RO(kexec_crash_loaded);
 137
 138 static 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, "%zd\n", size);
 147 }
 148 static 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(buf, 0, &cnt))
 156                 return -EINVAL;
 157
 158         ret = crash_shrink_memory(cnt);
 159         return ret < 0 ? ret : count;
 160 }
 161 KERNEL_ATTR_RW(kexec_crash_size);
 162
 163 #endif /* CONFIG_CRASH_DUMP*/
 164 #endif /* CONFIG_KEXEC_CORE */
 165
 166 #ifdef CONFIG_VMCORE_INFO
 167
 168 static 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, "%pa %x\n", &vmcore_base,
 173                           (unsigned int)VMCOREINFO_NOTE_SIZE);
 174 }
 175 KERNEL_ATTR_RO(vmcoreinfo);
 176
 177 #ifdef CONFIG_CRASH_HOTPLUG
 178 static 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, "%u\n", sz);
 184 }
 185 KERNEL_ATTR_RO(crash_elfcorehdr_size);
 186
 187 #endif
 188
 189 #endif /* CONFIG_VMCORE_INFO */
 190
 191 /* whether file capabilities are enabled */
 192 static ssize_t fscaps_show(struct kobject *kobj,
 193                                   struct kobj_attribute *attr, char *buf)
 194 {
 195         return sysfs_emit(buf, "%d\n", file_caps_enabled);
 196 }
 197 KERNEL_ATTR_RO(fscaps);
 198
 199 #ifndef CONFIG_TINY_RCU
 200 int rcu_expedited;
 201 static ssize_t rcu_expedited_show(struct kobject *kobj,
 202                                   struct kobj_attribute *attr, char *buf)
 203 {
 204         return sysfs_emit(buf, "%d\n", READ_ONCE(rcu_expedited));
 205 }
 206 static ssize_t rcu_expedited_store(struct kobject *kobj,
 207                                    struct kobj_attribute *attr,
 208                                    const char *buf, size_t count)
 209 {
 210         if (kstrtoint(buf, 0, &rcu_expedited))
 211                 return -EINVAL;
 212
 213         return count;
 214 }
 215 KERNEL_ATTR_RW(rcu_expedited);
 216
 217 int rcu_normal;
 218 static ssize_t rcu_normal_show(struct kobject *kobj,
 219                                struct kobj_attribute *attr, char *buf)
 220 {
 221         return sysfs_emit(buf, "%d\n", READ_ONCE(rcu_normal));
 222 }
 223 static ssize_t rcu_normal_store(struct kobject *kobj,
 224                                 struct kobj_attribute *attr,
 225                                 const char *buf, size_t count)
 226 {
 227         if (kstrtoint(buf, 0, &rcu_normal))
 228                 return -EINVAL;
 229
 230         return count;
 231 }
 232 KERNEL_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  */
 238 extern const void __start_notes;
 239 extern const void __stop_notes;
 240 #define notes_size (&__stop_notes - &__start_notes)
 241
 242 static ssize_t notes_read(struct file *filp, struct kobject *kobj,
 243                           struct bin_attribute *bin_attr,
 244                           char *buf, loff_t off, size_t count)
 245 {
 246         memcpy(buf, &__start_notes + off, count);
 247         return count;
 248 }
 249
 250 static struct bin_attribute notes_attr __ro_after_init  = {
 251         .attr = {
 252                 .name = "notes",
 253                 .mode = S_IRUGO,
 254         },
 255         .read = &notes_read,
 256 };
 257
 258 struct kobject *kernel_kobj;
 259 EXPORT_SYMBOL_GPL(kernel_kobj);
 260
 261 static struct attribute * kernel_attrs[] = {
 262         &fscaps_attr.attr,
 263         &uevent_seqnum_attr.attr,
 264         &cpu_byteorder_attr.attr,
 265         &address_bits_attr.attr,
 266 #ifdef CONFIG_UEVENT_HELPER
 267         &uevent_helper_attr.attr,
 268 #endif
 269 #ifdef CONFIG_PROFILING
 270         &profiling_attr.attr,
 271 #endif
 272 #ifdef CONFIG_KEXEC_CORE
 273         &kexec_loaded_attr.attr,
 274 #ifdef CONFIG_CRASH_DUMP
 275         &kexec_crash_loaded_attr.attr,
 276         &kexec_crash_size_attr.attr,
 277 #endif
 278 #endif
 279 #ifdef CONFIG_VMCORE_INFO
 280         &vmcoreinfo_attr.attr,
 281 #ifdef CONFIG_CRASH_HOTPLUG
 282         &crash_elfcorehdr_size_attr.attr,
 283 #endif
 284 #endif
 285 #ifndef CONFIG_TINY_RCU
 286         &rcu_expedited_attr.attr,
 287         &rcu_normal_attr.attr,
 288 #endif
 289         NULL
 290 };
 291
 292 static const struct attribute_group kernel_attr_group = {
 293         .attrs = kernel_attrs,
 294 };
 295
 296 static int __init ksysfs_init(void)
 297 {
 298         int error;
 299
 300         kernel_kobj = kobject_create_and_add("kernel", NULL);
 301         if (!kernel_kobj) {
 302                 error = -ENOMEM;
 303                 goto exit;
 304         }
 305         error = sysfs_create_group(kernel_kobj, &kernel_attr_group);
 306         if (error)
 307                 goto kset_exit;
 308
 309         if (notes_size > 0) {
 310                 notes_attr.size = notes_size;
 311                 error = sysfs_create_bin_file(kernel_kobj, &notes_attr);
 312                 if (error)
 313                         goto group_exit;
 314         }
 315
 316         return 0;
 317
 318 group_exit:
 319         sysfs_remove_group(kernel_kobj, &kernel_attr_group);
 320 kset_exit:
 321         kobject_put(kernel_kobj);
 322 exit:
 323         return error;
 324 }
 325
 326 core_initcall(ksysfs_init);