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 <[email protected]>
   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
  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
 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
 123 #ifdef CONFIG_CRASH_DUMP
 124 static ssize_t kexec_crash_loaded_show(struct kobject *kobj,
 125                                        struct kobj_attribute *attr, char *buf)
 126 {
 127         return sysfs_emit(buf, "%d\n", kexec_crash_loaded());
 128 }
 129 KERNEL_ATTR_RO(kexec_crash_loaded);
 130
 131 static ssize_t kexec_crash_size_show(struct kobject *kobj,
 132                                        struct kobj_attribute *attr, char *buf)
 133 {
 134         ssize_t size = crash_get_memory_size();
 135
 136         if (size < 0)
 137                 return size;
 138
 139         return sysfs_emit(buf, "%zd\n", size);
 140 }
 141 static ssize_t kexec_crash_size_store(struct kobject *kobj,
 142                                    struct kobj_attribute *attr,
 143                                    const char *buf, size_t count)
 144 {
 145         unsigned long cnt;
 146         int ret;
 147
 148         if (kstrtoul(buf, 0, &cnt))
 149                 return -EINVAL;
 150
 151         ret = crash_shrink_memory(cnt);
 152         return ret < 0 ? ret : count;
 153 }
 154 KERNEL_ATTR_RW(kexec_crash_size);
 155
 156 #endif /* CONFIG_CRASH_DUMP*/
 157 #endif /* CONFIG_KEXEC_CORE */
 158
 159 #ifdef CONFIG_VMCORE_INFO
 160
 161 static ssize_t vmcoreinfo_show(struct kobject *kobj,
 162                                struct kobj_attribute *attr, char *buf)
 163 {
 164         phys_addr_t vmcore_base = paddr_vmcoreinfo_note();
 165         return sysfs_emit(buf, "%pa %x\n", &vmcore_base,
 166                           (unsigned int)VMCOREINFO_NOTE_SIZE);
 167 }
 168 KERNEL_ATTR_RO(vmcoreinfo);
 169
 170 #ifdef CONFIG_CRASH_HOTPLUG
 171 static ssize_t crash_elfcorehdr_size_show(struct kobject *kobj,
 172                                struct kobj_attribute *attr, char *buf)
 173 {
 174         unsigned int sz = crash_get_elfcorehdr_size();
 175
 176         return sysfs_emit(buf, "%u\n", sz);
 177 }
 178 KERNEL_ATTR_RO(crash_elfcorehdr_size);
 179
 180 #endif
 181
 182 #endif /* CONFIG_VMCORE_INFO */
 183
 184 /* whether file capabilities are enabled */
 185 static ssize_t fscaps_show(struct kobject *kobj,
 186                                   struct kobj_attribute *attr, char *buf)
 187 {
 188         return sysfs_emit(buf, "%d\n", file_caps_enabled);
 189 }
 190 KERNEL_ATTR_RO(fscaps);
 191
 192 #ifndef CONFIG_TINY_RCU
 193 int rcu_expedited;
 194 static ssize_t rcu_expedited_show(struct kobject *kobj,
 195                                   struct kobj_attribute *attr, char *buf)
 196 {
 197         return sysfs_emit(buf, "%d\n", READ_ONCE(rcu_expedited));
 198 }
 199 static ssize_t rcu_expedited_store(struct kobject *kobj,
 200                                    struct kobj_attribute *attr,
 201                                    const char *buf, size_t count)
 202 {
 203         if (kstrtoint(buf, 0, &rcu_expedited))
 204                 return -EINVAL;
 205
 206         return count;
 207 }
 208 KERNEL_ATTR_RW(rcu_expedited);
 209
 210 int rcu_normal;
 211 static ssize_t rcu_normal_show(struct kobject *kobj,
 212                                struct kobj_attribute *attr, char *buf)
 213 {
 214         return sysfs_emit(buf, "%d\n", READ_ONCE(rcu_normal));
 215 }
 216 static ssize_t rcu_normal_store(struct kobject *kobj,
 217                                 struct kobj_attribute *attr,
 218                                 const char *buf, size_t count)
 219 {
 220         if (kstrtoint(buf, 0, &rcu_normal))
 221                 return -EINVAL;
 222
 223         return count;
 224 }
 225 KERNEL_ATTR_RW(rcu_normal);
 226 #endif /* #ifndef CONFIG_TINY_RCU */
 227
 228 /*
 229  * Make /sys/kernel/notes give the raw contents of our kernel .notes section.
 230  */
 231 extern const void __start_notes;
 232 extern const void __stop_notes;
 233 #define notes_size (&__stop_notes - &__start_notes)
 234
 235 static ssize_t notes_read(struct file *filp, struct kobject *kobj,
 236                           struct bin_attribute *bin_attr,
 237                           char *buf, loff_t off, size_t count)
 238 {
 239         memcpy(buf, &__start_notes + off, count);
 240         return count;
 241 }
 242
 243 static struct bin_attribute notes_attr __ro_after_init  = {
 244         .attr = {
 245                 .name = "notes",
 246                 .mode = S_IRUGO,
 247         },
 248         .read = &notes_read,
 249 };
 250
 251 struct kobject *kernel_kobj;
 252 EXPORT_SYMBOL_GPL(kernel_kobj);
 253
 254 static struct attribute * kernel_attrs[] = {
 255         &fscaps_attr.attr,
 256         &uevent_seqnum_attr.attr,
 257         &cpu_byteorder_attr.attr,
 258         &address_bits_attr.attr,
 259 #ifdef CONFIG_UEVENT_HELPER
 260         &uevent_helper_attr.attr,
 261 #endif
 262 #ifdef CONFIG_PROFILING
 263         &profiling_attr.attr,
 264 #endif
 265 #ifdef CONFIG_KEXEC_CORE
 266         &kexec_loaded_attr.attr,
 267 #ifdef CONFIG_CRASH_DUMP
 268         &kexec_crash_loaded_attr.attr,
 269         &kexec_crash_size_attr.attr,
 270 #endif
 271 #endif
 272 #ifdef CONFIG_VMCORE_INFO
 273         &vmcoreinfo_attr.attr,
 274 #ifdef CONFIG_CRASH_HOTPLUG
 275         &crash_elfcorehdr_size_attr.attr,
 276 #endif
 277 #endif
 278 #ifndef CONFIG_TINY_RCU
 279         &rcu_expedited_attr.attr,
 280         &rcu_normal_attr.attr,
 281 #endif
 282         NULL
 283 };
 284
 285 static const struct attribute_group kernel_attr_group = {
 286         .attrs = kernel_attrs,
 287 };
 288
 289 static int __init ksysfs_init(void)
 290 {
 291         int error;
 292
 293         kernel_kobj = kobject_create_and_add("kernel", NULL);
 294         if (!kernel_kobj) {
 295                 error = -ENOMEM;
 296                 goto exit;
 297         }
 298         error = sysfs_create_group(kernel_kobj, &kernel_attr_group);
 299         if (error)
 300                 goto kset_exit;
 301
 302         if (notes_size > 0) {
 303                 notes_attr.size = notes_size;
 304                 error = sysfs_create_bin_file(kernel_kobj, &notes_attr);
 305                 if (error)
 306                         goto group_exit;
 307         }
 308
 309         return 0;
 310
 311 group_exit:
 312         sysfs_remove_group(kernel_kobj, &kernel_attr_group);
 313 kset_exit:
 314         kobject_put(kernel_kobj);
 315 exit:
 316         return error;
 317 }
 318
 319 core_initcall(ksysfs_init);