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 sprintf(buf, "%llu\n", (unsigned long long)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 #ifdef CONFIG_UEVENT_HELPER
  55 /* uevent helper program, used during early boot */
  56 static ssize_t uevent_helper_show(struct kobject *kobj,
  57                                   struct kobj_attribute *attr, char *buf)
  58 {
  59         return sprintf(buf, "%s\n", uevent_helper);
  60 }
  61 static ssize_t uevent_helper_store(struct kobject *kobj,
  62                                    struct kobj_attribute *attr,
  63                                    const char *buf, size_t count)
  64 {
  65         if (count+1 > UEVENT_HELPER_PATH_LEN)
  66                 return -ENOENT;
  67         memcpy(uevent_helper, buf, count);
  68         uevent_helper[count] = '\0';
  69         if (count && uevent_helper[count-1] == '\n')
  70                 uevent_helper[count-1] = '\0';
  71         return count;
  72 }
  73 KERNEL_ATTR_RW(uevent_helper);
  74 #endif
  75
  76 #ifdef CONFIG_PROFILING
  77 static ssize_t profiling_show(struct kobject *kobj,
  78                                   struct kobj_attribute *attr, char *buf)
  79 {
  80         return sprintf(buf, "%d\n", prof_on);
  81 }
  82 static ssize_t profiling_store(struct kobject *kobj,
  83                                    struct kobj_attribute *attr,
  84                                    const char *buf, size_t count)
  85 {
  86         int ret;
  87
  88         if (prof_on)
  89                 return -EEXIST;
  90         /*
  91          * This eventually calls into get_option() which
  92          * has a ton of callers and is not const.  It is
  93          * easiest to cast it away here.
  94          */
  95         profile_setup((char *)buf);
  96         ret = profile_init();
  97         if (ret)
  98                 return ret;
  99         ret = create_proc_profile();
 100         if (ret)
 101                 return ret;
 102         return count;
 103 }
 104 KERNEL_ATTR_RW(profiling);
 105 #endif
 106
 107 #ifdef CONFIG_KEXEC_CORE
 108 static ssize_t kexec_loaded_show(struct kobject *kobj,
 109                                  struct kobj_attribute *attr, char *buf)
 110 {
 111         return sprintf(buf, "%d\n", !!kexec_image);
 112 }
 113 KERNEL_ATTR_RO(kexec_loaded);
 114
 115 static ssize_t kexec_crash_loaded_show(struct kobject *kobj,
 116                                        struct kobj_attribute *attr, char *buf)
 117 {
 118         return sprintf(buf, "%d\n", kexec_crash_loaded());
 119 }
 120 KERNEL_ATTR_RO(kexec_crash_loaded);
 121
 122 static ssize_t kexec_crash_size_show(struct kobject *kobj,
 123                                        struct kobj_attribute *attr, char *buf)
 124 {
 125         ssize_t size = crash_get_memory_size();
 126
 127         if (size < 0)
 128                 return size;
 129
 130         return sprintf(buf, "%zd\n", size);
 131 }
 132 static ssize_t kexec_crash_size_store(struct kobject *kobj,
 133                                    struct kobj_attribute *attr,
 134                                    const char *buf, size_t count)
 135 {
 136         unsigned long cnt;
 137         int ret;
 138
 139         if (kstrtoul(buf, 0, &cnt))
 140                 return -EINVAL;
 141
 142         ret = crash_shrink_memory(cnt);
 143         return ret < 0 ? ret : count;
 144 }
 145 KERNEL_ATTR_RW(kexec_crash_size);
 146
 147 #endif /* CONFIG_KEXEC_CORE */
 148
 149 #ifdef CONFIG_CRASH_CORE
 150
 151 static ssize_t vmcoreinfo_show(struct kobject *kobj,
 152                                struct kobj_attribute *attr, char *buf)
 153 {
 154         phys_addr_t vmcore_base = paddr_vmcoreinfo_note();
 155         return sprintf(buf, "%pa %x\n", &vmcore_base,
 156                         (unsigned int)VMCOREINFO_NOTE_SIZE);
 157 }
 158 KERNEL_ATTR_RO(vmcoreinfo);
 159
 160 #endif /* CONFIG_CRASH_CORE */
 161
 162 /* whether file capabilities are enabled */
 163 static ssize_t fscaps_show(struct kobject *kobj,
 164                                   struct kobj_attribute *attr, char *buf)
 165 {
 166         return sprintf(buf, "%d\n", file_caps_enabled);
 167 }
 168 KERNEL_ATTR_RO(fscaps);
 169
 170 #ifndef CONFIG_TINY_RCU
 171 int rcu_expedited;
 172 static ssize_t rcu_expedited_show(struct kobject *kobj,
 173                                   struct kobj_attribute *attr, char *buf)
 174 {
 175         return sprintf(buf, "%d\n", READ_ONCE(rcu_expedited));
 176 }
 177 static ssize_t rcu_expedited_store(struct kobject *kobj,
 178                                    struct kobj_attribute *attr,
 179                                    const char *buf, size_t count)
 180 {
 181         if (kstrtoint(buf, 0, &rcu_expedited))
 182                 return -EINVAL;
 183
 184         return count;
 185 }
 186 KERNEL_ATTR_RW(rcu_expedited);
 187
 188 int rcu_normal;
 189 static ssize_t rcu_normal_show(struct kobject *kobj,
 190                                struct kobj_attribute *attr, char *buf)
 191 {
 192         return sprintf(buf, "%d\n", READ_ONCE(rcu_normal));
 193 }
 194 static ssize_t rcu_normal_store(struct kobject *kobj,
 195                                 struct kobj_attribute *attr,
 196                                 const char *buf, size_t count)
 197 {
 198         if (kstrtoint(buf, 0, &rcu_normal))
 199                 return -EINVAL;
 200
 201         return count;
 202 }
 203 KERNEL_ATTR_RW(rcu_normal);
 204 #endif /* #ifndef CONFIG_TINY_RCU */
 205
 206 /*
 207  * Make /sys/kernel/notes give the raw contents of our kernel .notes section.
 208  */
 209 extern const void __start_notes __weak;
 210 extern const void __stop_notes __weak;
 211 #define notes_size (&__stop_notes - &__start_notes)
 212
 213 static ssize_t notes_read(struct file *filp, struct kobject *kobj,
 214                           struct bin_attribute *bin_attr,
 215                           char *buf, loff_t off, size_t count)
 216 {
 217         memcpy(buf, &__start_notes + off, count);
 218         return count;
 219 }
 220
 221 static struct bin_attribute notes_attr __ro_after_init  = {
 222         .attr = {
 223                 .name = "notes",
 224                 .mode = S_IRUGO,
 225         },
 226         .read = &notes_read,
 227 };
 228
 229 struct kobject *kernel_kobj;
 230 EXPORT_SYMBOL_GPL(kernel_kobj);
 231
 232 static struct attribute * kernel_attrs[] = {
 233         &fscaps_attr.attr,
 234         &uevent_seqnum_attr.attr,
 235         &cpu_byteorder_attr.attr,
 236 #ifdef CONFIG_UEVENT_HELPER
 237         &uevent_helper_attr.attr,
 238 #endif
 239 #ifdef CONFIG_PROFILING
 240         &profiling_attr.attr,
 241 #endif
 242 #ifdef CONFIG_KEXEC_CORE
 243         &kexec_loaded_attr.attr,
 244         &kexec_crash_loaded_attr.attr,
 245         &kexec_crash_size_attr.attr,
 246 #endif
 247 #ifdef CONFIG_CRASH_CORE
 248         &vmcoreinfo_attr.attr,
 249 #endif
 250 #ifndef CONFIG_TINY_RCU
 251         &rcu_expedited_attr.attr,
 252         &rcu_normal_attr.attr,
 253 #endif
 254         NULL
 255 };
 256
 257 static const struct attribute_group kernel_attr_group = {
 258         .attrs = kernel_attrs,
 259 };
 260
 261 static int __init ksysfs_init(void)
 262 {
 263         int error;
 264
 265         kernel_kobj = kobject_create_and_add("kernel", NULL);
 266         if (!kernel_kobj) {
 267                 error = -ENOMEM;
 268                 goto exit;
 269         }
 270         error = sysfs_create_group(kernel_kobj, &kernel_attr_group);
 271         if (error)
 272                 goto kset_exit;
 273
 274         if (notes_size > 0) {
 275                 notes_attr.size = notes_size;
 276                 error = sysfs_create_bin_file(kernel_kobj, &notes_attr);
 277                 if (error)
 278                         goto group_exit;
 279         }
 280
 281         return 0;
 282
 283 group_exit:
 284         sysfs_remove_group(kernel_kobj, &kernel_attr_group);
 285 kset_exit:
 286         kobject_put(kernel_kobj);
 287 exit:
 288         return error;
 289 }
 290
 291 core_initcall(ksysfs_init);