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 <linux/kobject.h>
  10 #include <linux/string.h>
  11 #include <linux/sysfs.h>
  12 #include <linux/export.h>
  13 #include <linux/init.h>
  14 #include <linux/kexec.h>
  15 #include <linux/profile.h>
  16 #include <linux/stat.h>
  17 #include <linux/sched.h>
  18 #include <linux/capability.h>
  19 #include <linux/compiler.h>
  20
  21 #include <linux/rcupdate.h>     /* rcu_expedited and rcu_normal */
  22
  23 #define KERNEL_ATTR_RO(_name) \
  24 static struct kobj_attribute _name##_attr = __ATTR_RO(_name)
  25
  26 #define KERNEL_ATTR_RW(_name) \
  27 static struct kobj_attribute _name##_attr = \
  28         __ATTR(_name, 0644, _name##_show, _name##_store)
  29
  30 /* current uevent sequence number */
  31 static ssize_t uevent_seqnum_show(struct kobject *kobj,
  32                                   struct kobj_attribute *attr, char *buf)
  33 {
  34         return sprintf(buf, "%llu\n", (unsigned long long)uevent_seqnum);
  35 }
  36 KERNEL_ATTR_RO(uevent_seqnum);
  37
  38 #ifdef CONFIG_UEVENT_HELPER
  39 /* uevent helper program, used during early boot */
  40 static ssize_t uevent_helper_show(struct kobject *kobj,
  41                                   struct kobj_attribute *attr, char *buf)
  42 {
  43         return sprintf(buf, "%s\n", uevent_helper);
  44 }
  45 static ssize_t uevent_helper_store(struct kobject *kobj,
  46                                    struct kobj_attribute *attr,
  47                                    const char *buf, size_t count)
  48 {
  49         if (count+1 > UEVENT_HELPER_PATH_LEN)
  50                 return -ENOENT;
  51         memcpy(uevent_helper, buf, count);
  52         uevent_helper[count] = '\0';
  53         if (count && uevent_helper[count-1] == '\n')
  54                 uevent_helper[count-1] = '\0';
  55         return count;
  56 }
  57 KERNEL_ATTR_RW(uevent_helper);
  58 #endif
  59
  60 #ifdef CONFIG_PROFILING
  61 static ssize_t profiling_show(struct kobject *kobj,
  62                                   struct kobj_attribute *attr, char *buf)
  63 {
  64         return sprintf(buf, "%d\n", prof_on);
  65 }
  66 static ssize_t profiling_store(struct kobject *kobj,
  67                                    struct kobj_attribute *attr,
  68                                    const char *buf, size_t count)
  69 {
  70         int ret;
  71
  72         if (prof_on)
  73                 return -EEXIST;
  74         /*
  75          * This eventually calls into get_option() which
  76          * has a ton of callers and is not const.  It is
  77          * easiest to cast it away here.
  78          */
  79         profile_setup((char *)buf);
  80         ret = profile_init();
  81         if (ret)
  82                 return ret;
  83         ret = create_proc_profile();
  84         if (ret)
  85                 return ret;
  86         return count;
  87 }
  88 KERNEL_ATTR_RW(profiling);
  89 #endif
  90
  91 #ifdef CONFIG_KEXEC_CORE
  92 static ssize_t kexec_loaded_show(struct kobject *kobj,
  93                                  struct kobj_attribute *attr, char *buf)
  94 {
  95         return sprintf(buf, "%d\n", !!kexec_image);
  96 }
  97 KERNEL_ATTR_RO(kexec_loaded);
  98
  99 static ssize_t kexec_crash_loaded_show(struct kobject *kobj,
 100                                        struct kobj_attribute *attr, char *buf)
 101 {
 102         return sprintf(buf, "%d\n", kexec_crash_loaded());
 103 }
 104 KERNEL_ATTR_RO(kexec_crash_loaded);
 105
 106 static ssize_t kexec_crash_size_show(struct kobject *kobj,
 107                                        struct kobj_attribute *attr, char *buf)
 108 {
 109         return sprintf(buf, "%zu\n", crash_get_memory_size());
 110 }
 111 static ssize_t kexec_crash_size_store(struct kobject *kobj,
 112                                    struct kobj_attribute *attr,
 113                                    const char *buf, size_t count)
 114 {
 115         unsigned long cnt;
 116         int ret;
 117
 118         if (kstrtoul(buf, 0, &cnt))
 119                 return -EINVAL;
 120
 121         ret = crash_shrink_memory(cnt);
 122         return ret < 0 ? ret : count;
 123 }
 124 KERNEL_ATTR_RW(kexec_crash_size);
 125
 126 #endif /* CONFIG_KEXEC_CORE */
 127
 128 #ifdef CONFIG_CRASH_CORE
 129
 130 static ssize_t vmcoreinfo_show(struct kobject *kobj,
 131                                struct kobj_attribute *attr, char *buf)
 132 {
 133         phys_addr_t vmcore_base = paddr_vmcoreinfo_note();
 134         return sprintf(buf, "%pa %x\n", &vmcore_base,
 135                         (unsigned int)VMCOREINFO_NOTE_SIZE);
 136 }
 137 KERNEL_ATTR_RO(vmcoreinfo);
 138
 139 #endif /* CONFIG_CRASH_CORE */
 140
 141 /* whether file capabilities are enabled */
 142 static ssize_t fscaps_show(struct kobject *kobj,
 143                                   struct kobj_attribute *attr, char *buf)
 144 {
 145         return sprintf(buf, "%d\n", file_caps_enabled);
 146 }
 147 KERNEL_ATTR_RO(fscaps);
 148
 149 #ifndef CONFIG_TINY_RCU
 150 int rcu_expedited;
 151 static ssize_t rcu_expedited_show(struct kobject *kobj,
 152                                   struct kobj_attribute *attr, char *buf)
 153 {
 154         return sprintf(buf, "%d\n", READ_ONCE(rcu_expedited));
 155 }
 156 static ssize_t rcu_expedited_store(struct kobject *kobj,
 157                                    struct kobj_attribute *attr,
 158                                    const char *buf, size_t count)
 159 {
 160         if (kstrtoint(buf, 0, &rcu_expedited))
 161                 return -EINVAL;
 162
 163         return count;
 164 }
 165 KERNEL_ATTR_RW(rcu_expedited);
 166
 167 int rcu_normal;
 168 static ssize_t rcu_normal_show(struct kobject *kobj,
 169                                struct kobj_attribute *attr, char *buf)
 170 {
 171         return sprintf(buf, "%d\n", READ_ONCE(rcu_normal));
 172 }
 173 static ssize_t rcu_normal_store(struct kobject *kobj,
 174                                 struct kobj_attribute *attr,
 175                                 const char *buf, size_t count)
 176 {
 177         if (kstrtoint(buf, 0, &rcu_normal))
 178                 return -EINVAL;
 179
 180         return count;
 181 }
 182 KERNEL_ATTR_RW(rcu_normal);
 183 #endif /* #ifndef CONFIG_TINY_RCU */
 184
 185 /*
 186  * Make /sys/kernel/notes give the raw contents of our kernel .notes section.
 187  */
 188 extern const void __start_notes __weak;
 189 extern const void __stop_notes __weak;
 190 #define notes_size (&__stop_notes - &__start_notes)
 191
 192 static ssize_t notes_read(struct file *filp, struct kobject *kobj,
 193                           struct bin_attribute *bin_attr,
 194                           char *buf, loff_t off, size_t count)
 195 {
 196         memcpy(buf, &__start_notes + off, count);
 197         return count;
 198 }
 199
 200 static struct bin_attribute notes_attr __ro_after_init  = {
 201         .attr = {
 202                 .name = "notes",
 203                 .mode = S_IRUGO,
 204         },
 205         .read = &notes_read,
 206 };
 207
 208 struct kobject *kernel_kobj;
 209 EXPORT_SYMBOL_GPL(kernel_kobj);
 210
 211 static struct attribute * kernel_attrs[] = {
 212         &fscaps_attr.attr,
 213         &uevent_seqnum_attr.attr,
 214 #ifdef CONFIG_UEVENT_HELPER
 215         &uevent_helper_attr.attr,
 216 #endif
 217 #ifdef CONFIG_PROFILING
 218         &profiling_attr.attr,
 219 #endif
 220 #ifdef CONFIG_KEXEC_CORE
 221         &kexec_loaded_attr.attr,
 222         &kexec_crash_loaded_attr.attr,
 223         &kexec_crash_size_attr.attr,
 224 #endif
 225 #ifdef CONFIG_CRASH_CORE
 226         &vmcoreinfo_attr.attr,
 227 #endif
 228 #ifndef CONFIG_TINY_RCU
 229         &rcu_expedited_attr.attr,
 230         &rcu_normal_attr.attr,
 231 #endif
 232         NULL
 233 };
 234
 235 static const struct attribute_group kernel_attr_group = {
 236         .attrs = kernel_attrs,
 237 };
 238
 239 static int __init ksysfs_init(void)
 240 {
 241         int error;
 242
 243         kernel_kobj = kobject_create_and_add("kernel", NULL);
 244         if (!kernel_kobj) {
 245                 error = -ENOMEM;
 246                 goto exit;
 247         }
 248         error = sysfs_create_group(kernel_kobj, &kernel_attr_group);
 249         if (error)
 250                 goto kset_exit;
 251
 252         if (notes_size > 0) {
 253                 notes_attr.size = notes_size;
 254                 error = sysfs_create_bin_file(kernel_kobj, &notes_attr);
 255                 if (error)
 256                         goto group_exit;
 257         }
 258
 259         return 0;
 260
 261 group_exit:
 262         sysfs_remove_group(kernel_kobj, &kernel_attr_group);
 263 kset_exit:
 264         kobject_put(kernel_kobj);
 265 exit:
 266         return error;
 267 }
 268
 269 core_initcall(ksysfs_init);