lib/error-inject.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 // error-inject.c: Function-level error injection table
   3 #include <linux/error-injection.h>
   4 #include <linux/debugfs.h>
   5 #include <linux/kallsyms.h>
   6 #include <linux/kprobes.h>
   7 #include <linux/module.h>
   8 #include <linux/mutex.h>
   9 #include <linux/list.h>
  10 #include <linux/slab.h>
  11
  12 /* Whitelist of symbols that can be overridden for error injection. */
  13 static LIST_HEAD(error_injection_list);
  14 static DEFINE_MUTEX(ei_mutex);
  15 struct ei_entry {
  16         struct list_head list;
  17         unsigned long start_addr;
  18         unsigned long end_addr;
  19         int etype;
  20         void *priv;
  21 };
  22
  23 bool within_error_injection_list(unsigned long addr)
  24 {
  25         struct ei_entry *ent;
  26         bool ret = false;
  27
  28         mutex_lock(&ei_mutex);
  29         list_for_each_entry(ent, &error_injection_list, list) {
  30                 if (addr >= ent->start_addr && addr < ent->end_addr) {
  31                         ret = true;
  32                         break;
  33                 }
  34         }
  35         mutex_unlock(&ei_mutex);
  36         return ret;
  37 }
  38
  39 int get_injectable_error_type(unsigned long addr)
  40 {
  41         struct ei_entry *ent;
  42
  43         list_for_each_entry(ent, &error_injection_list, list) {
  44                 if (addr >= ent->start_addr && addr < ent->end_addr)
  45                         return ent->etype;
  46         }
  47         return EI_ETYPE_NONE;
  48 }
  49
  50 /*
  51  * Lookup and populate the error_injection_list.
  52  *
  53  * For safety reasons we only allow certain functions to be overridden with
  54  * bpf_error_injection, so we need to populate the list of the symbols that have
  55  * been marked as safe for overriding.
  56  */
  57 static void populate_error_injection_list(struct error_injection_entry *start,
  58                                           struct error_injection_entry *end,
  59                                           void *priv)
  60 {
  61         struct error_injection_entry *iter;
  62         struct ei_entry *ent;
  63         unsigned long entry, offset = 0, size = 0;
  64
  65         mutex_lock(&ei_mutex);
  66         for (iter = start; iter < end; iter++) {
  67                 entry = arch_deref_entry_point((void *)iter->addr);
  68
  69                 if (!kernel_text_address(entry) ||
  70                     !kallsyms_lookup_size_offset(entry, &size, &offset)) {
  71                         pr_err("Failed to find error inject entry at %p\n",
  72                                 (void *)entry);
  73                         continue;
  74                 }
  75
  76                 ent = kmalloc(sizeof(*ent), GFP_KERNEL);
  77                 if (!ent)
  78                         break;
  79                 ent->start_addr = entry;
  80                 ent->end_addr = entry + size;
  81                 ent->etype = iter->etype;
  82                 ent->priv = priv;
  83                 INIT_LIST_HEAD(&ent->list);
  84                 list_add_tail(&ent->list, &error_injection_list);
  85         }
  86         mutex_unlock(&ei_mutex);
  87 }
  88
  89 /* Markers of the _error_inject_whitelist section */
  90 extern struct error_injection_entry __start_error_injection_whitelist[];
  91 extern struct error_injection_entry __stop_error_injection_whitelist[];
  92
  93 static void __init populate_kernel_ei_list(void)
  94 {
  95         populate_error_injection_list(__start_error_injection_whitelist,
  96                                       __stop_error_injection_whitelist,
  97                                       NULL);
  98 }
  99
 100 #ifdef CONFIG_MODULES
 101 static void module_load_ei_list(struct module *mod)
 102 {
 103         if (!mod->num_ei_funcs)
 104                 return;
 105
 106         populate_error_injection_list(mod->ei_funcs,
 107                                       mod->ei_funcs + mod->num_ei_funcs, mod);
 108 }
 109
 110 static void module_unload_ei_list(struct module *mod)
 111 {
 112         struct ei_entry *ent, *n;
 113
 114         if (!mod->num_ei_funcs)
 115                 return;
 116
 117         mutex_lock(&ei_mutex);
 118         list_for_each_entry_safe(ent, n, &error_injection_list, list) {
 119                 if (ent->priv == mod) {
 120                         list_del_init(&ent->list);
 121                         kfree(ent);
 122                 }
 123         }
 124         mutex_unlock(&ei_mutex);
 125 }
 126
 127 /* Module notifier call back, checking error injection table on the module */
 128 static int ei_module_callback(struct notifier_block *nb,
 129                               unsigned long val, void *data)
 130 {
 131         struct module *mod = data;
 132
 133         if (val == MODULE_STATE_COMING)
 134                 module_load_ei_list(mod);
 135         else if (val == MODULE_STATE_GOING)
 136                 module_unload_ei_list(mod);
 137
 138         return NOTIFY_DONE;
 139 }
 140
 141 static struct notifier_block ei_module_nb = {
 142         .notifier_call = ei_module_callback,
 143         .priority = 0
 144 };
 145
 146 static __init int module_ei_init(void)
 147 {
 148         return register_module_notifier(&ei_module_nb);
 149 }
 150 #else /* !CONFIG_MODULES */
 151 #define module_ei_init()        (0)
 152 #endif
 153
 154 /*
 155  * error_injection/whitelist -- shows which functions can be overridden for
 156  * error injection.
 157  */
 158 static void *ei_seq_start(struct seq_file *m, loff_t *pos)
 159 {
 160         mutex_lock(&ei_mutex);
 161         return seq_list_start(&error_injection_list, *pos);
 162 }
 163
 164 static void ei_seq_stop(struct seq_file *m, void *v)
 165 {
 166         mutex_unlock(&ei_mutex);
 167 }
 168
 169 static void *ei_seq_next(struct seq_file *m, void *v, loff_t *pos)
 170 {
 171         return seq_list_next(v, &error_injection_list, pos);
 172 }
 173
 174 static const char *error_type_string(int etype)
 175 {
 176         switch (etype) {
 177         case EI_ETYPE_NULL:
 178                 return "NULL";
 179         case EI_ETYPE_ERRNO:
 180                 return "ERRNO";
 181         case EI_ETYPE_ERRNO_NULL:
 182                 return "ERRNO_NULL";
 183         default:
 184                 return "(unknown)";
 185         }
 186 }
 187
 188 static int ei_seq_show(struct seq_file *m, void *v)
 189 {
 190         struct ei_entry *ent = list_entry(v, struct ei_entry, list);
 191
 192         seq_printf(m, "%pf\t%s\n", (void *)ent->start_addr,
 193                    error_type_string(ent->etype));
 194         return 0;
 195 }
 196
 197 static const struct seq_operations ei_seq_ops = {
 198         .start = ei_seq_start,
 199         .next  = ei_seq_next,
 200         .stop  = ei_seq_stop,
 201         .show  = ei_seq_show,
 202 };
 203
 204 static int ei_open(struct inode *inode, struct file *filp)
 205 {
 206         return seq_open(filp, &ei_seq_ops);
 207 }
 208
 209 static const struct file_operations debugfs_ei_ops = {
 210         .open           = ei_open,
 211         .read           = seq_read,
 212         .llseek         = seq_lseek,
 213         .release        = seq_release,
 214 };
 215
 216 static int __init ei_debugfs_init(void)
 217 {
 218         struct dentry *dir, *file;
 219
 220         dir = debugfs_create_dir("error_injection", NULL);
 221         if (!dir)
 222                 return -ENOMEM;
 223
 224         file = debugfs_create_file("list", 0444, dir, NULL, &debugfs_ei_ops);
 225         if (!file) {
 226                 debugfs_remove(dir);
 227                 return -ENOMEM;
 228         }
 229
 230         return 0;
 231 }
 232
 233 static int __init init_error_injection(void)
 234 {
 235         populate_kernel_ei_list();
 236
 237         if (!module_ei_init())
 238                 ei_debugfs_init();
 239
 240         return 0;
 241 }
 242 late_initcall(init_error_injection);