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Linux/lib/error-inject.c

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  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, "%ps\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);
243 

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