1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * fail_function.c: Function-based error injection 4 */ 5 #include <linux/error-injection.h> 6 #include <linux/debugfs.h> 7 #include <linux/fault-inject.h> 8 #include <linux/kallsyms.h> 9 #include <linux/kprobes.h> 10 #include <linux/module.h> 11 #include <linux/mutex.h> 12 #include <linux/slab.h> 13 #include <linux/uaccess.h> 14 15 static int fei_kprobe_handler(struct kprobe *kp, struct pt_regs *regs); 16 17 static void fei_post_handler(struct kprobe *kp, struct pt_regs *regs, 18 unsigned long flags) 19 { 20 /* 21 * A dummy post handler is required to prohibit optimizing, because 22 * jump optimization does not support execution path overriding. 23 */ 24 } 25 26 struct fei_attr { 27 struct list_head list; 28 struct kprobe kp; 29 unsigned long retval; 30 }; 31 static DEFINE_MUTEX(fei_lock); 32 static LIST_HEAD(fei_attr_list); 33 static DECLARE_FAULT_ATTR(fei_fault_attr); 34 static struct dentry *fei_debugfs_dir; 35 36 static unsigned long adjust_error_retval(unsigned long addr, unsigned long retv) 37 { 38 switch (get_injectable_error_type(addr)) { 39 case EI_ETYPE_NULL: 40 if (retv != 0) 41 return 0; 42 break; 43 case EI_ETYPE_ERRNO: 44 if (retv < (unsigned long)-MAX_ERRNO) 45 return (unsigned long)-EINVAL; 46 break; 47 case EI_ETYPE_ERRNO_NULL: 48 if (retv != 0 && retv < (unsigned long)-MAX_ERRNO) 49 return (unsigned long)-EINVAL; 50 break; 51 } 52 53 return retv; 54 } 55 56 static struct fei_attr *fei_attr_new(const char *sym, unsigned long addr) 57 { 58 struct fei_attr *attr; 59 60 attr = kzalloc(sizeof(*attr), GFP_KERNEL); 61 if (attr) { 62 attr->kp.symbol_name = kstrdup(sym, GFP_KERNEL); 63 if (!attr->kp.symbol_name) { 64 kfree(attr); 65 return NULL; 66 } 67 attr->kp.pre_handler = fei_kprobe_handler; 68 attr->kp.post_handler = fei_post_handler; 69 attr->retval = adjust_error_retval(addr, 0); 70 INIT_LIST_HEAD(&attr->list); 71 } 72 return attr; 73 } 74 75 static void fei_attr_free(struct fei_attr *attr) 76 { 77 if (attr) { 78 kfree(attr->kp.symbol_name); 79 kfree(attr); 80 } 81 } 82 83 static struct fei_attr *fei_attr_lookup(const char *sym) 84 { 85 struct fei_attr *attr; 86 87 list_for_each_entry(attr, &fei_attr_list, list) { 88 if (!strcmp(attr->kp.symbol_name, sym)) 89 return attr; 90 } 91 92 return NULL; 93 } 94 95 static bool fei_attr_is_valid(struct fei_attr *_attr) 96 { 97 struct fei_attr *attr; 98 99 list_for_each_entry(attr, &fei_attr_list, list) { 100 if (attr == _attr) 101 return true; 102 } 103 104 return false; 105 } 106 107 static int fei_retval_set(void *data, u64 val) 108 { 109 struct fei_attr *attr = data; 110 unsigned long retv = (unsigned long)val; 111 int err = 0; 112 113 mutex_lock(&fei_lock); 114 /* 115 * Since this operation can be done after retval file is removed, 116 * It is safer to check the attr is still valid before accessing 117 * its member. 118 */ 119 if (!fei_attr_is_valid(attr)) { 120 err = -ENOENT; 121 goto out; 122 } 123 124 if (attr->kp.addr) { 125 if (adjust_error_retval((unsigned long)attr->kp.addr, 126 val) != retv) 127 err = -EINVAL; 128 } 129 if (!err) 130 attr->retval = val; 131 out: 132 mutex_unlock(&fei_lock); 133 134 return err; 135 } 136 137 static int fei_retval_get(void *data, u64 *val) 138 { 139 struct fei_attr *attr = data; 140 int err = 0; 141 142 mutex_lock(&fei_lock); 143 /* Here we also validate @attr to ensure it still exists. */ 144 if (!fei_attr_is_valid(attr)) 145 err = -ENOENT; 146 else 147 *val = attr->retval; 148 mutex_unlock(&fei_lock); 149 150 return err; 151 } 152 DEFINE_DEBUGFS_ATTRIBUTE(fei_retval_ops, fei_retval_get, fei_retval_set, 153 "%llx\n"); 154 155 static void fei_debugfs_add_attr(struct fei_attr *attr) 156 { 157 struct dentry *dir; 158 159 dir = debugfs_create_dir(attr->kp.symbol_name, fei_debugfs_dir); 160 161 debugfs_create_file("retval", 0600, dir, attr, &fei_retval_ops); 162 } 163 164 static void fei_debugfs_remove_attr(struct fei_attr *attr) 165 { 166 struct dentry *dir; 167 168 dir = debugfs_lookup(attr->kp.symbol_name, fei_debugfs_dir); 169 debugfs_remove_recursive(dir); 170 } 171 172 static int fei_kprobe_handler(struct kprobe *kp, struct pt_regs *regs) 173 { 174 struct fei_attr *attr = container_of(kp, struct fei_attr, kp); 175 176 if (should_fail(&fei_fault_attr, 1)) { 177 regs_set_return_value(regs, attr->retval); 178 override_function_with_return(regs); 179 return 1; 180 } 181 182 return 0; 183 } 184 NOKPROBE_SYMBOL(fei_kprobe_handler) 185 186 static void *fei_seq_start(struct seq_file *m, loff_t *pos) 187 { 188 mutex_lock(&fei_lock); 189 return seq_list_start(&fei_attr_list, *pos); 190 } 191 192 static void fei_seq_stop(struct seq_file *m, void *v) 193 { 194 mutex_unlock(&fei_lock); 195 } 196 197 static void *fei_seq_next(struct seq_file *m, void *v, loff_t *pos) 198 { 199 return seq_list_next(v, &fei_attr_list, pos); 200 } 201 202 static int fei_seq_show(struct seq_file *m, void *v) 203 { 204 struct fei_attr *attr = list_entry(v, struct fei_attr, list); 205 206 seq_printf(m, "%ps\n", attr->kp.addr); 207 return 0; 208 } 209 210 static const struct seq_operations fei_seq_ops = { 211 .start = fei_seq_start, 212 .next = fei_seq_next, 213 .stop = fei_seq_stop, 214 .show = fei_seq_show, 215 }; 216 217 static int fei_open(struct inode *inode, struct file *file) 218 { 219 return seq_open(file, &fei_seq_ops); 220 } 221 222 static void fei_attr_remove(struct fei_attr *attr) 223 { 224 fei_debugfs_remove_attr(attr); 225 unregister_kprobe(&attr->kp); 226 list_del(&attr->list); 227 fei_attr_free(attr); 228 } 229 230 static void fei_attr_remove_all(void) 231 { 232 struct fei_attr *attr, *n; 233 234 list_for_each_entry_safe(attr, n, &fei_attr_list, list) { 235 fei_attr_remove(attr); 236 } 237 } 238 239 static ssize_t fei_write(struct file *file, const char __user *buffer, 240 size_t count, loff_t *ppos) 241 { 242 struct fei_attr *attr; 243 unsigned long addr; 244 char *buf, *sym; 245 int ret; 246 247 /* cut off if it is too long */ 248 if (count > KSYM_NAME_LEN) 249 count = KSYM_NAME_LEN; 250 buf = kmalloc(count + 1, GFP_KERNEL); 251 if (!buf) 252 return -ENOMEM; 253 254 if (copy_from_user(buf, buffer, count)) { 255 ret = -EFAULT; 256 goto out; 257 } 258 buf[count] = '\0'; 259 sym = strstrip(buf); 260 261 mutex_lock(&fei_lock); 262 263 /* Writing just spaces will remove all injection points */ 264 if (sym[0] == '\0') { 265 fei_attr_remove_all(); 266 ret = count; 267 goto out; 268 } 269 /* Writing !function will remove one injection point */ 270 if (sym[0] == '!') { 271 attr = fei_attr_lookup(sym + 1); 272 if (!attr) { 273 ret = -ENOENT; 274 goto out; 275 } 276 fei_attr_remove(attr); 277 ret = count; 278 goto out; 279 } 280 281 addr = kallsyms_lookup_name(sym); 282 if (!addr) { 283 ret = -EINVAL; 284 goto out; 285 } 286 if (!within_error_injection_list(addr)) { 287 ret = -ERANGE; 288 goto out; 289 } 290 if (fei_attr_lookup(sym)) { 291 ret = -EBUSY; 292 goto out; 293 } 294 attr = fei_attr_new(sym, addr); 295 if (!attr) { 296 ret = -ENOMEM; 297 goto out; 298 } 299 300 ret = register_kprobe(&attr->kp); 301 if (!ret) 302 fei_debugfs_add_attr(attr); 303 if (ret < 0) 304 fei_attr_remove(attr); 305 else { 306 list_add_tail(&attr->list, &fei_attr_list); 307 ret = count; 308 } 309 out: 310 kfree(buf); 311 mutex_unlock(&fei_lock); 312 return ret; 313 } 314 315 static const struct file_operations fei_ops = { 316 .open = fei_open, 317 .read = seq_read, 318 .write = fei_write, 319 .llseek = seq_lseek, 320 .release = seq_release, 321 }; 322 323 static int __init fei_debugfs_init(void) 324 { 325 struct dentry *dir; 326 327 dir = fault_create_debugfs_attr("fail_function", NULL, 328 &fei_fault_attr); 329 if (IS_ERR(dir)) 330 return PTR_ERR(dir); 331 332 /* injectable attribute is just a symlink of error_inject/list */ 333 debugfs_create_symlink("injectable", dir, "../error_injection/list"); 334 335 debugfs_create_file("inject", 0600, dir, NULL, &fei_ops); 336 337 fei_debugfs_dir = dir; 338 339 return 0; 340 } 341 342 late_initcall(fei_debugfs_init); 343