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 return 0; 41 case EI_ETYPE_ERRNO: 42 if (retv < (unsigned long)-MAX_ERRNO) 43 return (unsigned long)-EINVAL; 44 break; 45 case EI_ETYPE_ERRNO_NULL: 46 if (retv != 0 && retv < (unsigned long)-MAX_ERRNO) 47 return (unsigned long)-EINVAL; 48 break; 49 case EI_ETYPE_TRUE: 50 return 1; 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 debugfs_lookup_and_remove(attr->kp.symbol_name, fei_debugfs_dir); 167 } 168 169 static int fei_kprobe_handler(struct kprobe *kp, struct pt_regs *regs) 170 { 171 struct fei_attr *attr = container_of(kp, struct fei_attr, kp); 172 173 if (should_fail(&fei_fault_attr, 1)) { 174 regs_set_return_value(regs, attr->retval); 175 override_function_with_return(regs); 176 return 1; 177 } 178 179 return 0; 180 } 181 NOKPROBE_SYMBOL(fei_kprobe_handler) 182 183 static void *fei_seq_start(struct seq_file *m, loff_t *pos) 184 { 185 mutex_lock(&fei_lock); 186 return seq_list_start(&fei_attr_list, *pos); 187 } 188 189 static void fei_seq_stop(struct seq_file *m, void *v) 190 { 191 mutex_unlock(&fei_lock); 192 } 193 194 static void *fei_seq_next(struct seq_file *m, void *v, loff_t *pos) 195 { 196 return seq_list_next(v, &fei_attr_list, pos); 197 } 198 199 static int fei_seq_show(struct seq_file *m, void *v) 200 { 201 struct fei_attr *attr = list_entry(v, struct fei_attr, list); 202 203 seq_printf(m, "%ps\n", attr->kp.addr); 204 return 0; 205 } 206 207 static const struct seq_operations fei_seq_ops = { 208 .start = fei_seq_start, 209 .next = fei_seq_next, 210 .stop = fei_seq_stop, 211 .show = fei_seq_show, 212 }; 213 214 static int fei_open(struct inode *inode, struct file *file) 215 { 216 return seq_open(file, &fei_seq_ops); 217 } 218 219 static void fei_attr_remove(struct fei_attr *attr) 220 { 221 fei_debugfs_remove_attr(attr); 222 unregister_kprobe(&attr->kp); 223 list_del(&attr->list); 224 fei_attr_free(attr); 225 } 226 227 static void fei_attr_remove_all(void) 228 { 229 struct fei_attr *attr, *n; 230 231 list_for_each_entry_safe(attr, n, &fei_attr_list, list) { 232 fei_attr_remove(attr); 233 } 234 } 235 236 static ssize_t fei_write(struct file *file, const char __user *buffer, 237 size_t count, loff_t *ppos) 238 { 239 struct fei_attr *attr; 240 unsigned long addr; 241 char *buf, *sym; 242 int ret; 243 244 /* cut off if it is too long */ 245 if (count > KSYM_NAME_LEN) 246 count = KSYM_NAME_LEN; 247 248 buf = memdup_user_nul(buffer, count); 249 if (IS_ERR(buf)) 250 return PTR_ERR(buf); 251 252 sym = strstrip(buf); 253 254 mutex_lock(&fei_lock); 255 256 /* Writing just spaces will remove all injection points */ 257 if (sym[0] == '\0') { 258 fei_attr_remove_all(); 259 ret = count; 260 goto out; 261 } 262 /* Writing !function will remove one injection point */ 263 if (sym[0] == '!') { 264 attr = fei_attr_lookup(sym + 1); 265 if (!attr) { 266 ret = -ENOENT; 267 goto out; 268 } 269 fei_attr_remove(attr); 270 ret = count; 271 goto out; 272 } 273 274 addr = kallsyms_lookup_name(sym); 275 if (!addr) { 276 ret = -EINVAL; 277 goto out; 278 } 279 if (!within_error_injection_list(addr)) { 280 ret = -ERANGE; 281 goto out; 282 } 283 if (fei_attr_lookup(sym)) { 284 ret = -EBUSY; 285 goto out; 286 } 287 attr = fei_attr_new(sym, addr); 288 if (!attr) { 289 ret = -ENOMEM; 290 goto out; 291 } 292 293 ret = register_kprobe(&attr->kp); 294 if (ret) { 295 fei_attr_free(attr); 296 goto out; 297 } 298 fei_debugfs_add_attr(attr); 299 list_add_tail(&attr->list, &fei_attr_list); 300 ret = count; 301 out: 302 mutex_unlock(&fei_lock); 303 kfree(buf); 304 return ret; 305 } 306 307 static const struct file_operations fei_ops = { 308 .open = fei_open, 309 .read = seq_read, 310 .write = fei_write, 311 .llseek = seq_lseek, 312 .release = seq_release, 313 }; 314 315 static int __init fei_debugfs_init(void) 316 { 317 struct dentry *dir; 318 319 dir = fault_create_debugfs_attr("fail_function", NULL, 320 &fei_fault_attr); 321 if (IS_ERR(dir)) 322 return PTR_ERR(dir); 323 324 /* injectable attribute is just a symlink of error_inject/list */ 325 debugfs_create_symlink("injectable", dir, "../error_injection/list"); 326 327 debugfs_create_file("inject", 0600, dir, NULL, &fei_ops); 328 329 fei_debugfs_dir = dir; 330 331 return 0; 332 } 333 334 late_initcall(fei_debugfs_init); 335