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(size: sizeof(*attr), GFP_KERNEL); |
61 | if (attr) { |
62 | attr->kp.symbol_name = kstrdup(s: sym, GFP_KERNEL); |
63 | if (!attr->kp.symbol_name) { |
64 | kfree(objp: 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, retv: 0); |
70 | INIT_LIST_HEAD(list: &attr->list); |
71 | } |
72 | return attr; |
73 | } |
74 | |
75 | static void fei_attr_free(struct fei_attr *attr) |
76 | { |
77 | if (attr) { |
78 | kfree(objp: attr->kp.symbol_name); |
79 | kfree(objp: 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: attr)) { |
120 | err = -ENOENT; |
121 | goto out; |
122 | } |
123 | |
124 | if (attr->kp.addr) { |
125 | if (adjust_error_retval(addr: (unsigned long)attr->kp.addr, |
126 | retv: val) != retv) |
127 | err = -EINVAL; |
128 | } |
129 | if (!err) |
130 | attr->retval = val; |
131 | out: |
132 | mutex_unlock(lock: &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: attr)) |
145 | err = -ENOENT; |
146 | else |
147 | *val = attr->retval; |
148 | mutex_unlock(lock: &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(name: attr->kp.symbol_name, parent: fei_debugfs_dir); |
160 | |
161 | debugfs_create_file(name: "retval" , mode: 0600, parent: dir, data: attr, fops: &fei_retval_ops); |
162 | } |
163 | |
164 | static void fei_debugfs_remove_attr(struct fei_attr *attr) |
165 | { |
166 | debugfs_lookup_and_remove(name: attr->kp.symbol_name, parent: 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(attr: &fei_fault_attr, size: 1)) { |
174 | regs_set_return_value(regs, rc: 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(head: &fei_attr_list, pos: *pos); |
187 | } |
188 | |
189 | static void fei_seq_stop(struct seq_file *m, void *v) |
190 | { |
191 | mutex_unlock(lock: &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, head: &fei_attr_list, ppos: 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, fmt: "%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(p: &attr->kp); |
223 | list_del(entry: &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(ptr: buf)) |
250 | return PTR_ERR(ptr: buf); |
251 | |
252 | sym = strstrip(str: 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: 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(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(p: &attr->kp); |
294 | if (ret) { |
295 | fei_attr_free(attr); |
296 | goto out; |
297 | } |
298 | fei_debugfs_add_attr(attr); |
299 | list_add_tail(new: &attr->list, head: &fei_attr_list); |
300 | ret = count; |
301 | out: |
302 | mutex_unlock(lock: &fei_lock); |
303 | kfree(objp: 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(name: "fail_function" , NULL, |
320 | attr: &fei_fault_attr); |
321 | if (IS_ERR(ptr: dir)) |
322 | return PTR_ERR(ptr: dir); |
323 | |
324 | /* injectable attribute is just a symlink of error_inject/list */ |
325 | debugfs_create_symlink(name: "injectable" , parent: dir, dest: "../error_injection/list" ); |
326 | |
327 | debugfs_create_file(name: "inject" , mode: 0600, parent: dir, NULL, fops: &fei_ops); |
328 | |
329 | fei_debugfs_dir = dir; |
330 | |
331 | return 0; |
332 | } |
333 | |
334 | late_initcall(fei_debugfs_init); |
335 | |