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4b1a29a7 MH |
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 | struct fei_attr { | |
18 | struct list_head list; | |
19 | struct kprobe kp; | |
20 | unsigned long retval; | |
21 | }; | |
22 | static DEFINE_MUTEX(fei_lock); | |
23 | static LIST_HEAD(fei_attr_list); | |
24 | static DECLARE_FAULT_ATTR(fei_fault_attr); | |
25 | static struct dentry *fei_debugfs_dir; | |
26 | ||
27 | static unsigned long adjust_error_retval(unsigned long addr, unsigned long retv) | |
28 | { | |
29 | switch (get_injectable_error_type(addr)) { | |
30 | case EI_ETYPE_NULL: | |
31 | if (retv != 0) | |
32 | return 0; | |
33 | break; | |
34 | case EI_ETYPE_ERRNO: | |
35 | if (retv < (unsigned long)-MAX_ERRNO) | |
36 | return (unsigned long)-EINVAL; | |
37 | break; | |
38 | case EI_ETYPE_ERRNO_NULL: | |
39 | if (retv != 0 && retv < (unsigned long)-MAX_ERRNO) | |
40 | return (unsigned long)-EINVAL; | |
41 | break; | |
42 | } | |
43 | ||
44 | return retv; | |
45 | } | |
46 | ||
47 | static struct fei_attr *fei_attr_new(const char *sym, unsigned long addr) | |
48 | { | |
49 | struct fei_attr *attr; | |
50 | ||
51 | attr = kzalloc(sizeof(*attr), GFP_KERNEL); | |
52 | if (attr) { | |
53 | attr->kp.symbol_name = kstrdup(sym, GFP_KERNEL); | |
54 | if (!attr->kp.symbol_name) { | |
55 | kfree(attr); | |
56 | return NULL; | |
57 | } | |
58 | attr->kp.pre_handler = fei_kprobe_handler; | |
59 | attr->retval = adjust_error_retval(addr, 0); | |
60 | INIT_LIST_HEAD(&attr->list); | |
61 | } | |
62 | return attr; | |
63 | } | |
64 | ||
65 | static void fei_attr_free(struct fei_attr *attr) | |
66 | { | |
67 | if (attr) { | |
68 | kfree(attr->kp.symbol_name); | |
69 | kfree(attr); | |
70 | } | |
71 | } | |
72 | ||
73 | static struct fei_attr *fei_attr_lookup(const char *sym) | |
74 | { | |
75 | struct fei_attr *attr; | |
76 | ||
77 | list_for_each_entry(attr, &fei_attr_list, list) { | |
78 | if (!strcmp(attr->kp.symbol_name, sym)) | |
79 | return attr; | |
80 | } | |
81 | ||
82 | return NULL; | |
83 | } | |
84 | ||
85 | static bool fei_attr_is_valid(struct fei_attr *_attr) | |
86 | { | |
87 | struct fei_attr *attr; | |
88 | ||
89 | list_for_each_entry(attr, &fei_attr_list, list) { | |
90 | if (attr == _attr) | |
91 | return true; | |
92 | } | |
93 | ||
94 | return false; | |
95 | } | |
96 | ||
97 | static int fei_retval_set(void *data, u64 val) | |
98 | { | |
99 | struct fei_attr *attr = data; | |
100 | unsigned long retv = (unsigned long)val; | |
101 | int err = 0; | |
102 | ||
103 | mutex_lock(&fei_lock); | |
104 | /* | |
105 | * Since this operation can be done after retval file is removed, | |
106 | * It is safer to check the attr is still valid before accessing | |
107 | * its member. | |
108 | */ | |
109 | if (!fei_attr_is_valid(attr)) { | |
110 | err = -ENOENT; | |
111 | goto out; | |
112 | } | |
113 | ||
114 | if (attr->kp.addr) { | |
115 | if (adjust_error_retval((unsigned long)attr->kp.addr, | |
116 | val) != retv) | |
117 | err = -EINVAL; | |
118 | } | |
119 | if (!err) | |
120 | attr->retval = val; | |
121 | out: | |
122 | mutex_unlock(&fei_lock); | |
123 | ||
124 | return err; | |
125 | } | |
126 | ||
127 | static int fei_retval_get(void *data, u64 *val) | |
128 | { | |
129 | struct fei_attr *attr = data; | |
130 | int err = 0; | |
131 | ||
132 | mutex_lock(&fei_lock); | |
133 | /* Here we also validate @attr to ensure it still exists. */ | |
134 | if (!fei_attr_is_valid(attr)) | |
135 | err = -ENOENT; | |
136 | else | |
137 | *val = attr->retval; | |
138 | mutex_unlock(&fei_lock); | |
139 | ||
140 | return err; | |
141 | } | |
142 | DEFINE_DEBUGFS_ATTRIBUTE(fei_retval_ops, fei_retval_get, fei_retval_set, | |
143 | "%llx\n"); | |
144 | ||
145 | static int fei_debugfs_add_attr(struct fei_attr *attr) | |
146 | { | |
147 | struct dentry *dir; | |
148 | ||
149 | dir = debugfs_create_dir(attr->kp.symbol_name, fei_debugfs_dir); | |
150 | if (!dir) | |
151 | return -ENOMEM; | |
152 | ||
153 | if (!debugfs_create_file("retval", 0600, dir, attr, &fei_retval_ops)) { | |
154 | debugfs_remove_recursive(dir); | |
155 | return -ENOMEM; | |
156 | } | |
157 | ||
158 | return 0; | |
159 | } | |
160 | ||
161 | static void fei_debugfs_remove_attr(struct fei_attr *attr) | |
162 | { | |
163 | struct dentry *dir; | |
164 | ||
165 | dir = debugfs_lookup(attr->kp.symbol_name, fei_debugfs_dir); | |
166 | if (dir) | |
167 | debugfs_remove_recursive(dir); | |
168 | } | |
169 | ||
170 | static int fei_kprobe_handler(struct kprobe *kp, struct pt_regs *regs) | |
171 | { | |
172 | struct fei_attr *attr = container_of(kp, struct fei_attr, kp); | |
173 | ||
174 | if (should_fail(&fei_fault_attr, 1)) { | |
175 | regs_set_return_value(regs, attr->retval); | |
176 | override_function_with_return(regs); | |
177 | /* Kprobe specific fixup */ | |
178 | reset_current_kprobe(); | |
179 | preempt_enable_no_resched(); | |
180 | return 1; | |
181 | } | |
182 | ||
183 | return 0; | |
184 | } | |
185 | NOKPROBE_SYMBOL(fei_kprobe_handler) | |
186 | ||
187 | static void *fei_seq_start(struct seq_file *m, loff_t *pos) | |
188 | { | |
189 | mutex_lock(&fei_lock); | |
190 | return seq_list_start(&fei_attr_list, *pos); | |
191 | } | |
192 | ||
193 | static void fei_seq_stop(struct seq_file *m, void *v) | |
194 | { | |
195 | mutex_unlock(&fei_lock); | |
196 | } | |
197 | ||
198 | static void *fei_seq_next(struct seq_file *m, void *v, loff_t *pos) | |
199 | { | |
200 | return seq_list_next(v, &fei_attr_list, pos); | |
201 | } | |
202 | ||
203 | static int fei_seq_show(struct seq_file *m, void *v) | |
204 | { | |
205 | struct fei_attr *attr = list_entry(v, struct fei_attr, list); | |
206 | ||
207 | seq_printf(m, "%pf\n", attr->kp.addr); | |
208 | return 0; | |
209 | } | |
210 | ||
211 | static const struct seq_operations fei_seq_ops = { | |
212 | .start = fei_seq_start, | |
213 | .next = fei_seq_next, | |
214 | .stop = fei_seq_stop, | |
215 | .show = fei_seq_show, | |
216 | }; | |
217 | ||
218 | static int fei_open(struct inode *inode, struct file *file) | |
219 | { | |
220 | return seq_open(file, &fei_seq_ops); | |
221 | } | |
222 | ||
223 | static void fei_attr_remove(struct fei_attr *attr) | |
224 | { | |
225 | fei_debugfs_remove_attr(attr); | |
226 | unregister_kprobe(&attr->kp); | |
227 | list_del(&attr->list); | |
228 | fei_attr_free(attr); | |
229 | } | |
230 | ||
231 | static void fei_attr_remove_all(void) | |
232 | { | |
233 | struct fei_attr *attr, *n; | |
234 | ||
235 | list_for_each_entry_safe(attr, n, &fei_attr_list, list) { | |
236 | fei_attr_remove(attr); | |
237 | } | |
238 | } | |
239 | ||
240 | static ssize_t fei_write(struct file *file, const char __user *buffer, | |
241 | size_t count, loff_t *ppos) | |
242 | { | |
243 | struct fei_attr *attr; | |
244 | unsigned long addr; | |
245 | char *buf, *sym; | |
246 | int ret; | |
247 | ||
248 | /* cut off if it is too long */ | |
249 | if (count > KSYM_NAME_LEN) | |
250 | count = KSYM_NAME_LEN; | |
251 | buf = kmalloc(sizeof(char) * (count + 1), GFP_KERNEL); | |
252 | if (!buf) | |
253 | return -ENOMEM; | |
254 | ||
255 | if (copy_from_user(buf, buffer, count)) { | |
256 | ret = -EFAULT; | |
257 | goto out; | |
258 | } | |
259 | buf[count] = '\0'; | |
260 | sym = strstrip(buf); | |
261 | ||
262 | mutex_lock(&fei_lock); | |
263 | ||
264 | /* Writing just spaces will remove all injection points */ | |
265 | if (sym[0] == '\0') { | |
266 | fei_attr_remove_all(); | |
267 | ret = count; | |
268 | goto out; | |
269 | } | |
270 | /* Writing !function will remove one injection point */ | |
271 | if (sym[0] == '!') { | |
272 | attr = fei_attr_lookup(sym + 1); | |
273 | if (!attr) { | |
274 | ret = -ENOENT; | |
275 | goto out; | |
276 | } | |
277 | fei_attr_remove(attr); | |
278 | ret = count; | |
279 | goto out; | |
280 | } | |
281 | ||
282 | addr = kallsyms_lookup_name(sym); | |
283 | if (!addr) { | |
284 | ret = -EINVAL; | |
285 | goto out; | |
286 | } | |
287 | if (!within_error_injection_list(addr)) { | |
288 | ret = -ERANGE; | |
289 | goto out; | |
290 | } | |
291 | if (fei_attr_lookup(sym)) { | |
292 | ret = -EBUSY; | |
293 | goto out; | |
294 | } | |
295 | attr = fei_attr_new(sym, addr); | |
296 | if (!attr) { | |
297 | ret = -ENOMEM; | |
298 | goto out; | |
299 | } | |
300 | ||
301 | ret = register_kprobe(&attr->kp); | |
302 | if (!ret) | |
303 | ret = fei_debugfs_add_attr(attr); | |
304 | if (ret < 0) | |
305 | fei_attr_remove(attr); | |
306 | else { | |
307 | list_add_tail(&attr->list, &fei_attr_list); | |
308 | ret = count; | |
309 | } | |
310 | out: | |
311 | kfree(buf); | |
312 | mutex_unlock(&fei_lock); | |
313 | return ret; | |
314 | } | |
315 | ||
316 | static const struct file_operations fei_ops = { | |
317 | .open = fei_open, | |
318 | .read = seq_read, | |
319 | .write = fei_write, | |
320 | .llseek = seq_lseek, | |
321 | .release = seq_release, | |
322 | }; | |
323 | ||
324 | static int __init fei_debugfs_init(void) | |
325 | { | |
326 | struct dentry *dir; | |
327 | ||
328 | dir = fault_create_debugfs_attr("fail_function", NULL, | |
329 | &fei_fault_attr); | |
330 | if (IS_ERR(dir)) | |
331 | return PTR_ERR(dir); | |
332 | ||
333 | /* injectable attribute is just a symlink of error_inject/list */ | |
334 | if (!debugfs_create_symlink("injectable", dir, | |
335 | "../error_injection/list")) | |
336 | goto error; | |
337 | ||
338 | if (!debugfs_create_file("inject", 0600, dir, NULL, &fei_ops)) | |
339 | goto error; | |
340 | ||
341 | fei_debugfs_dir = dir; | |
342 | ||
343 | return 0; | |
344 | error: | |
345 | debugfs_remove_recursive(dir); | |
346 | return -ENOMEM; | |
347 | } | |
348 | ||
349 | late_initcall(fei_debugfs_init); |