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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 | ||
b6b76dd6 MH |
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 | ||
4b1a29a7 MH |
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: | |
537cd894 | 40 | return 0; |
4b1a29a7 MH |
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; | |
537cd894 BP |
49 | case EI_ETYPE_TRUE: |
50 | return 1; | |
4b1a29a7 MH |
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; | |
b6b76dd6 | 68 | attr->kp.post_handler = fei_post_handler; |
4b1a29a7 MH |
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 | ||
4aa3b1f6 | 155 | static void fei_debugfs_add_attr(struct fei_attr *attr) |
4b1a29a7 MH |
156 | { |
157 | struct dentry *dir; | |
158 | ||
159 | dir = debugfs_create_dir(attr->kp.symbol_name, fei_debugfs_dir); | |
4b1a29a7 | 160 | |
4aa3b1f6 | 161 | debugfs_create_file("retval", 0600, dir, attr, &fei_retval_ops); |
4b1a29a7 MH |
162 | } |
163 | ||
164 | static void fei_debugfs_remove_attr(struct fei_attr *attr) | |
165 | { | |
2bb3669f | 166 | debugfs_lookup_and_remove(attr->kp.symbol_name, fei_debugfs_dir); |
4b1a29a7 MH |
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); | |
4b1a29a7 MH |
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 | ||
d75f773c | 203 | seq_printf(m, "%ps\n", attr->kp.addr); |
4b1a29a7 MH |
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; | |
4b1a29a7 | 247 | |
f81259c6 YY |
248 | buf = memdup_user_nul(buffer, count); |
249 | if (IS_ERR(buf)) | |
250 | return PTR_ERR(buf); | |
251 | ||
4b1a29a7 MH |
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); | |
cef9f5f8 | 294 | if (ret) { |
d2e85432 | 295 | fei_attr_free(attr); |
cef9f5f8 | 296 | goto out; |
4b1a29a7 | 297 | } |
cef9f5f8 YY |
298 | fei_debugfs_add_attr(attr); |
299 | list_add_tail(&attr->list, &fei_attr_list); | |
300 | ret = count; | |
4b1a29a7 | 301 | out: |
4b1a29a7 | 302 | mutex_unlock(&fei_lock); |
2801a5da | 303 | kfree(buf); |
4b1a29a7 MH |
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 */ | |
4aa3b1f6 | 325 | debugfs_create_symlink("injectable", dir, "../error_injection/list"); |
4b1a29a7 | 326 | |
4aa3b1f6 | 327 | debugfs_create_file("inject", 0600, dir, NULL, &fei_ops); |
4b1a29a7 MH |
328 | |
329 | fei_debugfs_dir = dir; | |
330 | ||
331 | return 0; | |
4b1a29a7 MH |
332 | } |
333 | ||
334 | late_initcall(fei_debugfs_init); |