projects/linux·blob v4.16-rc4 · refs

349 lines · 7.0 KiB

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
15static int fei_kprobe_handler(struct kprobe *kp, struct pt_regs *regs);
16
17struct fei_attr {
18 struct list_head list;
19 struct kprobe kp;
20 unsigned long retval;
21};
22static DEFINE_MUTEX(fei_lock);
23static LIST_HEAD(fei_attr_list);
24static DECLARE_FAULT_ATTR(fei_fault_attr);
25static struct dentry *fei_debugfs_dir;
26
27static 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
47static 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
65static void fei_attr_free(struct fei_attr *attr)
66{
67 if (attr) {
68 kfree(attr->kp.symbol_name);
69 kfree(attr);
70 }
71}
72
73static 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
85static 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
97static 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;
121out:
122 mutex_unlock(&fei_lock);
123
124 return err;
125}
126
127static 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}
142DEFINE_DEBUGFS_ATTRIBUTE(fei_retval_ops, fei_retval_get, fei_retval_set,
143 "%llx\n");
144
145static 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
161static 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
170static 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}
185NOKPROBE_SYMBOL(fei_kprobe_handler)
186
187static 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
193static void fei_seq_stop(struct seq_file *m, void *v)
194{
195 mutex_unlock(&fei_lock);
196}
197
198static 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
203static 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
211static 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
218static int fei_open(struct inode *inode, struct file *file)
219{
220 return seq_open(file, &fei_seq_ops);
221}
222
223static 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
231static 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
240static 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 }
310out:
311 kfree(buf);
312 mutex_unlock(&fei_lock);
313 return ret;
314}
315
316static 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
324static 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;
344error:
345 debugfs_remove_recursive(dir);
346 return -ENOMEM;
347}
348
349late_initcall(fei_debugfs_init);