1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * fprobe - Simple ftrace probe wrapper for function entry.
4 */
5 #define pr_fmt(fmt) "fprobe: " fmt
6
7 #include <linux/err.h>
8 #include <linux/fprobe.h>
9 #include <linux/kallsyms.h>
10 #include <linux/kprobes.h>
11 #include <linux/rethook.h>
12 #include <linux/slab.h>
13 #include <linux/sort.h>
14
15 #include "trace.h"
16
17 struct fprobe_rethook_node {
18 struct rethook_node node;
19 unsigned long entry_ip;
20 unsigned long entry_parent_ip;
21 char data[];
22 };
23
24 static inline void __fprobe_handler(unsigned long ip, unsigned long parent_ip,
25 struct ftrace_ops *ops, struct ftrace_regs *fregs)
26 {
27 struct fprobe_rethook_node *fpr;
28 struct rethook_node *rh = NULL;
29 struct fprobe *fp;
30 void *entry_data = NULL;
31 int ret = 0;
32
33 fp = container_of(ops, struct fprobe, ops);
34
35 if (fp->exit_handler) {
36 rh = rethook_try_get(fp->rethook);
37 if (!rh) {
38 fp->nmissed++;
39 return;
40 }
41 fpr = container_of(rh, struct fprobe_rethook_node, node);
42 fpr->entry_ip = ip;
43 fpr->entry_parent_ip = parent_ip;
44 if (fp->entry_data_size)
45 entry_data = fpr->data;
46 }
47
48 if (fp->entry_handler)
49 ret = fp->entry_handler(fp, ip, parent_ip, ftrace_get_regs(fregs), entry_data);
50
51 /* If entry_handler returns !0, nmissed is not counted. */
52 if (rh) {
53 if (ret)
54 rethook_recycle(rh);
55 else
56 rethook_hook(rh, ftrace_get_regs(fregs), true);
57 }
58 }
59
60 static void fprobe_handler(unsigned long ip, unsigned long parent_ip,
61 struct ftrace_ops *ops, struct ftrace_regs *fregs)
62 {
63 struct fprobe *fp;
64 int bit;
65
66 fp = container_of(ops, struct fprobe, ops);
67 if (fprobe_disabled(fp))
68 return;
69
70 /* recursion detection has to go before any traceable function and
71 * all functions before this point should be marked as notrace
72 */
73 bit = ftrace_test_recursion_trylock(ip, parent_ip);
74 if (bit < 0) {
75 fp->nmissed++;
76 return;
77 }
78 __fprobe_handler(ip, parent_ip, ops, fregs);
79 ftrace_test_recursion_unlock(bit);
80
81 }
82 NOKPROBE_SYMBOL(fprobe_handler);
83
84 static void fprobe_kprobe_handler(unsigned long ip, unsigned long parent_ip,
85 struct ftrace_ops *ops, struct ftrace_regs *fregs)
86 {
87 struct fprobe *fp;
88 int bit;
89
90 fp = container_of(ops, struct fprobe, ops);
91 if (fprobe_disabled(fp))
92 return;
93
94 /* recursion detection has to go before any traceable function and
95 * all functions called before this point should be marked as notrace
96 */
97 bit = ftrace_test_recursion_trylock(ip, parent_ip);
98 if (bit < 0) {
99 fp->nmissed++;
100 return;
101 }
102
103 /*
104 * This user handler is shared with other kprobes and is not expected to be
105 * called recursively. So if any other kprobe handler is running, this will
106 * exit as kprobe does. See the section 'Share the callbacks with kprobes'
107 * in Documentation/trace/fprobe.rst for more information.
108 */
109 if (unlikely(kprobe_running())) {
110 fp->nmissed++;
111 goto recursion_unlock;
112 }
113
114 kprobe_busy_begin();
115 __fprobe_handler(ip, parent_ip, ops, fregs);
116 kprobe_busy_end();
117
118 recursion_unlock:
119 ftrace_test_recursion_unlock(bit);
120 }
121
122 static void fprobe_exit_handler(struct rethook_node *rh, void *data,
123 unsigned long ret_ip, struct pt_regs *regs)
124 {
125 struct fprobe *fp = (struct fprobe *)data;
126 struct fprobe_rethook_node *fpr;
127 int bit;
128
129 if (!fp || fprobe_disabled(fp))
130 return;
131
132 fpr = container_of(rh, struct fprobe_rethook_node, node);
133
134 /*
135 * we need to assure no calls to traceable functions in-between the
136 * end of fprobe_handler and the beginning of fprobe_exit_handler.
137 */
138 bit = ftrace_test_recursion_trylock(fpr->entry_ip, fpr->entry_parent_ip);
139 if (bit < 0) {
140 fp->nmissed++;
141 return;
142 }
143
144 fp->exit_handler(fp, fpr->entry_ip, ret_ip, regs,
145 fp->entry_data_size ? (void *)fpr->data : NULL);
146 ftrace_test_recursion_unlock(bit);
147 }
148 NOKPROBE_SYMBOL(fprobe_exit_handler);
149
150 static int symbols_cmp(const void *a, const void *b)
151 {
152 const char **str_a = (const char **) a;
153 const char **str_b = (const char **) b;
154
155 return strcmp(*str_a, *str_b);
156 }
157
158 /* Convert ftrace location address from symbols */
159 static unsigned long *get_ftrace_locations(const char **syms, int num)
160 {
161 unsigned long *addrs;
162
163 /* Convert symbols to symbol address */
164 addrs = kcalloc(num, sizeof(*addrs), GFP_KERNEL);
165 if (!addrs)
166 return ERR_PTR(-ENOMEM);
167
168 /* ftrace_lookup_symbols expects sorted symbols */
169 sort(syms, num, sizeof(*syms), symbols_cmp, NULL);
170
171 if (!ftrace_lookup_symbols(syms, num, addrs))
172 return addrs;
173
174 kfree(addrs);
175 return ERR_PTR(-ENOENT);
176 }
177
178 static void fprobe_init(struct fprobe *fp)
179 {
180 fp->nmissed = 0;
181 if (fprobe_shared_with_kprobes(fp))
182 fp->ops.func = fprobe_kprobe_handler;
183 else
184 fp->ops.func = fprobe_handler;
185 fp->ops.flags |= FTRACE_OPS_FL_SAVE_REGS;
186 }
187
188 static int fprobe_init_rethook(struct fprobe *fp, int num)
189 {
190 int size;
191
192 if (!fp->exit_handler) {
193 fp->rethook = NULL;
194 return 0;
195 }
196
197 /* Initialize rethook if needed */
198 if (fp->nr_maxactive)
199 num = fp->nr_maxactive;
200 else
201 num *= num_possible_cpus() * 2;
202 if (num <= 0)
203 return -EINVAL;
204
205 size = sizeof(struct fprobe_rethook_node) + fp->entry_data_size;
206
207 /* Initialize rethook */
208 fp->rethook = rethook_alloc((void *)fp, fprobe_exit_handler, size, num);
209 if (IS_ERR(fp->rethook))
210 return PTR_ERR(fp->rethook);
211
212 return 0;
213 }
214
215 static void fprobe_fail_cleanup(struct fprobe *fp)
216 {
217 if (!IS_ERR_OR_NULL(fp->rethook)) {
218 /* Don't need to cleanup rethook->handler because this is not used. */
219 rethook_free(fp->rethook);
220 fp->rethook = NULL;
221 }
222 ftrace_free_filter(&fp->ops);
223 }
224
225 /**
226 * register_fprobe() - Register fprobe to ftrace by pattern.
227 * @fp: A fprobe data structure to be registered.
228 * @filter: A wildcard pattern of probed symbols.
229 * @notfilter: A wildcard pattern of NOT probed symbols.
230 *
231 * Register @fp to ftrace for enabling the probe on the symbols matched to @filter.
232 * If @notfilter is not NULL, the symbols matched the @notfilter are not probed.
233 *
234 * Return 0 if @fp is registered successfully, -errno if not.
235 */
236 int register_fprobe(struct fprobe *fp, const char *filter, const char *notfilter)
237 {
238 struct ftrace_hash *hash;
239 unsigned char *str;
240 int ret, len;
241
242 if (!fp || !filter)
243 return -EINVAL;
244
245 fprobe_init(fp);
246
247 len = strlen(filter);
248 str = kstrdup(filter, GFP_KERNEL);
249 ret = ftrace_set_filter(&fp->ops, str, len, 0);
250 kfree(str);
251 if (ret)
252 return ret;
253
254 if (notfilter) {
255 len = strlen(notfilter);
256 str = kstrdup(notfilter, GFP_KERNEL);
257 ret = ftrace_set_notrace(&fp->ops, str, len, 0);
258 kfree(str);
259 if (ret)
260 goto out;
261 }
262
263 /* TODO:
264 * correctly calculate the total number of filtered symbols
265 * from both filter and notfilter.
266 */
267 hash = rcu_access_pointer(fp->ops.local_hash.filter_hash);
268 if (WARN_ON_ONCE(!hash))
269 goto out;
270
271 ret = fprobe_init_rethook(fp, (int)hash->count);
272 if (!ret)
273 ret = register_ftrace_function(&fp->ops);
274
275 out:
276 if (ret)
277 fprobe_fail_cleanup(fp);
278 return ret;
279 }
280 EXPORT_SYMBOL_GPL(register_fprobe);
281
282 /**
283 * register_fprobe_ips() - Register fprobe to ftrace by address.
284 * @fp: A fprobe data structure to be registered.
285 * @addrs: An array of target ftrace location addresses.
286 * @num: The number of entries of @addrs.
287 *
288 * Register @fp to ftrace for enabling the probe on the address given by @addrs.
289 * The @addrs must be the addresses of ftrace location address, which may be
290 * the symbol address + arch-dependent offset.
291 * If you unsure what this mean, please use other registration functions.
292 *
293 * Return 0 if @fp is registered successfully, -errno if not.
294 */
295 int register_fprobe_ips(struct fprobe *fp, unsigned long *addrs, int num)
296 {
297 int ret;
298
299 if (!fp || !addrs || num <= 0)
300 return -EINVAL;
301
302 fprobe_init(fp);
303
304 ret = ftrace_set_filter_ips(&fp->ops, addrs, num, 0, 0);
305 if (ret)
306 return ret;
307
308 ret = fprobe_init_rethook(fp, num);
309 if (!ret)
310 ret = register_ftrace_function(&fp->ops);
311
312 if (ret)
313 fprobe_fail_cleanup(fp);
314 return ret;
315 }
316 EXPORT_SYMBOL_GPL(register_fprobe_ips);
317
318 /**
319 * register_fprobe_syms() - Register fprobe to ftrace by symbols.
320 * @fp: A fprobe data structure to be registered.
321 * @syms: An array of target symbols.
322 * @num: The number of entries of @syms.
323 *
324 * Register @fp to the symbols given by @syms array. This will be useful if
325 * you are sure the symbols exist in the kernel.
326 *
327 * Return 0 if @fp is registered successfully, -errno if not.
328 */
329 int register_fprobe_syms(struct fprobe *fp, const char **syms, int num)
330 {
331 unsigned long *addrs;
332 int ret;
333
334 if (!fp || !syms || num <= 0)
335 return -EINVAL;
336
337 addrs = get_ftrace_locations(syms, num);
338 if (IS_ERR(addrs))
339 return PTR_ERR(addrs);
340
341 ret = register_fprobe_ips(fp, addrs, num);
342
343 kfree(addrs);
344
345 return ret;
346 }
347 EXPORT_SYMBOL_GPL(register_fprobe_syms);
348
349 bool fprobe_is_registered(struct fprobe *fp)
350 {
351 if (!fp || (fp->ops.saved_func != fprobe_handler &&
352 fp->ops.saved_func != fprobe_kprobe_handler))
353 return false;
354 return true;
355 }
356
357 /**
358 * unregister_fprobe() - Unregister fprobe from ftrace
359 * @fp: A fprobe data structure to be unregistered.
360 *
361 * Unregister fprobe (and remove ftrace hooks from the function entries).
362 *
363 * Return 0 if @fp is unregistered successfully, -errno if not.
364 */
365 int unregister_fprobe(struct fprobe *fp)
366 {
367 int ret;
368
369 if (!fprobe_is_registered(fp))
370 return -EINVAL;
371
372 if (!IS_ERR_OR_NULL(fp->rethook))
373 rethook_stop(fp->rethook);
374
375 ret = unregister_ftrace_function(&fp->ops);
376 if (ret < 0)
377 return ret;
378
379 if (!IS_ERR_OR_NULL(fp->rethook))
380 rethook_free(fp->rethook);
381
382 ftrace_free_filter(&fp->ops);
383
384 return ret;
385 }
386 EXPORT_SYMBOL_GPL(unregister_fprobe);
387
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