projects/linux·blob v6.7 · refs

388 lines · 9.2 KiB

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
17struct fprobe_rethook_node {
18 struct rethook_node node;
19 unsigned long entry_ip;
20 unsigned long entry_parent_ip;
21 char data[];
22};
23
24static 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
60static 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}
82NOKPROBE_SYMBOL(fprobe_handler);
83
84static 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
118recursion_unlock:
119 ftrace_test_recursion_unlock(bit);
120}
121
122static 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}
148NOKPROBE_SYMBOL(fprobe_exit_handler);
149
150static 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 */
159static 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
178static 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
188static int fprobe_init_rethook(struct fprobe *fp, int num)
189{
190 int size;
191
192 if (num <= 0)
193 return -EINVAL;
194
195 if (!fp->exit_handler) {
196 fp->rethook = NULL;
197 return 0;
198 }
199
200 /* Initialize rethook if needed */
201 if (fp->nr_maxactive)
202 size = fp->nr_maxactive;
203 else
204 size = num * num_possible_cpus() * 2;
205 if (size <= 0)
206 return -EINVAL;
207
208 /* Initialize rethook */
209 fp->rethook = rethook_alloc((void *)fp, fprobe_exit_handler,
210 sizeof(struct fprobe_rethook_node), size);
211 if (IS_ERR(fp->rethook))
212 return PTR_ERR(fp->rethook);
213
214 return 0;
215}
216
217static void fprobe_fail_cleanup(struct fprobe *fp)
218{
219 if (!IS_ERR_OR_NULL(fp->rethook)) {
220 /* Don't need to cleanup rethook->handler because this is not used. */
221 rethook_free(fp->rethook);
222 fp->rethook = NULL;
223 }
224 ftrace_free_filter(&fp->ops);
225}
226
227/**
228 * register_fprobe() - Register fprobe to ftrace by pattern.
229 * @fp: A fprobe data structure to be registered.
230 * @filter: A wildcard pattern of probed symbols.
231 * @notfilter: A wildcard pattern of NOT probed symbols.
232 *
233 * Register @fp to ftrace for enabling the probe on the symbols matched to @filter.
234 * If @notfilter is not NULL, the symbols matched the @notfilter are not probed.
235 *
236 * Return 0 if @fp is registered successfully, -errno if not.
237 */
238int register_fprobe(struct fprobe *fp, const char *filter, const char *notfilter)
239{
240 struct ftrace_hash *hash;
241 unsigned char *str;
242 int ret, len;
243
244 if (!fp || !filter)
245 return -EINVAL;
246
247 fprobe_init(fp);
248
249 len = strlen(filter);
250 str = kstrdup(filter, GFP_KERNEL);
251 ret = ftrace_set_filter(&fp->ops, str, len, 0);
252 kfree(str);
253 if (ret)
254 return ret;
255
256 if (notfilter) {
257 len = strlen(notfilter);
258 str = kstrdup(notfilter, GFP_KERNEL);
259 ret = ftrace_set_notrace(&fp->ops, str, len, 0);
260 kfree(str);
261 if (ret)
262 goto out;
263 }
264
265 /* TODO:
266 * correctly calculate the total number of filtered symbols
267 * from both filter and notfilter.
268 */
269 hash = rcu_access_pointer(fp->ops.local_hash.filter_hash);
270 if (WARN_ON_ONCE(!hash))
271 goto out;
272
273 ret = fprobe_init_rethook(fp, (int)hash->count);
274 if (!ret)
275 ret = register_ftrace_function(&fp->ops);
276
277out:
278 if (ret)
279 fprobe_fail_cleanup(fp);
280 return ret;
281}
282EXPORT_SYMBOL_GPL(register_fprobe);
283
284/**
285 * register_fprobe_ips() - Register fprobe to ftrace by address.
286 * @fp: A fprobe data structure to be registered.
287 * @addrs: An array of target ftrace location addresses.
288 * @num: The number of entries of @addrs.
289 *
290 * Register @fp to ftrace for enabling the probe on the address given by @addrs.
291 * The @addrs must be the addresses of ftrace location address, which may be
292 * the symbol address + arch-dependent offset.
293 * If you unsure what this mean, please use other registration functions.
294 *
295 * Return 0 if @fp is registered successfully, -errno if not.
296 */
297int register_fprobe_ips(struct fprobe *fp, unsigned long *addrs, int num)
298{
299 int ret;
300
301 if (!fp || !addrs || num <= 0)
302 return -EINVAL;
303
304 fprobe_init(fp);
305
306 ret = ftrace_set_filter_ips(&fp->ops, addrs, num, 0, 0);
307 if (ret)
308 return ret;
309
310 ret = fprobe_init_rethook(fp, num);
311 if (!ret)
312 ret = register_ftrace_function(&fp->ops);
313
314 if (ret)
315 fprobe_fail_cleanup(fp);
316 return ret;
317}
318EXPORT_SYMBOL_GPL(register_fprobe_ips);
319
320/**
321 * register_fprobe_syms() - Register fprobe to ftrace by symbols.
322 * @fp: A fprobe data structure to be registered.
323 * @syms: An array of target symbols.
324 * @num: The number of entries of @syms.
325 *
326 * Register @fp to the symbols given by @syms array. This will be useful if
327 * you are sure the symbols exist in the kernel.
328 *
329 * Return 0 if @fp is registered successfully, -errno if not.
330 */
331int register_fprobe_syms(struct fprobe *fp, const char **syms, int num)
332{
333 unsigned long *addrs;
334 int ret;
335
336 if (!fp || !syms || num <= 0)
337 return -EINVAL;
338
339 addrs = get_ftrace_locations(syms, num);
340 if (IS_ERR(addrs))
341 return PTR_ERR(addrs);
342
343 ret = register_fprobe_ips(fp, addrs, num);
344
345 kfree(addrs);
346
347 return ret;
348}
349EXPORT_SYMBOL_GPL(register_fprobe_syms);
350
351bool fprobe_is_registered(struct fprobe *fp)
352{
353 if (!fp || (fp->ops.saved_func != fprobe_handler &&
354 fp->ops.saved_func != fprobe_kprobe_handler))
355 return false;
356 return true;
357}
358
359/**
360 * unregister_fprobe() - Unregister fprobe from ftrace
361 * @fp: A fprobe data structure to be unregistered.
362 *
363 * Unregister fprobe (and remove ftrace hooks from the function entries).
364 *
365 * Return 0 if @fp is unregistered successfully, -errno if not.
366 */
367int unregister_fprobe(struct fprobe *fp)
368{
369 int ret;
370
371 if (!fprobe_is_registered(fp))
372 return -EINVAL;
373
374 if (!IS_ERR_OR_NULL(fp->rethook))
375 rethook_stop(fp->rethook);
376
377 ret = unregister_ftrace_function(&fp->ops);
378 if (ret < 0)
379 return ret;
380
381 if (!IS_ERR_OR_NULL(fp->rethook))
382 rethook_free(fp->rethook);
383
384 ftrace_free_filter(&fp->ops);
385
386 return ret;
387}
388EXPORT_SYMBOL_GPL(unregister_fprobe);