1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * trace event based perf event profiling/tracing
4 *
5 * Copyright (C) 2009 Red Hat Inc, Peter Zijlstra
6 * Copyright (C) 2009-2010 Frederic Weisbecker <fweisbec@gmail.com>
7 */
8
9 #include <linux/module.h>
10 #include <linux/kprobes.h>
11 #include <linux/security.h>
12 #include "trace.h"
13 #include "trace_probe.h"
14
15 static char __percpu *perf_trace_buf[PERF_NR_CONTEXTS];
16
17 /*
18 * Force it to be aligned to unsigned long to avoid misaligned accesses
19 * surprises
20 */
21 typedef typeof(unsigned long [PERF_MAX_TRACE_SIZE / sizeof(unsigned long)])
22 perf_trace_t;
23
24 /* Count the events in use (per event id, not per instance) */
25 static int total_ref_count;
26
27 static int perf_trace_event_perm(struct trace_event_call *tp_event,
28 struct perf_event *p_event)
29 {
30 int ret;
31
32 if (tp_event->perf_perm) {
33 ret = tp_event->perf_perm(tp_event, p_event);
34 if (ret)
35 return ret;
36 }
37
38 /*
39 * We checked and allowed to create parent,
40 * allow children without checking.
41 */
42 if (p_event->parent)
43 return 0;
44
45 /*
46 * It's ok to check current process (owner) permissions in here,
47 * because code below is called only via perf_event_open syscall.
48 */
49
50 /* The ftrace function trace is allowed only for root. */
51 if (ftrace_event_is_function(tp_event)) {
52 ret = perf_allow_tracepoint(&p_event->attr);
53 if (ret)
54 return ret;
55
56 if (!is_sampling_event(p_event))
57 return 0;
58
59 /*
60 * We don't allow user space callchains for function trace
61 * event, due to issues with page faults while tracing page
62 * fault handler and its overall trickiness nature.
63 */
64 if (!p_event->attr.exclude_callchain_user)
65 return -EINVAL;
66
67 /*
68 * Same reason to disable user stack dump as for user space
69 * callchains above.
70 */
71 if (p_event->attr.sample_type & PERF_SAMPLE_STACK_USER)
72 return -EINVAL;
73 }
74
75 /* No tracing, just counting, so no obvious leak */
76 if (!(p_event->attr.sample_type & PERF_SAMPLE_RAW))
77 return 0;
78
79 /* Some events are ok to be traced by non-root users... */
80 if (p_event->attach_state == PERF_ATTACH_TASK) {
81 if (tp_event->flags & TRACE_EVENT_FL_CAP_ANY)
82 return 0;
83 }
84
85 /*
86 * ...otherwise raw tracepoint data can be a severe data leak,
87 * only allow root to have these.
88 */
89 ret = perf_allow_tracepoint(&p_event->attr);
90 if (ret)
91 return ret;
92
93 return 0;
94 }
95
96 static int perf_trace_event_reg(struct trace_event_call *tp_event,
97 struct perf_event *p_event)
98 {
99 struct hlist_head __percpu *list;
100 int ret = -ENOMEM;
101 int cpu;
102
103 p_event->tp_event = tp_event;
104 if (tp_event->perf_refcount++ > 0)
105 return 0;
106
107 list = alloc_percpu(struct hlist_head);
108 if (!list)
109 goto fail;
110
111 for_each_possible_cpu(cpu)
112 INIT_HLIST_HEAD(per_cpu_ptr(list, cpu));
113
114 tp_event->perf_events = list;
115
116 if (!total_ref_count) {
117 char __percpu *buf;
118 int i;
119
120 for (i = 0; i < PERF_NR_CONTEXTS; i++) {
121 buf = (char __percpu *)alloc_percpu(perf_trace_t);
122 if (!buf)
123 goto fail;
124
125 perf_trace_buf[i] = buf;
126 }
127 }
128
129 ret = tp_event->class->reg(tp_event, TRACE_REG_PERF_REGISTER, NULL);
130 if (ret)
131 goto fail;
132
133 total_ref_count++;
134 return 0;
135
136 fail:
137 if (!total_ref_count) {
138 int i;
139
140 for (i = 0; i < PERF_NR_CONTEXTS; i++) {
141 free_percpu(perf_trace_buf[i]);
142 perf_trace_buf[i] = NULL;
143 }
144 }
145
146 if (!--tp_event->perf_refcount) {
147 free_percpu(tp_event->perf_events);
148 tp_event->perf_events = NULL;
149 }
150
151 return ret;
152 }
153
154 static void perf_trace_event_unreg(struct perf_event *p_event)
155 {
156 struct trace_event_call *tp_event = p_event->tp_event;
157 int i;
158
159 if (--tp_event->perf_refcount > 0)
160 return;
161
162 tp_event->class->reg(tp_event, TRACE_REG_PERF_UNREGISTER, NULL);
163
164 /*
165 * Ensure our callback won't be called anymore. The buffers
166 * will be freed after that.
167 */
168 tracepoint_synchronize_unregister();
169
170 free_percpu(tp_event->perf_events);
171 tp_event->perf_events = NULL;
172
173 if (!--total_ref_count) {
174 for (i = 0; i < PERF_NR_CONTEXTS; i++) {
175 free_percpu(perf_trace_buf[i]);
176 perf_trace_buf[i] = NULL;
177 }
178 }
179 }
180
181 static int perf_trace_event_open(struct perf_event *p_event)
182 {
183 struct trace_event_call *tp_event = p_event->tp_event;
184 return tp_event->class->reg(tp_event, TRACE_REG_PERF_OPEN, p_event);
185 }
186
187 static void perf_trace_event_close(struct perf_event *p_event)
188 {
189 struct trace_event_call *tp_event = p_event->tp_event;
190 tp_event->class->reg(tp_event, TRACE_REG_PERF_CLOSE, p_event);
191 }
192
193 static int perf_trace_event_init(struct trace_event_call *tp_event,
194 struct perf_event *p_event)
195 {
196 int ret;
197
198 ret = perf_trace_event_perm(tp_event, p_event);
199 if (ret)
200 return ret;
201
202 ret = perf_trace_event_reg(tp_event, p_event);
203 if (ret)
204 return ret;
205
206 ret = perf_trace_event_open(p_event);
207 if (ret) {
208 perf_trace_event_unreg(p_event);
209 return ret;
210 }
211
212 return 0;
213 }
214
215 int perf_trace_init(struct perf_event *p_event)
216 {
217 struct trace_event_call *tp_event;
218 u64 event_id = p_event->attr.config;
219 int ret = -EINVAL;
220
221 mutex_lock(&event_mutex);
222 list_for_each_entry(tp_event, &ftrace_events, list) {
223 if (tp_event->event.type == event_id &&
224 tp_event->class && tp_event->class->reg &&
225 trace_event_try_get_ref(tp_event)) {
226 ret = perf_trace_event_init(tp_event, p_event);
227 if (ret)
228 trace_event_put_ref(tp_event);
229 break;
230 }
231 }
232 mutex_unlock(&event_mutex);
233
234 return ret;
235 }
236
237 void perf_trace_destroy(struct perf_event *p_event)
238 {
239 mutex_lock(&event_mutex);
240 perf_trace_event_close(p_event);
241 perf_trace_event_unreg(p_event);
242 trace_event_put_ref(p_event->tp_event);
243 mutex_unlock(&event_mutex);
244 }
245
246 #ifdef CONFIG_KPROBE_EVENTS
247 int perf_kprobe_init(struct perf_event *p_event, bool is_retprobe)
248 {
249 int ret;
250 char *func = NULL;
251 struct trace_event_call *tp_event;
252
253 if (p_event->attr.kprobe_func) {
254 func = strndup_user(u64_to_user_ptr(p_event->attr.kprobe_func),
255 KSYM_NAME_LEN);
256 if (IS_ERR(func)) {
257 ret = PTR_ERR(func);
258 return (ret == -EINVAL) ? -E2BIG : ret;
259 }
260
261 if (func[0] == '\0') {
262 kfree(func);
263 func = NULL;
264 }
265 }
266
267 tp_event = create_local_trace_kprobe(
268 func, (void *)(unsigned long)(p_event->attr.kprobe_addr),
269 p_event->attr.probe_offset, is_retprobe);
270 if (IS_ERR(tp_event)) {
271 ret = PTR_ERR(tp_event);
272 goto out;
273 }
274
275 mutex_lock(&event_mutex);
276 ret = perf_trace_event_init(tp_event, p_event);
277 if (ret)
278 destroy_local_trace_kprobe(tp_event);
279 mutex_unlock(&event_mutex);
280 out:
281 kfree(func);
282 return ret;
283 }
284
285 void perf_kprobe_destroy(struct perf_event *p_event)
286 {
287 mutex_lock(&event_mutex);
288 perf_trace_event_close(p_event);
289 perf_trace_event_unreg(p_event);
290 trace_event_put_ref(p_event->tp_event);
291 mutex_unlock(&event_mutex);
292
293 destroy_local_trace_kprobe(p_event->tp_event);
294 }
295 #endif /* CONFIG_KPROBE_EVENTS */
296
297 #ifdef CONFIG_UPROBE_EVENTS
298 int perf_uprobe_init(struct perf_event *p_event,
299 unsigned long ref_ctr_offset, bool is_retprobe)
300 {
301 int ret;
302 char *path = NULL;
303 struct trace_event_call *tp_event;
304
305 if (!p_event->attr.uprobe_path)
306 return -EINVAL;
307
308 path = strndup_user(u64_to_user_ptr(p_event->attr.uprobe_path),
309 PATH_MAX);
310 if (IS_ERR(path)) {
311 ret = PTR_ERR(path);
312 return (ret == -EINVAL) ? -E2BIG : ret;
313 }
314 if (path[0] == '\0') {
315 ret = -EINVAL;
316 goto out;
317 }
318
319 tp_event = create_local_trace_uprobe(path, p_event->attr.probe_offset,
320 ref_ctr_offset, is_retprobe);
321 if (IS_ERR(tp_event)) {
322 ret = PTR_ERR(tp_event);
323 goto out;
324 }
325
326 /*
327 * local trace_uprobe need to hold event_mutex to call
328 * uprobe_buffer_enable() and uprobe_buffer_disable().
329 * event_mutex is not required for local trace_kprobes.
330 */
331 mutex_lock(&event_mutex);
332 ret = perf_trace_event_init(tp_event, p_event);
333 if (ret)
334 destroy_local_trace_uprobe(tp_event);
335 mutex_unlock(&event_mutex);
336 out:
337 kfree(path);
338 return ret;
339 }
340
341 void perf_uprobe_destroy(struct perf_event *p_event)
342 {
343 mutex_lock(&event_mutex);
344 perf_trace_event_close(p_event);
345 perf_trace_event_unreg(p_event);
346 trace_event_put_ref(p_event->tp_event);
347 mutex_unlock(&event_mutex);
348 destroy_local_trace_uprobe(p_event->tp_event);
349 }
350 #endif /* CONFIG_UPROBE_EVENTS */
351
352 int perf_trace_add(struct perf_event *p_event, int flags)
353 {
354 struct trace_event_call *tp_event = p_event->tp_event;
355
356 if (!(flags & PERF_EF_START))
357 p_event->hw.state = PERF_HES_STOPPED;
358
359 /*
360 * If TRACE_REG_PERF_ADD returns false; no custom action was performed
361 * and we need to take the default action of enqueueing our event on
362 * the right per-cpu hlist.
363 */
364 if (!tp_event->class->reg(tp_event, TRACE_REG_PERF_ADD, p_event)) {
365 struct hlist_head __percpu *pcpu_list;
366 struct hlist_head *list;
367
368 pcpu_list = tp_event->perf_events;
369 if (WARN_ON_ONCE(!pcpu_list))
370 return -EINVAL;
371
372 list = this_cpu_ptr(pcpu_list);
373 hlist_add_head_rcu(&p_event->hlist_entry, list);
374 }
375
376 return 0;
377 }
378
379 void perf_trace_del(struct perf_event *p_event, int flags)
380 {
381 struct trace_event_call *tp_event = p_event->tp_event;
382
383 /*
384 * If TRACE_REG_PERF_DEL returns false; no custom action was performed
385 * and we need to take the default action of dequeueing our event from
386 * the right per-cpu hlist.
387 */
388 if (!tp_event->class->reg(tp_event, TRACE_REG_PERF_DEL, p_event))
389 hlist_del_rcu(&p_event->hlist_entry);
390 }
391
392 void *perf_trace_buf_alloc(int size, struct pt_regs **regs, int *rctxp)
393 {
394 char *raw_data;
395 int rctx;
396
397 BUILD_BUG_ON(PERF_MAX_TRACE_SIZE % sizeof(unsigned long));
398
399 if (WARN_ONCE(size > PERF_MAX_TRACE_SIZE,
400 "perf buffer not large enough, wanted %d, have %d",
401 size, PERF_MAX_TRACE_SIZE))
402 return NULL;
403
404 *rctxp = rctx = perf_swevent_get_recursion_context();
405 if (rctx < 0)
406 return NULL;
407
408 if (regs)
409 *regs = this_cpu_ptr(&__perf_regs[rctx]);
410 raw_data = this_cpu_ptr(perf_trace_buf[rctx]);
411
412 /* zero the dead bytes from align to not leak stack to user */
413 memset(&raw_data[size - sizeof(u64)], 0, sizeof(u64));
414 return raw_data;
415 }
416 EXPORT_SYMBOL_GPL(perf_trace_buf_alloc);
417 NOKPROBE_SYMBOL(perf_trace_buf_alloc);
418
419 void perf_trace_buf_update(void *record, u16 type)
420 {
421 struct trace_entry *entry = record;
422
423 tracing_generic_entry_update(entry, type, tracing_gen_ctx());
424 }
425 NOKPROBE_SYMBOL(perf_trace_buf_update);
426
427 #ifdef CONFIG_FUNCTION_TRACER
428 static void
429 perf_ftrace_function_call(unsigned long ip, unsigned long parent_ip,
430 struct ftrace_ops *ops, struct ftrace_regs *fregs)
431 {
432 struct ftrace_entry *entry;
433 struct perf_event *event;
434 struct hlist_head head;
435 struct pt_regs regs;
436 int rctx;
437 int bit;
438
439 if (!rcu_is_watching())
440 return;
441
442 bit = ftrace_test_recursion_trylock(ip, parent_ip);
443 if (bit < 0)
444 return;
445
446 if ((unsigned long)ops->private != smp_processor_id())
447 goto out;
448
449 event = container_of(ops, struct perf_event, ftrace_ops);
450
451 /*
452 * @event->hlist entry is NULL (per INIT_HLIST_NODE), and all
453 * the perf code does is hlist_for_each_entry_rcu(), so we can
454 * get away with simply setting the @head.first pointer in order
455 * to create a singular list.
456 */
457 head.first = &event->hlist_entry;
458
459 #define ENTRY_SIZE (ALIGN(sizeof(struct ftrace_entry) + sizeof(u32), \
460 sizeof(u64)) - sizeof(u32))
461
462 BUILD_BUG_ON(ENTRY_SIZE > PERF_MAX_TRACE_SIZE);
463
464 memset(®s, 0, sizeof(regs));
465 perf_fetch_caller_regs(®s);
466
467 entry = perf_trace_buf_alloc(ENTRY_SIZE, NULL, &rctx);
468 if (!entry)
469 goto out;
470
471 entry->ip = ip;
472 entry->parent_ip = parent_ip;
473 perf_trace_buf_submit(entry, ENTRY_SIZE, rctx, TRACE_FN,
474 1, ®s, &head, NULL);
475
476 out:
477 ftrace_test_recursion_unlock(bit);
478 #undef ENTRY_SIZE
479 }
480
481 static int perf_ftrace_function_register(struct perf_event *event)
482 {
483 struct ftrace_ops *ops = &event->ftrace_ops;
484
485 ops->func = perf_ftrace_function_call;
486 ops->private = (void *)(unsigned long)nr_cpu_ids;
487
488 return register_ftrace_function(ops);
489 }
490
491 static int perf_ftrace_function_unregister(struct perf_event *event)
492 {
493 struct ftrace_ops *ops = &event->ftrace_ops;
494 int ret = unregister_ftrace_function(ops);
495 ftrace_free_filter(ops);
496 return ret;
497 }
498
499 int perf_ftrace_event_register(struct trace_event_call *call,
500 enum trace_reg type, void *data)
501 {
502 struct perf_event *event = data;
503
504 switch (type) {
505 case TRACE_REG_REGISTER:
506 case TRACE_REG_UNREGISTER:
507 break;
508 case TRACE_REG_PERF_REGISTER:
509 case TRACE_REG_PERF_UNREGISTER:
510 return 0;
511 case TRACE_REG_PERF_OPEN:
512 return perf_ftrace_function_register(data);
513 case TRACE_REG_PERF_CLOSE:
514 return perf_ftrace_function_unregister(data);
515 case TRACE_REG_PERF_ADD:
516 event->ftrace_ops.private = (void *)(unsigned long)smp_processor_id();
517 return 1;
518 case TRACE_REG_PERF_DEL:
519 event->ftrace_ops.private = (void *)(unsigned long)nr_cpu_ids;
520 return 1;
521 }
522
523 return -EINVAL;
524 }
525 #endif /* CONFIG_FUNCTION_TRACER */
526
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