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(&regs, 0, sizeof(regs));
465 	perf_fetch_caller_regs(&regs);
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, &regs, &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