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  * suprises
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 		goto out;
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 out:
180 	module_put(tp_event->mod);
181 }
182 
183 static int perf_trace_event_open(struct perf_event *p_event)
184 {
185 	struct trace_event_call *tp_event = p_event->tp_event;
186 	return tp_event->class->reg(tp_event, TRACE_REG_PERF_OPEN, p_event);
187 }
188 
189 static void perf_trace_event_close(struct perf_event *p_event)
190 {
191 	struct trace_event_call *tp_event = p_event->tp_event;
192 	tp_event->class->reg(tp_event, TRACE_REG_PERF_CLOSE, p_event);
193 }
194 
195 static int perf_trace_event_init(struct trace_event_call *tp_event,
196 				 struct perf_event *p_event)
197 {
198 	int ret;
199 
200 	ret = perf_trace_event_perm(tp_event, p_event);
201 	if (ret)
202 		return ret;
203 
204 	ret = perf_trace_event_reg(tp_event, p_event);
205 	if (ret)
206 		return ret;
207 
208 	ret = perf_trace_event_open(p_event);
209 	if (ret) {
210 		perf_trace_event_unreg(p_event);
211 		return ret;
212 	}
213 
214 	return 0;
215 }
216 
217 int perf_trace_init(struct perf_event *p_event)
218 {
219 	struct trace_event_call *tp_event;
220 	u64 event_id = p_event->attr.config;
221 	int ret = -EINVAL;
222 
223 	mutex_lock(&event_mutex);
224 	list_for_each_entry(tp_event, &ftrace_events, list) {
225 		if (tp_event->event.type == event_id &&
226 		    tp_event->class && tp_event->class->reg &&
227 		    try_module_get(tp_event->mod)) {
228 			ret = perf_trace_event_init(tp_event, p_event);
229 			if (ret)
230 				module_put(tp_event->mod);
231 			break;
232 		}
233 	}
234 	mutex_unlock(&event_mutex);
235 
236 	return ret;
237 }
238 
239 void perf_trace_destroy(struct perf_event *p_event)
240 {
241 	mutex_lock(&event_mutex);
242 	perf_trace_event_close(p_event);
243 	perf_trace_event_unreg(p_event);
244 	mutex_unlock(&event_mutex);
245 }
246 
247 #ifdef CONFIG_KPROBE_EVENTS
248 int perf_kprobe_init(struct perf_event *p_event, bool is_retprobe)
249 {
250 	int ret;
251 	char *func = NULL;
252 	struct trace_event_call *tp_event;
253 
254 	if (p_event->attr.kprobe_func) {
255 		func = kzalloc(KSYM_NAME_LEN, GFP_KERNEL);
256 		if (!func)
257 			return -ENOMEM;
258 		ret = strncpy_from_user(
259 			func, u64_to_user_ptr(p_event->attr.kprobe_func),
260 			KSYM_NAME_LEN);
261 		if (ret == KSYM_NAME_LEN)
262 			ret = -E2BIG;
263 		if (ret < 0)
264 			goto out;
265 
266 		if (func[0] == '\0') {
267 			kfree(func);
268 			func = NULL;
269 		}
270 	}
271 
272 	tp_event = create_local_trace_kprobe(
273 		func, (void *)(unsigned long)(p_event->attr.kprobe_addr),
274 		p_event->attr.probe_offset, is_retprobe);
275 	if (IS_ERR(tp_event)) {
276 		ret = PTR_ERR(tp_event);
277 		goto out;
278 	}
279 
280 	mutex_lock(&event_mutex);
281 	ret = perf_trace_event_init(tp_event, p_event);
282 	if (ret)
283 		destroy_local_trace_kprobe(tp_event);
284 	mutex_unlock(&event_mutex);
285 out:
286 	kfree(func);
287 	return ret;
288 }
289 
290 void perf_kprobe_destroy(struct perf_event *p_event)
291 {
292 	mutex_lock(&event_mutex);
293 	perf_trace_event_close(p_event);
294 	perf_trace_event_unreg(p_event);
295 	mutex_unlock(&event_mutex);
296 
297 	destroy_local_trace_kprobe(p_event->tp_event);
298 }
299 #endif /* CONFIG_KPROBE_EVENTS */
300 
301 #ifdef CONFIG_UPROBE_EVENTS
302 int perf_uprobe_init(struct perf_event *p_event,
303 		     unsigned long ref_ctr_offset, bool is_retprobe)
304 {
305 	int ret;
306 	char *path = NULL;
307 	struct trace_event_call *tp_event;
308 
309 	if (!p_event->attr.uprobe_path)
310 		return -EINVAL;
311 
312 	path = strndup_user(u64_to_user_ptr(p_event->attr.uprobe_path),
313 			    PATH_MAX);
314 	if (IS_ERR(path)) {
315 		ret = PTR_ERR(path);
316 		return (ret == -EINVAL) ? -E2BIG : ret;
317 	}
318 	if (path[0] == '\0') {
319 		ret = -EINVAL;
320 		goto out;
321 	}
322 
323 	tp_event = create_local_trace_uprobe(path, p_event->attr.probe_offset,
324 					     ref_ctr_offset, is_retprobe);
325 	if (IS_ERR(tp_event)) {
326 		ret = PTR_ERR(tp_event);
327 		goto out;
328 	}
329 
330 	/*
331 	 * local trace_uprobe need to hold event_mutex to call
332 	 * uprobe_buffer_enable() and uprobe_buffer_disable().
333 	 * event_mutex is not required for local trace_kprobes.
334 	 */
335 	mutex_lock(&event_mutex);
336 	ret = perf_trace_event_init(tp_event, p_event);
337 	if (ret)
338 		destroy_local_trace_uprobe(tp_event);
339 	mutex_unlock(&event_mutex);
340 out:
341 	kfree(path);
342 	return ret;
343 }
344 
345 void perf_uprobe_destroy(struct perf_event *p_event)
346 {
347 	mutex_lock(&event_mutex);
348 	perf_trace_event_close(p_event);
349 	perf_trace_event_unreg(p_event);
350 	mutex_unlock(&event_mutex);
351 	destroy_local_trace_uprobe(p_event->tp_event);
352 }
353 #endif /* CONFIG_UPROBE_EVENTS */
354 
355 int perf_trace_add(struct perf_event *p_event, int flags)
356 {
357 	struct trace_event_call *tp_event = p_event->tp_event;
358 
359 	if (!(flags & PERF_EF_START))
360 		p_event->hw.state = PERF_HES_STOPPED;
361 
362 	/*
363 	 * If TRACE_REG_PERF_ADD returns false; no custom action was performed
364 	 * and we need to take the default action of enqueueing our event on
365 	 * the right per-cpu hlist.
366 	 */
367 	if (!tp_event->class->reg(tp_event, TRACE_REG_PERF_ADD, p_event)) {
368 		struct hlist_head __percpu *pcpu_list;
369 		struct hlist_head *list;
370 
371 		pcpu_list = tp_event->perf_events;
372 		if (WARN_ON_ONCE(!pcpu_list))
373 			return -EINVAL;
374 
375 		list = this_cpu_ptr(pcpu_list);
376 		hlist_add_head_rcu(&p_event->hlist_entry, list);
377 	}
378 
379 	return 0;
380 }
381 
382 void perf_trace_del(struct perf_event *p_event, int flags)
383 {
384 	struct trace_event_call *tp_event = p_event->tp_event;
385 
386 	/*
387 	 * If TRACE_REG_PERF_DEL returns false; no custom action was performed
388 	 * and we need to take the default action of dequeueing our event from
389 	 * the right per-cpu hlist.
390 	 */
391 	if (!tp_event->class->reg(tp_event, TRACE_REG_PERF_DEL, p_event))
392 		hlist_del_rcu(&p_event->hlist_entry);
393 }
394 
395 void *perf_trace_buf_alloc(int size, struct pt_regs **regs, int *rctxp)
396 {
397 	char *raw_data;
398 	int rctx;
399 
400 	BUILD_BUG_ON(PERF_MAX_TRACE_SIZE % sizeof(unsigned long));
401 
402 	if (WARN_ONCE(size > PERF_MAX_TRACE_SIZE,
403 		      "perf buffer not large enough"))
404 		return NULL;
405 
406 	*rctxp = rctx = perf_swevent_get_recursion_context();
407 	if (rctx < 0)
408 		return NULL;
409 
410 	if (regs)
411 		*regs = this_cpu_ptr(&__perf_regs[rctx]);
412 	raw_data = this_cpu_ptr(perf_trace_buf[rctx]);
413 
414 	/* zero the dead bytes from align to not leak stack to user */
415 	memset(&raw_data[size - sizeof(u64)], 0, sizeof(u64));
416 	return raw_data;
417 }
418 EXPORT_SYMBOL_GPL(perf_trace_buf_alloc);
419 NOKPROBE_SYMBOL(perf_trace_buf_alloc);
420 
421 void perf_trace_buf_update(void *record, u16 type)
422 {
423 	struct trace_entry *entry = record;
424 
425 	tracing_generic_entry_update(entry, type, tracing_gen_ctx());
426 }
427 NOKPROBE_SYMBOL(perf_trace_buf_update);
428 
429 #ifdef CONFIG_FUNCTION_TRACER
430 static void
431 perf_ftrace_function_call(unsigned long ip, unsigned long parent_ip,
432 			  struct ftrace_ops *ops,  struct ftrace_regs *fregs)
433 {
434 	struct ftrace_entry *entry;
435 	struct perf_event *event;
436 	struct hlist_head head;
437 	struct pt_regs regs;
438 	int rctx;
439 	int bit;
440 
441 	if (!rcu_is_watching())
442 		return;
443 
444 	if ((unsigned long)ops->private != smp_processor_id())
445 		return;
446 
447 	bit = ftrace_test_recursion_trylock(ip, parent_ip);
448 	if (bit < 0)
449 		return;
450 
451 	event = container_of(ops, struct perf_event, ftrace_ops);
452 
453 	/*
454 	 * @event->hlist entry is NULL (per INIT_HLIST_NODE), and all
455 	 * the perf code does is hlist_for_each_entry_rcu(), so we can
456 	 * get away with simply setting the @head.first pointer in order
457 	 * to create a singular list.
458 	 */
459 	head.first = &event->hlist_entry;
460 
461 #define ENTRY_SIZE (ALIGN(sizeof(struct ftrace_entry) + sizeof(u32), \
462 		    sizeof(u64)) - sizeof(u32))
463 
464 	BUILD_BUG_ON(ENTRY_SIZE > PERF_MAX_TRACE_SIZE);
465 
466 	memset(&regs, 0, sizeof(regs));
467 	perf_fetch_caller_regs(&regs);
468 
469 	entry = perf_trace_buf_alloc(ENTRY_SIZE, NULL, &rctx);
470 	if (!entry)
471 		goto out;
472 
473 	entry->ip = ip;
474 	entry->parent_ip = parent_ip;
475 	perf_trace_buf_submit(entry, ENTRY_SIZE, rctx, TRACE_FN,
476 			      1, &regs, &head, NULL);
477 
478 out:
479 	ftrace_test_recursion_unlock(bit);
480 #undef ENTRY_SIZE
481 }
482 
483 static int perf_ftrace_function_register(struct perf_event *event)
484 {
485 	struct ftrace_ops *ops = &event->ftrace_ops;
486 
487 	ops->func    = perf_ftrace_function_call;
488 	ops->private = (void *)(unsigned long)nr_cpu_ids;
489 
490 	return register_ftrace_function(ops);
491 }
492 
493 static int perf_ftrace_function_unregister(struct perf_event *event)
494 {
495 	struct ftrace_ops *ops = &event->ftrace_ops;
496 	int ret = unregister_ftrace_function(ops);
497 	ftrace_free_filter(ops);
498 	return ret;
499 }
500 
501 int perf_ftrace_event_register(struct trace_event_call *call,
502 			       enum trace_reg type, void *data)
503 {
504 	struct perf_event *event = data;
505 
506 	switch (type) {
507 	case TRACE_REG_REGISTER:
508 	case TRACE_REG_UNREGISTER:
509 		break;
510 	case TRACE_REG_PERF_REGISTER:
511 	case TRACE_REG_PERF_UNREGISTER:
512 		return 0;
513 	case TRACE_REG_PERF_OPEN:
514 		return perf_ftrace_function_register(data);
515 	case TRACE_REG_PERF_CLOSE:
516 		return perf_ftrace_function_unregister(data);
517 	case TRACE_REG_PERF_ADD:
518 		event->ftrace_ops.private = (void *)(unsigned long)smp_processor_id();
519 		return 1;
520 	case TRACE_REG_PERF_DEL:
521 		event->ftrace_ops.private = (void *)(unsigned long)nr_cpu_ids;
522 		return 1;
523 	}
524 
525 	return -EINVAL;
526 }
527 #endif /* CONFIG_FUNCTION_TRACER */
528