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1/*
2 * thread-stack.c: Synthesize a thread's stack using call / return events
3 * Copyright (c) 2014, Intel Corporation.
4 *
5 * This program is free software; you can redistribute it and/or modify it
6 * under the terms and conditions of the GNU General Public License,
7 * version 2, as published by the Free Software Foundation.
8 *
9 * This program is distributed in the hope it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
12 * more details.
13 *
14 */
15
16#include <linux/rbtree.h>
17#include <linux/list.h>
18#include <errno.h>
19#include "thread.h"
20#include "event.h"
21#include "machine.h"
22#include "util.h"
23#include "debug.h"
24#include "symbol.h"
25#include "comm.h"
26#include "call-path.h"
27#include "thread-stack.h"
28
29#define STACK_GROWTH 2048
30
31/**
32 * struct thread_stack_entry - thread stack entry.
33 * @ret_addr: return address
34 * @timestamp: timestamp (if known)
35 * @ref: external reference (e.g. db_id of sample)
36 * @branch_count: the branch count when the entry was created
37 * @cp: call path
38 * @no_call: a 'call' was not seen
39 */
40struct thread_stack_entry {
41 u64 ret_addr;
42 u64 timestamp;
43 u64 ref;
44 u64 branch_count;
45 struct call_path *cp;
46 bool no_call;
47};
48
49/**
50 * struct thread_stack - thread stack constructed from 'call' and 'return'
51 * branch samples.
52 * @stack: array that holds the stack
53 * @cnt: number of entries in the stack
54 * @sz: current maximum stack size
55 * @trace_nr: current trace number
56 * @branch_count: running branch count
57 * @kernel_start: kernel start address
58 * @last_time: last timestamp
59 * @crp: call/return processor
60 * @comm: current comm
61 */
62struct thread_stack {
63 struct thread_stack_entry *stack;
64 size_t cnt;
65 size_t sz;
66 u64 trace_nr;
67 u64 branch_count;
68 u64 kernel_start;
69 u64 last_time;
70 struct call_return_processor *crp;
71 struct comm *comm;
72};
73
74static int thread_stack__grow(struct thread_stack *ts)
75{
76 struct thread_stack_entry *new_stack;
77 size_t sz, new_sz;
78
79 new_sz = ts->sz + STACK_GROWTH;
80 sz = new_sz * sizeof(struct thread_stack_entry);
81
82 new_stack = realloc(ts->stack, sz);
83 if (!new_stack)
84 return -ENOMEM;
85
86 ts->stack = new_stack;
87 ts->sz = new_sz;
88
89 return 0;
90}
91
92static struct thread_stack *thread_stack__new(struct thread *thread,
93 struct call_return_processor *crp)
94{
95 struct thread_stack *ts;
96
97 ts = zalloc(sizeof(struct thread_stack));
98 if (!ts)
99 return NULL;
100
101 if (thread_stack__grow(ts)) {
102 free(ts);
103 return NULL;
104 }
105
106 if (thread->mg && thread->mg->machine)
107 ts->kernel_start = machine__kernel_start(thread->mg->machine);
108 else
109 ts->kernel_start = 1ULL << 63;
110 ts->crp = crp;
111
112 return ts;
113}
114
115static int thread_stack__push(struct thread_stack *ts, u64 ret_addr)
116{
117 int err = 0;
118
119 if (ts->cnt == ts->sz) {
120 err = thread_stack__grow(ts);
121 if (err) {
122 pr_warning("Out of memory: discarding thread stack\n");
123 ts->cnt = 0;
124 }
125 }
126
127 ts->stack[ts->cnt++].ret_addr = ret_addr;
128
129 return err;
130}
131
132static void thread_stack__pop(struct thread_stack *ts, u64 ret_addr)
133{
134 size_t i;
135
136 /*
137 * In some cases there may be functions which are not seen to return.
138 * For example when setjmp / longjmp has been used. Or the perf context
139 * switch in the kernel which doesn't stop and start tracing in exactly
140 * the same code path. When that happens the return address will be
141 * further down the stack. If the return address is not found at all,
142 * we assume the opposite (i.e. this is a return for a call that wasn't
143 * seen for some reason) and leave the stack alone.
144 */
145 for (i = ts->cnt; i; ) {
146 if (ts->stack[--i].ret_addr == ret_addr) {
147 ts->cnt = i;
148 return;
149 }
150 }
151}
152
153static bool thread_stack__in_kernel(struct thread_stack *ts)
154{
155 if (!ts->cnt)
156 return false;
157
158 return ts->stack[ts->cnt - 1].cp->in_kernel;
159}
160
161static int thread_stack__call_return(struct thread *thread,
162 struct thread_stack *ts, size_t idx,
163 u64 timestamp, u64 ref, bool no_return)
164{
165 struct call_return_processor *crp = ts->crp;
166 struct thread_stack_entry *tse;
167 struct call_return cr = {
168 .thread = thread,
169 .comm = ts->comm,
170 .db_id = 0,
171 };
172
173 tse = &ts->stack[idx];
174 cr.cp = tse->cp;
175 cr.call_time = tse->timestamp;
176 cr.return_time = timestamp;
177 cr.branch_count = ts->branch_count - tse->branch_count;
178 cr.call_ref = tse->ref;
179 cr.return_ref = ref;
180 if (tse->no_call)
181 cr.flags |= CALL_RETURN_NO_CALL;
182 if (no_return)
183 cr.flags |= CALL_RETURN_NO_RETURN;
184
185 return crp->process(&cr, crp->data);
186}
187
188static int __thread_stack__flush(struct thread *thread, struct thread_stack *ts)
189{
190 struct call_return_processor *crp = ts->crp;
191 int err;
192
193 if (!crp) {
194 ts->cnt = 0;
195 return 0;
196 }
197
198 while (ts->cnt) {
199 err = thread_stack__call_return(thread, ts, --ts->cnt,
200 ts->last_time, 0, true);
201 if (err) {
202 pr_err("Error flushing thread stack!\n");
203 ts->cnt = 0;
204 return err;
205 }
206 }
207
208 return 0;
209}
210
211int thread_stack__flush(struct thread *thread)
212{
213 if (thread->ts)
214 return __thread_stack__flush(thread, thread->ts);
215
216 return 0;
217}
218
219int thread_stack__event(struct thread *thread, u32 flags, u64 from_ip,
220 u64 to_ip, u16 insn_len, u64 trace_nr)
221{
222 if (!thread)
223 return -EINVAL;
224
225 if (!thread->ts) {
226 thread->ts = thread_stack__new(thread, NULL);
227 if (!thread->ts) {
228 pr_warning("Out of memory: no thread stack\n");
229 return -ENOMEM;
230 }
231 thread->ts->trace_nr = trace_nr;
232 }
233
234 /*
235 * When the trace is discontinuous, the trace_nr changes. In that case
236 * the stack might be completely invalid. Better to report nothing than
237 * to report something misleading, so flush the stack.
238 */
239 if (trace_nr != thread->ts->trace_nr) {
240 if (thread->ts->trace_nr)
241 __thread_stack__flush(thread, thread->ts);
242 thread->ts->trace_nr = trace_nr;
243 }
244
245 /* Stop here if thread_stack__process() is in use */
246 if (thread->ts->crp)
247 return 0;
248
249 if (flags & PERF_IP_FLAG_CALL) {
250 u64 ret_addr;
251
252 if (!to_ip)
253 return 0;
254 ret_addr = from_ip + insn_len;
255 if (ret_addr == to_ip)
256 return 0; /* Zero-length calls are excluded */
257 return thread_stack__push(thread->ts, ret_addr);
258 } else if (flags & PERF_IP_FLAG_RETURN) {
259 if (!from_ip)
260 return 0;
261 thread_stack__pop(thread->ts, to_ip);
262 }
263
264 return 0;
265}
266
267void thread_stack__set_trace_nr(struct thread *thread, u64 trace_nr)
268{
269 if (!thread || !thread->ts)
270 return;
271
272 if (trace_nr != thread->ts->trace_nr) {
273 if (thread->ts->trace_nr)
274 __thread_stack__flush(thread, thread->ts);
275 thread->ts->trace_nr = trace_nr;
276 }
277}
278
279void thread_stack__free(struct thread *thread)
280{
281 if (thread->ts) {
282 __thread_stack__flush(thread, thread->ts);
283 zfree(&thread->ts->stack);
284 zfree(&thread->ts);
285 }
286}
287
288void thread_stack__sample(struct thread *thread, struct ip_callchain *chain,
289 size_t sz, u64 ip)
290{
291 size_t i;
292
293 if (!thread || !thread->ts)
294 chain->nr = 1;
295 else
296 chain->nr = min(sz, thread->ts->cnt + 1);
297
298 chain->ips[0] = ip;
299
300 for (i = 1; i < chain->nr; i++)
301 chain->ips[i] = thread->ts->stack[thread->ts->cnt - i].ret_addr;
302}
303
304struct call_return_processor *
305call_return_processor__new(int (*process)(struct call_return *cr, void *data),
306 void *data)
307{
308 struct call_return_processor *crp;
309
310 crp = zalloc(sizeof(struct call_return_processor));
311 if (!crp)
312 return NULL;
313 crp->cpr = call_path_root__new();
314 if (!crp->cpr)
315 goto out_free;
316 crp->process = process;
317 crp->data = data;
318 return crp;
319
320out_free:
321 free(crp);
322 return NULL;
323}
324
325void call_return_processor__free(struct call_return_processor *crp)
326{
327 if (crp) {
328 call_path_root__free(crp->cpr);
329 free(crp);
330 }
331}
332
333static int thread_stack__push_cp(struct thread_stack *ts, u64 ret_addr,
334 u64 timestamp, u64 ref, struct call_path *cp,
335 bool no_call)
336{
337 struct thread_stack_entry *tse;
338 int err;
339
340 if (ts->cnt == ts->sz) {
341 err = thread_stack__grow(ts);
342 if (err)
343 return err;
344 }
345
346 tse = &ts->stack[ts->cnt++];
347 tse->ret_addr = ret_addr;
348 tse->timestamp = timestamp;
349 tse->ref = ref;
350 tse->branch_count = ts->branch_count;
351 tse->cp = cp;
352 tse->no_call = no_call;
353
354 return 0;
355}
356
357static int thread_stack__pop_cp(struct thread *thread, struct thread_stack *ts,
358 u64 ret_addr, u64 timestamp, u64 ref,
359 struct symbol *sym)
360{
361 int err;
362
363 if (!ts->cnt)
364 return 1;
365
366 if (ts->cnt == 1) {
367 struct thread_stack_entry *tse = &ts->stack[0];
368
369 if (tse->cp->sym == sym)
370 return thread_stack__call_return(thread, ts, --ts->cnt,
371 timestamp, ref, false);
372 }
373
374 if (ts->stack[ts->cnt - 1].ret_addr == ret_addr) {
375 return thread_stack__call_return(thread, ts, --ts->cnt,
376 timestamp, ref, false);
377 } else {
378 size_t i = ts->cnt - 1;
379
380 while (i--) {
381 if (ts->stack[i].ret_addr != ret_addr)
382 continue;
383 i += 1;
384 while (ts->cnt > i) {
385 err = thread_stack__call_return(thread, ts,
386 --ts->cnt,
387 timestamp, ref,
388 true);
389 if (err)
390 return err;
391 }
392 return thread_stack__call_return(thread, ts, --ts->cnt,
393 timestamp, ref, false);
394 }
395 }
396
397 return 1;
398}
399
400static int thread_stack__bottom(struct thread *thread, struct thread_stack *ts,
401 struct perf_sample *sample,
402 struct addr_location *from_al,
403 struct addr_location *to_al, u64 ref)
404{
405 struct call_path_root *cpr = ts->crp->cpr;
406 struct call_path *cp;
407 struct symbol *sym;
408 u64 ip;
409
410 if (sample->ip) {
411 ip = sample->ip;
412 sym = from_al->sym;
413 } else if (sample->addr) {
414 ip = sample->addr;
415 sym = to_al->sym;
416 } else {
417 return 0;
418 }
419
420 cp = call_path__findnew(cpr, &cpr->call_path, sym, ip,
421 ts->kernel_start);
422 if (!cp)
423 return -ENOMEM;
424
425 return thread_stack__push_cp(thread->ts, ip, sample->time, ref, cp,
426 true);
427}
428
429static int thread_stack__no_call_return(struct thread *thread,
430 struct thread_stack *ts,
431 struct perf_sample *sample,
432 struct addr_location *from_al,
433 struct addr_location *to_al, u64 ref)
434{
435 struct call_path_root *cpr = ts->crp->cpr;
436 struct call_path *cp, *parent;
437 u64 ks = ts->kernel_start;
438 int err;
439
440 if (sample->ip >= ks && sample->addr < ks) {
441 /* Return to userspace, so pop all kernel addresses */
442 while (thread_stack__in_kernel(ts)) {
443 err = thread_stack__call_return(thread, ts, --ts->cnt,
444 sample->time, ref,
445 true);
446 if (err)
447 return err;
448 }
449
450 /* If the stack is empty, push the userspace address */
451 if (!ts->cnt) {
452 cp = call_path__findnew(cpr, &cpr->call_path,
453 to_al->sym, sample->addr,
454 ts->kernel_start);
455 if (!cp)
456 return -ENOMEM;
457 return thread_stack__push_cp(ts, 0, sample->time, ref,
458 cp, true);
459 }
460 } else if (thread_stack__in_kernel(ts) && sample->ip < ks) {
461 /* Return to userspace, so pop all kernel addresses */
462 while (thread_stack__in_kernel(ts)) {
463 err = thread_stack__call_return(thread, ts, --ts->cnt,
464 sample->time, ref,
465 true);
466 if (err)
467 return err;
468 }
469 }
470
471 if (ts->cnt)
472 parent = ts->stack[ts->cnt - 1].cp;
473 else
474 parent = &cpr->call_path;
475
476 /* This 'return' had no 'call', so push and pop top of stack */
477 cp = call_path__findnew(cpr, parent, from_al->sym, sample->ip,
478 ts->kernel_start);
479 if (!cp)
480 return -ENOMEM;
481
482 err = thread_stack__push_cp(ts, sample->addr, sample->time, ref, cp,
483 true);
484 if (err)
485 return err;
486
487 return thread_stack__pop_cp(thread, ts, sample->addr, sample->time, ref,
488 to_al->sym);
489}
490
491static int thread_stack__trace_begin(struct thread *thread,
492 struct thread_stack *ts, u64 timestamp,
493 u64 ref)
494{
495 struct thread_stack_entry *tse;
496 int err;
497
498 if (!ts->cnt)
499 return 0;
500
501 /* Pop trace end */
502 tse = &ts->stack[ts->cnt - 1];
503 if (tse->cp->sym == NULL && tse->cp->ip == 0) {
504 err = thread_stack__call_return(thread, ts, --ts->cnt,
505 timestamp, ref, false);
506 if (err)
507 return err;
508 }
509
510 return 0;
511}
512
513static int thread_stack__trace_end(struct thread_stack *ts,
514 struct perf_sample *sample, u64 ref)
515{
516 struct call_path_root *cpr = ts->crp->cpr;
517 struct call_path *cp;
518 u64 ret_addr;
519
520 /* No point having 'trace end' on the bottom of the stack */
521 if (!ts->cnt || (ts->cnt == 1 && ts->stack[0].ref == ref))
522 return 0;
523
524 cp = call_path__findnew(cpr, ts->stack[ts->cnt - 1].cp, NULL, 0,
525 ts->kernel_start);
526 if (!cp)
527 return -ENOMEM;
528
529 ret_addr = sample->ip + sample->insn_len;
530
531 return thread_stack__push_cp(ts, ret_addr, sample->time, ref, cp,
532 false);
533}
534
535int thread_stack__process(struct thread *thread, struct comm *comm,
536 struct perf_sample *sample,
537 struct addr_location *from_al,
538 struct addr_location *to_al, u64 ref,
539 struct call_return_processor *crp)
540{
541 struct thread_stack *ts = thread->ts;
542 int err = 0;
543
544 if (ts) {
545 if (!ts->crp) {
546 /* Supersede thread_stack__event() */
547 thread_stack__free(thread);
548 thread->ts = thread_stack__new(thread, crp);
549 if (!thread->ts)
550 return -ENOMEM;
551 ts = thread->ts;
552 ts->comm = comm;
553 }
554 } else {
555 thread->ts = thread_stack__new(thread, crp);
556 if (!thread->ts)
557 return -ENOMEM;
558 ts = thread->ts;
559 ts->comm = comm;
560 }
561
562 /* Flush stack on exec */
563 if (ts->comm != comm && thread->pid_ == thread->tid) {
564 err = __thread_stack__flush(thread, ts);
565 if (err)
566 return err;
567 ts->comm = comm;
568 }
569
570 /* If the stack is empty, put the current symbol on the stack */
571 if (!ts->cnt) {
572 err = thread_stack__bottom(thread, ts, sample, from_al, to_al,
573 ref);
574 if (err)
575 return err;
576 }
577
578 ts->branch_count += 1;
579 ts->last_time = sample->time;
580
581 if (sample->flags & PERF_IP_FLAG_CALL) {
582 struct call_path_root *cpr = ts->crp->cpr;
583 struct call_path *cp;
584 u64 ret_addr;
585
586 if (!sample->ip || !sample->addr)
587 return 0;
588
589 ret_addr = sample->ip + sample->insn_len;
590 if (ret_addr == sample->addr)
591 return 0; /* Zero-length calls are excluded */
592
593 cp = call_path__findnew(cpr, ts->stack[ts->cnt - 1].cp,
594 to_al->sym, sample->addr,
595 ts->kernel_start);
596 if (!cp)
597 return -ENOMEM;
598 err = thread_stack__push_cp(ts, ret_addr, sample->time, ref,
599 cp, false);
600 } else if (sample->flags & PERF_IP_FLAG_RETURN) {
601 if (!sample->ip || !sample->addr)
602 return 0;
603
604 err = thread_stack__pop_cp(thread, ts, sample->addr,
605 sample->time, ref, from_al->sym);
606 if (err) {
607 if (err < 0)
608 return err;
609 err = thread_stack__no_call_return(thread, ts, sample,
610 from_al, to_al, ref);
611 }
612 } else if (sample->flags & PERF_IP_FLAG_TRACE_BEGIN) {
613 err = thread_stack__trace_begin(thread, ts, sample->time, ref);
614 } else if (sample->flags & PERF_IP_FLAG_TRACE_END) {
615 err = thread_stack__trace_end(ts, sample, ref);
616 }
617
618 return err;
619}
620
621size_t thread_stack__depth(struct thread *thread)
622{
623 if (!thread->ts)
624 return 0;
625 return thread->ts->cnt;
626}