Loading...
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}
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * thread-stack.c: Synthesize a thread's stack using call / return events
4 * Copyright (c) 2014, Intel Corporation.
5 */
6
7#include <linux/rbtree.h>
8#include <linux/list.h>
9#include <linux/log2.h>
10#include <linux/zalloc.h>
11#include <errno.h>
12#include <stdlib.h>
13#include <string.h>
14#include "thread.h"
15#include "event.h"
16#include "machine.h"
17#include "env.h"
18#include "debug.h"
19#include "symbol.h"
20#include "comm.h"
21#include "call-path.h"
22#include "thread-stack.h"
23
24#define STACK_GROWTH 2048
25
26/*
27 * State of retpoline detection.
28 *
29 * RETPOLINE_NONE: no retpoline detection
30 * X86_RETPOLINE_POSSIBLE: x86 retpoline possible
31 * X86_RETPOLINE_DETECTED: x86 retpoline detected
32 */
33enum retpoline_state_t {
34 RETPOLINE_NONE,
35 X86_RETPOLINE_POSSIBLE,
36 X86_RETPOLINE_DETECTED,
37};
38
39/**
40 * struct thread_stack_entry - thread stack entry.
41 * @ret_addr: return address
42 * @timestamp: timestamp (if known)
43 * @ref: external reference (e.g. db_id of sample)
44 * @branch_count: the branch count when the entry was created
45 * @insn_count: the instruction count when the entry was created
46 * @cyc_count the cycle count when the entry was created
47 * @db_id: id used for db-export
48 * @cp: call path
49 * @no_call: a 'call' was not seen
50 * @trace_end: a 'call' but trace ended
51 * @non_call: a branch but not a 'call' to the start of a different symbol
52 */
53struct thread_stack_entry {
54 u64 ret_addr;
55 u64 timestamp;
56 u64 ref;
57 u64 branch_count;
58 u64 insn_count;
59 u64 cyc_count;
60 u64 db_id;
61 struct call_path *cp;
62 bool no_call;
63 bool trace_end;
64 bool non_call;
65};
66
67/**
68 * struct thread_stack - thread stack constructed from 'call' and 'return'
69 * branch samples.
70 * @stack: array that holds the stack
71 * @cnt: number of entries in the stack
72 * @sz: current maximum stack size
73 * @trace_nr: current trace number
74 * @branch_count: running branch count
75 * @insn_count: running instruction count
76 * @cyc_count running cycle count
77 * @kernel_start: kernel start address
78 * @last_time: last timestamp
79 * @crp: call/return processor
80 * @comm: current comm
81 * @arr_sz: size of array if this is the first element of an array
82 * @rstate: used to detect retpolines
83 */
84struct thread_stack {
85 struct thread_stack_entry *stack;
86 size_t cnt;
87 size_t sz;
88 u64 trace_nr;
89 u64 branch_count;
90 u64 insn_count;
91 u64 cyc_count;
92 u64 kernel_start;
93 u64 last_time;
94 struct call_return_processor *crp;
95 struct comm *comm;
96 unsigned int arr_sz;
97 enum retpoline_state_t rstate;
98};
99
100/*
101 * Assume pid == tid == 0 identifies the idle task as defined by
102 * perf_session__register_idle_thread(). The idle task is really 1 task per cpu,
103 * and therefore requires a stack for each cpu.
104 */
105static inline bool thread_stack__per_cpu(struct thread *thread)
106{
107 return !(thread->tid || thread->pid_);
108}
109
110static int thread_stack__grow(struct thread_stack *ts)
111{
112 struct thread_stack_entry *new_stack;
113 size_t sz, new_sz;
114
115 new_sz = ts->sz + STACK_GROWTH;
116 sz = new_sz * sizeof(struct thread_stack_entry);
117
118 new_stack = realloc(ts->stack, sz);
119 if (!new_stack)
120 return -ENOMEM;
121
122 ts->stack = new_stack;
123 ts->sz = new_sz;
124
125 return 0;
126}
127
128static int thread_stack__init(struct thread_stack *ts, struct thread *thread,
129 struct call_return_processor *crp)
130{
131 int err;
132
133 err = thread_stack__grow(ts);
134 if (err)
135 return err;
136
137 if (thread->mg && thread->mg->machine) {
138 struct machine *machine = thread->mg->machine;
139 const char *arch = perf_env__arch(machine->env);
140
141 ts->kernel_start = machine__kernel_start(machine);
142 if (!strcmp(arch, "x86"))
143 ts->rstate = X86_RETPOLINE_POSSIBLE;
144 } else {
145 ts->kernel_start = 1ULL << 63;
146 }
147 ts->crp = crp;
148
149 return 0;
150}
151
152static struct thread_stack *thread_stack__new(struct thread *thread, int cpu,
153 struct call_return_processor *crp)
154{
155 struct thread_stack *ts = thread->ts, *new_ts;
156 unsigned int old_sz = ts ? ts->arr_sz : 0;
157 unsigned int new_sz = 1;
158
159 if (thread_stack__per_cpu(thread) && cpu > 0)
160 new_sz = roundup_pow_of_two(cpu + 1);
161
162 if (!ts || new_sz > old_sz) {
163 new_ts = calloc(new_sz, sizeof(*ts));
164 if (!new_ts)
165 return NULL;
166 if (ts)
167 memcpy(new_ts, ts, old_sz * sizeof(*ts));
168 new_ts->arr_sz = new_sz;
169 zfree(&thread->ts);
170 thread->ts = new_ts;
171 ts = new_ts;
172 }
173
174 if (thread_stack__per_cpu(thread) && cpu > 0 &&
175 (unsigned int)cpu < ts->arr_sz)
176 ts += cpu;
177
178 if (!ts->stack &&
179 thread_stack__init(ts, thread, crp))
180 return NULL;
181
182 return ts;
183}
184
185static struct thread_stack *thread__cpu_stack(struct thread *thread, int cpu)
186{
187 struct thread_stack *ts = thread->ts;
188
189 if (cpu < 0)
190 cpu = 0;
191
192 if (!ts || (unsigned int)cpu >= ts->arr_sz)
193 return NULL;
194
195 ts += cpu;
196
197 if (!ts->stack)
198 return NULL;
199
200 return ts;
201}
202
203static inline struct thread_stack *thread__stack(struct thread *thread,
204 int cpu)
205{
206 if (!thread)
207 return NULL;
208
209 if (thread_stack__per_cpu(thread))
210 return thread__cpu_stack(thread, cpu);
211
212 return thread->ts;
213}
214
215static int thread_stack__push(struct thread_stack *ts, u64 ret_addr,
216 bool trace_end)
217{
218 int err = 0;
219
220 if (ts->cnt == ts->sz) {
221 err = thread_stack__grow(ts);
222 if (err) {
223 pr_warning("Out of memory: discarding thread stack\n");
224 ts->cnt = 0;
225 }
226 }
227
228 ts->stack[ts->cnt].trace_end = trace_end;
229 ts->stack[ts->cnt++].ret_addr = ret_addr;
230
231 return err;
232}
233
234static void thread_stack__pop(struct thread_stack *ts, u64 ret_addr)
235{
236 size_t i;
237
238 /*
239 * In some cases there may be functions which are not seen to return.
240 * For example when setjmp / longjmp has been used. Or the perf context
241 * switch in the kernel which doesn't stop and start tracing in exactly
242 * the same code path. When that happens the return address will be
243 * further down the stack. If the return address is not found at all,
244 * we assume the opposite (i.e. this is a return for a call that wasn't
245 * seen for some reason) and leave the stack alone.
246 */
247 for (i = ts->cnt; i; ) {
248 if (ts->stack[--i].ret_addr == ret_addr) {
249 ts->cnt = i;
250 return;
251 }
252 }
253}
254
255static void thread_stack__pop_trace_end(struct thread_stack *ts)
256{
257 size_t i;
258
259 for (i = ts->cnt; i; ) {
260 if (ts->stack[--i].trace_end)
261 ts->cnt = i;
262 else
263 return;
264 }
265}
266
267static bool thread_stack__in_kernel(struct thread_stack *ts)
268{
269 if (!ts->cnt)
270 return false;
271
272 return ts->stack[ts->cnt - 1].cp->in_kernel;
273}
274
275static int thread_stack__call_return(struct thread *thread,
276 struct thread_stack *ts, size_t idx,
277 u64 timestamp, u64 ref, bool no_return)
278{
279 struct call_return_processor *crp = ts->crp;
280 struct thread_stack_entry *tse;
281 struct call_return cr = {
282 .thread = thread,
283 .comm = ts->comm,
284 .db_id = 0,
285 };
286 u64 *parent_db_id;
287
288 tse = &ts->stack[idx];
289 cr.cp = tse->cp;
290 cr.call_time = tse->timestamp;
291 cr.return_time = timestamp;
292 cr.branch_count = ts->branch_count - tse->branch_count;
293 cr.insn_count = ts->insn_count - tse->insn_count;
294 cr.cyc_count = ts->cyc_count - tse->cyc_count;
295 cr.db_id = tse->db_id;
296 cr.call_ref = tse->ref;
297 cr.return_ref = ref;
298 if (tse->no_call)
299 cr.flags |= CALL_RETURN_NO_CALL;
300 if (no_return)
301 cr.flags |= CALL_RETURN_NO_RETURN;
302 if (tse->non_call)
303 cr.flags |= CALL_RETURN_NON_CALL;
304
305 /*
306 * The parent db_id must be assigned before exporting the child. Note
307 * it is not possible to export the parent first because its information
308 * is not yet complete because its 'return' has not yet been processed.
309 */
310 parent_db_id = idx ? &(tse - 1)->db_id : NULL;
311
312 return crp->process(&cr, parent_db_id, crp->data);
313}
314
315static int __thread_stack__flush(struct thread *thread, struct thread_stack *ts)
316{
317 struct call_return_processor *crp = ts->crp;
318 int err;
319
320 if (!crp) {
321 ts->cnt = 0;
322 return 0;
323 }
324
325 while (ts->cnt) {
326 err = thread_stack__call_return(thread, ts, --ts->cnt,
327 ts->last_time, 0, true);
328 if (err) {
329 pr_err("Error flushing thread stack!\n");
330 ts->cnt = 0;
331 return err;
332 }
333 }
334
335 return 0;
336}
337
338int thread_stack__flush(struct thread *thread)
339{
340 struct thread_stack *ts = thread->ts;
341 unsigned int pos;
342 int err = 0;
343
344 if (ts) {
345 for (pos = 0; pos < ts->arr_sz; pos++) {
346 int ret = __thread_stack__flush(thread, ts + pos);
347
348 if (ret)
349 err = ret;
350 }
351 }
352
353 return err;
354}
355
356int thread_stack__event(struct thread *thread, int cpu, u32 flags, u64 from_ip,
357 u64 to_ip, u16 insn_len, u64 trace_nr)
358{
359 struct thread_stack *ts = thread__stack(thread, cpu);
360
361 if (!thread)
362 return -EINVAL;
363
364 if (!ts) {
365 ts = thread_stack__new(thread, cpu, NULL);
366 if (!ts) {
367 pr_warning("Out of memory: no thread stack\n");
368 return -ENOMEM;
369 }
370 ts->trace_nr = trace_nr;
371 }
372
373 /*
374 * When the trace is discontinuous, the trace_nr changes. In that case
375 * the stack might be completely invalid. Better to report nothing than
376 * to report something misleading, so flush the stack.
377 */
378 if (trace_nr != ts->trace_nr) {
379 if (ts->trace_nr)
380 __thread_stack__flush(thread, ts);
381 ts->trace_nr = trace_nr;
382 }
383
384 /* Stop here if thread_stack__process() is in use */
385 if (ts->crp)
386 return 0;
387
388 if (flags & PERF_IP_FLAG_CALL) {
389 u64 ret_addr;
390
391 if (!to_ip)
392 return 0;
393 ret_addr = from_ip + insn_len;
394 if (ret_addr == to_ip)
395 return 0; /* Zero-length calls are excluded */
396 return thread_stack__push(ts, ret_addr,
397 flags & PERF_IP_FLAG_TRACE_END);
398 } else if (flags & PERF_IP_FLAG_TRACE_BEGIN) {
399 /*
400 * If the caller did not change the trace number (which would
401 * have flushed the stack) then try to make sense of the stack.
402 * Possibly, tracing began after returning to the current
403 * address, so try to pop that. Also, do not expect a call made
404 * when the trace ended, to return, so pop that.
405 */
406 thread_stack__pop(ts, to_ip);
407 thread_stack__pop_trace_end(ts);
408 } else if ((flags & PERF_IP_FLAG_RETURN) && from_ip) {
409 thread_stack__pop(ts, to_ip);
410 }
411
412 return 0;
413}
414
415void thread_stack__set_trace_nr(struct thread *thread, int cpu, u64 trace_nr)
416{
417 struct thread_stack *ts = thread__stack(thread, cpu);
418
419 if (!ts)
420 return;
421
422 if (trace_nr != ts->trace_nr) {
423 if (ts->trace_nr)
424 __thread_stack__flush(thread, ts);
425 ts->trace_nr = trace_nr;
426 }
427}
428
429static void __thread_stack__free(struct thread *thread, struct thread_stack *ts)
430{
431 __thread_stack__flush(thread, ts);
432 zfree(&ts->stack);
433}
434
435static void thread_stack__reset(struct thread *thread, struct thread_stack *ts)
436{
437 unsigned int arr_sz = ts->arr_sz;
438
439 __thread_stack__free(thread, ts);
440 memset(ts, 0, sizeof(*ts));
441 ts->arr_sz = arr_sz;
442}
443
444void thread_stack__free(struct thread *thread)
445{
446 struct thread_stack *ts = thread->ts;
447 unsigned int pos;
448
449 if (ts) {
450 for (pos = 0; pos < ts->arr_sz; pos++)
451 __thread_stack__free(thread, ts + pos);
452 zfree(&thread->ts);
453 }
454}
455
456static inline u64 callchain_context(u64 ip, u64 kernel_start)
457{
458 return ip < kernel_start ? PERF_CONTEXT_USER : PERF_CONTEXT_KERNEL;
459}
460
461void thread_stack__sample(struct thread *thread, int cpu,
462 struct ip_callchain *chain,
463 size_t sz, u64 ip, u64 kernel_start)
464{
465 struct thread_stack *ts = thread__stack(thread, cpu);
466 u64 context = callchain_context(ip, kernel_start);
467 u64 last_context;
468 size_t i, j;
469
470 if (sz < 2) {
471 chain->nr = 0;
472 return;
473 }
474
475 chain->ips[0] = context;
476 chain->ips[1] = ip;
477
478 if (!ts) {
479 chain->nr = 2;
480 return;
481 }
482
483 last_context = context;
484
485 for (i = 2, j = 1; i < sz && j <= ts->cnt; i++, j++) {
486 ip = ts->stack[ts->cnt - j].ret_addr;
487 context = callchain_context(ip, kernel_start);
488 if (context != last_context) {
489 if (i >= sz - 1)
490 break;
491 chain->ips[i++] = context;
492 last_context = context;
493 }
494 chain->ips[i] = ip;
495 }
496
497 chain->nr = i;
498}
499
500struct call_return_processor *
501call_return_processor__new(int (*process)(struct call_return *cr, u64 *parent_db_id, void *data),
502 void *data)
503{
504 struct call_return_processor *crp;
505
506 crp = zalloc(sizeof(struct call_return_processor));
507 if (!crp)
508 return NULL;
509 crp->cpr = call_path_root__new();
510 if (!crp->cpr)
511 goto out_free;
512 crp->process = process;
513 crp->data = data;
514 return crp;
515
516out_free:
517 free(crp);
518 return NULL;
519}
520
521void call_return_processor__free(struct call_return_processor *crp)
522{
523 if (crp) {
524 call_path_root__free(crp->cpr);
525 free(crp);
526 }
527}
528
529static int thread_stack__push_cp(struct thread_stack *ts, u64 ret_addr,
530 u64 timestamp, u64 ref, struct call_path *cp,
531 bool no_call, bool trace_end)
532{
533 struct thread_stack_entry *tse;
534 int err;
535
536 if (!cp)
537 return -ENOMEM;
538
539 if (ts->cnt == ts->sz) {
540 err = thread_stack__grow(ts);
541 if (err)
542 return err;
543 }
544
545 tse = &ts->stack[ts->cnt++];
546 tse->ret_addr = ret_addr;
547 tse->timestamp = timestamp;
548 tse->ref = ref;
549 tse->branch_count = ts->branch_count;
550 tse->insn_count = ts->insn_count;
551 tse->cyc_count = ts->cyc_count;
552 tse->cp = cp;
553 tse->no_call = no_call;
554 tse->trace_end = trace_end;
555 tse->non_call = false;
556 tse->db_id = 0;
557
558 return 0;
559}
560
561static int thread_stack__pop_cp(struct thread *thread, struct thread_stack *ts,
562 u64 ret_addr, u64 timestamp, u64 ref,
563 struct symbol *sym)
564{
565 int err;
566
567 if (!ts->cnt)
568 return 1;
569
570 if (ts->cnt == 1) {
571 struct thread_stack_entry *tse = &ts->stack[0];
572
573 if (tse->cp->sym == sym)
574 return thread_stack__call_return(thread, ts, --ts->cnt,
575 timestamp, ref, false);
576 }
577
578 if (ts->stack[ts->cnt - 1].ret_addr == ret_addr &&
579 !ts->stack[ts->cnt - 1].non_call) {
580 return thread_stack__call_return(thread, ts, --ts->cnt,
581 timestamp, ref, false);
582 } else {
583 size_t i = ts->cnt - 1;
584
585 while (i--) {
586 if (ts->stack[i].ret_addr != ret_addr ||
587 ts->stack[i].non_call)
588 continue;
589 i += 1;
590 while (ts->cnt > i) {
591 err = thread_stack__call_return(thread, ts,
592 --ts->cnt,
593 timestamp, ref,
594 true);
595 if (err)
596 return err;
597 }
598 return thread_stack__call_return(thread, ts, --ts->cnt,
599 timestamp, ref, false);
600 }
601 }
602
603 return 1;
604}
605
606static int thread_stack__bottom(struct thread_stack *ts,
607 struct perf_sample *sample,
608 struct addr_location *from_al,
609 struct addr_location *to_al, u64 ref)
610{
611 struct call_path_root *cpr = ts->crp->cpr;
612 struct call_path *cp;
613 struct symbol *sym;
614 u64 ip;
615
616 if (sample->ip) {
617 ip = sample->ip;
618 sym = from_al->sym;
619 } else if (sample->addr) {
620 ip = sample->addr;
621 sym = to_al->sym;
622 } else {
623 return 0;
624 }
625
626 cp = call_path__findnew(cpr, &cpr->call_path, sym, ip,
627 ts->kernel_start);
628
629 return thread_stack__push_cp(ts, ip, sample->time, ref, cp,
630 true, false);
631}
632
633static int thread_stack__pop_ks(struct thread *thread, struct thread_stack *ts,
634 struct perf_sample *sample, u64 ref)
635{
636 u64 tm = sample->time;
637 int err;
638
639 /* Return to userspace, so pop all kernel addresses */
640 while (thread_stack__in_kernel(ts)) {
641 err = thread_stack__call_return(thread, ts, --ts->cnt,
642 tm, ref, true);
643 if (err)
644 return err;
645 }
646
647 return 0;
648}
649
650static int thread_stack__no_call_return(struct thread *thread,
651 struct thread_stack *ts,
652 struct perf_sample *sample,
653 struct addr_location *from_al,
654 struct addr_location *to_al, u64 ref)
655{
656 struct call_path_root *cpr = ts->crp->cpr;
657 struct call_path *root = &cpr->call_path;
658 struct symbol *fsym = from_al->sym;
659 struct symbol *tsym = to_al->sym;
660 struct call_path *cp, *parent;
661 u64 ks = ts->kernel_start;
662 u64 addr = sample->addr;
663 u64 tm = sample->time;
664 u64 ip = sample->ip;
665 int err;
666
667 if (ip >= ks && addr < ks) {
668 /* Return to userspace, so pop all kernel addresses */
669 err = thread_stack__pop_ks(thread, ts, sample, ref);
670 if (err)
671 return err;
672
673 /* If the stack is empty, push the userspace address */
674 if (!ts->cnt) {
675 cp = call_path__findnew(cpr, root, tsym, addr, ks);
676 return thread_stack__push_cp(ts, 0, tm, ref, cp, true,
677 false);
678 }
679 } else if (thread_stack__in_kernel(ts) && ip < ks) {
680 /* Return to userspace, so pop all kernel addresses */
681 err = thread_stack__pop_ks(thread, ts, sample, ref);
682 if (err)
683 return err;
684 }
685
686 if (ts->cnt)
687 parent = ts->stack[ts->cnt - 1].cp;
688 else
689 parent = root;
690
691 if (parent->sym == from_al->sym) {
692 /*
693 * At the bottom of the stack, assume the missing 'call' was
694 * before the trace started. So, pop the current symbol and push
695 * the 'to' symbol.
696 */
697 if (ts->cnt == 1) {
698 err = thread_stack__call_return(thread, ts, --ts->cnt,
699 tm, ref, false);
700 if (err)
701 return err;
702 }
703
704 if (!ts->cnt) {
705 cp = call_path__findnew(cpr, root, tsym, addr, ks);
706
707 return thread_stack__push_cp(ts, addr, tm, ref, cp,
708 true, false);
709 }
710
711 /*
712 * Otherwise assume the 'return' is being used as a jump (e.g.
713 * retpoline) and just push the 'to' symbol.
714 */
715 cp = call_path__findnew(cpr, parent, tsym, addr, ks);
716
717 err = thread_stack__push_cp(ts, 0, tm, ref, cp, true, false);
718 if (!err)
719 ts->stack[ts->cnt - 1].non_call = true;
720
721 return err;
722 }
723
724 /*
725 * Assume 'parent' has not yet returned, so push 'to', and then push and
726 * pop 'from'.
727 */
728
729 cp = call_path__findnew(cpr, parent, tsym, addr, ks);
730
731 err = thread_stack__push_cp(ts, addr, tm, ref, cp, true, false);
732 if (err)
733 return err;
734
735 cp = call_path__findnew(cpr, cp, fsym, ip, ks);
736
737 err = thread_stack__push_cp(ts, ip, tm, ref, cp, true, false);
738 if (err)
739 return err;
740
741 return thread_stack__call_return(thread, ts, --ts->cnt, tm, ref, false);
742}
743
744static int thread_stack__trace_begin(struct thread *thread,
745 struct thread_stack *ts, u64 timestamp,
746 u64 ref)
747{
748 struct thread_stack_entry *tse;
749 int err;
750
751 if (!ts->cnt)
752 return 0;
753
754 /* Pop trace end */
755 tse = &ts->stack[ts->cnt - 1];
756 if (tse->trace_end) {
757 err = thread_stack__call_return(thread, ts, --ts->cnt,
758 timestamp, ref, false);
759 if (err)
760 return err;
761 }
762
763 return 0;
764}
765
766static int thread_stack__trace_end(struct thread_stack *ts,
767 struct perf_sample *sample, u64 ref)
768{
769 struct call_path_root *cpr = ts->crp->cpr;
770 struct call_path *cp;
771 u64 ret_addr;
772
773 /* No point having 'trace end' on the bottom of the stack */
774 if (!ts->cnt || (ts->cnt == 1 && ts->stack[0].ref == ref))
775 return 0;
776
777 cp = call_path__findnew(cpr, ts->stack[ts->cnt - 1].cp, NULL, 0,
778 ts->kernel_start);
779
780 ret_addr = sample->ip + sample->insn_len;
781
782 return thread_stack__push_cp(ts, ret_addr, sample->time, ref, cp,
783 false, true);
784}
785
786static bool is_x86_retpoline(const char *name)
787{
788 const char *p = strstr(name, "__x86_indirect_thunk_");
789
790 return p == name || !strcmp(name, "__indirect_thunk_start");
791}
792
793/*
794 * x86 retpoline functions pollute the call graph. This function removes them.
795 * This does not handle function return thunks, nor is there any improvement
796 * for the handling of inline thunks or extern thunks.
797 */
798static int thread_stack__x86_retpoline(struct thread_stack *ts,
799 struct perf_sample *sample,
800 struct addr_location *to_al)
801{
802 struct thread_stack_entry *tse = &ts->stack[ts->cnt - 1];
803 struct call_path_root *cpr = ts->crp->cpr;
804 struct symbol *sym = tse->cp->sym;
805 struct symbol *tsym = to_al->sym;
806 struct call_path *cp;
807
808 if (sym && is_x86_retpoline(sym->name)) {
809 /*
810 * This is a x86 retpoline fn. It pollutes the call graph by
811 * showing up everywhere there is an indirect branch, but does
812 * not itself mean anything. Here the top-of-stack is removed,
813 * by decrementing the stack count, and then further down, the
814 * resulting top-of-stack is replaced with the actual target.
815 * The result is that the retpoline functions will no longer
816 * appear in the call graph. Note this only affects the call
817 * graph, since all the original branches are left unchanged.
818 */
819 ts->cnt -= 1;
820 sym = ts->stack[ts->cnt - 2].cp->sym;
821 if (sym && sym == tsym && to_al->addr != tsym->start) {
822 /*
823 * Target is back to the middle of the symbol we came
824 * from so assume it is an indirect jmp and forget it
825 * altogether.
826 */
827 ts->cnt -= 1;
828 return 0;
829 }
830 } else if (sym && sym == tsym) {
831 /*
832 * Target is back to the symbol we came from so assume it is an
833 * indirect jmp and forget it altogether.
834 */
835 ts->cnt -= 1;
836 return 0;
837 }
838
839 cp = call_path__findnew(cpr, ts->stack[ts->cnt - 2].cp, tsym,
840 sample->addr, ts->kernel_start);
841 if (!cp)
842 return -ENOMEM;
843
844 /* Replace the top-of-stack with the actual target */
845 ts->stack[ts->cnt - 1].cp = cp;
846
847 return 0;
848}
849
850int thread_stack__process(struct thread *thread, struct comm *comm,
851 struct perf_sample *sample,
852 struct addr_location *from_al,
853 struct addr_location *to_al, u64 ref,
854 struct call_return_processor *crp)
855{
856 struct thread_stack *ts = thread__stack(thread, sample->cpu);
857 enum retpoline_state_t rstate;
858 int err = 0;
859
860 if (ts && !ts->crp) {
861 /* Supersede thread_stack__event() */
862 thread_stack__reset(thread, ts);
863 ts = NULL;
864 }
865
866 if (!ts) {
867 ts = thread_stack__new(thread, sample->cpu, crp);
868 if (!ts)
869 return -ENOMEM;
870 ts->comm = comm;
871 }
872
873 rstate = ts->rstate;
874 if (rstate == X86_RETPOLINE_DETECTED)
875 ts->rstate = X86_RETPOLINE_POSSIBLE;
876
877 /* Flush stack on exec */
878 if (ts->comm != comm && thread->pid_ == thread->tid) {
879 err = __thread_stack__flush(thread, ts);
880 if (err)
881 return err;
882 ts->comm = comm;
883 }
884
885 /* If the stack is empty, put the current symbol on the stack */
886 if (!ts->cnt) {
887 err = thread_stack__bottom(ts, sample, from_al, to_al, ref);
888 if (err)
889 return err;
890 }
891
892 ts->branch_count += 1;
893 ts->insn_count += sample->insn_cnt;
894 ts->cyc_count += sample->cyc_cnt;
895 ts->last_time = sample->time;
896
897 if (sample->flags & PERF_IP_FLAG_CALL) {
898 bool trace_end = sample->flags & PERF_IP_FLAG_TRACE_END;
899 struct call_path_root *cpr = ts->crp->cpr;
900 struct call_path *cp;
901 u64 ret_addr;
902
903 if (!sample->ip || !sample->addr)
904 return 0;
905
906 ret_addr = sample->ip + sample->insn_len;
907 if (ret_addr == sample->addr)
908 return 0; /* Zero-length calls are excluded */
909
910 cp = call_path__findnew(cpr, ts->stack[ts->cnt - 1].cp,
911 to_al->sym, sample->addr,
912 ts->kernel_start);
913 err = thread_stack__push_cp(ts, ret_addr, sample->time, ref,
914 cp, false, trace_end);
915
916 /*
917 * A call to the same symbol but not the start of the symbol,
918 * may be the start of a x86 retpoline.
919 */
920 if (!err && rstate == X86_RETPOLINE_POSSIBLE && to_al->sym &&
921 from_al->sym == to_al->sym &&
922 to_al->addr != to_al->sym->start)
923 ts->rstate = X86_RETPOLINE_DETECTED;
924
925 } else if (sample->flags & PERF_IP_FLAG_RETURN) {
926 if (!sample->addr) {
927 u32 return_from_kernel = PERF_IP_FLAG_SYSCALLRET |
928 PERF_IP_FLAG_INTERRUPT;
929
930 if (!(sample->flags & return_from_kernel))
931 return 0;
932
933 /* Pop kernel stack */
934 return thread_stack__pop_ks(thread, ts, sample, ref);
935 }
936
937 if (!sample->ip)
938 return 0;
939
940 /* x86 retpoline 'return' doesn't match the stack */
941 if (rstate == X86_RETPOLINE_DETECTED && ts->cnt > 2 &&
942 ts->stack[ts->cnt - 1].ret_addr != sample->addr)
943 return thread_stack__x86_retpoline(ts, sample, to_al);
944
945 err = thread_stack__pop_cp(thread, ts, sample->addr,
946 sample->time, ref, from_al->sym);
947 if (err) {
948 if (err < 0)
949 return err;
950 err = thread_stack__no_call_return(thread, ts, sample,
951 from_al, to_al, ref);
952 }
953 } else if (sample->flags & PERF_IP_FLAG_TRACE_BEGIN) {
954 err = thread_stack__trace_begin(thread, ts, sample->time, ref);
955 } else if (sample->flags & PERF_IP_FLAG_TRACE_END) {
956 err = thread_stack__trace_end(ts, sample, ref);
957 } else if (sample->flags & PERF_IP_FLAG_BRANCH &&
958 from_al->sym != to_al->sym && to_al->sym &&
959 to_al->addr == to_al->sym->start) {
960 struct call_path_root *cpr = ts->crp->cpr;
961 struct call_path *cp;
962
963 /*
964 * The compiler might optimize a call/ret combination by making
965 * it a jmp. Make that visible by recording on the stack a
966 * branch to the start of a different symbol. Note, that means
967 * when a ret pops the stack, all jmps must be popped off first.
968 */
969 cp = call_path__findnew(cpr, ts->stack[ts->cnt - 1].cp,
970 to_al->sym, sample->addr,
971 ts->kernel_start);
972 err = thread_stack__push_cp(ts, 0, sample->time, ref, cp, false,
973 false);
974 if (!err)
975 ts->stack[ts->cnt - 1].non_call = true;
976 }
977
978 return err;
979}
980
981size_t thread_stack__depth(struct thread *thread, int cpu)
982{
983 struct thread_stack *ts = thread__stack(thread, cpu);
984
985 if (!ts)
986 return 0;
987 return ts->cnt;
988}