tools/perf/util/thread-stack.c

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This source file includes following definitions.
thread_stack__per_cpu
thread_stack__grow
thread_stack__init
thread_stack__new
thread__cpu_stack
thread__stack
thread_stack__push
thread_stack__pop
thread_stack__pop_trace_end
thread_stack__in_kernel
thread_stack__call_return
__thread_stack__flush
thread_stack__flush
thread_stack__event
thread_stack__set_trace_nr
__thread_stack__free
thread_stack__reset
thread_stack__free
callchain_context
thread_stack__sample
call_return_processor__new
call_return_processor__free
thread_stack__push_cp
thread_stack__pop_cp
thread_stack__bottom
thread_stack__pop_ks
thread_stack__no_call_return
thread_stack__trace_begin
thread_stack__trace_end
is_x86_retpoline
thread_stack__x86_retpoline
thread_stack__process
thread_stack__depth
   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  */
  33 enum 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  */
  53 struct 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  */
  84 struct 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  */
 105 static inline bool thread_stack__per_cpu(struct thread *thread)
 106 {
 107         return !(thread->tid || thread->pid_);
 108 }
 109 
 110 static 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 
 128 static 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 
 152 static 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 
 185 static 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 
 203 static 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 
 215 static 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 
 234 static 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 
 255 static 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 
 267 static 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 
 275 static 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 
 315 static 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 
 338 int 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 
 356 int 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 
 415 void 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 
 429 static void __thread_stack__free(struct thread *thread, struct thread_stack *ts)
 430 {
 431         __thread_stack__flush(thread, ts);
 432         zfree(&ts->stack);
 433 }
 434 
 435 static 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 
 444 void 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 
 456 static inline u64 callchain_context(u64 ip, u64 kernel_start)
 457 {
 458         return ip < kernel_start ? PERF_CONTEXT_USER : PERF_CONTEXT_KERNEL;
 459 }
 460 
 461 void 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 
 500 struct call_return_processor *
 501 call_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 
 516 out_free:
 517         free(crp);
 518         return NULL;
 519 }
 520 
 521 void 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 
 529 static 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 
 561 static 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 
 606 static 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 
 633 static 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 
 650 static 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 
 744 static 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 
 766 static 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 
 786 static 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  */
 798 static 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 
 850 int 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 
 981 size_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 }
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root/tools/perf/util/thread-stack.c

DEFINITIONS
