kernel/trace/trace_functions_graph.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *
   4  * Function graph tracer.
   5  * Copyright (c) 2008-2009 Frederic Weisbecker <fweisbec@gmail.com>
   6  * Mostly borrowed from function tracer which
   7  * is Copyright (c) Steven Rostedt <srostedt@redhat.com>
   8  *
   9  */
  10 #include <linux/uaccess.h>
  11 #include <linux/ftrace.h>
  12 #include <linux/interrupt.h>
  13 #include <linux/slab.h>
  14 #include <linux/fs.h>
  15
  16 #include "trace.h"
  17 #include "trace_output.h"
  18
  19 /* When set, irq functions will be ignored */
  20 static int ftrace_graph_skip_irqs;
  21
  22 struct fgraph_cpu_data {
  23         pid_t           last_pid;
  24         int             depth;
  25         int             depth_irq;
  26         int             ignore;
  27         unsigned long   enter_funcs[FTRACE_RETFUNC_DEPTH];
  28 };
  29
  30 struct fgraph_data {
  31         struct fgraph_cpu_data __percpu *cpu_data;
  32
  33         /* Place to preserve last processed entry. */
  34         struct ftrace_graph_ent_entry   ent;
  35         struct ftrace_graph_ret_entry   ret;
  36         int                             failed;
  37         int                             cpu;
  38 };
  39
  40 #define TRACE_GRAPH_INDENT      2
  41
  42 unsigned int fgraph_max_depth;
  43
  44 static struct tracer_opt trace_opts[] = {
  45         /* Display overruns? (for self-debug purpose) */
  46         { TRACER_OPT(funcgraph-overrun, TRACE_GRAPH_PRINT_OVERRUN) },
  47         /* Display CPU ? */
  48         { TRACER_OPT(funcgraph-cpu, TRACE_GRAPH_PRINT_CPU) },
  49         /* Display Overhead ? */
  50         { TRACER_OPT(funcgraph-overhead, TRACE_GRAPH_PRINT_OVERHEAD) },
  51         /* Display proc name/pid */
  52         { TRACER_OPT(funcgraph-proc, TRACE_GRAPH_PRINT_PROC) },
  53         /* Display duration of execution */
  54         { TRACER_OPT(funcgraph-duration, TRACE_GRAPH_PRINT_DURATION) },
  55         /* Display absolute time of an entry */
  56         { TRACER_OPT(funcgraph-abstime, TRACE_GRAPH_PRINT_ABS_TIME) },
  57         /* Display interrupts */
  58         { TRACER_OPT(funcgraph-irqs, TRACE_GRAPH_PRINT_IRQS) },
  59         /* Display function name after trailing } */
  60         { TRACER_OPT(funcgraph-tail, TRACE_GRAPH_PRINT_TAIL) },
  61         /* Include sleep time (scheduled out) between entry and return */
  62         { TRACER_OPT(sleep-time, TRACE_GRAPH_SLEEP_TIME) },
  63
  64 #ifdef CONFIG_FUNCTION_PROFILER
  65         /* Include time within nested functions */
  66         { TRACER_OPT(graph-time, TRACE_GRAPH_GRAPH_TIME) },
  67 #endif
  68
  69         { } /* Empty entry */
  70 };
  71
  72 static struct tracer_flags tracer_flags = {
  73         /* Don't display overruns, proc, or tail by default */
  74         .val = TRACE_GRAPH_PRINT_CPU | TRACE_GRAPH_PRINT_OVERHEAD |
  75                TRACE_GRAPH_PRINT_DURATION | TRACE_GRAPH_PRINT_IRQS |
  76                TRACE_GRAPH_SLEEP_TIME | TRACE_GRAPH_GRAPH_TIME,
  77         .opts = trace_opts
  78 };
  79
  80 static struct trace_array *graph_array;
  81
  82 /*
  83  * DURATION column is being also used to display IRQ signs,
  84  * following values are used by print_graph_irq and others
  85  * to fill in space into DURATION column.
  86  */
  87 enum {
  88         FLAGS_FILL_FULL  = 1 << TRACE_GRAPH_PRINT_FILL_SHIFT,
  89         FLAGS_FILL_START = 2 << TRACE_GRAPH_PRINT_FILL_SHIFT,
  90         FLAGS_FILL_END   = 3 << TRACE_GRAPH_PRINT_FILL_SHIFT,
  91 };
  92
  93 static void
  94 print_graph_duration(struct trace_array *tr, unsigned long long duration,
  95                      struct trace_seq *s, u32 flags);
  96
  97 int __trace_graph_entry(struct trace_array *tr,
  98                                 struct ftrace_graph_ent *trace,
  99                                 unsigned long flags,
 100                                 int pc)
 101 {
 102         struct trace_event_call *call = &event_funcgraph_entry;
 103         struct ring_buffer_event *event;
 104         struct ring_buffer *buffer = tr->trace_buffer.buffer;
 105         struct ftrace_graph_ent_entry *entry;
 106
 107         event = trace_buffer_lock_reserve(buffer, TRACE_GRAPH_ENT,
 108                                           sizeof(*entry), flags, pc);
 109         if (!event)
 110                 return 0;
 111         entry   = ring_buffer_event_data(event);
 112         entry->graph_ent                        = *trace;
 113         if (!call_filter_check_discard(call, entry, buffer, event))
 114                 trace_buffer_unlock_commit_nostack(buffer, event);
 115
 116         return 1;
 117 }
 118
 119 static inline int ftrace_graph_ignore_irqs(void)
 120 {
 121         if (!ftrace_graph_skip_irqs || trace_recursion_test(TRACE_IRQ_BIT))
 122                 return 0;
 123
 124         return in_irq();
 125 }
 126
 127 int trace_graph_entry(struct ftrace_graph_ent *trace)
 128 {
 129         struct trace_array *tr = graph_array;
 130         struct trace_array_cpu *data;
 131         unsigned long flags;
 132         long disabled;
 133         int ret;
 134         int cpu;
 135         int pc;
 136
 137         if (trace_recursion_test(TRACE_GRAPH_NOTRACE_BIT))
 138                 return 0;
 139
 140         if (ftrace_graph_notrace_addr(trace->func)) {
 141                 trace_recursion_set(TRACE_GRAPH_NOTRACE_BIT);
 142                 /*
 143                  * Need to return 1 to have the return called
 144                  * that will clear the NOTRACE bit.
 145                  */
 146                 return 1;
 147         }
 148
 149         if (!ftrace_trace_task(tr))
 150                 return 0;
 151
 152         if (ftrace_graph_ignore_func(trace))
 153                 return 0;
 154
 155         if (ftrace_graph_ignore_irqs())
 156                 return 0;
 157
 158         /*
 159          * Do not trace a function if it's filtered by set_graph_notrace.
 160          * Make the index of ret stack negative to indicate that it should
 161          * ignore further functions.  But it needs its own ret stack entry
 162          * to recover the original index in order to continue tracing after
 163          * returning from the function.
 164          */
 165         if (ftrace_graph_notrace_addr(trace->func))
 166                 return 1;
 167
 168         /*
 169          * Stop here if tracing_threshold is set. We only write function return
 170          * events to the ring buffer.
 171          */
 172         if (tracing_thresh)
 173                 return 1;
 174
 175         local_irq_save(flags);
 176         cpu = raw_smp_processor_id();
 177         data = per_cpu_ptr(tr->trace_buffer.data, cpu);
 178         disabled = atomic_inc_return(&data->disabled);
 179         if (likely(disabled == 1)) {
 180                 pc = preempt_count();
 181                 ret = __trace_graph_entry(tr, trace, flags, pc);
 182         } else {
 183                 ret = 0;
 184         }
 185
 186         atomic_dec(&data->disabled);
 187         local_irq_restore(flags);
 188
 189         return ret;
 190 }
 191
 192 static void
 193 __trace_graph_function(struct trace_array *tr,
 194                 unsigned long ip, unsigned long flags, int pc)
 195 {
 196         u64 time = trace_clock_local();
 197         struct ftrace_graph_ent ent = {
 198                 .func  = ip,
 199                 .depth = 0,
 200         };
 201         struct ftrace_graph_ret ret = {
 202                 .func     = ip,
 203                 .depth    = 0,
 204                 .calltime = time,
 205                 .rettime  = time,
 206         };
 207
 208         __trace_graph_entry(tr, &ent, flags, pc);
 209         __trace_graph_return(tr, &ret, flags, pc);
 210 }
 211
 212 void
 213 trace_graph_function(struct trace_array *tr,
 214                 unsigned long ip, unsigned long parent_ip,
 215                 unsigned long flags, int pc)
 216 {
 217         __trace_graph_function(tr, ip, flags, pc);
 218 }
 219
 220 void __trace_graph_return(struct trace_array *tr,
 221                                 struct ftrace_graph_ret *trace,
 222                                 unsigned long flags,
 223                                 int pc)
 224 {
 225         struct trace_event_call *call = &event_funcgraph_exit;
 226         struct ring_buffer_event *event;
 227         struct ring_buffer *buffer = tr->trace_buffer.buffer;
 228         struct ftrace_graph_ret_entry *entry;
 229
 230         event = trace_buffer_lock_reserve(buffer, TRACE_GRAPH_RET,
 231                                           sizeof(*entry), flags, pc);
 232         if (!event)
 233                 return;
 234         entry   = ring_buffer_event_data(event);
 235         entry->ret                              = *trace;
 236         if (!call_filter_check_discard(call, entry, buffer, event))
 237                 trace_buffer_unlock_commit_nostack(buffer, event);
 238 }
 239
 240 void trace_graph_return(struct ftrace_graph_ret *trace)
 241 {
 242         struct trace_array *tr = graph_array;
 243         struct trace_array_cpu *data;
 244         unsigned long flags;
 245         long disabled;
 246         int cpu;
 247         int pc;
 248
 249         ftrace_graph_addr_finish(trace);
 250
 251         if (trace_recursion_test(TRACE_GRAPH_NOTRACE_BIT)) {
 252                 trace_recursion_clear(TRACE_GRAPH_NOTRACE_BIT);
 253                 return;
 254         }
 255
 256         local_irq_save(flags);
 257         cpu = raw_smp_processor_id();
 258         data = per_cpu_ptr(tr->trace_buffer.data, cpu);
 259         disabled = atomic_inc_return(&data->disabled);
 260         if (likely(disabled == 1)) {
 261                 pc = preempt_count();
 262                 __trace_graph_return(tr, trace, flags, pc);
 263         }
 264         atomic_dec(&data->disabled);
 265         local_irq_restore(flags);
 266 }
 267
 268 void set_graph_array(struct trace_array *tr)
 269 {
 270         graph_array = tr;
 271
 272         /* Make graph_array visible before we start tracing */
 273
 274         smp_mb();
 275 }
 276
 277 static void trace_graph_thresh_return(struct ftrace_graph_ret *trace)
 278 {
 279         ftrace_graph_addr_finish(trace);
 280
 281         if (trace_recursion_test(TRACE_GRAPH_NOTRACE_BIT)) {
 282                 trace_recursion_clear(TRACE_GRAPH_NOTRACE_BIT);
 283                 return;
 284         }
 285
 286         if (tracing_thresh &&
 287             (trace->rettime - trace->calltime < tracing_thresh))
 288                 return;
 289         else
 290                 trace_graph_return(trace);
 291 }
 292
 293 static struct fgraph_ops funcgraph_thresh_ops = {
 294         .entryfunc = &trace_graph_entry,
 295         .retfunc = &trace_graph_thresh_return,
 296 };
 297
 298 static struct fgraph_ops funcgraph_ops = {
 299         .entryfunc = &trace_graph_entry,
 300         .retfunc = &trace_graph_return,
 301 };
 302
 303 static int graph_trace_init(struct trace_array *tr)
 304 {
 305         int ret;
 306
 307         set_graph_array(tr);
 308         if (tracing_thresh)
 309                 ret = register_ftrace_graph(&funcgraph_thresh_ops);
 310         else
 311                 ret = register_ftrace_graph(&funcgraph_ops);
 312         if (ret)
 313                 return ret;
 314         tracing_start_cmdline_record();
 315
 316         return 0;
 317 }
 318
 319 static void graph_trace_reset(struct trace_array *tr)
 320 {
 321         tracing_stop_cmdline_record();
 322         if (tracing_thresh)
 323                 unregister_ftrace_graph(&funcgraph_thresh_ops);
 324         else
 325                 unregister_ftrace_graph(&funcgraph_ops);
 326 }
 327
 328 static int graph_trace_update_thresh(struct trace_array *tr)
 329 {
 330         graph_trace_reset(tr);
 331         return graph_trace_init(tr);
 332 }
 333
 334 static int max_bytes_for_cpu;
 335
 336 static void print_graph_cpu(struct trace_seq *s, int cpu)
 337 {
 338         /*
 339          * Start with a space character - to make it stand out
 340          * to the right a bit when trace output is pasted into
 341          * email:
 342          */
 343         trace_seq_printf(s, " %*d) ", max_bytes_for_cpu, cpu);
 344 }
 345
 346 #define TRACE_GRAPH_PROCINFO_LENGTH     14
 347
 348 static void print_graph_proc(struct trace_seq *s, pid_t pid)
 349 {
 350         char comm[TASK_COMM_LEN];
 351         /* sign + log10(MAX_INT) + '\0' */
 352         char pid_str[11];
 353         int spaces = 0;
 354         int len;
 355         int i;
 356
 357         trace_find_cmdline(pid, comm);
 358         comm[7] = '\0';
 359         sprintf(pid_str, "%d", pid);
 360
 361         /* 1 stands for the "-" character */
 362         len = strlen(comm) + strlen(pid_str) + 1;
 363
 364         if (len < TRACE_GRAPH_PROCINFO_LENGTH)
 365                 spaces = TRACE_GRAPH_PROCINFO_LENGTH - len;
 366
 367         /* First spaces to align center */
 368         for (i = 0; i < spaces / 2; i++)
 369                 trace_seq_putc(s, ' ');
 370
 371         trace_seq_printf(s, "%s-%s", comm, pid_str);
 372
 373         /* Last spaces to align center */
 374         for (i = 0; i < spaces - (spaces / 2); i++)
 375                 trace_seq_putc(s, ' ');
 376 }
 377
 378
 379 static void print_graph_lat_fmt(struct trace_seq *s, struct trace_entry *entry)
 380 {
 381         trace_seq_putc(s, ' ');
 382         trace_print_lat_fmt(s, entry);
 383         trace_seq_puts(s, " | ");
 384 }
 385
 386 /* If the pid changed since the last trace, output this event */
 387 static void
 388 verif_pid(struct trace_seq *s, pid_t pid, int cpu, struct fgraph_data *data)
 389 {
 390         pid_t prev_pid;
 391         pid_t *last_pid;
 392
 393         if (!data)
 394                 return;
 395
 396         last_pid = &(per_cpu_ptr(data->cpu_data, cpu)->last_pid);
 397
 398         if (*last_pid == pid)
 399                 return;
 400
 401         prev_pid = *last_pid;
 402         *last_pid = pid;
 403
 404         if (prev_pid == -1)
 405                 return;
 406 /*
 407  * Context-switch trace line:
 408
 409  ------------------------------------------
 410  | 1)  migration/0--1  =>  sshd-1755
 411  ------------------------------------------
 412
 413  */
 414         trace_seq_puts(s, " ------------------------------------------\n");
 415         print_graph_cpu(s, cpu);
 416         print_graph_proc(s, prev_pid);
 417         trace_seq_puts(s, " => ");
 418         print_graph_proc(s, pid);
 419         trace_seq_puts(s, "\n ------------------------------------------\n\n");
 420 }
 421
 422 static struct ftrace_graph_ret_entry *
 423 get_return_for_leaf(struct trace_iterator *iter,
 424                 struct ftrace_graph_ent_entry *curr)
 425 {
 426         struct fgraph_data *data = iter->private;
 427         struct ring_buffer_iter *ring_iter = NULL;
 428         struct ring_buffer_event *event;
 429         struct ftrace_graph_ret_entry *next;
 430
 431         /*
 432          * If the previous output failed to write to the seq buffer,
 433          * then we just reuse the data from before.
 434          */
 435         if (data && data->failed) {
 436                 curr = &data->ent;
 437                 next = &data->ret;
 438         } else {
 439
 440                 ring_iter = trace_buffer_iter(iter, iter->cpu);
 441
 442                 /* First peek to compare current entry and the next one */
 443                 if (ring_iter)
 444                         event = ring_buffer_iter_peek(ring_iter, NULL);
 445                 else {
 446                         /*
 447                          * We need to consume the current entry to see
 448                          * the next one.
 449                          */
 450                         ring_buffer_consume(iter->trace_buffer->buffer, iter->cpu,
 451                                             NULL, NULL);
 452                         event = ring_buffer_peek(iter->trace_buffer->buffer, iter->cpu,
 453                                                  NULL, NULL);
 454                 }
 455
 456                 if (!event)
 457                         return NULL;
 458
 459                 next = ring_buffer_event_data(event);
 460
 461                 if (data) {
 462                         /*
 463                          * Save current and next entries for later reference
 464                          * if the output fails.
 465                          */
 466                         data->ent = *curr;
 467                         /*
 468                          * If the next event is not a return type, then
 469                          * we only care about what type it is. Otherwise we can
 470                          * safely copy the entire event.
 471                          */
 472                         if (next->ent.type == TRACE_GRAPH_RET)
 473                                 data->ret = *next;
 474                         else
 475                                 data->ret.ent.type = next->ent.type;
 476                 }
 477         }
 478
 479         if (next->ent.type != TRACE_GRAPH_RET)
 480                 return NULL;
 481
 482         if (curr->ent.pid != next->ent.pid ||
 483                         curr->graph_ent.func != next->ret.func)
 484                 return NULL;
 485
 486         /* this is a leaf, now advance the iterator */
 487         if (ring_iter)
 488                 ring_buffer_read(ring_iter, NULL);
 489
 490         return next;
 491 }
 492
 493 static void print_graph_abs_time(u64 t, struct trace_seq *s)
 494 {
 495         unsigned long usecs_rem;
 496
 497         usecs_rem = do_div(t, NSEC_PER_SEC);
 498         usecs_rem /= 1000;
 499
 500         trace_seq_printf(s, "%5lu.%06lu |  ",
 501                          (unsigned long)t, usecs_rem);
 502 }
 503
 504 static void
 505 print_graph_rel_time(struct trace_iterator *iter, struct trace_seq *s)
 506 {
 507         unsigned long long usecs;
 508
 509         usecs = iter->ts - iter->trace_buffer->time_start;
 510         do_div(usecs, NSEC_PER_USEC);
 511
 512         trace_seq_printf(s, "%9llu us |  ", usecs);
 513 }
 514
 515 static void
 516 print_graph_irq(struct trace_iterator *iter, unsigned long addr,
 517                 enum trace_type type, int cpu, pid_t pid, u32 flags)
 518 {
 519         struct trace_array *tr = iter->tr;
 520         struct trace_seq *s = &iter->seq;
 521         struct trace_entry *ent = iter->ent;
 522
 523         if (addr < (unsigned long)__irqentry_text_start ||
 524                 addr >= (unsigned long)__irqentry_text_end)
 525                 return;
 526
 527         if (tr->trace_flags & TRACE_ITER_CONTEXT_INFO) {
 528                 /* Absolute time */
 529                 if (flags & TRACE_GRAPH_PRINT_ABS_TIME)
 530                         print_graph_abs_time(iter->ts, s);
 531
 532                 /* Relative time */
 533                 if (flags & TRACE_GRAPH_PRINT_REL_TIME)
 534                         print_graph_rel_time(iter, s);
 535
 536                 /* Cpu */
 537                 if (flags & TRACE_GRAPH_PRINT_CPU)
 538                         print_graph_cpu(s, cpu);
 539
 540                 /* Proc */
 541                 if (flags & TRACE_GRAPH_PRINT_PROC) {
 542                         print_graph_proc(s, pid);
 543                         trace_seq_puts(s, " | ");
 544                 }
 545
 546                 /* Latency format */
 547                 if (tr->trace_flags & TRACE_ITER_LATENCY_FMT)
 548                         print_graph_lat_fmt(s, ent);
 549         }
 550
 551         /* No overhead */
 552         print_graph_duration(tr, 0, s, flags | FLAGS_FILL_START);
 553
 554         if (type == TRACE_GRAPH_ENT)
 555                 trace_seq_puts(s, "==========>");
 556         else
 557                 trace_seq_puts(s, "<==========");
 558
 559         print_graph_duration(tr, 0, s, flags | FLAGS_FILL_END);
 560         trace_seq_putc(s, '\n');
 561 }
 562
 563 void
 564 trace_print_graph_duration(unsigned long long duration, struct trace_seq *s)
 565 {
 566         unsigned long nsecs_rem = do_div(duration, 1000);
 567         /* log10(ULONG_MAX) + '\0' */
 568         char usecs_str[21];
 569         char nsecs_str[5];
 570         int len;
 571         int i;
 572
 573         sprintf(usecs_str, "%lu", (unsigned long) duration);
 574
 575         /* Print msecs */
 576         trace_seq_printf(s, "%s", usecs_str);
 577
 578         len = strlen(usecs_str);
 579
 580         /* Print nsecs (we don't want to exceed 7 numbers) */
 581         if (len < 7) {
 582                 size_t slen = min_t(size_t, sizeof(nsecs_str), 8UL - len);
 583
 584                 snprintf(nsecs_str, slen, "%03lu", nsecs_rem);
 585                 trace_seq_printf(s, ".%s", nsecs_str);
 586                 len += strlen(nsecs_str) + 1;
 587         }
 588
 589         trace_seq_puts(s, " us ");
 590
 591         /* Print remaining spaces to fit the row's width */
 592         for (i = len; i < 8; i++)
 593                 trace_seq_putc(s, ' ');
 594 }
 595
 596 static void
 597 print_graph_duration(struct trace_array *tr, unsigned long long duration,
 598                      struct trace_seq *s, u32 flags)
 599 {
 600         if (!(flags & TRACE_GRAPH_PRINT_DURATION) ||
 601             !(tr->trace_flags & TRACE_ITER_CONTEXT_INFO))
 602                 return;
 603
 604         /* No real adata, just filling the column with spaces */
 605         switch (flags & TRACE_GRAPH_PRINT_FILL_MASK) {
 606         case FLAGS_FILL_FULL:
 607                 trace_seq_puts(s, "              |  ");
 608                 return;
 609         case FLAGS_FILL_START:
 610                 trace_seq_puts(s, "  ");
 611                 return;
 612         case FLAGS_FILL_END:
 613                 trace_seq_puts(s, " |");
 614                 return;
 615         }
 616
 617         /* Signal a overhead of time execution to the output */
 618         if (flags & TRACE_GRAPH_PRINT_OVERHEAD)
 619                 trace_seq_printf(s, "%c ", trace_find_mark(duration));
 620         else
 621                 trace_seq_puts(s, "  ");
 622
 623         trace_print_graph_duration(duration, s);
 624         trace_seq_puts(s, "|  ");
 625 }
 626
 627 /* Case of a leaf function on its call entry */
 628 static enum print_line_t
 629 print_graph_entry_leaf(struct trace_iterator *iter,
 630                 struct ftrace_graph_ent_entry *entry,
 631                 struct ftrace_graph_ret_entry *ret_entry,
 632                 struct trace_seq *s, u32 flags)
 633 {
 634         struct fgraph_data *data = iter->private;
 635         struct trace_array *tr = iter->tr;
 636         struct ftrace_graph_ret *graph_ret;
 637         struct ftrace_graph_ent *call;
 638         unsigned long long duration;
 639         int cpu = iter->cpu;
 640         int i;
 641
 642         graph_ret = &ret_entry->ret;
 643         call = &entry->graph_ent;
 644         duration = graph_ret->rettime - graph_ret->calltime;
 645
 646         if (data) {
 647                 struct fgraph_cpu_data *cpu_data;
 648
 649                 cpu_data = per_cpu_ptr(data->cpu_data, cpu);
 650
 651                 /*
 652                  * Comments display at + 1 to depth. Since
 653                  * this is a leaf function, keep the comments
 654                  * equal to this depth.
 655                  */
 656                 cpu_data->depth = call->depth - 1;
 657
 658                 /* No need to keep this function around for this depth */
 659                 if (call->depth < FTRACE_RETFUNC_DEPTH &&
 660                     !WARN_ON_ONCE(call->depth < 0))
 661                         cpu_data->enter_funcs[call->depth] = 0;
 662         }
 663
 664         /* Overhead and duration */
 665         print_graph_duration(tr, duration, s, flags);
 666
 667         /* Function */
 668         for (i = 0; i < call->depth * TRACE_GRAPH_INDENT; i++)
 669                 trace_seq_putc(s, ' ');
 670
 671         trace_seq_printf(s, "%ps();\n", (void *)call->func);
 672
 673         print_graph_irq(iter, graph_ret->func, TRACE_GRAPH_RET,
 674                         cpu, iter->ent->pid, flags);
 675
 676         return trace_handle_return(s);
 677 }
 678
 679 static enum print_line_t
 680 print_graph_entry_nested(struct trace_iterator *iter,
 681                          struct ftrace_graph_ent_entry *entry,
 682                          struct trace_seq *s, int cpu, u32 flags)
 683 {
 684         struct ftrace_graph_ent *call = &entry->graph_ent;
 685         struct fgraph_data *data = iter->private;
 686         struct trace_array *tr = iter->tr;
 687         int i;
 688
 689         if (data) {
 690                 struct fgraph_cpu_data *cpu_data;
 691                 int cpu = iter->cpu;
 692
 693                 cpu_data = per_cpu_ptr(data->cpu_data, cpu);
 694                 cpu_data->depth = call->depth;
 695
 696                 /* Save this function pointer to see if the exit matches */
 697                 if (call->depth < FTRACE_RETFUNC_DEPTH &&
 698                     !WARN_ON_ONCE(call->depth < 0))
 699                         cpu_data->enter_funcs[call->depth] = call->func;
 700         }
 701
 702         /* No time */
 703         print_graph_duration(tr, 0, s, flags | FLAGS_FILL_FULL);
 704
 705         /* Function */
 706         for (i = 0; i < call->depth * TRACE_GRAPH_INDENT; i++)
 707                 trace_seq_putc(s, ' ');
 708
 709         trace_seq_printf(s, "%ps() {\n", (void *)call->func);
 710
 711         if (trace_seq_has_overflowed(s))
 712                 return TRACE_TYPE_PARTIAL_LINE;
 713
 714         /*
 715          * we already consumed the current entry to check the next one
 716          * and see if this is a leaf.
 717          */
 718         return TRACE_TYPE_NO_CONSUME;
 719 }
 720
 721 static void
 722 print_graph_prologue(struct trace_iterator *iter, struct trace_seq *s,
 723                      int type, unsigned long addr, u32 flags)
 724 {
 725         struct fgraph_data *data = iter->private;
 726         struct trace_entry *ent = iter->ent;
 727         struct trace_array *tr = iter->tr;
 728         int cpu = iter->cpu;
 729
 730         /* Pid */
 731         verif_pid(s, ent->pid, cpu, data);
 732
 733         if (type)
 734                 /* Interrupt */
 735                 print_graph_irq(iter, addr, type, cpu, ent->pid, flags);
 736
 737         if (!(tr->trace_flags & TRACE_ITER_CONTEXT_INFO))
 738                 return;
 739
 740         /* Absolute time */
 741         if (flags & TRACE_GRAPH_PRINT_ABS_TIME)
 742                 print_graph_abs_time(iter->ts, s);
 743
 744         /* Relative time */
 745         if (flags & TRACE_GRAPH_PRINT_REL_TIME)
 746                 print_graph_rel_time(iter, s);
 747
 748         /* Cpu */
 749         if (flags & TRACE_GRAPH_PRINT_CPU)
 750                 print_graph_cpu(s, cpu);
 751
 752         /* Proc */
 753         if (flags & TRACE_GRAPH_PRINT_PROC) {
 754                 print_graph_proc(s, ent->pid);
 755                 trace_seq_puts(s, " | ");
 756         }
 757
 758         /* Latency format */
 759         if (tr->trace_flags & TRACE_ITER_LATENCY_FMT)
 760                 print_graph_lat_fmt(s, ent);
 761
 762         return;
 763 }
 764
 765 /*
 766  * Entry check for irq code
 767  *
 768  * returns 1 if
 769  *  - we are inside irq code
 770  *  - we just entered irq code
 771  *
 772  * retunns 0 if
 773  *  - funcgraph-interrupts option is set
 774  *  - we are not inside irq code
 775  */
 776 static int
 777 check_irq_entry(struct trace_iterator *iter, u32 flags,
 778                 unsigned long addr, int depth)
 779 {
 780         int cpu = iter->cpu;
 781         int *depth_irq;
 782         struct fgraph_data *data = iter->private;
 783
 784         /*
 785          * If we are either displaying irqs, or we got called as
 786          * a graph event and private data does not exist,
 787          * then we bypass the irq check.
 788          */
 789         if ((flags & TRACE_GRAPH_PRINT_IRQS) ||
 790             (!data))
 791                 return 0;
 792
 793         depth_irq = &(per_cpu_ptr(data->cpu_data, cpu)->depth_irq);
 794
 795         /*
 796          * We are inside the irq code
 797          */
 798         if (*depth_irq >= 0)
 799                 return 1;
 800
 801         if ((addr < (unsigned long)__irqentry_text_start) ||
 802             (addr >= (unsigned long)__irqentry_text_end))
 803                 return 0;
 804
 805         /*
 806          * We are entering irq code.
 807          */
 808         *depth_irq = depth;
 809         return 1;
 810 }
 811
 812 /*
 813  * Return check for irq code
 814  *
 815  * returns 1 if
 816  *  - we are inside irq code
 817  *  - we just left irq code
 818  *
 819  * returns 0 if
 820  *  - funcgraph-interrupts option is set
 821  *  - we are not inside irq code
 822  */
 823 static int
 824 check_irq_return(struct trace_iterator *iter, u32 flags, int depth)
 825 {
 826         int cpu = iter->cpu;
 827         int *depth_irq;
 828         struct fgraph_data *data = iter->private;
 829
 830         /*
 831          * If we are either displaying irqs, or we got called as
 832          * a graph event and private data does not exist,
 833          * then we bypass the irq check.
 834          */
 835         if ((flags & TRACE_GRAPH_PRINT_IRQS) ||
 836             (!data))
 837                 return 0;
 838
 839         depth_irq = &(per_cpu_ptr(data->cpu_data, cpu)->depth_irq);
 840
 841         /*
 842          * We are not inside the irq code.
 843          */
 844         if (*depth_irq == -1)
 845                 return 0;
 846
 847         /*
 848          * We are inside the irq code, and this is returning entry.
 849          * Let's not trace it and clear the entry depth, since
 850          * we are out of irq code.
 851          *
 852          * This condition ensures that we 'leave the irq code' once
 853          * we are out of the entry depth. Thus protecting us from
 854          * the RETURN entry loss.
 855          */
 856         if (*depth_irq >= depth) {
 857                 *depth_irq = -1;
 858                 return 1;
 859         }
 860
 861         /*
 862          * We are inside the irq code, and this is not the entry.
 863          */
 864         return 1;
 865 }
 866
 867 static enum print_line_t
 868 print_graph_entry(struct ftrace_graph_ent_entry *field, struct trace_seq *s,
 869                         struct trace_iterator *iter, u32 flags)
 870 {
 871         struct fgraph_data *data = iter->private;
 872         struct ftrace_graph_ent *call = &field->graph_ent;
 873         struct ftrace_graph_ret_entry *leaf_ret;
 874         static enum print_line_t ret;
 875         int cpu = iter->cpu;
 876
 877         if (check_irq_entry(iter, flags, call->func, call->depth))
 878                 return TRACE_TYPE_HANDLED;
 879
 880         print_graph_prologue(iter, s, TRACE_GRAPH_ENT, call->func, flags);
 881
 882         leaf_ret = get_return_for_leaf(iter, field);
 883         if (leaf_ret)
 884                 ret = print_graph_entry_leaf(iter, field, leaf_ret, s, flags);
 885         else
 886                 ret = print_graph_entry_nested(iter, field, s, cpu, flags);
 887
 888         if (data) {
 889                 /*
 890                  * If we failed to write our output, then we need to make
 891                  * note of it. Because we already consumed our entry.
 892                  */
 893                 if (s->full) {
 894                         data->failed = 1;
 895                         data->cpu = cpu;
 896                 } else
 897                         data->failed = 0;
 898         }
 899
 900         return ret;
 901 }
 902
 903 static enum print_line_t
 904 print_graph_return(struct ftrace_graph_ret *trace, struct trace_seq *s,
 905                    struct trace_entry *ent, struct trace_iterator *iter,
 906                    u32 flags)
 907 {
 908         unsigned long long duration = trace->rettime - trace->calltime;
 909         struct fgraph_data *data = iter->private;
 910         struct trace_array *tr = iter->tr;
 911         pid_t pid = ent->pid;
 912         int cpu = iter->cpu;
 913         int func_match = 1;
 914         int i;
 915
 916         if (check_irq_return(iter, flags, trace->depth))
 917                 return TRACE_TYPE_HANDLED;
 918
 919         if (data) {
 920                 struct fgraph_cpu_data *cpu_data;
 921                 int cpu = iter->cpu;
 922
 923                 cpu_data = per_cpu_ptr(data->cpu_data, cpu);
 924
 925                 /*
 926                  * Comments display at + 1 to depth. This is the
 927                  * return from a function, we now want the comments
 928                  * to display at the same level of the bracket.
 929                  */
 930                 cpu_data->depth = trace->depth - 1;
 931
 932                 if (trace->depth < FTRACE_RETFUNC_DEPTH &&
 933                     !WARN_ON_ONCE(trace->depth < 0)) {
 934                         if (cpu_data->enter_funcs[trace->depth] != trace->func)
 935                                 func_match = 0;
 936                         cpu_data->enter_funcs[trace->depth] = 0;
 937                 }
 938         }
 939
 940         print_graph_prologue(iter, s, 0, 0, flags);
 941
 942         /* Overhead and duration */
 943         print_graph_duration(tr, duration, s, flags);
 944
 945         /* Closing brace */
 946         for (i = 0; i < trace->depth * TRACE_GRAPH_INDENT; i++)
 947                 trace_seq_putc(s, ' ');
 948
 949         /*
 950          * If the return function does not have a matching entry,
 951          * then the entry was lost. Instead of just printing
 952          * the '}' and letting the user guess what function this
 953          * belongs to, write out the function name. Always do
 954          * that if the funcgraph-tail option is enabled.
 955          */
 956         if (func_match && !(flags & TRACE_GRAPH_PRINT_TAIL))
 957                 trace_seq_puts(s, "}\n");
 958         else
 959                 trace_seq_printf(s, "} /* %ps */\n", (void *)trace->func);
 960
 961         /* Overrun */
 962         if (flags & TRACE_GRAPH_PRINT_OVERRUN)
 963                 trace_seq_printf(s, " (Overruns: %lu)\n",
 964                                  trace->overrun);
 965
 966         print_graph_irq(iter, trace->func, TRACE_GRAPH_RET,
 967                         cpu, pid, flags);
 968
 969         return trace_handle_return(s);
 970 }
 971
 972 static enum print_line_t
 973 print_graph_comment(struct trace_seq *s, struct trace_entry *ent,
 974                     struct trace_iterator *iter, u32 flags)
 975 {
 976         struct trace_array *tr = iter->tr;
 977         unsigned long sym_flags = (tr->trace_flags & TRACE_ITER_SYM_MASK);
 978         struct fgraph_data *data = iter->private;
 979         struct trace_event *event;
 980         int depth = 0;
 981         int ret;
 982         int i;
 983
 984         if (data)
 985                 depth = per_cpu_ptr(data->cpu_data, iter->cpu)->depth;
 986
 987         print_graph_prologue(iter, s, 0, 0, flags);
 988
 989         /* No time */
 990         print_graph_duration(tr, 0, s, flags | FLAGS_FILL_FULL);
 991
 992         /* Indentation */
 993         if (depth > 0)
 994                 for (i = 0; i < (depth + 1) * TRACE_GRAPH_INDENT; i++)
 995                         trace_seq_putc(s, ' ');
 996
 997         /* The comment */
 998         trace_seq_puts(s, "/* ");
 999
1000         switch (iter->ent->type) {
1001         case TRACE_BPUTS:
1002                 ret = trace_print_bputs_msg_only(iter);
1003                 if (ret != TRACE_TYPE_HANDLED)
1004                         return ret;
1005                 break;
1006         case TRACE_BPRINT:
1007                 ret = trace_print_bprintk_msg_only(iter);
1008                 if (ret != TRACE_TYPE_HANDLED)
1009                         return ret;
1010                 break;
1011         case TRACE_PRINT:
1012                 ret = trace_print_printk_msg_only(iter);
1013                 if (ret != TRACE_TYPE_HANDLED)
1014                         return ret;
1015                 break;
1016         default:
1017                 event = ftrace_find_event(ent->type);
1018                 if (!event)
1019                         return TRACE_TYPE_UNHANDLED;
1020
1021                 ret = event->funcs->trace(iter, sym_flags, event);
1022                 if (ret != TRACE_TYPE_HANDLED)
1023                         return ret;
1024         }
1025
1026         if (trace_seq_has_overflowed(s))
1027                 goto out;
1028
1029         /* Strip ending newline */
1030         if (s->buffer[s->seq.len - 1] == '\n') {
1031                 s->buffer[s->seq.len - 1] = '\0';
1032                 s->seq.len--;
1033         }
1034
1035         trace_seq_puts(s, " */\n");
1036  out:
1037         return trace_handle_return(s);
1038 }
1039
1040
1041 enum print_line_t
1042 print_graph_function_flags(struct trace_iterator *iter, u32 flags)
1043 {
1044         struct ftrace_graph_ent_entry *field;
1045         struct fgraph_data *data = iter->private;
1046         struct trace_entry *entry = iter->ent;
1047         struct trace_seq *s = &iter->seq;
1048         int cpu = iter->cpu;
1049         int ret;
1050
1051         if (data && per_cpu_ptr(data->cpu_data, cpu)->ignore) {
1052                 per_cpu_ptr(data->cpu_data, cpu)->ignore = 0;
1053                 return TRACE_TYPE_HANDLED;
1054         }
1055
1056         /*
1057          * If the last output failed, there's a possibility we need
1058          * to print out the missing entry which would never go out.
1059          */
1060         if (data && data->failed) {
1061                 field = &data->ent;
1062                 iter->cpu = data->cpu;
1063                 ret = print_graph_entry(field, s, iter, flags);
1064                 if (ret == TRACE_TYPE_HANDLED && iter->cpu != cpu) {
1065                         per_cpu_ptr(data->cpu_data, iter->cpu)->ignore = 1;
1066                         ret = TRACE_TYPE_NO_CONSUME;
1067                 }
1068                 iter->cpu = cpu;
1069                 return ret;
1070         }
1071
1072         switch (entry->type) {
1073         case TRACE_GRAPH_ENT: {
1074                 /*
1075                  * print_graph_entry() may consume the current event,
1076                  * thus @field may become invalid, so we need to save it.
1077                  * sizeof(struct ftrace_graph_ent_entry) is very small,
1078                  * it can be safely saved at the stack.
1079                  */
1080                 struct ftrace_graph_ent_entry saved;
1081                 trace_assign_type(field, entry);
1082                 saved = *field;
1083                 return print_graph_entry(&saved, s, iter, flags);
1084         }
1085         case TRACE_GRAPH_RET: {
1086                 struct ftrace_graph_ret_entry *field;
1087                 trace_assign_type(field, entry);
1088                 return print_graph_return(&field->ret, s, entry, iter, flags);
1089         }
1090         case TRACE_STACK:
1091         case TRACE_FN:
1092                 /* dont trace stack and functions as comments */
1093                 return TRACE_TYPE_UNHANDLED;
1094
1095         default:
1096                 return print_graph_comment(s, entry, iter, flags);
1097         }
1098
1099         return TRACE_TYPE_HANDLED;
1100 }
1101
1102 static enum print_line_t
1103 print_graph_function(struct trace_iterator *iter)
1104 {
1105         return print_graph_function_flags(iter, tracer_flags.val);
1106 }
1107
1108 static enum print_line_t
1109 print_graph_function_event(struct trace_iterator *iter, int flags,
1110                            struct trace_event *event)
1111 {
1112         return print_graph_function(iter);
1113 }
1114
1115 static void print_lat_header(struct seq_file *s, u32 flags)
1116 {
1117         static const char spaces[] = "                " /* 16 spaces */
1118                 "    "                                  /* 4 spaces */
1119                 "                 ";                    /* 17 spaces */
1120         int size = 0;
1121
1122         if (flags & TRACE_GRAPH_PRINT_ABS_TIME)
1123                 size += 16;
1124         if (flags & TRACE_GRAPH_PRINT_REL_TIME)
1125                 size += 16;
1126         if (flags & TRACE_GRAPH_PRINT_CPU)
1127                 size += 4;
1128         if (flags & TRACE_GRAPH_PRINT_PROC)
1129                 size += 17;
1130
1131         seq_printf(s, "#%.*s  _-----=> irqs-off        \n", size, spaces);
1132         seq_printf(s, "#%.*s / _----=> need-resched    \n", size, spaces);
1133         seq_printf(s, "#%.*s| / _---=> hardirq/softirq \n", size, spaces);
1134         seq_printf(s, "#%.*s|| / _--=> preempt-depth   \n", size, spaces);
1135         seq_printf(s, "#%.*s||| /                      \n", size, spaces);
1136 }
1137
1138 static void __print_graph_headers_flags(struct trace_array *tr,
1139                                         struct seq_file *s, u32 flags)
1140 {
1141         int lat = tr->trace_flags & TRACE_ITER_LATENCY_FMT;
1142
1143         if (lat)
1144                 print_lat_header(s, flags);
1145
1146         /* 1st line */
1147         seq_putc(s, '#');
1148         if (flags & TRACE_GRAPH_PRINT_ABS_TIME)
1149                 seq_puts(s, "     TIME       ");
1150         if (flags & TRACE_GRAPH_PRINT_REL_TIME)
1151                 seq_puts(s, "   REL TIME     ");
1152         if (flags & TRACE_GRAPH_PRINT_CPU)
1153                 seq_puts(s, " CPU");
1154         if (flags & TRACE_GRAPH_PRINT_PROC)
1155                 seq_puts(s, "  TASK/PID       ");
1156         if (lat)
1157                 seq_puts(s, "||||   ");
1158         if (flags & TRACE_GRAPH_PRINT_DURATION)
1159                 seq_puts(s, "  DURATION   ");
1160         seq_puts(s, "               FUNCTION CALLS\n");
1161
1162         /* 2nd line */
1163         seq_putc(s, '#');
1164         if (flags & TRACE_GRAPH_PRINT_ABS_TIME)
1165                 seq_puts(s, "      |         ");
1166         if (flags & TRACE_GRAPH_PRINT_REL_TIME)
1167                 seq_puts(s, "      |         ");
1168         if (flags & TRACE_GRAPH_PRINT_CPU)
1169                 seq_puts(s, " |  ");
1170         if (flags & TRACE_GRAPH_PRINT_PROC)
1171                 seq_puts(s, "   |    |        ");
1172         if (lat)
1173                 seq_puts(s, "||||   ");
1174         if (flags & TRACE_GRAPH_PRINT_DURATION)
1175                 seq_puts(s, "   |   |      ");
1176         seq_puts(s, "               |   |   |   |\n");
1177 }
1178
1179 static void print_graph_headers(struct seq_file *s)
1180 {
1181         print_graph_headers_flags(s, tracer_flags.val);
1182 }
1183
1184 void print_graph_headers_flags(struct seq_file *s, u32 flags)
1185 {
1186         struct trace_iterator *iter = s->private;
1187         struct trace_array *tr = iter->tr;
1188
1189         if (!(tr->trace_flags & TRACE_ITER_CONTEXT_INFO))
1190                 return;
1191
1192         if (tr->trace_flags & TRACE_ITER_LATENCY_FMT) {
1193                 /* print nothing if the buffers are empty */
1194                 if (trace_empty(iter))
1195                         return;
1196
1197                 print_trace_header(s, iter);
1198         }
1199
1200         __print_graph_headers_flags(tr, s, flags);
1201 }
1202
1203 void graph_trace_open(struct trace_iterator *iter)
1204 {
1205         /* pid and depth on the last trace processed */
1206         struct fgraph_data *data;
1207         gfp_t gfpflags;
1208         int cpu;
1209
1210         iter->private = NULL;
1211
1212         /* We can be called in atomic context via ftrace_dump() */
1213         gfpflags = (in_atomic() || irqs_disabled()) ? GFP_ATOMIC : GFP_KERNEL;
1214
1215         data = kzalloc(sizeof(*data), gfpflags);
1216         if (!data)
1217                 goto out_err;
1218
1219         data->cpu_data = alloc_percpu_gfp(struct fgraph_cpu_data, gfpflags);
1220         if (!data->cpu_data)
1221                 goto out_err_free;
1222
1223         for_each_possible_cpu(cpu) {
1224                 pid_t *pid = &(per_cpu_ptr(data->cpu_data, cpu)->last_pid);
1225                 int *depth = &(per_cpu_ptr(data->cpu_data, cpu)->depth);
1226                 int *ignore = &(per_cpu_ptr(data->cpu_data, cpu)->ignore);
1227                 int *depth_irq = &(per_cpu_ptr(data->cpu_data, cpu)->depth_irq);
1228
1229                 *pid = -1;
1230                 *depth = 0;
1231                 *ignore = 0;
1232                 *depth_irq = -1;
1233         }
1234
1235         iter->private = data;
1236
1237         return;
1238
1239  out_err_free:
1240         kfree(data);
1241  out_err:
1242         pr_warn("function graph tracer: not enough memory\n");
1243 }
1244
1245 void graph_trace_close(struct trace_iterator *iter)
1246 {
1247         struct fgraph_data *data = iter->private;
1248
1249         if (data) {
1250                 free_percpu(data->cpu_data);
1251                 kfree(data);
1252         }
1253 }
1254
1255 static int
1256 func_graph_set_flag(struct trace_array *tr, u32 old_flags, u32 bit, int set)
1257 {
1258         if (bit == TRACE_GRAPH_PRINT_IRQS)
1259                 ftrace_graph_skip_irqs = !set;
1260
1261         if (bit == TRACE_GRAPH_SLEEP_TIME)
1262                 ftrace_graph_sleep_time_control(set);
1263
1264         if (bit == TRACE_GRAPH_GRAPH_TIME)
1265                 ftrace_graph_graph_time_control(set);
1266
1267         return 0;
1268 }
1269
1270 static struct trace_event_functions graph_functions = {
1271         .trace          = print_graph_function_event,
1272 };
1273
1274 static struct trace_event graph_trace_entry_event = {
1275         .type           = TRACE_GRAPH_ENT,
1276         .funcs          = &graph_functions,
1277 };
1278
1279 static struct trace_event graph_trace_ret_event = {
1280         .type           = TRACE_GRAPH_RET,
1281         .funcs          = &graph_functions
1282 };
1283
1284 static struct tracer graph_trace __tracer_data = {
1285         .name           = "function_graph",
1286         .update_thresh  = graph_trace_update_thresh,
1287         .open           = graph_trace_open,
1288         .pipe_open      = graph_trace_open,
1289         .close          = graph_trace_close,
1290         .pipe_close     = graph_trace_close,
1291         .init           = graph_trace_init,
1292         .reset          = graph_trace_reset,
1293         .print_line     = print_graph_function,
1294         .print_header   = print_graph_headers,
1295         .flags          = &tracer_flags,
1296         .set_flag       = func_graph_set_flag,
1297 #ifdef CONFIG_FTRACE_SELFTEST
1298         .selftest       = trace_selftest_startup_function_graph,
1299 #endif
1300 };
1301
1302
1303 static ssize_t
1304 graph_depth_write(struct file *filp, const char __user *ubuf, size_t cnt,
1305                   loff_t *ppos)
1306 {
1307         unsigned long val;
1308         int ret;
1309
1310         ret = kstrtoul_from_user(ubuf, cnt, 10, &val);
1311         if (ret)
1312                 return ret;
1313
1314         fgraph_max_depth = val;
1315
1316         *ppos += cnt;
1317
1318         return cnt;
1319 }
1320
1321 static ssize_t
1322 graph_depth_read(struct file *filp, char __user *ubuf, size_t cnt,
1323                  loff_t *ppos)
1324 {
1325         char buf[15]; /* More than enough to hold UINT_MAX + "\n"*/
1326         int n;
1327
1328         n = sprintf(buf, "%d\n", fgraph_max_depth);
1329
1330         return simple_read_from_buffer(ubuf, cnt, ppos, buf, n);
1331 }
1332
1333 static const struct file_operations graph_depth_fops = {
1334         .open           = tracing_open_generic,
1335         .write          = graph_depth_write,
1336         .read           = graph_depth_read,
1337         .llseek         = generic_file_llseek,
1338 };
1339
1340 static __init int init_graph_tracefs(void)
1341 {
1342         struct dentry *d_tracer;
1343
1344         d_tracer = tracing_init_dentry();
1345         if (IS_ERR(d_tracer))
1346                 return 0;
1347
1348         trace_create_file("max_graph_depth", 0644, d_tracer,
1349                           NULL, &graph_depth_fops);
1350
1351         return 0;
1352 }
1353 fs_initcall(init_graph_tracefs);
1354
1355 static __init int init_graph_trace(void)
1356 {
1357         max_bytes_for_cpu = snprintf(NULL, 0, "%u", nr_cpu_ids - 1);
1358
1359         if (!register_trace_event(&graph_trace_entry_event)) {
1360                 pr_warn("Warning: could not register graph trace events\n");
1361                 return 1;
1362         }
1363
1364         if (!register_trace_event(&graph_trace_ret_event)) {
1365                 pr_warn("Warning: could not register graph trace events\n");
1366                 return 1;
1367         }
1368
1369         return register_tracer(&graph_trace);
1370 }
1371
1372 core_initcall(init_graph_trace);