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TOMOYO Linux Cross Reference
Linux/kernel/trace/trace_functions_graph.c

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  1 /*
  2  *
  3  * Function graph tracer.
  4  * Copyright (c) 2008-2009 Frederic Weisbecker <fweisbec@gmail.com>
  5  * Mostly borrowed from function tracer which
  6  * is Copyright (c) Steven Rostedt <srostedt@redhat.com>
  7  *
  8  */
  9 #include <linux/debugfs.h>
 10 #include <linux/uaccess.h>
 11 #include <linux/ftrace.h>
 12 #include <linux/slab.h>
 13 #include <linux/fs.h>
 14 
 15 #include "trace.h"
 16 #include "trace_output.h"
 17 
 18 static bool kill_ftrace_graph;
 19 
 20 /**
 21  * ftrace_graph_is_dead - returns true if ftrace_graph_stop() was called
 22  *
 23  * ftrace_graph_stop() is called when a severe error is detected in
 24  * the function graph tracing. This function is called by the critical
 25  * paths of function graph to keep those paths from doing any more harm.
 26  */
 27 bool ftrace_graph_is_dead(void)
 28 {
 29         return kill_ftrace_graph;
 30 }
 31 
 32 /**
 33  * ftrace_graph_stop - set to permanently disable function graph tracincg
 34  *
 35  * In case of an error int function graph tracing, this is called
 36  * to try to keep function graph tracing from causing any more harm.
 37  * Usually this is pretty severe and this is called to try to at least
 38  * get a warning out to the user.
 39  */
 40 void ftrace_graph_stop(void)
 41 {
 42         kill_ftrace_graph = true;
 43 }
 44 
 45 /* When set, irq functions will be ignored */
 46 static int ftrace_graph_skip_irqs;
 47 
 48 struct fgraph_cpu_data {
 49         pid_t           last_pid;
 50         int             depth;
 51         int             depth_irq;
 52         int             ignore;
 53         unsigned long   enter_funcs[FTRACE_RETFUNC_DEPTH];
 54 };
 55 
 56 struct fgraph_data {
 57         struct fgraph_cpu_data __percpu *cpu_data;
 58 
 59         /* Place to preserve last processed entry. */
 60         struct ftrace_graph_ent_entry   ent;
 61         struct ftrace_graph_ret_entry   ret;
 62         int                             failed;
 63         int                             cpu;
 64 };
 65 
 66 #define TRACE_GRAPH_INDENT      2
 67 
 68 static unsigned int max_depth;
 69 
 70 static struct tracer_opt trace_opts[] = {
 71         /* Display overruns? (for self-debug purpose) */
 72         { TRACER_OPT(funcgraph-overrun, TRACE_GRAPH_PRINT_OVERRUN) },
 73         /* Display CPU ? */
 74         { TRACER_OPT(funcgraph-cpu, TRACE_GRAPH_PRINT_CPU) },
 75         /* Display Overhead ? */
 76         { TRACER_OPT(funcgraph-overhead, TRACE_GRAPH_PRINT_OVERHEAD) },
 77         /* Display proc name/pid */
 78         { TRACER_OPT(funcgraph-proc, TRACE_GRAPH_PRINT_PROC) },
 79         /* Display duration of execution */
 80         { TRACER_OPT(funcgraph-duration, TRACE_GRAPH_PRINT_DURATION) },
 81         /* Display absolute time of an entry */
 82         { TRACER_OPT(funcgraph-abstime, TRACE_GRAPH_PRINT_ABS_TIME) },
 83         /* Display interrupts */
 84         { TRACER_OPT(funcgraph-irqs, TRACE_GRAPH_PRINT_IRQS) },
 85         /* Display function name after trailing } */
 86         { TRACER_OPT(funcgraph-tail, TRACE_GRAPH_PRINT_TAIL) },
 87         { } /* Empty entry */
 88 };
 89 
 90 static struct tracer_flags tracer_flags = {
 91         /* Don't display overruns, proc, or tail by default */
 92         .val = TRACE_GRAPH_PRINT_CPU | TRACE_GRAPH_PRINT_OVERHEAD |
 93                TRACE_GRAPH_PRINT_DURATION | TRACE_GRAPH_PRINT_IRQS,
 94         .opts = trace_opts
 95 };
 96 
 97 static struct trace_array *graph_array;
 98 
 99 /*
100  * DURATION column is being also used to display IRQ signs,
101  * following values are used by print_graph_irq and others
102  * to fill in space into DURATION column.
103  */
104 enum {
105         FLAGS_FILL_FULL  = 1 << TRACE_GRAPH_PRINT_FILL_SHIFT,
106         FLAGS_FILL_START = 2 << TRACE_GRAPH_PRINT_FILL_SHIFT,
107         FLAGS_FILL_END   = 3 << TRACE_GRAPH_PRINT_FILL_SHIFT,
108 };
109 
110 static void
111 print_graph_duration(unsigned long long duration, struct trace_seq *s,
112                      u32 flags);
113 
114 /* Add a function return address to the trace stack on thread info.*/
115 int
116 ftrace_push_return_trace(unsigned long ret, unsigned long func, int *depth,
117                          unsigned long frame_pointer)
118 {
119         unsigned long long calltime;
120         int index;
121 
122         if (unlikely(ftrace_graph_is_dead()))
123                 return -EBUSY;
124 
125         if (!current->ret_stack)
126                 return -EBUSY;
127 
128         /*
129          * We must make sure the ret_stack is tested before we read
130          * anything else.
131          */
132         smp_rmb();
133 
134         /* The return trace stack is full */
135         if (current->curr_ret_stack == FTRACE_RETFUNC_DEPTH - 1) {
136                 atomic_inc(&current->trace_overrun);
137                 return -EBUSY;
138         }
139 
140         /*
141          * The curr_ret_stack is an index to ftrace return stack of
142          * current task.  Its value should be in [0, FTRACE_RETFUNC_
143          * DEPTH) when the function graph tracer is used.  To support
144          * filtering out specific functions, it makes the index
145          * negative by subtracting huge value (FTRACE_NOTRACE_DEPTH)
146          * so when it sees a negative index the ftrace will ignore
147          * the record.  And the index gets recovered when returning
148          * from the filtered function by adding the FTRACE_NOTRACE_
149          * DEPTH and then it'll continue to record functions normally.
150          *
151          * The curr_ret_stack is initialized to -1 and get increased
152          * in this function.  So it can be less than -1 only if it was
153          * filtered out via ftrace_graph_notrace_addr() which can be
154          * set from set_graph_notrace file in debugfs by user.
155          */
156         if (current->curr_ret_stack < -1)
157                 return -EBUSY;
158 
159         calltime = trace_clock_local();
160 
161         index = ++current->curr_ret_stack;
162         if (ftrace_graph_notrace_addr(func))
163                 current->curr_ret_stack -= FTRACE_NOTRACE_DEPTH;
164         barrier();
165         current->ret_stack[index].ret = ret;
166         current->ret_stack[index].func = func;
167         current->ret_stack[index].calltime = calltime;
168         current->ret_stack[index].subtime = 0;
169         current->ret_stack[index].fp = frame_pointer;
170         *depth = current->curr_ret_stack;
171 
172         return 0;
173 }
174 
175 /* Retrieve a function return address to the trace stack on thread info.*/
176 static void
177 ftrace_pop_return_trace(struct ftrace_graph_ret *trace, unsigned long *ret,
178                         unsigned long frame_pointer)
179 {
180         int index;
181 
182         index = current->curr_ret_stack;
183 
184         /*
185          * A negative index here means that it's just returned from a
186          * notrace'd function.  Recover index to get an original
187          * return address.  See ftrace_push_return_trace().
188          *
189          * TODO: Need to check whether the stack gets corrupted.
190          */
191         if (index < 0)
192                 index += FTRACE_NOTRACE_DEPTH;
193 
194         if (unlikely(index < 0 || index >= FTRACE_RETFUNC_DEPTH)) {
195                 ftrace_graph_stop();
196                 WARN_ON(1);
197                 /* Might as well panic, otherwise we have no where to go */
198                 *ret = (unsigned long)panic;
199                 return;
200         }
201 
202 #if defined(CONFIG_HAVE_FUNCTION_GRAPH_FP_TEST) && !defined(CC_USING_FENTRY)
203         /*
204          * The arch may choose to record the frame pointer used
205          * and check it here to make sure that it is what we expect it
206          * to be. If gcc does not set the place holder of the return
207          * address in the frame pointer, and does a copy instead, then
208          * the function graph trace will fail. This test detects this
209          * case.
210          *
211          * Currently, x86_32 with optimize for size (-Os) makes the latest
212          * gcc do the above.
213          *
214          * Note, -mfentry does not use frame pointers, and this test
215          *  is not needed if CC_USING_FENTRY is set.
216          */
217         if (unlikely(current->ret_stack[index].fp != frame_pointer)) {
218                 ftrace_graph_stop();
219                 WARN(1, "Bad frame pointer: expected %lx, received %lx\n"
220                      "  from func %ps return to %lx\n",
221                      current->ret_stack[index].fp,
222                      frame_pointer,
223                      (void *)current->ret_stack[index].func,
224                      current->ret_stack[index].ret);
225                 *ret = (unsigned long)panic;
226                 return;
227         }
228 #endif
229 
230         *ret = current->ret_stack[index].ret;
231         trace->func = current->ret_stack[index].func;
232         trace->calltime = current->ret_stack[index].calltime;
233         trace->overrun = atomic_read(&current->trace_overrun);
234         trace->depth = index;
235 }
236 
237 /*
238  * Send the trace to the ring-buffer.
239  * @return the original return address.
240  */
241 unsigned long ftrace_return_to_handler(unsigned long frame_pointer)
242 {
243         struct ftrace_graph_ret trace;
244         unsigned long ret;
245 
246         ftrace_pop_return_trace(&trace, &ret, frame_pointer);
247         trace.rettime = trace_clock_local();
248         barrier();
249         current->curr_ret_stack--;
250         /*
251          * The curr_ret_stack can be less than -1 only if it was
252          * filtered out and it's about to return from the function.
253          * Recover the index and continue to trace normal functions.
254          */
255         if (current->curr_ret_stack < -1) {
256                 current->curr_ret_stack += FTRACE_NOTRACE_DEPTH;
257                 return ret;
258         }
259 
260         /*
261          * The trace should run after decrementing the ret counter
262          * in case an interrupt were to come in. We don't want to
263          * lose the interrupt if max_depth is set.
264          */
265         ftrace_graph_return(&trace);
266 
267         if (unlikely(!ret)) {
268                 ftrace_graph_stop();
269                 WARN_ON(1);
270                 /* Might as well panic. What else to do? */
271                 ret = (unsigned long)panic;
272         }
273 
274         return ret;
275 }
276 
277 int __trace_graph_entry(struct trace_array *tr,
278                                 struct ftrace_graph_ent *trace,
279                                 unsigned long flags,
280                                 int pc)
281 {
282         struct ftrace_event_call *call = &event_funcgraph_entry;
283         struct ring_buffer_event *event;
284         struct ring_buffer *buffer = tr->trace_buffer.buffer;
285         struct ftrace_graph_ent_entry *entry;
286 
287         if (unlikely(__this_cpu_read(ftrace_cpu_disabled)))
288                 return 0;
289 
290         event = trace_buffer_lock_reserve(buffer, TRACE_GRAPH_ENT,
291                                           sizeof(*entry), flags, pc);
292         if (!event)
293                 return 0;
294         entry   = ring_buffer_event_data(event);
295         entry->graph_ent                        = *trace;
296         if (!call_filter_check_discard(call, entry, buffer, event))
297                 __buffer_unlock_commit(buffer, event);
298 
299         return 1;
300 }
301 
302 static inline int ftrace_graph_ignore_irqs(void)
303 {
304         if (!ftrace_graph_skip_irqs || trace_recursion_test(TRACE_IRQ_BIT))
305                 return 0;
306 
307         return in_irq();
308 }
309 
310 int trace_graph_entry(struct ftrace_graph_ent *trace)
311 {
312         struct trace_array *tr = graph_array;
313         struct trace_array_cpu *data;
314         unsigned long flags;
315         long disabled;
316         int ret;
317         int cpu;
318         int pc;
319 
320         if (!ftrace_trace_task(current))
321                 return 0;
322 
323         /* trace it when it is-nested-in or is a function enabled. */
324         if ((!(trace->depth || ftrace_graph_addr(trace->func)) ||
325              ftrace_graph_ignore_irqs()) || (trace->depth < 0) ||
326             (max_depth && trace->depth >= max_depth))
327                 return 0;
328 
329         /*
330          * Do not trace a function if it's filtered by set_graph_notrace.
331          * Make the index of ret stack negative to indicate that it should
332          * ignore further functions.  But it needs its own ret stack entry
333          * to recover the original index in order to continue tracing after
334          * returning from the function.
335          */
336         if (ftrace_graph_notrace_addr(trace->func))
337                 return 1;
338 
339         local_irq_save(flags);
340         cpu = raw_smp_processor_id();
341         data = per_cpu_ptr(tr->trace_buffer.data, cpu);
342         disabled = atomic_inc_return(&data->disabled);
343         if (likely(disabled == 1)) {
344                 pc = preempt_count();
345                 ret = __trace_graph_entry(tr, trace, flags, pc);
346         } else {
347                 ret = 0;
348         }
349 
350         atomic_dec(&data->disabled);
351         local_irq_restore(flags);
352 
353         return ret;
354 }
355 
356 static int trace_graph_thresh_entry(struct ftrace_graph_ent *trace)
357 {
358         if (tracing_thresh)
359                 return 1;
360         else
361                 return trace_graph_entry(trace);
362 }
363 
364 static void
365 __trace_graph_function(struct trace_array *tr,
366                 unsigned long ip, unsigned long flags, int pc)
367 {
368         u64 time = trace_clock_local();
369         struct ftrace_graph_ent ent = {
370                 .func  = ip,
371                 .depth = 0,
372         };
373         struct ftrace_graph_ret ret = {
374                 .func     = ip,
375                 .depth    = 0,
376                 .calltime = time,
377                 .rettime  = time,
378         };
379 
380         __trace_graph_entry(tr, &ent, flags, pc);
381         __trace_graph_return(tr, &ret, flags, pc);
382 }
383 
384 void
385 trace_graph_function(struct trace_array *tr,
386                 unsigned long ip, unsigned long parent_ip,
387                 unsigned long flags, int pc)
388 {
389         __trace_graph_function(tr, ip, flags, pc);
390 }
391 
392 void __trace_graph_return(struct trace_array *tr,
393                                 struct ftrace_graph_ret *trace,
394                                 unsigned long flags,
395                                 int pc)
396 {
397         struct ftrace_event_call *call = &event_funcgraph_exit;
398         struct ring_buffer_event *event;
399         struct ring_buffer *buffer = tr->trace_buffer.buffer;
400         struct ftrace_graph_ret_entry *entry;
401 
402         if (unlikely(__this_cpu_read(ftrace_cpu_disabled)))
403                 return;
404 
405         event = trace_buffer_lock_reserve(buffer, TRACE_GRAPH_RET,
406                                           sizeof(*entry), flags, pc);
407         if (!event)
408                 return;
409         entry   = ring_buffer_event_data(event);
410         entry->ret                              = *trace;
411         if (!call_filter_check_discard(call, entry, buffer, event))
412                 __buffer_unlock_commit(buffer, event);
413 }
414 
415 void trace_graph_return(struct ftrace_graph_ret *trace)
416 {
417         struct trace_array *tr = graph_array;
418         struct trace_array_cpu *data;
419         unsigned long flags;
420         long disabled;
421         int cpu;
422         int pc;
423 
424         local_irq_save(flags);
425         cpu = raw_smp_processor_id();
426         data = per_cpu_ptr(tr->trace_buffer.data, cpu);
427         disabled = atomic_inc_return(&data->disabled);
428         if (likely(disabled == 1)) {
429                 pc = preempt_count();
430                 __trace_graph_return(tr, trace, flags, pc);
431         }
432         atomic_dec(&data->disabled);
433         local_irq_restore(flags);
434 }
435 
436 void set_graph_array(struct trace_array *tr)
437 {
438         graph_array = tr;
439 
440         /* Make graph_array visible before we start tracing */
441 
442         smp_mb();
443 }
444 
445 static void trace_graph_thresh_return(struct ftrace_graph_ret *trace)
446 {
447         if (tracing_thresh &&
448             (trace->rettime - trace->calltime < tracing_thresh))
449                 return;
450         else
451                 trace_graph_return(trace);
452 }
453 
454 static int graph_trace_init(struct trace_array *tr)
455 {
456         int ret;
457 
458         set_graph_array(tr);
459         if (tracing_thresh)
460                 ret = register_ftrace_graph(&trace_graph_thresh_return,
461                                             &trace_graph_thresh_entry);
462         else
463                 ret = register_ftrace_graph(&trace_graph_return,
464                                             &trace_graph_entry);
465         if (ret)
466                 return ret;
467         tracing_start_cmdline_record();
468 
469         return 0;
470 }
471 
472 static void graph_trace_reset(struct trace_array *tr)
473 {
474         tracing_stop_cmdline_record();
475         unregister_ftrace_graph();
476 }
477 
478 static int graph_trace_update_thresh(struct trace_array *tr)
479 {
480         graph_trace_reset(tr);
481         return graph_trace_init(tr);
482 }
483 
484 static int max_bytes_for_cpu;
485 
486 static void print_graph_cpu(struct trace_seq *s, int cpu)
487 {
488         /*
489          * Start with a space character - to make it stand out
490          * to the right a bit when trace output is pasted into
491          * email:
492          */
493         trace_seq_printf(s, " %*d) ", max_bytes_for_cpu, cpu);
494 }
495 
496 #define TRACE_GRAPH_PROCINFO_LENGTH     14
497 
498 static void print_graph_proc(struct trace_seq *s, pid_t pid)
499 {
500         char comm[TASK_COMM_LEN];
501         /* sign + log10(MAX_INT) + '\0' */
502         char pid_str[11];
503         int spaces = 0;
504         int len;
505         int i;
506 
507         trace_find_cmdline(pid, comm);
508         comm[7] = '\0';
509         sprintf(pid_str, "%d", pid);
510 
511         /* 1 stands for the "-" character */
512         len = strlen(comm) + strlen(pid_str) + 1;
513 
514         if (len < TRACE_GRAPH_PROCINFO_LENGTH)
515                 spaces = TRACE_GRAPH_PROCINFO_LENGTH - len;
516 
517         /* First spaces to align center */
518         for (i = 0; i < spaces / 2; i++)
519                 trace_seq_putc(s, ' ');
520 
521         trace_seq_printf(s, "%s-%s", comm, pid_str);
522 
523         /* Last spaces to align center */
524         for (i = 0; i < spaces - (spaces / 2); i++)
525                 trace_seq_putc(s, ' ');
526 }
527 
528 
529 static void print_graph_lat_fmt(struct trace_seq *s, struct trace_entry *entry)
530 {
531         trace_seq_putc(s, ' ');
532         trace_print_lat_fmt(s, entry);
533 }
534 
535 /* If the pid changed since the last trace, output this event */
536 static void
537 verif_pid(struct trace_seq *s, pid_t pid, int cpu, struct fgraph_data *data)
538 {
539         pid_t prev_pid;
540         pid_t *last_pid;
541 
542         if (!data)
543                 return;
544 
545         last_pid = &(per_cpu_ptr(data->cpu_data, cpu)->last_pid);
546 
547         if (*last_pid == pid)
548                 return;
549 
550         prev_pid = *last_pid;
551         *last_pid = pid;
552 
553         if (prev_pid == -1)
554                 return;
555 /*
556  * Context-switch trace line:
557 
558  ------------------------------------------
559  | 1)  migration/0--1  =>  sshd-1755
560  ------------------------------------------
561 
562  */
563         trace_seq_puts(s, " ------------------------------------------\n");
564         print_graph_cpu(s, cpu);
565         print_graph_proc(s, prev_pid);
566         trace_seq_puts(s, " => ");
567         print_graph_proc(s, pid);
568         trace_seq_puts(s, "\n ------------------------------------------\n\n");
569 }
570 
571 static struct ftrace_graph_ret_entry *
572 get_return_for_leaf(struct trace_iterator *iter,
573                 struct ftrace_graph_ent_entry *curr)
574 {
575         struct fgraph_data *data = iter->private;
576         struct ring_buffer_iter *ring_iter = NULL;
577         struct ring_buffer_event *event;
578         struct ftrace_graph_ret_entry *next;
579 
580         /*
581          * If the previous output failed to write to the seq buffer,
582          * then we just reuse the data from before.
583          */
584         if (data && data->failed) {
585                 curr = &data->ent;
586                 next = &data->ret;
587         } else {
588 
589                 ring_iter = trace_buffer_iter(iter, iter->cpu);
590 
591                 /* First peek to compare current entry and the next one */
592                 if (ring_iter)
593                         event = ring_buffer_iter_peek(ring_iter, NULL);
594                 else {
595                         /*
596                          * We need to consume the current entry to see
597                          * the next one.
598                          */
599                         ring_buffer_consume(iter->trace_buffer->buffer, iter->cpu,
600                                             NULL, NULL);
601                         event = ring_buffer_peek(iter->trace_buffer->buffer, iter->cpu,
602                                                  NULL, NULL);
603                 }
604 
605                 if (!event)
606                         return NULL;
607 
608                 next = ring_buffer_event_data(event);
609 
610                 if (data) {
611                         /*
612                          * Save current and next entries for later reference
613                          * if the output fails.
614                          */
615                         data->ent = *curr;
616                         /*
617                          * If the next event is not a return type, then
618                          * we only care about what type it is. Otherwise we can
619                          * safely copy the entire event.
620                          */
621                         if (next->ent.type == TRACE_GRAPH_RET)
622                                 data->ret = *next;
623                         else
624                                 data->ret.ent.type = next->ent.type;
625                 }
626         }
627 
628         if (next->ent.type != TRACE_GRAPH_RET)
629                 return NULL;
630 
631         if (curr->ent.pid != next->ent.pid ||
632                         curr->graph_ent.func != next->ret.func)
633                 return NULL;
634 
635         /* this is a leaf, now advance the iterator */
636         if (ring_iter)
637                 ring_buffer_read(ring_iter, NULL);
638 
639         return next;
640 }
641 
642 static void print_graph_abs_time(u64 t, struct trace_seq *s)
643 {
644         unsigned long usecs_rem;
645 
646         usecs_rem = do_div(t, NSEC_PER_SEC);
647         usecs_rem /= 1000;
648 
649         trace_seq_printf(s, "%5lu.%06lu |  ",
650                          (unsigned long)t, usecs_rem);
651 }
652 
653 static void
654 print_graph_irq(struct trace_iterator *iter, unsigned long addr,
655                 enum trace_type type, int cpu, pid_t pid, u32 flags)
656 {
657         struct trace_seq *s = &iter->seq;
658         struct trace_entry *ent = iter->ent;
659 
660         if (addr < (unsigned long)__irqentry_text_start ||
661                 addr >= (unsigned long)__irqentry_text_end)
662                 return;
663 
664         if (trace_flags & TRACE_ITER_CONTEXT_INFO) {
665                 /* Absolute time */
666                 if (flags & TRACE_GRAPH_PRINT_ABS_TIME)
667                         print_graph_abs_time(iter->ts, s);
668 
669                 /* Cpu */
670                 if (flags & TRACE_GRAPH_PRINT_CPU)
671                         print_graph_cpu(s, cpu);
672 
673                 /* Proc */
674                 if (flags & TRACE_GRAPH_PRINT_PROC) {
675                         print_graph_proc(s, pid);
676                         trace_seq_puts(s, " | ");
677                 }
678 
679                 /* Latency format */
680                 if (trace_flags & TRACE_ITER_LATENCY_FMT)
681                         print_graph_lat_fmt(s, ent);
682         }
683 
684         /* No overhead */
685         print_graph_duration(0, s, flags | FLAGS_FILL_START);
686 
687         if (type == TRACE_GRAPH_ENT)
688                 trace_seq_puts(s, "==========>");
689         else
690                 trace_seq_puts(s, "<==========");
691 
692         print_graph_duration(0, s, flags | FLAGS_FILL_END);
693         trace_seq_putc(s, '\n');
694 }
695 
696 void
697 trace_print_graph_duration(unsigned long long duration, struct trace_seq *s)
698 {
699         unsigned long nsecs_rem = do_div(duration, 1000);
700         /* log10(ULONG_MAX) + '\0' */
701         char usecs_str[21];
702         char nsecs_str[5];
703         int len;
704         int i;
705 
706         sprintf(usecs_str, "%lu", (unsigned long) duration);
707 
708         /* Print msecs */
709         trace_seq_printf(s, "%s", usecs_str);
710 
711         len = strlen(usecs_str);
712 
713         /* Print nsecs (we don't want to exceed 7 numbers) */
714         if (len < 7) {
715                 size_t slen = min_t(size_t, sizeof(nsecs_str), 8UL - len);
716 
717                 snprintf(nsecs_str, slen, "%03lu", nsecs_rem);
718                 trace_seq_printf(s, ".%s", nsecs_str);
719                 len += strlen(nsecs_str);
720         }
721 
722         trace_seq_puts(s, " us ");
723 
724         /* Print remaining spaces to fit the row's width */
725         for (i = len; i < 7; i++)
726                 trace_seq_putc(s, ' ');
727 }
728 
729 static void
730 print_graph_duration(unsigned long long duration, struct trace_seq *s,
731                      u32 flags)
732 {
733         if (!(flags & TRACE_GRAPH_PRINT_DURATION) ||
734             !(trace_flags & TRACE_ITER_CONTEXT_INFO))
735                 return;
736 
737         /* No real adata, just filling the column with spaces */
738         switch (flags & TRACE_GRAPH_PRINT_FILL_MASK) {
739         case FLAGS_FILL_FULL:
740                 trace_seq_puts(s, "              |  ");
741                 return;
742         case FLAGS_FILL_START:
743                 trace_seq_puts(s, "  ");
744                 return;
745         case FLAGS_FILL_END:
746                 trace_seq_puts(s, " |");
747                 return;
748         }
749 
750         /* Signal a overhead of time execution to the output */
751         if (flags & TRACE_GRAPH_PRINT_OVERHEAD)
752                 trace_seq_printf(s, "%c ", trace_find_mark(duration));
753         else
754                 trace_seq_puts(s, "  ");
755 
756         trace_print_graph_duration(duration, s);
757         trace_seq_puts(s, "|  ");
758 }
759 
760 /* Case of a leaf function on its call entry */
761 static enum print_line_t
762 print_graph_entry_leaf(struct trace_iterator *iter,
763                 struct ftrace_graph_ent_entry *entry,
764                 struct ftrace_graph_ret_entry *ret_entry,
765                 struct trace_seq *s, u32 flags)
766 {
767         struct fgraph_data *data = iter->private;
768         struct ftrace_graph_ret *graph_ret;
769         struct ftrace_graph_ent *call;
770         unsigned long long duration;
771         int i;
772 
773         graph_ret = &ret_entry->ret;
774         call = &entry->graph_ent;
775         duration = graph_ret->rettime - graph_ret->calltime;
776 
777         if (data) {
778                 struct fgraph_cpu_data *cpu_data;
779                 int cpu = iter->cpu;
780 
781                 cpu_data = per_cpu_ptr(data->cpu_data, cpu);
782 
783                 /*
784                  * Comments display at + 1 to depth. Since
785                  * this is a leaf function, keep the comments
786                  * equal to this depth.
787                  */
788                 cpu_data->depth = call->depth - 1;
789 
790                 /* No need to keep this function around for this depth */
791                 if (call->depth < FTRACE_RETFUNC_DEPTH)
792                         cpu_data->enter_funcs[call->depth] = 0;
793         }
794 
795         /* Overhead and duration */
796         print_graph_duration(duration, s, flags);
797 
798         /* Function */
799         for (i = 0; i < call->depth * TRACE_GRAPH_INDENT; i++)
800                 trace_seq_putc(s, ' ');
801 
802         trace_seq_printf(s, "%ps();\n", (void *)call->func);
803 
804         return trace_handle_return(s);
805 }
806 
807 static enum print_line_t
808 print_graph_entry_nested(struct trace_iterator *iter,
809                          struct ftrace_graph_ent_entry *entry,
810                          struct trace_seq *s, int cpu, u32 flags)
811 {
812         struct ftrace_graph_ent *call = &entry->graph_ent;
813         struct fgraph_data *data = iter->private;
814         int i;
815 
816         if (data) {
817                 struct fgraph_cpu_data *cpu_data;
818                 int cpu = iter->cpu;
819 
820                 cpu_data = per_cpu_ptr(data->cpu_data, cpu);
821                 cpu_data->depth = call->depth;
822 
823                 /* Save this function pointer to see if the exit matches */
824                 if (call->depth < FTRACE_RETFUNC_DEPTH)
825                         cpu_data->enter_funcs[call->depth] = call->func;
826         }
827 
828         /* No time */
829         print_graph_duration(0, s, flags | FLAGS_FILL_FULL);
830 
831         /* Function */
832         for (i = 0; i < call->depth * TRACE_GRAPH_INDENT; i++)
833                 trace_seq_putc(s, ' ');
834 
835         trace_seq_printf(s, "%ps() {\n", (void *)call->func);
836 
837         if (trace_seq_has_overflowed(s))
838                 return TRACE_TYPE_PARTIAL_LINE;
839 
840         /*
841          * we already consumed the current entry to check the next one
842          * and see if this is a leaf.
843          */
844         return TRACE_TYPE_NO_CONSUME;
845 }
846 
847 static void
848 print_graph_prologue(struct trace_iterator *iter, struct trace_seq *s,
849                      int type, unsigned long addr, u32 flags)
850 {
851         struct fgraph_data *data = iter->private;
852         struct trace_entry *ent = iter->ent;
853         int cpu = iter->cpu;
854 
855         /* Pid */
856         verif_pid(s, ent->pid, cpu, data);
857 
858         if (type)
859                 /* Interrupt */
860                 print_graph_irq(iter, addr, type, cpu, ent->pid, flags);
861 
862         if (!(trace_flags & TRACE_ITER_CONTEXT_INFO))
863                 return;
864 
865         /* Absolute time */
866         if (flags & TRACE_GRAPH_PRINT_ABS_TIME)
867                 print_graph_abs_time(iter->ts, s);
868 
869         /* Cpu */
870         if (flags & TRACE_GRAPH_PRINT_CPU)
871                 print_graph_cpu(s, cpu);
872 
873         /* Proc */
874         if (flags & TRACE_GRAPH_PRINT_PROC) {
875                 print_graph_proc(s, ent->pid);
876                 trace_seq_puts(s, " | ");
877         }
878 
879         /* Latency format */
880         if (trace_flags & TRACE_ITER_LATENCY_FMT)
881                 print_graph_lat_fmt(s, ent);
882 
883         return;
884 }
885 
886 /*
887  * Entry check for irq code
888  *
889  * returns 1 if
890  *  - we are inside irq code
891  *  - we just entered irq code
892  *
893  * retunns 0 if
894  *  - funcgraph-interrupts option is set
895  *  - we are not inside irq code
896  */
897 static int
898 check_irq_entry(struct trace_iterator *iter, u32 flags,
899                 unsigned long addr, int depth)
900 {
901         int cpu = iter->cpu;
902         int *depth_irq;
903         struct fgraph_data *data = iter->private;
904 
905         /*
906          * If we are either displaying irqs, or we got called as
907          * a graph event and private data does not exist,
908          * then we bypass the irq check.
909          */
910         if ((flags & TRACE_GRAPH_PRINT_IRQS) ||
911             (!data))
912                 return 0;
913 
914         depth_irq = &(per_cpu_ptr(data->cpu_data, cpu)->depth_irq);
915 
916         /*
917          * We are inside the irq code
918          */
919         if (*depth_irq >= 0)
920                 return 1;
921 
922         if ((addr < (unsigned long)__irqentry_text_start) ||
923             (addr >= (unsigned long)__irqentry_text_end))
924                 return 0;
925 
926         /*
927          * We are entering irq code.
928          */
929         *depth_irq = depth;
930         return 1;
931 }
932 
933 /*
934  * Return check for irq code
935  *
936  * returns 1 if
937  *  - we are inside irq code
938  *  - we just left irq code
939  *
940  * returns 0 if
941  *  - funcgraph-interrupts option is set
942  *  - we are not inside irq code
943  */
944 static int
945 check_irq_return(struct trace_iterator *iter, u32 flags, int depth)
946 {
947         int cpu = iter->cpu;
948         int *depth_irq;
949         struct fgraph_data *data = iter->private;
950 
951         /*
952          * If we are either displaying irqs, or we got called as
953          * a graph event and private data does not exist,
954          * then we bypass the irq check.
955          */
956         if ((flags & TRACE_GRAPH_PRINT_IRQS) ||
957             (!data))
958                 return 0;
959 
960         depth_irq = &(per_cpu_ptr(data->cpu_data, cpu)->depth_irq);
961 
962         /*
963          * We are not inside the irq code.
964          */
965         if (*depth_irq == -1)
966                 return 0;
967 
968         /*
969          * We are inside the irq code, and this is returning entry.
970          * Let's not trace it and clear the entry depth, since
971          * we are out of irq code.
972          *
973          * This condition ensures that we 'leave the irq code' once
974          * we are out of the entry depth. Thus protecting us from
975          * the RETURN entry loss.
976          */
977         if (*depth_irq >= depth) {
978                 *depth_irq = -1;
979                 return 1;
980         }
981 
982         /*
983          * We are inside the irq code, and this is not the entry.
984          */
985         return 1;
986 }
987 
988 static enum print_line_t
989 print_graph_entry(struct ftrace_graph_ent_entry *field, struct trace_seq *s,
990                         struct trace_iterator *iter, u32 flags)
991 {
992         struct fgraph_data *data = iter->private;
993         struct ftrace_graph_ent *call = &field->graph_ent;
994         struct ftrace_graph_ret_entry *leaf_ret;
995         static enum print_line_t ret;
996         int cpu = iter->cpu;
997 
998         if (check_irq_entry(iter, flags, call->func, call->depth))
999                 return TRACE_TYPE_HANDLED;
1000 
1001         print_graph_prologue(iter, s, TRACE_GRAPH_ENT, call->func, flags);
1002 
1003         leaf_ret = get_return_for_leaf(iter, field);
1004         if (leaf_ret)
1005                 ret = print_graph_entry_leaf(iter, field, leaf_ret, s, flags);
1006         else
1007                 ret = print_graph_entry_nested(iter, field, s, cpu, flags);
1008 
1009         if (data) {
1010                 /*
1011                  * If we failed to write our output, then we need to make
1012                  * note of it. Because we already consumed our entry.
1013                  */
1014                 if (s->full) {
1015                         data->failed = 1;
1016                         data->cpu = cpu;
1017                 } else
1018                         data->failed = 0;
1019         }
1020 
1021         return ret;
1022 }
1023 
1024 static enum print_line_t
1025 print_graph_return(struct ftrace_graph_ret *trace, struct trace_seq *s,
1026                    struct trace_entry *ent, struct trace_iterator *iter,
1027                    u32 flags)
1028 {
1029         unsigned long long duration = trace->rettime - trace->calltime;
1030         struct fgraph_data *data = iter->private;
1031         pid_t pid = ent->pid;
1032         int cpu = iter->cpu;
1033         int func_match = 1;
1034         int i;
1035 
1036         if (check_irq_return(iter, flags, trace->depth))
1037                 return TRACE_TYPE_HANDLED;
1038 
1039         if (data) {
1040                 struct fgraph_cpu_data *cpu_data;
1041                 int cpu = iter->cpu;
1042 
1043                 cpu_data = per_cpu_ptr(data->cpu_data, cpu);
1044 
1045                 /*
1046                  * Comments display at + 1 to depth. This is the
1047                  * return from a function, we now want the comments
1048                  * to display at the same level of the bracket.
1049                  */
1050                 cpu_data->depth = trace->depth - 1;
1051 
1052                 if (trace->depth < FTRACE_RETFUNC_DEPTH) {
1053                         if (cpu_data->enter_funcs[trace->depth] != trace->func)
1054                                 func_match = 0;
1055                         cpu_data->enter_funcs[trace->depth] = 0;
1056                 }
1057         }
1058 
1059         print_graph_prologue(iter, s, 0, 0, flags);
1060 
1061         /* Overhead and duration */
1062         print_graph_duration(duration, s, flags);
1063 
1064         /* Closing brace */
1065         for (i = 0; i < trace->depth * TRACE_GRAPH_INDENT; i++)
1066                 trace_seq_putc(s, ' ');
1067 
1068         /*
1069          * If the return function does not have a matching entry,
1070          * then the entry was lost. Instead of just printing
1071          * the '}' and letting the user guess what function this
1072          * belongs to, write out the function name. Always do
1073          * that if the funcgraph-tail option is enabled.
1074          */
1075         if (func_match && !(flags & TRACE_GRAPH_PRINT_TAIL))
1076                 trace_seq_puts(s, "}\n");
1077         else
1078                 trace_seq_printf(s, "} /* %ps */\n", (void *)trace->func);
1079 
1080         /* Overrun */
1081         if (flags & TRACE_GRAPH_PRINT_OVERRUN)
1082                 trace_seq_printf(s, " (Overruns: %lu)\n",
1083                                  trace->overrun);
1084 
1085         print_graph_irq(iter, trace->func, TRACE_GRAPH_RET,
1086                         cpu, pid, flags);
1087 
1088         return trace_handle_return(s);
1089 }
1090 
1091 static enum print_line_t
1092 print_graph_comment(struct trace_seq *s, struct trace_entry *ent,
1093                     struct trace_iterator *iter, u32 flags)
1094 {
1095         unsigned long sym_flags = (trace_flags & TRACE_ITER_SYM_MASK);
1096         struct fgraph_data *data = iter->private;
1097         struct trace_event *event;
1098         int depth = 0;
1099         int ret;
1100         int i;
1101 
1102         if (data)
1103                 depth = per_cpu_ptr(data->cpu_data, iter->cpu)->depth;
1104 
1105         print_graph_prologue(iter, s, 0, 0, flags);
1106 
1107         /* No time */
1108         print_graph_duration(0, s, flags | FLAGS_FILL_FULL);
1109 
1110         /* Indentation */
1111         if (depth > 0)
1112                 for (i = 0; i < (depth + 1) * TRACE_GRAPH_INDENT; i++)
1113                         trace_seq_putc(s, ' ');
1114 
1115         /* The comment */
1116         trace_seq_puts(s, "/* ");
1117 
1118         switch (iter->ent->type) {
1119         case TRACE_BPRINT:
1120                 ret = trace_print_bprintk_msg_only(iter);
1121                 if (ret != TRACE_TYPE_HANDLED)
1122                         return ret;
1123                 break;
1124         case TRACE_PRINT:
1125                 ret = trace_print_printk_msg_only(iter);
1126                 if (ret != TRACE_TYPE_HANDLED)
1127                         return ret;
1128                 break;
1129         default:
1130                 event = ftrace_find_event(ent->type);
1131                 if (!event)
1132                         return TRACE_TYPE_UNHANDLED;
1133 
1134                 ret = event->funcs->trace(iter, sym_flags, event);
1135                 if (ret != TRACE_TYPE_HANDLED)
1136                         return ret;
1137         }
1138 
1139         if (trace_seq_has_overflowed(s))
1140                 goto out;
1141 
1142         /* Strip ending newline */
1143         if (s->buffer[s->seq.len - 1] == '\n') {
1144                 s->buffer[s->seq.len - 1] = '\0';
1145                 s->seq.len--;
1146         }
1147 
1148         trace_seq_puts(s, " */\n");
1149  out:
1150         return trace_handle_return(s);
1151 }
1152 
1153 
1154 enum print_line_t
1155 print_graph_function_flags(struct trace_iterator *iter, u32 flags)
1156 {
1157         struct ftrace_graph_ent_entry *field;
1158         struct fgraph_data *data = iter->private;
1159         struct trace_entry *entry = iter->ent;
1160         struct trace_seq *s = &iter->seq;
1161         int cpu = iter->cpu;
1162         int ret;
1163 
1164         if (data && per_cpu_ptr(data->cpu_data, cpu)->ignore) {
1165                 per_cpu_ptr(data->cpu_data, cpu)->ignore = 0;
1166                 return TRACE_TYPE_HANDLED;
1167         }
1168 
1169         /*
1170          * If the last output failed, there's a possibility we need
1171          * to print out the missing entry which would never go out.
1172          */
1173         if (data && data->failed) {
1174                 field = &data->ent;
1175                 iter->cpu = data->cpu;
1176                 ret = print_graph_entry(field, s, iter, flags);
1177                 if (ret == TRACE_TYPE_HANDLED && iter->cpu != cpu) {
1178                         per_cpu_ptr(data->cpu_data, iter->cpu)->ignore = 1;
1179                         ret = TRACE_TYPE_NO_CONSUME;
1180                 }
1181                 iter->cpu = cpu;
1182                 return ret;
1183         }
1184 
1185         switch (entry->type) {
1186         case TRACE_GRAPH_ENT: {
1187                 /*
1188                  * print_graph_entry() may consume the current event,
1189                  * thus @field may become invalid, so we need to save it.
1190                  * sizeof(struct ftrace_graph_ent_entry) is very small,
1191                  * it can be safely saved at the stack.
1192                  */
1193                 struct ftrace_graph_ent_entry saved;
1194                 trace_assign_type(field, entry);
1195                 saved = *field;
1196                 return print_graph_entry(&saved, s, iter, flags);
1197         }
1198         case TRACE_GRAPH_RET: {
1199                 struct ftrace_graph_ret_entry *field;
1200                 trace_assign_type(field, entry);
1201                 return print_graph_return(&field->ret, s, entry, iter, flags);
1202         }
1203         case TRACE_STACK:
1204         case TRACE_FN:
1205                 /* dont trace stack and functions as comments */
1206                 return TRACE_TYPE_UNHANDLED;
1207 
1208         default:
1209                 return print_graph_comment(s, entry, iter, flags);
1210         }
1211 
1212         return TRACE_TYPE_HANDLED;
1213 }
1214 
1215 static enum print_line_t
1216 print_graph_function(struct trace_iterator *iter)
1217 {
1218         return print_graph_function_flags(iter, tracer_flags.val);
1219 }
1220 
1221 static enum print_line_t
1222 print_graph_function_event(struct trace_iterator *iter, int flags,
1223                            struct trace_event *event)
1224 {
1225         return print_graph_function(iter);
1226 }
1227 
1228 static void print_lat_header(struct seq_file *s, u32 flags)
1229 {
1230         static const char spaces[] = "                " /* 16 spaces */
1231                 "    "                                  /* 4 spaces */
1232                 "                 ";                    /* 17 spaces */
1233         int size = 0;
1234 
1235         if (flags & TRACE_GRAPH_PRINT_ABS_TIME)
1236                 size += 16;
1237         if (flags & TRACE_GRAPH_PRINT_CPU)
1238                 size += 4;
1239         if (flags & TRACE_GRAPH_PRINT_PROC)
1240                 size += 17;
1241 
1242         seq_printf(s, "#%.*s  _-----=> irqs-off        \n", size, spaces);
1243         seq_printf(s, "#%.*s / _----=> need-resched    \n", size, spaces);
1244         seq_printf(s, "#%.*s| / _---=> hardirq/softirq \n", size, spaces);
1245         seq_printf(s, "#%.*s|| / _--=> preempt-depth   \n", size, spaces);
1246         seq_printf(s, "#%.*s||| /                      \n", size, spaces);
1247 }
1248 
1249 static void __print_graph_headers_flags(struct seq_file *s, u32 flags)
1250 {
1251         int lat = trace_flags & TRACE_ITER_LATENCY_FMT;
1252 
1253         if (lat)
1254                 print_lat_header(s, flags);
1255 
1256         /* 1st line */
1257         seq_putc(s, '#');
1258         if (flags & TRACE_GRAPH_PRINT_ABS_TIME)
1259                 seq_puts(s, "     TIME       ");
1260         if (flags & TRACE_GRAPH_PRINT_CPU)
1261                 seq_puts(s, " CPU");
1262         if (flags & TRACE_GRAPH_PRINT_PROC)
1263                 seq_puts(s, "  TASK/PID       ");
1264         if (lat)
1265                 seq_puts(s, "||||");
1266         if (flags & TRACE_GRAPH_PRINT_DURATION)
1267                 seq_puts(s, "  DURATION   ");
1268         seq_puts(s, "               FUNCTION CALLS\n");
1269 
1270         /* 2nd line */
1271         seq_putc(s, '#');
1272         if (flags & TRACE_GRAPH_PRINT_ABS_TIME)
1273                 seq_puts(s, "      |         ");
1274         if (flags & TRACE_GRAPH_PRINT_CPU)
1275                 seq_puts(s, " |  ");
1276         if (flags & TRACE_GRAPH_PRINT_PROC)
1277                 seq_puts(s, "   |    |        ");
1278         if (lat)
1279                 seq_puts(s, "||||");
1280         if (flags & TRACE_GRAPH_PRINT_DURATION)
1281                 seq_puts(s, "   |   |      ");
1282         seq_puts(s, "               |   |   |   |\n");
1283 }
1284 
1285 static void print_graph_headers(struct seq_file *s)
1286 {
1287         print_graph_headers_flags(s, tracer_flags.val);
1288 }
1289 
1290 void print_graph_headers_flags(struct seq_file *s, u32 flags)
1291 {
1292         struct trace_iterator *iter = s->private;
1293 
1294         if (!(trace_flags & TRACE_ITER_CONTEXT_INFO))
1295                 return;
1296 
1297         if (trace_flags & TRACE_ITER_LATENCY_FMT) {
1298                 /* print nothing if the buffers are empty */
1299                 if (trace_empty(iter))
1300                         return;
1301 
1302                 print_trace_header(s, iter);
1303         }
1304 
1305         __print_graph_headers_flags(s, flags);
1306 }
1307 
1308 void graph_trace_open(struct trace_iterator *iter)
1309 {
1310         /* pid and depth on the last trace processed */
1311         struct fgraph_data *data;
1312         gfp_t gfpflags;
1313         int cpu;
1314 
1315         iter->private = NULL;
1316 
1317         /* We can be called in atomic context via ftrace_dump() */
1318         gfpflags = (in_atomic() || irqs_disabled()) ? GFP_ATOMIC : GFP_KERNEL;
1319 
1320         data = kzalloc(sizeof(*data), gfpflags);
1321         if (!data)
1322                 goto out_err;
1323 
1324         data->cpu_data = alloc_percpu_gfp(struct fgraph_cpu_data, gfpflags);
1325         if (!data->cpu_data)
1326                 goto out_err_free;
1327 
1328         for_each_possible_cpu(cpu) {
1329                 pid_t *pid = &(per_cpu_ptr(data->cpu_data, cpu)->last_pid);
1330                 int *depth = &(per_cpu_ptr(data->cpu_data, cpu)->depth);
1331                 int *ignore = &(per_cpu_ptr(data->cpu_data, cpu)->ignore);
1332                 int *depth_irq = &(per_cpu_ptr(data->cpu_data, cpu)->depth_irq);
1333 
1334                 *pid = -1;
1335                 *depth = 0;
1336                 *ignore = 0;
1337                 *depth_irq = -1;
1338         }
1339 
1340         iter->private = data;
1341 
1342         return;
1343 
1344  out_err_free:
1345         kfree(data);
1346  out_err:
1347         pr_warning("function graph tracer: not enough memory\n");
1348 }
1349 
1350 void graph_trace_close(struct trace_iterator *iter)
1351 {
1352         struct fgraph_data *data = iter->private;
1353 
1354         if (data) {
1355                 free_percpu(data->cpu_data);
1356                 kfree(data);
1357         }
1358 }
1359 
1360 static int
1361 func_graph_set_flag(struct trace_array *tr, u32 old_flags, u32 bit, int set)
1362 {
1363         if (bit == TRACE_GRAPH_PRINT_IRQS)
1364                 ftrace_graph_skip_irqs = !set;
1365 
1366         return 0;
1367 }
1368 
1369 static struct trace_event_functions graph_functions = {
1370         .trace          = print_graph_function_event,
1371 };
1372 
1373 static struct trace_event graph_trace_entry_event = {
1374         .type           = TRACE_GRAPH_ENT,
1375         .funcs          = &graph_functions,
1376 };
1377 
1378 static struct trace_event graph_trace_ret_event = {
1379         .type           = TRACE_GRAPH_RET,
1380         .funcs          = &graph_functions
1381 };
1382 
1383 static struct tracer graph_trace __tracer_data = {
1384         .name           = "function_graph",
1385         .update_thresh  = graph_trace_update_thresh,
1386         .open           = graph_trace_open,
1387         .pipe_open      = graph_trace_open,
1388         .close          = graph_trace_close,
1389         .pipe_close     = graph_trace_close,
1390         .init           = graph_trace_init,
1391         .reset          = graph_trace_reset,
1392         .print_line     = print_graph_function,
1393         .print_header   = print_graph_headers,
1394         .flags          = &tracer_flags,
1395         .set_flag       = func_graph_set_flag,
1396 #ifdef CONFIG_FTRACE_SELFTEST
1397         .selftest       = trace_selftest_startup_function_graph,
1398 #endif
1399 };
1400 
1401 
1402 static ssize_t
1403 graph_depth_write(struct file *filp, const char __user *ubuf, size_t cnt,
1404                   loff_t *ppos)
1405 {
1406         unsigned long val;
1407         int ret;
1408 
1409         ret = kstrtoul_from_user(ubuf, cnt, 10, &val);
1410         if (ret)
1411                 return ret;
1412 
1413         max_depth = val;
1414 
1415         *ppos += cnt;
1416 
1417         return cnt;
1418 }
1419 
1420 static ssize_t
1421 graph_depth_read(struct file *filp, char __user *ubuf, size_t cnt,
1422                  loff_t *ppos)
1423 {
1424         char buf[15]; /* More than enough to hold UINT_MAX + "\n"*/
1425         int n;
1426 
1427         n = sprintf(buf, "%d\n", max_depth);
1428 
1429         return simple_read_from_buffer(ubuf, cnt, ppos, buf, n);
1430 }
1431 
1432 static const struct file_operations graph_depth_fops = {
1433         .open           = tracing_open_generic,
1434         .write          = graph_depth_write,
1435         .read           = graph_depth_read,
1436         .llseek         = generic_file_llseek,
1437 };
1438 
1439 static __init int init_graph_debugfs(void)
1440 {
1441         struct dentry *d_tracer;
1442 
1443         d_tracer = tracing_init_dentry();
1444         if (IS_ERR(d_tracer))
1445                 return 0;
1446 
1447         trace_create_file("max_graph_depth", 0644, d_tracer,
1448                           NULL, &graph_depth_fops);
1449 
1450         return 0;
1451 }
1452 fs_initcall(init_graph_debugfs);
1453 
1454 static __init int init_graph_trace(void)
1455 {
1456         max_bytes_for_cpu = snprintf(NULL, 0, "%d", nr_cpu_ids - 1);
1457 
1458         if (!register_ftrace_event(&graph_trace_entry_event)) {
1459                 pr_warning("Warning: could not register graph trace events\n");
1460                 return 1;
1461         }
1462 
1463         if (!register_ftrace_event(&graph_trace_ret_event)) {
1464                 pr_warning("Warning: could not register graph trace events\n");
1465                 return 1;
1466         }
1467 
1468         return register_tracer(&graph_trace);
1469 }
1470 
1471 core_initcall(init_graph_trace);
1472 

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