kernel/trace/trace_functions_return.c

   1 /*
   2  *
   3  * Function return tracer.
   4  * Copyright (c) 2008 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/fs.h>
  13
  14 #include "trace.h"
  15
  16
  17 static void start_return_trace(struct trace_array *tr)
  18 {
  19         register_ftrace_return(&trace_function_return);
  20 }
  21
  22 static void stop_return_trace(struct trace_array *tr)
  23 {
  24         unregister_ftrace_return();
  25 }
  26
  27 static void return_trace_init(struct trace_array *tr)
  28 {
  29         int cpu;
  30         for_each_online_cpu(cpu)
  31                 tracing_reset(tr, cpu);
  32
  33         start_return_trace(tr);
  34 }
  35
  36 static void return_trace_reset(struct trace_array *tr)
  37 {
  38                 stop_return_trace(tr);
  39 }
  40
  41
  42 enum print_line_t
  43 print_return_function(struct trace_iterator *iter)
  44 {
  45         struct trace_seq *s = &iter->seq;
  46         struct trace_entry *entry = iter->ent;
  47         struct ftrace_ret_entry *field;
  48         int ret;
  49
  50         if (entry->type == TRACE_FN_RET) {
  51                 trace_assign_type(field, entry);
  52                 ret = trace_seq_printf(s, "%pF -> ", (void *)field->parent_ip);
  53                 if (!ret)
  54                         return TRACE_TYPE_PARTIAL_LINE;
  55                 ret = seq_print_ip_sym(s, field->ip,
  56                                         trace_flags & TRACE_ITER_SYM_MASK);
  57                 if (!ret)
  58                         return TRACE_TYPE_PARTIAL_LINE;
  59                 ret = trace_seq_printf(s, " (%llu ns)\n",
  60                                         field->rettime - field->calltime);
  61                 if (!ret)
  62                         return TRACE_TYPE_PARTIAL_LINE;
  63                 else
  64                         return TRACE_TYPE_HANDLED;
  65         }
  66         return TRACE_TYPE_UNHANDLED;
  67 }
  68
  69 static struct tracer return_trace __read_mostly =
  70 {
  71         .name        = "return",
  72         .init        = return_trace_init,
  73         .reset       = return_trace_reset,
  74         .print_line = print_return_function
  75 };
  76
  77 static __init int init_return_trace(void)
  78 {
  79         return register_tracer(&return_trace);
  80 }
  81
  82 device_initcall(init_return_trace);