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 int 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         return 0;
  35 }
  36
  37 static void return_trace_reset(struct trace_array *tr)
  38 {
  39                 stop_return_trace(tr);
  40 }
  41
  42
  43 enum print_line_t
  44 print_return_function(struct trace_iterator *iter)
  45 {
  46         struct trace_seq *s = &iter->seq;
  47         struct trace_entry *entry = iter->ent;
  48         struct ftrace_ret_entry *field;
  49         int ret;
  50
  51         if (entry->type == TRACE_FN_RET) {
  52                 trace_assign_type(field, entry);
  53                 ret = trace_seq_printf(s, "%pF -> ", (void *)field->parent_ip);
  54                 if (!ret)
  55                         return TRACE_TYPE_PARTIAL_LINE;
  56                 ret = seq_print_ip_sym(s, field->ip,
  57                                         trace_flags & TRACE_ITER_SYM_MASK);
  58                 if (!ret)
  59                         return TRACE_TYPE_PARTIAL_LINE;
  60                 ret = trace_seq_printf(s, " (%llu ns)\n",
  61                                         field->rettime - field->calltime);
  62                 if (!ret)
  63                         return TRACE_TYPE_PARTIAL_LINE;
  64                 else
  65                         return TRACE_TYPE_HANDLED;
  66         }
  67         return TRACE_TYPE_UNHANDLED;
  68 }
  69
  70 static struct tracer return_trace __read_mostly =
  71 {
  72         .name        = "return",
  73         .init        = return_trace_init,
  74         .reset       = return_trace_reset,
  75         .print_line = print_return_function
  76 };
  77
  78 static __init int init_return_trace(void)
  79 {
  80         return register_tracer(&return_trace);
  81 }
  82
  83 device_initcall(init_return_trace);