trace/ftrace.c

   1 /*
   2  * Ftrace trace backend
   3  *
   4  * Copyright (C) 2013 Hitachi, Ltd.
   5  * Created by Eiichi Tsukata <eiichi.tsukata.xh@hitachi.com>
   6  *
   7  * This work is licensed under the terms of the GNU GPL, version 2.  See
   8  * the COPYING file in the top-level directory.
   9  *
  10  */
  11
  12 #include <stdio.h>
  13 #include <string.h>
  14 #include <fcntl.h>
  15 #include <limits.h>
  16 #include "trace.h"
  17 #include "trace/control.h"
  18
  19 int trace_marker_fd;
  20
  21 static int find_debugfs(char *debugfs)
  22 {
  23     char type[100];
  24     FILE *fp;
  25
  26     fp = fopen("/proc/mounts", "r");
  27     if (fp == NULL) {
  28         return 0;
  29     }
  30
  31     while (fscanf(fp, "%*s %" STR(PATH_MAX) "s %99s %*s %*d %*d\n",
  32                   debugfs, type) == 2) {
  33         if (strcmp(type, "debugfs") == 0) {
  34             break;
  35         }
  36     }
  37     fclose(fp);
  38
  39     if (strcmp(type, "debugfs") != 0) {
  40         return 0;
  41     }
  42     return 1;
  43 }
  44
  45 void trace_print_events(FILE *stream, fprintf_function stream_printf)
  46 {
  47     TraceEventID i;
  48
  49     for (i = 0; i < trace_event_count(); i++) {
  50         TraceEvent *ev = trace_event_id(i);
  51         stream_printf(stream, "%s [Event ID %u] : state %u\n",
  52                       trace_event_get_name(ev), i, trace_event_get_state_dynamic(ev));
  53     }
  54 }
  55
  56 void trace_event_set_state_dynamic_backend(TraceEvent *ev, bool state)
  57 {
  58     ev->dstate = state;
  59 }
  60
  61 bool trace_backend_init(const char *events, const char *file)
  62 {
  63     char debugfs[PATH_MAX];
  64     char path[PATH_MAX];
  65     int debugfs_found;
  66     int trace_fd = -1;
  67
  68     if (file) {
  69         fprintf(stderr, "error: -trace file=...: "
  70                 "option not supported by the selected tracing backend\n");
  71         return false;
  72     }
  73
  74     debugfs_found = find_debugfs(debugfs);
  75     if (debugfs_found) {
  76         snprintf(path, PATH_MAX, "%s/tracing/tracing_on", debugfs);
  77         trace_fd = open(path, O_WRONLY);
  78         if (trace_fd < 0) {
  79             perror("Could not open ftrace 'tracing_on' file");
  80             return false;
  81         } else {
  82             if (write(trace_fd, "1", 1) < 0) {
  83                 perror("Could not write to 'tracing_on' file");
  84                 close(trace_fd);
  85                 return false;
  86             }
  87             close(trace_fd);
  88         }
  89         snprintf(path, PATH_MAX, "%s/tracing/trace_marker", debugfs);
  90         trace_marker_fd = open(path, O_WRONLY);
  91         if (trace_marker_fd < 0) {
  92             perror("Could not open ftrace 'trace_marker' file");
  93             return false;
  94         }
  95     } else {
  96         fprintf(stderr, "debugfs is not mounted\n");
  97         return false;
  98     }
  99
 100     trace_backend_init_events(events);
 101     return true;
 102 }