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 bool ftrace_init(void)
  46 {
  47     char debugfs[PATH_MAX];
  48     char path[PATH_MAX];
  49     int debugfs_found;
  50     int trace_fd = -1;
  51
  52     debugfs_found = find_debugfs(debugfs);
  53     if (debugfs_found) {
  54         snprintf(path, PATH_MAX, "%s/tracing/tracing_on", debugfs);
  55         trace_fd = open(path, O_WRONLY);
  56         if (trace_fd < 0) {
  57             perror("Could not open ftrace 'tracing_on' file");
  58             return false;
  59         } else {
  60             if (write(trace_fd, "1", 1) < 0) {
  61                 perror("Could not write to 'tracing_on' file");
  62                 close(trace_fd);
  63                 return false;
  64             }
  65             close(trace_fd);
  66         }
  67         snprintf(path, PATH_MAX, "%s/tracing/trace_marker", debugfs);
  68         trace_marker_fd = open(path, O_WRONLY);
  69         if (trace_marker_fd < 0) {
  70             perror("Could not open ftrace 'trace_marker' file");
  71             return false;
  72         }
  73     } else {
  74         fprintf(stderr, "debugfs is not mounted\n");
  75         return false;
  76     }
  77
  78     return true;
  79 }