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 } 80