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 "qemu/osdep.h" 13 #include "trace/control.h" 14 #include "trace/ftrace.h" 15 16 int trace_marker_fd; 17 18 static int find_mount(char *mount_point, const char *fstype) 19 { 20 char type[100]; 21 FILE *fp; 22 int ret = 0; 23 24 fp = fopen("/proc/mounts", "r"); 25 if (fp == NULL) { 26 return 0; 27 } 28 29 while (fscanf(fp, "%*s %" STR(PATH_MAX) "s %99s %*s %*d %*d\n", 30 mount_point, type) == 2) { 31 if (strcmp(type, fstype) == 0) { 32 ret = 1; 33 break; 34 } 35 } 36 fclose(fp); 37 38 return ret; 39 } 40 41 bool ftrace_init(void) 42 { 43 char mount_point[PATH_MAX]; 44 char path[PATH_MAX]; 45 int tracefs_found; 46 int trace_fd = -1; 47 const char *subdir = ""; 48 49 tracefs_found = find_mount(mount_point, "tracefs"); 50 if (!tracefs_found) { 51 tracefs_found = find_mount(mount_point, "debugfs"); 52 subdir = "/tracing"; 53 } 54 55 if (tracefs_found) { 56 snprintf(path, PATH_MAX, "%s%s/tracing_on", mount_point, subdir); 57 trace_fd = open(path, O_WRONLY); 58 if (trace_fd < 0) { 59 if (errno == EACCES) { 60 trace_marker_fd = open("/dev/null", O_WRONLY); 61 if (trace_marker_fd != -1) { 62 return true; 63 } 64 } 65 perror("Could not open ftrace 'tracing_on' file"); 66 return false; 67 } else { 68 if (write(trace_fd, "1", 1) < 0) { 69 perror("Could not write to 'tracing_on' file"); 70 close(trace_fd); 71 return false; 72 } 73 close(trace_fd); 74 } 75 snprintf(path, PATH_MAX, "%s%s/trace_marker", mount_point, subdir); 76 trace_marker_fd = open(path, O_WRONLY); 77 if (trace_marker_fd < 0) { 78 perror("Could not open ftrace 'trace_marker' file"); 79 return false; 80 } 81 } else { 82 fprintf(stderr, "tracefs is not mounted\n"); 83 return false; 84 } 85 86 return true; 87 } 88