/* * Ftrace trace backend * * Copyright (C) 2013 Hitachi, Ltd. * Created by Eiichi Tsukata <eiichi.tsukata.xh@hitachi.com> * * This work is licensed under the terms of the GNU GPL, version 2. See * the COPYING file in the top-level directory. * */ #include "qemu/osdep.h" #include "trace/control.h" #include "trace/ftrace.h" int trace_marker_fd; static int find_mount(char *mount_point, const char *fstype) { char type[100]; FILE *fp; int ret = 0; fp = fopen("/proc/mounts", "r"); if (fp == NULL) { return 0; } while (fscanf(fp, "%*s %" STR(PATH_MAX) "s %99s %*s %*d %*d\n", mount_point, type) == 2) { if (strcmp(type, fstype) == 0) { ret = 1; break; } } fclose(fp); return ret; } bool ftrace_init(void) { char mount_point[PATH_MAX]; char path[PATH_MAX]; int tracefs_found; int trace_fd = -1; const char *subdir = ""; tracefs_found = find_mount(mount_point, "tracefs"); if (!tracefs_found) { tracefs_found = find_mount(mount_point, "debugfs"); subdir = "/tracing"; } if (tracefs_found) { if (snprintf(path, PATH_MAX, "%s%s/tracing_on", mount_point, subdir) >= sizeof(path)) { fprintf(stderr, "Using tracefs mountpoint would exceed PATH_MAX\n"); return false; } trace_fd = open(path, O_WRONLY); if (trace_fd < 0) { if (errno == EACCES) { trace_marker_fd = open("/dev/null", O_WRONLY); if (trace_marker_fd != -1) { return true; } } perror("Could not open ftrace 'tracing_on' file"); return false; } else { if (write(trace_fd, "1", 1) < 0) { perror("Could not write to 'tracing_on' file"); close(trace_fd); return false; } close(trace_fd); } if (snprintf(path, PATH_MAX, "%s%s/trace_marker", mount_point, subdir) >= sizeof(path)) { fprintf(stderr, "Using tracefs mountpoint would exceed PATH_MAX\n"); return false; } trace_marker_fd = open(path, O_WRONLY); if (trace_marker_fd < 0) { perror("Could not open ftrace 'trace_marker' file"); return false; } } else { fprintf(stderr, "tracefs is not mounted\n"); return false; } return true; }