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c9add62195
Recent Linux kernel provides separate tracefs which doesn't need to be mounted on the debugfs. Although most systems mount it at the traditional place on the debugfs, it'd be safer to check tracefs first. Signed-off-by: Namhyung Kim <namhyung@gmail.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
88 lines
2.2 KiB
C
88 lines
2.2 KiB
C
/*
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* Ftrace trace backend
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*
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* Copyright (C) 2013 Hitachi, Ltd.
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* Created by Eiichi Tsukata <eiichi.tsukata.xh@hitachi.com>
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*
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* This work is licensed under the terms of the GNU GPL, version 2. See
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* the COPYING file in the top-level directory.
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*
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*/
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#include "qemu/osdep.h"
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#include "trace/control.h"
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#include "trace/ftrace.h"
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int trace_marker_fd;
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static int find_mount(char *mount_point, const char *fstype)
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{
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char type[100];
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FILE *fp;
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int ret = 0;
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fp = fopen("/proc/mounts", "r");
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if (fp == NULL) {
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return 0;
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}
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while (fscanf(fp, "%*s %" STR(PATH_MAX) "s %99s %*s %*d %*d\n",
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mount_point, type) == 2) {
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if (strcmp(type, fstype) == 0) {
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ret = 1;
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break;
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}
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}
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fclose(fp);
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return ret;
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}
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bool ftrace_init(void)
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{
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char mount_point[PATH_MAX];
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char path[PATH_MAX];
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int tracefs_found;
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int trace_fd = -1;
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const char *subdir = "";
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tracefs_found = find_mount(mount_point, "tracefs");
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if (!tracefs_found) {
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tracefs_found = find_mount(mount_point, "debugfs");
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subdir = "/tracing";
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}
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if (tracefs_found) {
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snprintf(path, PATH_MAX, "%s%s/tracing_on", mount_point, subdir);
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trace_fd = open(path, O_WRONLY);
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if (trace_fd < 0) {
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if (errno == EACCES) {
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trace_marker_fd = open("/dev/null", O_WRONLY);
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if (trace_marker_fd != -1) {
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return true;
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}
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}
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perror("Could not open ftrace 'tracing_on' file");
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return false;
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} else {
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if (write(trace_fd, "1", 1) < 0) {
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perror("Could not write to 'tracing_on' file");
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close(trace_fd);
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return false;
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}
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close(trace_fd);
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}
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snprintf(path, PATH_MAX, "%s%s/trace_marker", mount_point, subdir);
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trace_marker_fd = open(path, O_WRONLY);
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if (trace_marker_fd < 0) {
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perror("Could not open ftrace 'trace_marker' file");
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return false;
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}
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} else {
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fprintf(stderr, "tracefs is not mounted\n");
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return false;
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}
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return true;
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}
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