1 files changed, 95 insertions, 0 deletions
diff --git a/trace/ftrace.c b/trace/ftrace.c
new file mode 100644
index 000000000..9749543d9
--- /dev/null
+++ b/trace/ftrace.c
@@ -0,0 +1,95 @@
+/*
+ * 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;
+}