From 3f2546b2ef55b661fd8dd69682b38992225e86f6 Mon Sep 17 00:00:00 2001
From: fishsoupisgood <github@madingley.org>
Date: Mon, 29 Apr 2019 01:17:54 +0100
Subject: Initial import of qemu-2.4.1

---
 trace/ftrace.c | 79 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 79 insertions(+)
 create mode 100644 trace/ftrace.c

(limited to 'trace/ftrace.c')

diff --git a/trace/ftrace.c b/trace/ftrace.c
new file mode 100644
index 00000000..a7ae371e
--- /dev/null
+++ b/trace/ftrace.c
@@ -0,0 +1,79 @@
+/*
+ * 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 <stdio.h>
+#include <string.h>
+#include <fcntl.h>
+#include <limits.h>
+#include "trace.h"
+#include "trace/control.h"
+
+int trace_marker_fd;
+
+static int find_debugfs(char *debugfs)
+{
+    char type[100];
+    FILE *fp;
+
+    fp = fopen("/proc/mounts", "r");
+    if (fp == NULL) {
+        return 0;
+    }
+
+    while (fscanf(fp, "%*s %" STR(PATH_MAX) "s %99s %*s %*d %*d\n",
+                  debugfs, type) == 2) {
+        if (strcmp(type, "debugfs") == 0) {
+            break;
+        }
+    }
+    fclose(fp);
+
+    if (strcmp(type, "debugfs") != 0) {
+        return 0;
+    }
+    return 1;
+}
+
+bool ftrace_init(void)
+{
+    char debugfs[PATH_MAX];
+    char path[PATH_MAX];
+    int debugfs_found;
+    int trace_fd = -1;
+
+    debugfs_found = find_debugfs(debugfs);
+    if (debugfs_found) {
+        snprintf(path, PATH_MAX, "%s/tracing/tracing_on", debugfs);
+        trace_fd = open(path, O_WRONLY);
+        if (trace_fd < 0) {
+            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);
+        }
+        snprintf(path, PATH_MAX, "%s/tracing/trace_marker", debugfs);
+        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, "debugfs is not mounted\n");
+        return false;
+    }
+
+    return true;
+}
-- 
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