trace: Add ftrace tracing backend

This patch adds a ftrace tracing backend which sends trace event to
ftrace marker file. You can effectively compare qemu trace data and
kernel(especially, kvm.ko when using KVM) trace data.
The ftrace backend is restricted to Linux only.

To try out the ftrace backend:

 $ ./configure --trace-backend=ftrace
 $ make

if you use KVM, enable kvm events in ftrace:

 # sudo echo 1 > /sys/kernel/debug/tracing/events/kvm/enable

After running qemu by root user, you can get the trace:

 # cat /sys/kernel/debug/tracing/trace

Signed-off-by: Eiichi Tsukata <eiichi.tsukata.xh@hitachi.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

diff --git a/configure b/configure
index c4d85ba51d86640b851602cae14ec11eed007188..e818e8b357e65ab2b6c6cd7b6cbb08e975c687c4 100755 (executable)
--- a/configure
+++ b/configure
@@ -4004,6 +4004,14 @@ if test "$trace_backend" = "dtrace"; then
     echo "CONFIG_TRACE_SYSTEMTAP=y" >> $config_host_mak
   fi
 fi
     echo "CONFIG_TRACE_SYSTEMTAP=y" >> $config_host_mak
   fi
 fi

+if test "$trace_backend" = "ftrace"; then
+  if test "$linux" = "yes" ; then
+    echo "CONFIG_TRACE_FTRACE=y" >> $config_host_mak
+    trace_default=no
+  else
+    feature_not_found "ftrace(trace backend)"
+  fi
+fi

 echo "CONFIG_TRACE_FILE=$trace_file" >> $config_host_mak
 if test "$trace_default" = "yes"; then
   echo "CONFIG_TRACE_DEFAULT=y" >> $config_host_mak
 echo "CONFIG_TRACE_FILE=$trace_file" >> $config_host_mak
 if test "$trace_default" = "yes"; then
   echo "CONFIG_TRACE_DEFAULT=y" >> $config_host_mak

diff --git a/scripts/tracetool/backend/ftrace.py b/scripts/tracetool/backend/ftrace.py
new file mode 100644 (file)
index 0000000..888c361
--- /dev/null
+++ b/scripts/tracetool/backend/ftrace.py
@@ -0,0 +1,54 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+
+"""
+Ftrace built-in backend.
+"""
+
+__author__     = "Eiichi Tsukata <eiichi.tsukata.xh@hitachi.com>"
+__copyright__  = "Copyright (C) 2013 Hitachi, Ltd."
+__license__    = "GPL version 2 or (at your option) any later version"
+
+__maintainer__ = "Stefan Hajnoczi"
+__email__      = "stefanha@redhat.com"
+
+
+from tracetool import out
+
+
+PUBLIC = True
+
+
+def c(events):
+    pass
+
+def h(events):
+    out('#include "trace/ftrace.h"',
+        '#include "trace/control.h"',
+        '',
+        )
+
+    for e in events:
+        argnames = ", ".join(e.args.names())
+        if len(e.args) > 0:
+            argnames = ", " + argnames
+
+        out('static inline void trace_%(name)s(%(args)s)',
+            '{',
+            '    char ftrace_buf[MAX_TRACE_STRLEN];',
+            '    int unused __attribute__ ((unused));',
+            '    int trlen;',
+            '    bool _state = trace_event_get_state(%(event_id)s);',
+            '    if (_state) {',
+            '        trlen = snprintf(ftrace_buf, MAX_TRACE_STRLEN,',
+            '                         "%(name)s " %(fmt)s "\\n" %(argnames)s);',
+            '        trlen = MIN(trlen, MAX_TRACE_STRLEN - 1);',
+            '        unused = write(trace_marker_fd, ftrace_buf, trlen);',
+            '    }',
+            '}',
+            name = e.name,
+            args = e.args,
+            event_id = "TRACE_" + e.name.upper(),
+            fmt = e.fmt.rstrip("\n"),
+            argnames = argnames,
+            )

diff --git a/trace/Makefile.objs b/trace/Makefile.objs
index a0430721062fd4963a03149ead379ccfdad22d61..3b88e498b5ff0f39812f7f43da5560cc79b397ca 100644 (file)
--- a/trace/Makefile.objs
+++ b/trace/Makefile.objs
@@ -76,5 +76,6 @@ endif
 util-obj-$(CONFIG_TRACE_DEFAULT) += default.o
 util-obj-$(CONFIG_TRACE_SIMPLE) += simple.o
 util-obj-$(CONFIG_TRACE_STDERR) += stderr.o
 util-obj-$(CONFIG_TRACE_DEFAULT) += default.o
 util-obj-$(CONFIG_TRACE_SIMPLE) += simple.o
 util-obj-$(CONFIG_TRACE_STDERR) += stderr.o

+util-obj-$(CONFIG_TRACE_FTRACE) += ftrace.o

 util-obj-y += control.o
 util-obj-y += generated-tracers.o
 util-obj-y += control.o
 util-obj-y += generated-tracers.o

diff --git a/trace/ftrace.c b/trace/ftrace.c
new file mode 100644 (file)
index 0000000..46b7fdb
--- /dev/null
+++ b/trace/ftrace.c
@@ -0,0 +1,102 @@
+/*
+ * 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;
+}
+
+void trace_print_events(FILE *stream, fprintf_function stream_printf)
+{
+    TraceEventID i;
+
+    for (i = 0; i < trace_event_count(); i++) {
+        TraceEvent *ev = trace_event_id(i);
+        stream_printf(stream, "%s [Event ID %u] : state %u\n",
+                      trace_event_get_name(ev), i, trace_event_get_state_dynamic(ev));
+    }
+}
+
+void trace_event_set_state_dynamic_backend(TraceEvent *ev, bool state)
+{
+    ev->dstate = state;
+}
+
+bool trace_backend_init(const char *events, const char *file)
+{
+    char debugfs[PATH_MAX];
+    char path[PATH_MAX];
+    int debugfs_found;
+    int trace_fd = -1;
+
+    if (file) {
+        fprintf(stderr, "error: -trace file=...: "
+                "option not supported by the selected tracing backend\n");
+        return false;
+    }
+
+    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;
+    }
+
+    trace_backend_init_events(events);
+    return true;
+}

diff --git a/trace/ftrace.h b/trace/ftrace.h
new file mode 100644 (file)
index 0000000..94cb8d5
--- /dev/null
+++ b/trace/ftrace.h
@@ -0,0 +1,10 @@
+#ifndef TRACE_FTRACE_H
+#define TRACE_FTRACE_H
+
+#define MAX_TRACE_STRLEN 512
+#define _STR(x) #x
+#define STR(x) _STR(x)
+
+extern int trace_marker_fd;
+
+#endif /* ! TRACE_FTRACE_H */