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>
This commit is contained in:
Eiichi Tsukata 2013-04-11 20:25:15 +09:00 committed by Stefan Hajnoczi
parent b76ac80a5c
commit 781e9545db
5 changed files with 175 additions and 0 deletions

8
configure vendored
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@ -4004,6 +4004,14 @@ if test "$trace_backend" = "dtrace"; then
echo "CONFIG_TRACE_SYSTEMTAP=y" >> $config_host_mak echo "CONFIG_TRACE_SYSTEMTAP=y" >> $config_host_mak
fi fi
fi fi
if test "$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" >> $config_host_mak echo "CONFIG_TRACE_FILE=$trace_file" >> $config_host_mak
if test "$trace_default" = "yes"; then if test "$trace_default" = "yes"; then
echo "CONFIG_TRACE_DEFAULT=y" >> $config_host_mak echo "CONFIG_TRACE_DEFAULT=y" >> $config_host_mak

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@ -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,
)

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@ -76,5 +76,6 @@ endif
util-obj-$(CONFIG_TRACE_DEFAULT) += default.o util-obj-$(CONFIG_TRACE_DEFAULT) += default.o
util-obj-$(CONFIG_TRACE_SIMPLE) += simple.o util-obj-$(CONFIG_TRACE_SIMPLE) += simple.o
util-obj-$(CONFIG_TRACE_STDERR) += stderr.o util-obj-$(CONFIG_TRACE_STDERR) += stderr.o
util-obj-$(CONFIG_TRACE_FTRACE) += ftrace.o
util-obj-y += control.o util-obj-y += control.o
util-obj-y += generated-tracers.o util-obj-y += generated-tracers.o

102
trace/ftrace.c Normal file
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@ -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;
}

10
trace/ftrace.h Normal file
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@ -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 */