[PATCH 2/5] trace: Add simple built-in tracing backend

Stefan Hajnoczi
2010-05-22T21:08:37Z

This patch adds a simple tracer which produces binary trace files and is
built into QEMU. The main purpose of this patch is to show how new
tracing backends can be added to tracetool.

To try out the simple backend:

./configure --trace-backend=simple
make

After running QEMU you can pretty-print the trace:

./tracetool --simple --py <trace-events >events.py # first time only
./simpletrace.py /tmp/trace.log

Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
---
This is the same trivial tracer that I posted previously.

.gitignore | 2 +
Makefile.objs | 3 +
configure | 2 +-
simpletrace.c | 64 ++++++++++++++++++++++++++++
simpletrace.py | 38 +++++++++++++++++
tracetool | 127 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-
6 files changed, 232 insertions(+), 4 deletions(-)
create mode 100644 simpletrace.c
create mode 100755 simpletrace.py

diff --git a/.gitignore b/.gitignore
index 4644557..68fb21d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -4,6 +4,7 @@ config-host.*
config-target.*
trace.h
trace.c
+events.py
*-softmmu
*-darwin-user
*-linux-user
@@ -39,6 +40,7 @@ qemu-monitor.texi
*.log
*.pdf
*.pg
+*.pyc
*.toc
*.tp
*.vr
diff --git a/Makefile.objs b/Makefile.objs
index 9bbdf6f..d870767 100644
--- a/Makefile.objs
+++ b/Makefile.objs
@@ -252,6 +252,9 @@ libdis-$(CONFIG_SPARC_DIS) += sparc-dis.o
# trace

trace-obj-y = trace.o
+ifeq ($(TRACE_BACKEND),simple)
+trace-obj-y += simpletrace.o
+endif

vl.o: QEMU_CFLAGS+=$(GPROF_CFLAGS)

diff --git a/configure b/configure
index 5e66f3a..d599879 100755
--- a/configure
+++ b/configure
@@ -829,7 +829,7 @@ echo " --enable-docs enable documentation build"
echo " --disable-docs disable documentation build"
echo " --disable-vhost-net disable vhost-net acceleration support"
echo " --enable-vhost-net enable vhost-net acceleration support"
-echo " --trace-backend=B Trace backend nop"
+echo " --trace-backend=B Trace backend nop simple"
echo ""
echo "NOTE: The object files are built at the place where configure is launched"
exit 1
diff --git a/simpletrace.c b/simpletrace.c
new file mode 100644
index 0000000..2fec4d3
--- /dev/null
+++ b/simpletrace.c
@@ -0,0 +1,64 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include "trace.h"
+
+typedef struct {
+ unsigned long event;
+ unsigned long x1;
+ unsigned long x2;
+ unsigned long x3;
+ unsigned long x4;
+ unsigned long x5;
+} TraceRecord;
+
+enum {
+ TRACE_BUF_LEN = 64 * 1024 / sizeof(TraceRecord),
+};
+
+static TraceRecord trace_buf[TRACE_BUF_LEN];
+static unsigned int trace_idx;
+static FILE *trace_fp;
+
+static void trace(TraceEvent event, unsigned long x1,
+ unsigned long x2, unsigned long x3,
+ unsigned long x4, unsigned long x5) {
+ TraceRecord *rec = &trace_buf[trace_idx];
+ rec->event = event;
+ rec->x1 = x1;
+ rec->x2 = x2;
+ rec->x3 = x3;
+ rec->x4 = x4;
+ rec->x5 = x5;
+
+ if (++trace_idx == TRACE_BUF_LEN) {
+ trace_idx = 0;
+
+ if (!trace_fp) {
+ trace_fp = fopen("/tmp/trace.log", "w");
+ }
+ if (trace_fp) {
+ size_t result = fwrite(trace_buf, sizeof trace_buf, 1, trace_fp);
+ result = result;
+ }
+ }
+}
+
+void trace1(TraceEvent event, unsigned long x1) {
+ trace(event, x1, 0, 0, 0, 0);
+}
+
+void trace2(TraceEvent event, unsigned long x1, unsigned long x2) {
+ trace(event, x1, x2, 0, 0, 0);
+}
+
+void trace3(TraceEvent event, unsigned long x1, unsigned long x2, unsigned long x3) {
+ trace(event, x1, x2, x3, 0, 0);
+}
+
+void trace4(TraceEvent event, unsigned long x1, unsigned long x2, unsigned long x3, unsigned long x4) {
+ trace(event, x1, x2, x3, x4, 0);
+}
+
+void trace5(TraceEvent event, unsigned long x1, unsigned long x2, unsigned long x3, unsigned long x4, unsigned long x5) {
+ trace(event, x1, x2, x3, x4, x5);
+}
diff --git a/simpletrace.py b/simpletrace.py
new file mode 100755
index 0000000..70609cf
--- /dev/null
+++ b/simpletrace.py
@@ -0,0 +1,38 @@
+#!/usr/bin/env python
+import sys
+import struct
+
+try:
+ from events import events
+except ImportError:
+ sys.stderr.write('''Unable to import trace events from current working directory. Please run:
+tracetool --simple --py <trace-events >events.py\n''')
+ sys.exit(1)
+
+trace_fmt = 'LLLLLL'
+trace_len = struct.calcsize(trace_fmt)
+
+def read_record(fobj):
+ s = fobj.read(trace_len)
+ if len(s) != trace_len:
+ return None
+ return struct.unpack(trace_fmt, s)
+
+def format_record(rec):
+ event = events[rec[0]]
+ fields = [event[0]]
+ for i in xrange(1, len(event)):
+ fields.append('%s=0x%x' % (event[i], rec[i]))
+ return ' '.join(fields)
+
+if len(sys.argv) != 2:
+ sys.stderr.write('usage: %s <trace-file>\n' % sys.argv[0])
+ sys.exit(1)
+
+f = open(sys.argv[1], 'rb')
+while True:
+ rec = read_record(f)
+ if rec is None:
+ break
+
+ print format_record(rec)
diff --git a/tracetool b/tracetool
index e243d42..bcd163e 100755
--- a/tracetool
+++ b/tracetool
@@ -3,15 +3,17 @@
usage()
{
cat >&2 <<EOF
-usage: $0 --nop [-h | -c]
+usage: $0 [--nop | --simple] [-h | -c | --py]
Generate tracing code for a file on stdin.

Backends:
- --nop Tracing disabled
+ --nop Tracing disabled
+ --simple Simple built-in backend

Output formats:
-h Generate .h file
-c Generate .c file
+ --py Generate .py file (simple backend only)
EOF
exit 1
}
@@ -48,6 +50,17 @@ get_argnames()
echo -n "$name"
}

+# Get the number of arguments to a trace event
+get_argc()
+{
+ local name argc
+ argc=0
+ for name in $(get_argnames "$1"); do
+ argc=$((argc + 1))
+ done
+ echo $argc
+}
+
# Get the format string for a trace event
get_fmt()
{
@@ -67,6 +80,11 @@ warn_autogen_h()
echo "/* This file is autogenerated by tracetool, do not edit. */"
}

+warn_autogen_py()
+{
+ echo "# This file is autogenerated by tracetool, do not edit."
+}
+
linetoh_begin_nop()
{
return
@@ -107,6 +125,101 @@ linetoc_end_nop()
return
}

+linetoh_begin_simple()
+{
+ cat <<EOF
+typedef unsigned int TraceEvent;
+
+void trace1(TraceEvent event, unsigned long x1);
+void trace2(TraceEvent event, unsigned long x1, unsigned long x2);
+void trace3(TraceEvent event, unsigned long x1, unsigned long x2, unsigned long x3);
+void trace4(TraceEvent event, unsigned long x1, unsigned long x2, unsigned long x3, unsigned long x4);
+void trace5(TraceEvent event, unsigned long x1, unsigned long x2, unsigned long x3, unsigned long x4, unsigned long x5);
+EOF
+
+ simple_event_num=0
+}
+
+cast_args_to_ulong()
+{
+ local arg
+ for arg in $(get_argnames "$1"); do
+ echo -n "(unsigned long)$arg"
+ done
+}
+
+linetoh_simple()
+{
+ local name args argc ulong_args
+ name=$(get_name "$1")
+ args=$(get_args "$1")
+ argc=$(get_argc "$1")
+ ulong_args=$(cast_args_to_ulong "$1")
+
+ cat <<EOF
+static inline void trace_$name($args) {
+ trace$argc($simple_event_num, $ulong_args);
+}
+EOF
+
+ simple_event_num=$((simple_event_num + 1))
+}
+
+linetoh_end_simple()
+{
+ return
+}
+
+linetoc_begin_simple()
+{
+ return
+}
+
+linetoc_simple()
+{
+ return
+}
+
+linetoc_end_simple()
+{
+ return
+}
+
+linetopy_begin_simple()
+{
+ echo "events = {"
+
+ simple_event_num=0
+}
+
+quote_args()
+{
+ local arg first
+ first=""
+ for arg in $(get_argnames "$1"); do
+ echo -n "$first'${arg%,}'"
+ first=", "
+ done
+}
+
+linetopy_simple()
+{
+ local name quoted_args
+ name=$(get_name "$1")
+ quoted_args=$(quote_args "$1")
+
+ cat <<EOF
+ $simple_event_num: ('$name', $quoted_args),
+EOF
+
+ simple_event_num=$((simple_event_num + 1))
+}
+
+linetopy_end_simple()
+{
+ echo "}"
+}
+
# Process stdin by calling begin, line, and end functions for the backend
convert()
{
@@ -145,9 +258,16 @@ tracetoc()
convert c
}

+tracetopy()
+{
+ test "$backend" = "simple" || usage
+
+ convert py
+}
+
# Choose backend
case "$1" in
-"--nop") backend="${1#--}" ;;
+"--nop" | "--simple") backend="${1#--}" ;;
*) usage ;;
esac
shift
@@ -155,6 +275,7 @@ shift
case "$1" in
"-h") tracetoh ;;
"-c") tracetoc ;;
+"--py") tracetopy ;;
"--check-backend") exit 0 ;; # used by ./configure to test for backend
*) usage ;;
esac
--
1.7.1