[Qemu-devel] [PATCH 1/2] trace: Add simple tracing support

[Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>]

Trace events should be defined in trace.h.  Events are written to
/tmp/trace.log and can be formatted using trace.py.  Remember to add
events to trace.py for pretty-printing.

Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
---
 Makefile.objs |    2 +-
 trace.c       |   64 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 trace.h       |    9 ++++++++
 trace.py      |   30 ++++++++++++++++++++++++++
 4 files changed, 104 insertions(+), 1 deletions(-)
 create mode 100644 trace.c
 create mode 100644 trace.h
 create mode 100755 trace.py

diff --git a/Makefile.objs b/Makefile.objs
index acbaf22..307e989 100644
--- a/Makefile.objs
+++ b/Makefile.objs
@@ -8,7 +8,7 @@ qobject-obj-y += qerror.o
 # block-obj-y is code used by both qemu system emulation and qemu-img
 
 block-obj-y = cutils.o cache-utils.o qemu-malloc.o qemu-option.o module.o
-block-obj-y += nbd.o block.o aio.o aes.o osdep.o qemu-config.o
+block-obj-y += nbd.o block.o aio.o aes.o osdep.o qemu-config.o trace.o
 block-obj-$(CONFIG_POSIX) += posix-aio-compat.o
 block-obj-$(CONFIG_LINUX_AIO) += linux-aio.o
 
diff --git a/trace.c b/trace.c
new file mode 100644
index 0000000..2fec4d3
--- /dev/null
+++ b/trace.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/trace.h b/trace.h
new file mode 100644
index 0000000..144aa1e
--- /dev/null
+++ b/trace.h
@@ -0,0 +1,9 @@
+typedef enum {
+    TRACE_MAX
+} 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);
diff --git a/trace.py b/trace.py
new file mode 100755
index 0000000..f38ab6b
--- /dev/null
+++ b/trace.py
@@ -0,0 +1,30 @@
+#!/usr/bin/env python
+import sys
+import struct
+
+trace_fmt = 'LLLLLL'
+trace_len = struct.calcsize(trace_fmt)
+
+events = {
+}
+
+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)
+
+f = open(sys.argv[1], 'rb')
+while True:
+    rec = read_record(f)
+    if rec is None:
+        break
+
+    print format_record(rec)
-- 
1.7.1