Add a systemtap script for watching QEMU monitor interactions

This change adds some systemtap/dtrace probes to the QEMU monitor
client code. In particular it allows watching of all operations
for a VM

* examples/systemtap/qemu-monitor.stp: Watch all monitor commands
* src/Makefile.am: Passing libdir/bindir/sbindir to dtrace2systemtap.pl
* src/dtrace2systemtap.pl: Accept libdir/bindir/sbindir as args
  and look for '# binary:' comment to mark probes against libvirtd
  vs libvirt.so
* src/qemu/qemu_monitor.c, src/qemu/qemu_monitor_json.c,
  src/qemu/qemu_monitor_text.c: Add probes for key functions

examples/systemtap/qemu-monitor.stp

+#!/usr/bin/stap
+#
+# Copyright (C) 2011 Red Hat, Inc.
+#
+# This library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2.1 of the License, or (at your option) any later version.
+#
+# This library is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this library; if not, write to the Free Software
+# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307  USA
+#
+# Author: Daniel P. Berrange <berrange@redhat.com>
+#
+# This script will monitor all messages sent/received between libvirt
+# and the QEMU monitor
+#
+# stap qemu-monitor.stp
+#  0.000 begin
+#  3.848 ! 0x7f2dc00017b0 {"timestamp": {"seconds": 1319466931, "microseconds": 187755}, "event": "SHUTDOWN"}
+#  5.773 > 0x7f2dc0007960 {"execute":"qmp_capabilities","id":"libvirt-1"}
+#  5.774 < 0x7f2dc0007960 {"return": {}, "id": "libvirt-1"}
+#  5.774 > 0x7f2dc0007960 {"execute":"query-commands","id":"libvirt-2"}
+#  5.777 < 0x7f2dc0007960 {"return": [{"name": "quit"}, {"name": ....snip....
+#  5.777 > 0x7f2dc0007960 {"execute":"query-chardev","id":"libvirt-3"}
+#  5.778 < 0x7f2dc0007960 {"return": [{"filename": ....snip....
+#  5.779 > 0x7f2dc0007960 {"execute":"query-cpus","id":"libvirt-4"}
+#  5.780 < 0x7f2dc0007960 {"return": [{"current": true, "CPU": 0, "pc": 1048560, "halted": false, "thread_id": 13299}], "id": "libvirt-4"}
+#  5.780 > 0x7f2dc0007960 {"execute":"set_password","arguments":{"protocol":"vnc","password":"123456","connected":"keep"},"id":"libvirt-5"}
+#  5.782 < 0x7f2dc0007960 {"return": {}, "id": "libvirt-5"}
+#  5.782 > 0x7f2dc0007960 {"execute":"expire_password","arguments":{"protocol":"vnc","time":"never"},"id":"libvirt-6"}
+#  5.783 < 0x7f2dc0007960 {"return": {}, "id": "libvirt-6"}
+#  5.783 > 0x7f2dc0007960 {"execute":"balloon","arguments":{"value":224395264},"id":"libvirt-7"}
+#  5.785 < 0x7f2dc0007960 {"return": {}, "id": "libvirt-7"}
+#  5.785 > 0x7f2dc0007960 {"execute":"cont","id":"libvirt-8"}
+#  5.789 ! 0x7f2dc0007960 {"timestamp": {"seconds": 1319466933, "microseconds": 129980}, "event": "RESUME"}
+#  5.789 < 0x7f2dc0007960 {"return": {}, "id": "libvirt-8"}
+#  7.537 ! 0x7f2dc0007960 {"timestamp": {"seconds": 1319466934, "microseconds": 881214}, "event": "SHUTDOWN"}
+#
+
+
+global start
+
+# Print a string, with a timestamp relative to the start of the script
+function print_ts(msg)
+{
+  now = gettimeofday_ns() / (1000*1000)
+  delta = (now - start)
+
+  printf("%3d.%03d %s\n", (delta / 1000), (delta % 1000), msg);
+}
+
+
+# Just so we know the script is now running
+probe begin {
+  start = gettimeofday_ns() / (1000*1000)
+  print_ts("begin")
+}
+
+probe libvirt.qemu.monitor_send_msg {
+  if (fd != -1) {
+    print_ts(sprintf("> %p %s (fd=%d)", mon, substr(msg, 0, strlen(msg)-2), fd));
+  } else {
+    print_ts(sprintf("> %p %s", mon, substr(msg, 0, strlen(msg)-2)));
+  }
+}
+
+probe libvirt.qemu.monitor_recv_reply {
+  print_ts(sprintf("< %p %s", mon, reply));
+}
+
+probe libvirt.qemu.monitor_recv_event {
+  print_ts(sprintf("! %p %s", mon, event));
+}

src/Makefile.am

@@ -1288,7 +1288,7 @@ libvirt_functions.stp: $(RPC_PROBE_FILES) $(srcdir)/rpc/gensystemtap.pl
 	$(AM_V_GEN)perl -w $(srcdir)/rpc/gensystemtap.pl $(RPC_PROBE_FILES) > $@
 
 libvirt_probes.stp: probes.d $(srcdir)/dtrace2systemtap.pl
-	$(AM_V_GEN)perl -w $(srcdir)/dtrace2systemtap.pl $< > $@
+	$(AM_V_GEN)perl -w $(srcdir)/dtrace2systemtap.pl $(bindir) $(sbindir) $(libdir) $< > $@
 
 CLEANFILES += probes.h probes.o libvirt_functions.stp libvirt_probes.stp
 endif

src/dtrace2systemtap.pl

@@ -31,6 +31,10 @@ my $file;
 my @files;
 my %files;
 
+my $bindir = shift @ARGV;
+my $sbindir = shift @ARGV;
+my $libdir = shift @ARGV;
+
 my $probe;
 my $args;
 
@@ -41,12 +45,18 @@ while (<>) {
     next if /^\s*provider\s+\w+\s*{\s*$/;
     next if /^\s*};\s*$/;
 
-    if (m,^\s*\#\s*file:\s*(\S+)\s*$,) {
-	$file = $1;
-	push @files, $file;
-	$files{$file} = { prefix => undef, probes => [] };
-    } elsif (m,^\s*\#\s*prefix:\s*(\S+)\s*$,) {
-	$files{$file}->{prefix} = $1;
+    if (m,^\s*\#,) {
+	if (m,^\s*\#\s*file:\s*(\S+)\s*$,) {
+	    $file = $1;
+	    push @files, $file;
+	    $files{$file} = { prefix => undef, probes => [] };
+	} elsif (m,^\s*\#\s*prefix:\s*(\S+)\s*$,) {
+	    $files{$file}->{prefix} = $1;
+	} elsif (m,^\s*\#\s*binary:\s*(\S+)\s*$,) {
+	    $files{$file}->{binary} = $1;
+	} else {
+	    # ignore unknown comments
+	}
     } else {
 	if (m,\s*probe\s+([a-zA-Z0-9_]+)\((.*?)(\);)?$,) {
 	    $probe = $1;
@@ -84,7 +94,12 @@ foreach my $file (@files) {
 	my $pname = $name;
 	$pname =~ s/${prefix}_/libvirt.$prefix./;
 
-	print "probe $pname = process(\"libvirt.so\").mark(\"$name\") {\n";
+	my $binary = "$libdir/libvirt.so";
+	if (exists $files{$file}->{binary}) {
+	    $binary = $sbindir . "/" . $files{$file}->{binary};
+	}
+
+	print "probe $pname = process(\"$binary\").mark(\"$name\") {\n";
 
 	my @args = split /,/, $args;
 	for (my $i = 0 ; $i <= $#args ; $i++) {

src/probes.d

@@ -69,4 +69,24 @@ provider libvirt {
 	probe rpc_tls_session_handshake_pass(void *sess);
 	probe rpc_tls_session_handshake_fail(void *sess);
 
+
+        # file: src/qemu/qemu_monitor.c
+        # prefix: qemu
+        # binary: libvirtd
+        # Monitor lifecycle
+        probe qemu_monitor_new(void *mon, int refs, int fd);
+        probe qemu_monitor_ref(void *mon, int refs);
+        probe qemu_monitor_unref(void *mon, int refs);
+        probe qemu_monitor_close(void *monm, int refs);
+
+        # High level monitor message processing
+        probe qemu_monitor_send_msg(void *mon, const char *msg, int fd);
+        probe qemu_monitor_recv_reply(void *mon, const char *reply);
+        probe qemu_monitor_recv_event(void *mon, const char *event);
+
+        # Low level monitor I/O processing
+        probe qemu_monitor_io_process(void *mon, const char *buf, unsigned int len);
+        probe qemu_monitor_io_read(void *mon, const char *buf, unsigned int len, int ret, int errno);
+        probe qemu_monitor_io_write(void *mon, const char *buf, unsigned int len, int ret, int errno);
+        probe qemu_monitor_io_send_fd(void *mon, int fd, int ret, int errno);
 };

src/qemu/qemu_monitor.c

@@ -183,6 +183,8 @@ static void qemuMonitorFree(qemuMonitorPtr mon)
 int qemuMonitorRef(qemuMonitorPtr mon)
 {
     mon->refs++;
+    PROBE(QEMU_MONITOR_REF,
+          "mon=%p refs=%d", mon, mon->refs);
     return mon->refs;
 }
 
@@ -190,6 +192,8 @@ int qemuMonitorUnref(qemuMonitorPtr mon)
 {
     mon->refs--;
 
+    PROBE(QEMU_MONITOR_UNREF,
+          "mon=%p refs=%d", mon, mon->refs);
     if (mon->refs == 0) {
         qemuMonitorUnlock(mon);
         qemuMonitorFree(mon);
@@ -305,6 +309,9 @@ qemuMonitorIOProcess(qemuMonitorPtr mon)
 # endif
 #endif
 
+    PROBE(QEMU_MONITOR_IO_PROCESS,
+          "mon=%p buf=%s len=%zu", mon, mon->buffer, mon->bufferOffset);
+
     if (mon->json)
         len = qemuMonitorJSONIOProcess(mon,
                                        mon->buffer, mon->bufferOffset,
@@ -403,6 +410,18 @@ qemuMonitorIOWrite(qemuMonitorPtr mon)
                                         mon->msg->txLength - mon->msg->txOffset,
                                         mon->msg->txFD);
 
+    PROBE(QEMU_MONITOR_IO_WRITE,
+          "mon=%p buf=%s len=%d ret=%d errno=%d",
+          mon,
+          mon->msg->txBuffer + mon->msg->txOffset,
+          mon->msg->txLength - mon->msg->txOffset,
+          done, errno);
+
+    if (mon->msg->txFD != -1)
+        PROBE(QEMU_MONITOR_IO_SEND_FD,
+              "mon=%p fd=%d ret=%d errno=%d",
+              mon, mon->msg->txFD, done, errno);
+
     if (done < 0) {
         if (errno == EAGAIN)
             return 0;
@@ -696,7 +715,9 @@ qemuMonitorOpen(virDomainObjPtr vm,
     }
     qemuMonitorRef(mon);
 
-    VIR_DEBUG("New mon %p fd =%d watch=%d", mon, mon->fd, mon->watch);
+    PROBE(QEMU_MONITOR_NEW,
+          "mon=%p refs=%d fd=%d",
+          mon, mon->refs, mon->fd);
     qemuMonitorUnlock(mon);
 
     return mon;
@@ -719,9 +740,9 @@ void qemuMonitorClose(qemuMonitorPtr mon)
     if (!mon)
         return;
 
-    VIR_DEBUG("mon=%p", mon);
-
     qemuMonitorLock(mon);
+    PROBE(QEMU_MONITOR_CLOSE,
+          "mon=%p refs=%d", mon, mon->refs);
 
     if (mon->fd >= 0) {
         if (mon->watch)
@@ -762,6 +783,10 @@ int qemuMonitorSend(qemuMonitorPtr mon,
     mon->msg = msg;
     qemuMonitorUpdateWatch(mon);
 
+    PROBE(QEMU_MONITOR_SEND_MSG,
+          "mon=%p msg=%s fd=%d",
+          mon, mon->msg->txBuffer, mon->msg->txFD);
+
     while (!mon->msg->finished) {
         if (virCondWait(&mon->notify, &mon->lock) < 0) {
             qemuReportError(VIR_ERR_INTERNAL_ERROR, "%s",

src/qemu/qemu_monitor_json.c

@@ -126,9 +126,13 @@ qemuMonitorJSONIOProcessLine(qemuMonitorPtr mon,
     if (virJSONValueObjectHasKey(obj, "QMP") == 1) {
         ret = 0;
     } else if (virJSONValueObjectHasKey(obj, "event") == 1) {
+        PROBE(QEMU_MONITOR_RECV_EVENT,
+              "mon=%p event=%s", mon, line);
         ret = qemuMonitorJSONIOProcessEvent(mon, obj);
     } else if (virJSONValueObjectHasKey(obj, "error") == 1 ||
                virJSONValueObjectHasKey(obj, "return") == 1) {
+        PROBE(QEMU_MONITOR_RECV_REPLY,
+              "mon=%p reply=%s", mon, line);
         if (msg) {
             msg->rxObject = obj;
             msg->finished = 1;

src/qemu/qemu_monitor_text.c

@@ -198,6 +198,9 @@ int qemuMonitorTextIOProcess(qemuMonitorPtr mon ATTRIBUTE_UNUSED,
                 VIR_DEBUG("Finished 0 byte reply");
 #endif
             }
+            PROBE(QEMU_MONITOR_RECV_REPLY,
+                  "mon=%p reply=%s",
+                  mon, msg->rxBuffer);
             msg->finished = 1;
             used += end - (data + used);
             used += strlen(BASIC_PROMPT);