[Qemu-devel] [PATCH 08/14] trace: Add LTTng Userspace Tracer backend

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

This patch adds LTTng Userspace Tracer (UST) backend support.  The UST
system requires no kernel support but libust and liburcu must be
installed.

$ ./configure --trace-backend ust
$ make

Start the UST daemon:
$ ustd &

List available tracepoints and enable some:
$ ustctl --list-markers $(pgrep qemu)
[...]
{PID: 5458, channel/marker: ust/paio_submit, state: 0, fmt: "acb %p
opaque %p sector_num %lu nb_sectors %lu type %lu" 0x4b32ba}
$ ustctl --enable-marker "ust/paio_submit" $(pgrep qemu)

Run the trace:
$ ustctl --create-trace $(pgrep qemu)
$ ustctl --start-trace $(pgrep qemu)
[...]
$ ustctl --stop-trace $(pgrep qemu)
$ ustctl --destroy-trace $(pgrep qemu)

Trace results can be viewed using lttv-gui.

More information about UST:
http://lttng.org/ust

Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>

trace: Check for LTTng Userspace Tracer headers

When using the 'ust' backend, check if the relevant headers are
available at host.

Signed-off-by: Prerna Saxena <prerna@linux.vnet.ibm.com>
Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
---
 configure |   22 +++++++++++++++-
 tracetool |   85 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 104 insertions(+), 3 deletions(-)

diff --git a/configure b/configure
index ad21c58..d3b275d 100755
--- a/configure
+++ b/configure
@@ -904,7 +904,7 @@ 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 simple"
+echo "  --trace-backend=B        Trace backend nop simple ust"
 echo "  --trace-file=NAME        Full PATH,NAME of file to store traces"
 echo "                           Default:/tmp/trace-<pid>"
 echo "                           Default:trace-<pid> on Windows"
@@ -2082,6 +2082,23 @@ if test "$?" -ne 0 ; then
   exit 1
 fi
 
+##########################################
+# For 'ust' backend, test if ust headers are present
+if test "$trace_backend" = "ust"; then
+  cat > $TMPC << EOF
+#include <ust/tracepoint.h>
+#include <ust/marker.h>
+int main(void) { return 0; }
+EOF
+  if compile_prog "" "" ; then
+    LIBS="-lust $LIBS"
+  else
+    echo "ERROR: Trace backend 'ust' does not have relevant headers available"
+    echo "       on the host. Pls choose a different backend."
+    exit 1
+  fi
+fi
+##########################################
 # End of CC checks
 # After here, no more $cc or $ld runs
 
@@ -2484,6 +2501,9 @@ if test "$trace_backend" = "simple"; then
   trace_file="\"$trace_file-%u\""
 fi
 echo "CONFIG_TRACE_FILE=$trace_file" >> $config_host_mak
+if test "$trace_backend" = "ust"; then
+  LIBS="-lust $LIBS"
+fi
 
 echo "TOOLS=$tools" >> $config_host_mak
 echo "ROMS=$roms" >> $config_host_mak
diff --git a/tracetool b/tracetool
index d840e6f..d10c9ee 100755
--- a/tracetool
+++ b/tracetool
@@ -13,12 +13,13 @@ set -f
 usage()
 {
     cat >&2 <<EOF
-usage: $0 [--nop | --simple] [-h | -c]
+usage: $0 [--nop | --simple | --ust] [-h | -c]
 Generate tracing code for a file on stdin.
 
 Backends:
   --nop     Tracing disabled
   --simple  Simple built-in backend
+  --ust     LTTng User Space Tracing backend
 
 Output formats:
   -h    Generate .h file
@@ -225,6 +226,86 @@ linetoc_end_simple()
 EOF
 }
 
+# Clean up after UST headers which pollute the namespace
+ust_clean_namespace() {
+    cat <<EOF
+#undef mutex_lock
+#undef mutex_unlock
+#undef inline
+#undef wmb
+EOF
+}
+
+linetoh_begin_ust()
+{
+    echo "#include <ust/tracepoint.h>"
+    ust_clean_namespace
+}
+
+linetoh_ust()
+{
+    local name args argnames
+    name=$(get_name "$1")
+    args=$(get_args "$1")
+    argnames=$(get_argnames "$1")
+
+    cat <<EOF
+DECLARE_TRACE(ust_$name, TPPROTO($args), TPARGS($argnames));
+#define trace_$name trace_ust_$name
+EOF
+}
+
+linetoh_end_ust()
+{
+    return
+}
+
+linetoc_begin_ust()
+{
+    cat <<EOF
+#include <ust/marker.h>
+$(ust_clean_namespace)
+#include "trace.h"
+EOF
+}
+
+linetoc_ust()
+{
+    local name args argnames fmt
+    name=$(get_name "$1")
+    args=$(get_args "$1")
+    argnames=$(get_argnames "$1")
+    fmt=$(get_fmt "$1")
+
+    cat <<EOF
+DEFINE_TRACE(ust_$name);
+
+static void ust_${name}_probe($args)
+{
+    trace_mark(ust, $name, "$fmt", $argnames);
+}
+EOF
+
+    # Collect names for later
+    names="$names $name"
+}
+
+linetoc_end_ust()
+{
+    cat <<EOF
+static void __attribute__((constructor)) trace_init(void)
+{
+EOF
+
+    for name in $names; do
+        cat <<EOF
+    register_trace_ust_$name(ust_${name}_probe);
+EOF
+    done
+
+    echo "}"
+}
+
 # Process stdin by calling begin, line, and end functions for the backend
 convert()
 {
@@ -282,7 +363,7 @@ tracetoc()
 
 # Choose backend
 case "$1" in
-"--nop" | "--simple") backend="${1#--}" ;;
+"--nop" | "--simple" | "--ust") backend="${1#--}" ;;
 *) usage ;;
 esac
 shift
-- 
1.7.1