Add a DTrace tracing backend targetted for SystemTAP compatability

This introduces a new tracing backend that targets the SystemTAP
implementation of DTrace userspace tracing. The core functionality
should be applicable and standard across any DTrace implementation
on Solaris, OS-X, *BSD, but the Makefile rules will likely need
some small additional changes to cope with OS specific build
requirements.

This backend builds a little differently from the other tracing
backends. Specifically there is no 'trace.c' file, because the
'dtrace' command line tool generates a '.o' file directly from
the dtrace probe definition file. The probe definition is usually
named with a '.d' extension but QEMU uses '.d' files for its
external makefile dependancy tracking, so this uses '.dtrace' as
the extension for the probe definition file.

The 'tracetool' program gains the ability to generate a trace.h
file for DTrace, and also to generate the trace.d file containing
the dtrace probe definition.

Example usage of a dtrace probe in systemtap looks like:

  probe process("qemu").mark("qemu_malloc") {
    printf("Malloc %d %p\n", $arg1, $arg2);
  }

* .gitignore: Ignore trace-dtrace.*
* Makefile: Extra rules for generating DTrace files
* Makefile.obj: Don't build trace.o for DTrace, use
  trace-dtrace.o generated by 'dtrace' instead
* tracetool: Support for generating DTrace data files

Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

.gitignore

@@ -4,6 +4,8 @@ config-host.*
 config-target.*
 trace.h
 trace.c
+trace-dtrace.h
+trace-dtrace.dtrace
 *-timestamp
 *-softmmu
 *-darwin-user

Makefile

@@ -1,6 +1,9 @@
 # Makefile for QEMU.
 
 GENERATED_HEADERS = config-host.h trace.h qemu-options.def
+ifeq ($(TRACE_BACKEND),dtrace)
+GENERATED_HEADERS += trace-dtrace.h
+endif
 
 ifneq ($(wildcard config-host.mak),)
 # Put the all: rule here so that config-host.mak can contain dependencies.
@@ -108,7 +111,11 @@ ui/vnc.o: QEMU_CFLAGS += $(VNC_TLS_CFLAGS)
 
 bt-host.o: QEMU_CFLAGS += $(BLUEZ_CFLAGS)
 
+ifeq ($(TRACE_BACKEND),dtrace)
+trace.h: trace.h-timestamp trace-dtrace.h
+else
 trace.h: trace.h-timestamp
+endif
 trace.h-timestamp: $(SRC_PATH)/trace-events config-host.mak
 	$(call quiet-command,sh $(SRC_PATH)/tracetool --$(TRACE_BACKEND) -h < $< > $@,"  GEN   trace.h")
 	@cmp -s $@ trace.h || cp $@ trace.h
@@ -120,6 +127,20 @@ trace.c-timestamp: $(SRC_PATH)/trace-events config-host.mak
 
 trace.o: trace.c $(GENERATED_HEADERS)
 
+trace-dtrace.h: trace-dtrace.dtrace
+	$(call quiet-command,dtrace -o $@ -h -s $<, "  GEN   trace-dtrace.h")
+
+# Normal practice is to name DTrace probe file with a '.d' extension
+# but that gets picked up by QEMU's Makefile as an external dependancy
+# rule file. So we use '.dtrace' instead
+trace-dtrace.dtrace: trace-dtrace.dtrace-timestamp
+trace-dtrace.dtrace-timestamp: $(SRC_PATH)/trace-events config-host.mak
+	$(call quiet-command,sh $(SRC_PATH)/tracetool --$(TRACE_BACKEND) -d < $< > $@,"  GEN   trace-dtrace.dtrace")
+	@cmp -s $@ trace-dtrace.dtrace || cp $@ trace-dtrace.dtrace
+
+trace-dtrace.o: trace-dtrace.dtrace $(GENERATED_HEADERS)
+	$(call quiet-command,dtrace -o $@ -G -s $<, "  GEN trace-dtrace.o")
+
 simpletrace.o: simpletrace.c $(GENERATED_HEADERS)
 
 version.o: $(SRC_PATH)/version.rc config-host.mak
@@ -157,6 +178,8 @@ clean:
 	rm -f slirp/*.o slirp/*.d audio/*.o audio/*.d block/*.o block/*.d net/*.o net/*.d fsdev/*.o fsdev/*.d ui/*.o ui/*.d
 	rm -f qemu-img-cmds.h
 	rm -f trace.c trace.h trace.c-timestamp trace.h-timestamp
+	rm -f trace-dtrace.dtrace trace-dtrace.dtrace-timestamp
+	rm -f trace-dtrace.h trace-dtrace.h-timestamp
 	$(MAKE) -C tests clean
 	for d in $(ALL_SUBDIRS) libhw32 libhw64 libuser libdis libdis-user; do \
 	if test -d $$d; then $(MAKE) -C $$d $@ || exit 1; fi; \

Makefile.objs

@@ -286,11 +286,15 @@ libdis-$(CONFIG_SPARC_DIS) += sparc-dis.o
 ######################################################################
 # trace
 
+ifeq ($(TRACE_BACKEND),dtrace)
+trace-obj-y = trace-dtrace.o
+else
 trace-obj-y = trace.o
 ifeq ($(TRACE_BACKEND),simple)
 trace-obj-y += simpletrace.o
 user-obj-y += qemu-timer-common.o
 endif
+endif
 
 vl.o: QEMU_CFLAGS+=$(GPROF_CFLAGS)
 

configure

@@ -929,7 +929,7 @@ 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 ust"
+echo "  --trace-backend=B        Trace backend nop simple ust dtrace"
 echo "  --trace-file=NAME        Full PATH,NAME of file to store traces"
 echo "                           Default:trace-<pid>"
 echo "  --disable-spice          disable spice"
@@ -2193,6 +2193,18 @@ EOF
     exit 1
   fi
 fi
+
+##########################################
+# For 'dtrace' backend, test if 'dtrace' command is present
+if test "$trace_backend" = "dtrace"; then
+  if ! has 'dtrace' ; then
+    echo
+    echo "Error: dtrace command is not found in PATH $PATH"
+    echo
+    exit 1
+  fi
+fi
+
 ##########################################
 # End of CC checks
 # After here, no more $cc or $ld runs

tracetool

@@ -20,10 +20,12 @@ Backends:
   --nop     Tracing disabled
   --simple  Simple built-in backend
   --ust     LTTng User Space Tracing backend
+  --dtrace  DTrace/SystemTAP backend
 
 Output formats:
   -h    Generate .h file
   -c    Generate .c file
+  -d    Generate .d file (DTrace only)
 EOF
     exit 1
 }
@@ -46,8 +48,9 @@ get_args()
 # Get the argument name list of a trace event
 get_argnames()
 {
-    local nfields field name
+    local nfields field name sep
     nfields=0
+    sep="$2"
     for field in $(get_args "$1"); do
         nfields=$((nfields + 1))
 
@@ -58,7 +61,7 @@ get_argnames()
         name=${field%,}
         test "$field" = "$name" && continue
 
-        printf "%s" "$name, "
+        printf "%s%s " $name $sep
     done
 
     # Last argument name
@@ -73,7 +76,7 @@ get_argc()
 {
     local name argc
     argc=0
-    for name in $(get_argnames "$1"); do
+    for name in $(get_argnames "$1", ","); do
         argc=$((argc + 1))
     done
     echo $argc
@@ -154,7 +157,7 @@ EOF
 cast_args_to_uint64_t()
 {
     local arg
-    for arg in $(get_argnames "$1"); do
+    for arg in $(get_argnames "$1", ","); do
         printf "%s" "(uint64_t)(uintptr_t)$arg"
     done
 }
@@ -247,7 +250,7 @@ linetoh_ust()
     local name args argnames
     name=$(get_name "$1")
     args=$(get_args "$1")
-    argnames=$(get_argnames "$1")
+    argnames=$(get_argnames "$1", ",")
 
     cat <<EOF
 DECLARE_TRACE(ust_$name, TP_PROTO($args), TP_ARGS($argnames));
@@ -274,7 +277,7 @@ linetoc_ust()
     local name args argnames fmt
     name=$(get_name "$1")
     args=$(get_args "$1")
-    argnames=$(get_argnames "$1")
+    argnames=$(get_argnames "$1", ",")
     fmt=$(get_fmt "$1")
 
     cat <<EOF
@@ -306,6 +309,93 @@ EOF
     echo "}"
 }
 
+linetoh_begin_dtrace()
+{
+    cat <<EOF
+#include "trace-dtrace.h"
+EOF
+}
+
+linetoh_dtrace()
+{
+    local name args argnames state nameupper
+    name=$(get_name "$1")
+    args=$(get_args "$1")
+    argnames=$(get_argnames "$1", ",")
+    state=$(get_state "$1")
+    if [ "$state" = "0" ] ; then
+        name=${name##disable }
+    fi
+
+    nameupper=`echo $name | tr '[:lower:]' '[:upper:]'`
+
+    # Define an empty function for the trace event
+    cat <<EOF
+static inline void trace_$name($args) {
+    if (QEMU_${nameupper}_ENABLED()) {
+        QEMU_${nameupper}($argnames);
+    }
+}
+EOF
+}
+
+linetoh_end_dtrace()
+{
+    return
+}
+
+linetoc_begin_dtrace()
+{
+    return
+}
+
+linetoc_dtrace()
+{
+    # No need for function definitions in dtrace backend
+    return
+}
+
+linetoc_end_dtrace()
+{
+    return
+}
+
+linetod_begin_dtrace()
+{
+    cat <<EOF
+provider qemu {
+EOF
+}
+
+linetod_dtrace()
+{
+    local name args state
+    name=$(get_name "$1")
+    args=$(get_args "$1")
+    state=$(get_state "$1")
+    if [ "$state" = "0" ] ; then
+        name=${name##disable }
+    fi
+
+    # DTrace provider syntax expects foo() for empty
+    # params, not foo(void)
+    if [ "$args" = "void" ]; then
+       args=""
+    fi
+
+    # Define prototype for probe arguments
+    cat <<EOF
+        probe $name($args);
+EOF
+}
+
+linetod_end_dtrace()
+{
+    cat <<EOF
+};
+EOF
+}
+
 # Process stdin by calling begin, line, and end functions for the backend
 convert()
 {
@@ -324,9 +414,10 @@ convert()
         disable=${str%%disable *}
         echo
         if test -z "$disable"; then
-            # Pass the disabled state as an arg to lineto$1_simple().
-            # For all other cases, call lineto$1_nop()
-            if [ $backend = "simple" ]; then
+            # Pass the disabled state as an arg for the simple
+            # or DTrace backends which handle it dynamically.
+            # For all other backends, call lineto$1_nop()
+            if [ $backend = "simple" -o "$backend" = "dtrace" ]; then
                 "$process_line" "$str"
             else
                 "lineto$1_nop" "${str##disable }"
@@ -360,16 +451,27 @@ tracetoc()
     convert c
 }
 
+tracetod()
+{
+    if [ $backend != "dtrace" ]; then
+       echo "DTrace probe generator not applicable to $backend backend"
+       exit 1
+    fi
+    echo "/* This file is autogenerated by tracetool, do not edit. */"
+    convert d
+}
+
 # Choose backend
 case "$1" in
-"--nop" | "--simple" | "--ust") backend="${1#--}" ;;
+"--nop" | "--simple" | "--ust" | "--dtrace") backend="${1#--}" ;;
 *) usage ;;
 esac
 shift
 
 case "$1" in
 "-h") tracetoh ;;
 "-c") tracetoc ;;
+"-d") tracetod ;;
 "--check-backend") exit 0 ;; # used by ./configure to test for backend
 *) usage ;;
 esac