sysprofd: implement org.gnome.Sysprof2 compatability API

This allows the new sysprofd to service requests for older clients
expecting to talk to or.gnome.Sysprof2.

src/org.gnome.Sysprof2.xml

@@ -0,0 +1,39 @@
+<!DOCTYPE node PUBLIC "-//freedesktop//DTD D-BUS Object Introspection 1.0//EN"
+"http://www.freedesktop.org/standards/dbus/1.0/introspect.dtd">
+<node>
+ <interface name="org.gnome.Sysprof2">
+  <!--
+    PerfEventOpen:
+    @options: key-value pair of attributes for the perf_event_open() syscall.
+    @pid: the process id to monitor, or -1 for system-wide.
+    @cpu: affinity to cpu.
+    @flags: flags for perf_event_open() syscall.
+    @perf_stream_fd: (out): A fd to communicate with perf.
+
+    Performs the perf_event_open() syscall with elevated privileges and passes
+    the resulting fd back to the calling process.
+  -->
+  <method name="PerfEventOpen">
+   <arg name="options" type="a{sv}" direction="in"/>
+   <arg name="pid" type="i" direction="in"/>
+   <arg name="cpu" type="i" direction="in"/>
+   <arg name="flags" type="t" direction="in"/>
+   <arg name="perf_stream_fd" type="h" direction="out"/>
+  </method>
+
+  <!--
+    GetKernelSymbols:
+
+    Loads the name, type, and address of Linux kernel symbols. This is useful
+    if your system does not provide access to /proc/kallsyms to non-root users.
+
+    Returns: an array of (tys) tuples. t is the address, y is the type, and s
+      is the name.
+
+    Since: 3.28
+  -->
+  <method name="GetKernelSymbols">
+   <arg name="symbols" type="a(tys)" direction="out"/>
+  </method>
+ </interface>
+</node>