[RFC 4/4] tcg/plugins: Add example pair of QPP plugins

[Andrew Fasano <fasano@mit.edu>]

The first plugin, qpp_srv exposes two functions and one callback that other
plugins can leverage. These functions are described in the corresponding
header file.

The second plugin, qpp_client, imports this header file, registers its
own function to run on a qpp_srv-provided callback, and directly calls
into the two exposed functions in qpp_srv.

Signed-off-by: Andrew Fasano <fasano@mit.edu>
---
 contrib/plugins/Makefile     |  2 ++
 contrib/plugins/qpp_client.c | 42 ++++++++++++++++++++++++++++++++++++
 contrib/plugins/qpp_client.h |  1 +
 contrib/plugins/qpp_srv.c    | 33 ++++++++++++++++++++++++++++
 contrib/plugins/qpp_srv.h    | 17 +++++++++++++++
 5 files changed, 95 insertions(+)
 create mode 100644 contrib/plugins/qpp_client.c
 create mode 100644 contrib/plugins/qpp_client.h
 create mode 100644 contrib/plugins/qpp_srv.c
 create mode 100644 contrib/plugins/qpp_srv.h

diff --git a/contrib/plugins/Makefile b/contrib/plugins/Makefile
index b7720fea0f..b7510de89c 100644
--- a/contrib/plugins/Makefile
+++ b/contrib/plugins/Makefile
@@ -21,6 +21,8 @@ NAMES += lockstep
 NAMES += hwprofile
 NAMES += cache
 NAMES += drcov
+NAMES += qpp_srv
+NAMES += qpp_client
 
 SONAMES := $(addsuffix .so,$(addprefix lib,$(NAMES)))
 
diff --git a/contrib/plugins/qpp_client.c b/contrib/plugins/qpp_client.c
new file mode 100644
index 0000000000..de3335e167
--- /dev/null
+++ b/contrib/plugins/qpp_client.c
@@ -0,0 +1,42 @@
+#include <stdio.h>
+#include <qemu-plugin.h>
+#include <plugin-qpp.h>
+#include <glib.h>
+#include "qpp_srv.h"
+
+QEMU_PLUGIN_EXPORT int qemu_plugin_version = QEMU_PLUGIN_VERSION;
+
+void my_on_exit(int x, bool b)
+{
+  g_autoptr(GString) report = g_string_new("Client: on_exit runs with args: ");
+  g_string_append_printf(report, "%d, %d\n", x, b);
+  qemu_plugin_outs(report->str);
+
+  g_string_printf(report, "Client: calls qpp_srv's do_add(1): %d\n",
+                          qpp_srv_do_add(1));
+  qemu_plugin_outs(report->str);
+
+  g_string_printf(report, "Client: calls qpp_srv's do_sub(1): %d\n",
+                           qpp_srv_do_sub(1));
+  qemu_plugin_outs(report->str);
+}
+
+
+QEMU_PLUGIN_EXPORT int qemu_plugin_install(qemu_plugin_id_t id,
+                   const qemu_info_t *info, int argc, char **argv) {
+
+    /*
+     * Register our "my_on_exit" function to run on the on_exit QPP-callback
+     * exported by qpp_srv
+     */
+    QPP_REG_CB("qpp_srv", on_exit, my_on_exit);
+
+    g_autoptr(GString) report = g_string_new(CURRENT_PLUGIN ": Call "
+                                             "qpp_srv's do_add(0) => ");
+    g_string_append_printf(report, "%d\n", qpp_srv_do_add(0));
+    qemu_plugin_outs(report->str);
+
+    g_string_printf(report, "Client: registered on_exit callback\n");
+    return 0;
+}
+
diff --git a/contrib/plugins/qpp_client.h b/contrib/plugins/qpp_client.h
new file mode 100644
index 0000000000..573923f580
--- /dev/null
+++ b/contrib/plugins/qpp_client.h
@@ -0,0 +1 @@
+void my_on_exit(int, bool);
diff --git a/contrib/plugins/qpp_srv.c b/contrib/plugins/qpp_srv.c
new file mode 100644
index 0000000000..61a6ab38ed
--- /dev/null
+++ b/contrib/plugins/qpp_srv.c
@@ -0,0 +1,33 @@
+#include <stdio.h>
+#include <qemu-plugin.h>
+#include <plugin-qpp.h>
+#include <gmodule.h>
+#include "qpp_srv.h"
+
+QEMU_PLUGIN_EXPORT int qemu_plugin_version = QEMU_PLUGIN_VERSION;
+
+QPP_CREATE_CB(on_exit);
+
+static void plugin_exit(qemu_plugin_id_t id, void *p)
+{
+  qemu_plugin_outs(CURRENT_PLUGIN "exit triggered, running all registered"
+                  " QPP callbacks\n");
+  QPP_RUN_CB(on_exit, 0, true);
+}
+
+QEMU_PLUGIN_EXPORT int do_add(int x)
+{
+  return x + 1;
+}
+
+QEMU_PLUGIN_EXPORT int do_sub(int x)
+{
+  return x - 1;
+}
+
+QEMU_PLUGIN_EXPORT int qemu_plugin_install(qemu_plugin_id_t id,
+                   const qemu_info_t *info, int argc, char **argv) {
+    qemu_plugin_outs("qpp_srv loaded\n");
+    qemu_plugin_register_atexit_cb(id, plugin_exit, NULL);
+    return 0;
+}
diff --git a/contrib/plugins/qpp_srv.h b/contrib/plugins/qpp_srv.h
new file mode 100644
index 0000000000..ceb26e3d2c
--- /dev/null
+++ b/contrib/plugins/qpp_srv.h
@@ -0,0 +1,17 @@
+#ifndef QPP_SRV_H
+#define QPP_SRV_H
+
+/*
+ * Prototype for the on_exit callback: callback functions should be
+ * of type `void f(int, bool)`
+ */
+QPP_CB_PROTOTYPE(void, on_exit, int, bool);
+
+/*
+ * Prototypes for the do_add and do_sub functions. Both return an int and
+ * take an int as an argument.
+ */
+QPP_FUN_PROTOTYPE(qpp_srv, int, do_add, int);
+QPP_FUN_PROTOTYPE(qpp_srv, int, do_sub, int);
+
+#endif /* QPP_SRV_H */
-- 
2.34.1