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

[Alex Bennée]

Andrew Fasano <fasano@mit.edu> writes:

> 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.

I'll just sketch out how I would change the API in this example plugin:

>
> 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;

QEMU_PLUGIN_EXPORT const char *qemu_plugin_name = "qpp_client";
QEMU_PLUGIN_EXPORT const char *qemu_plugin_uses = "qpp_server";

> +
> +void my_on_exit(int x, bool b)

void my_on_exit(gpointer evdata, gpointer udata)
{
  struct qpp_exit_event *info = (struct qpp_exit_event *) evdata;
  x = info->x;
  b = info->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);

   qemu_plugin_register_event_listener("qpp_server", "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;

QEMU_PLUGIN_EXPORT const char *qemu_plugin_name = "qpp_server";

> +
> +QPP_CREATE_CB(on_exit);

void *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);

     struct qpp_exit_event *info = g_new0(qpp_exit_event, 1);
     info->x = 0;
     info->b = true;
     qemu_plugin_trigger_event(on_exit, info);

> +}
> +
> +QEMU_PLUGIN_EXPORT int do_add(int x)

QEMU_PLUGIN_EXPORT int qpp_srv_do_add(int x)

> +{
> +  return x + 1;
> +}
> +
> +QEMU_PLUGIN_EXPORT int do_sub(int x)

QEMU_PLUGIN_EXPORT int qpp_srv_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);

can be dropped.

> +
> +/*
> + * 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);

int qpp_srv_do_add(int);
int qpp_srv_do_sub(int);

the linking is dealt with by loader.

> +
> +#endif /* QPP_SRV_H */


-- 
Alex Bennée