plugins: allow plugin arguments to be passed directly

Passing arguments to plugins had to be done through "arg=<argname>".
This is redundant and introduces confusion especially when the argument
has a name and value (e.g. `-plugin plugin_name,arg="argname=argvalue"`).

This allows passing plugin arguments directly e.g:

    `-plugin plugin_name,argname=argvalue`

For now, passing arguments through "arg=" is still supports but outputs
a deprecation warning.

Also, this commit makes boolean arguments passed to plugins in the
`argname=on|off` form instead of the deprecated short-boolean form.

Signed-off-by: Mahmoud Mandour <ma.mandourr@gmail.com>
Tested-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20210730135817.17816-2-ma.mandourr@gmail.com>

linux-user/main.c

@@ -463,7 +463,7 @@ static const struct qemu_argument arg_table[] = {
      "",           "[[enable=]<pattern>][,events=<file>][,file=<file>]"},
 #ifdef CONFIG_PLUGIN
     {"plugin",     "QEMU_PLUGIN",      true,  handle_arg_plugin,
-     "",           "[file=]<file>[,arg=<string>]"},
+     "",           "[file=]<file>[,<argname>=<argvalue>]"},
 #endif
     {"version",    "QEMU_VERSION",     false, handle_arg_version,
      "",           "display version information and exit"},

plugins/loader.c

@@ -94,6 +94,8 @@ static int plugin_add(void *opaque, const char *name, const char *value,
 {
     struct qemu_plugin_parse_arg *arg = opaque;
     struct qemu_plugin_desc *p;
+    bool is_on;
+    char *fullarg;
 
     if (strcmp(name, "file") == 0) {
         if (strcmp(value, "") == 0) {
@@ -107,18 +109,32 @@ static int plugin_add(void *opaque, const char *name, const char *value,
             QTAILQ_INSERT_TAIL(arg->head, p, entry);
         }
         arg->curr = p;
-    } else if (strcmp(name, "arg") == 0) {
+    } else {
         if (arg->curr == NULL) {
             error_setg(errp, "missing earlier '-plugin file=' option");
             return 1;
         }
+
+        if (g_strcmp0(name, "arg") == 0 &&
+                !qapi_bool_parse(name, value, &is_on, NULL)) {
+            if (strchr(value, '=') == NULL) {
+                /* Will treat arg="argname" as "argname=on" */
+                fullarg = g_strdup_printf("%s=%s", value, "on");
+            } else {
+                fullarg = g_strdup_printf("%s", value);
+            }
+            warn_report("using 'arg=%s' is deprecated", value);
+            error_printf("Please use '%s' directly\n", fullarg);
+        } else {
+            fullarg = g_strdup_printf("%s=%s", name, value);
+        }
+
         p = arg->curr;
         p->argc++;
         p->argv = g_realloc_n(p->argv, p->argc, sizeof(char *));
-        p->argv[p->argc - 1] = g_strdup(value);
-    } else {
-        error_setg(errp, "-plugin: unexpected parameter '%s'; ignored", name);
+        p->argv[p->argc - 1] = fullarg;
     }
+
     return 0;
 }
 

qemu-options.hx

@@ -4532,19 +4532,18 @@ SRST
 
 ERST
 DEF("plugin", HAS_ARG, QEMU_OPTION_plugin,
-    "-plugin [file=]<file>[,arg=<string>]\n"
+    "-plugin [file=]<file>[,<argname>=<argvalue>]\n"
     "                load a plugin\n",
     QEMU_ARCH_ALL)
 SRST
-``-plugin file=file[,arg=string]``
+``-plugin file=file[,argname=argvalue]``
     Load a plugin.
 
     ``file=file``
         Load the given plugin from a shared library file.
 
-    ``arg=string``
-        Argument string passed to the plugin. (Can be given multiple
-        times.)
+    ``argname=argvalue``
+        Argument passed to the plugin. (Can be given multiple times.)
 ERST
 
 HXCOMM Internal use