qapi/qmp-dispatch.c

   1 /*
   2  * Core Definitions for QAPI/QMP Dispatch
   3  *
   4  * Copyright IBM, Corp. 2011
   5  *
   6  * Authors:
   7  *  Anthony Liguori   <aliguori@us.ibm.com>
   8  *
   9  * This work is licensed under the terms of the GNU LGPL, version 2.1 or later.
  10  * See the COPYING.LIB file in the top-level directory.
  11  *
  12  */
  13
  14 #include "qemu/osdep.h"
  15
  16 #include "block/aio.h"
  17 #include "qapi/compat-policy.h"
  18 #include "qapi/error.h"
  19 #include "qapi/qmp/dispatch.h"
  20 #include "qapi/qmp/qdict.h"
  21 #include "qapi/qmp/qjson.h"
  22 #include "qapi/qobject-input-visitor.h"
  23 #include "qapi/qobject-output-visitor.h"
  24 #include "qapi/qmp/qbool.h"
  25 #include "qemu/coroutine.h"
  26 #include "qemu/main-loop.h"
  27
  28 Visitor *qobject_input_visitor_new_qmp(QObject *obj)
  29 {
  30     Visitor *v = qobject_input_visitor_new(obj);
  31
  32     visit_set_policy(v, &compat_policy);
  33     return v;
  34 }
  35
  36 Visitor *qobject_output_visitor_new_qmp(QObject **result)
  37 {
  38     Visitor *v = qobject_output_visitor_new(result);
  39
  40     visit_set_policy(v, &compat_policy);
  41     return v;
  42 }
  43
  44 static QDict *qmp_dispatch_check_obj(QDict *dict, bool allow_oob,
  45                                      Error **errp)
  46 {
  47     const char *exec_key = NULL;
  48     const QDictEntry *ent;
  49     const char *arg_name;
  50     const QObject *arg_obj;
  51
  52     for (ent = qdict_first(dict); ent;
  53          ent = qdict_next(dict, ent)) {
  54         arg_name = qdict_entry_key(ent);
  55         arg_obj = qdict_entry_value(ent);
  56
  57         if (!strcmp(arg_name, "execute")
  58             || (!strcmp(arg_name, "exec-oob") && allow_oob)) {
  59             if (qobject_type(arg_obj) != QTYPE_QSTRING) {
  60                 error_setg(errp, "QMP input member '%s' must be a string",
  61                            arg_name);
  62                 return NULL;
  63             }
  64             if (exec_key) {
  65                 error_setg(errp, "QMP input member '%s' clashes with '%s'",
  66                            arg_name, exec_key);
  67                 return NULL;
  68             }
  69             exec_key = arg_name;
  70         } else if (!strcmp(arg_name, "arguments")) {
  71             if (qobject_type(arg_obj) != QTYPE_QDICT) {
  72                 error_setg(errp,
  73                            "QMP input member 'arguments' must be an object");
  74                 return NULL;
  75             }
  76         } else if (!strcmp(arg_name, "id")) {
  77             continue;
  78         } else {
  79             error_setg(errp, "QMP input member '%s' is unexpected",
  80                        arg_name);
  81             return NULL;
  82         }
  83     }
  84
  85     if (!exec_key) {
  86         error_setg(errp, "QMP input lacks member 'execute'");
  87         return NULL;
  88     }
  89
  90     return dict;
  91 }
  92
  93 QDict *qmp_error_response(Error *err)
  94 {
  95     QDict *rsp;
  96
  97     rsp = qdict_from_jsonf_nofail("{ 'error': { 'class': %s, 'desc': %s } }",
  98                                   QapiErrorClass_str(error_get_class(err)),
  99                                   error_get_pretty(err));
 100     error_free(err);
 101     return rsp;
 102 }
 103
 104 /*
 105  * Does @qdict look like a command to be run out-of-band?
 106  */
 107 bool qmp_is_oob(const QDict *dict)
 108 {
 109     return qdict_haskey(dict, "exec-oob")
 110         && !qdict_haskey(dict, "execute");
 111 }
 112
 113 typedef struct QmpDispatchBH {
 114     const QmpCommand *cmd;
 115     Monitor *cur_mon;
 116     QDict *args;
 117     QObject **ret;
 118     Error **errp;
 119     Coroutine *co;
 120 } QmpDispatchBH;
 121
 122 static void do_qmp_dispatch_bh(void *opaque)
 123 {
 124     QmpDispatchBH *data = opaque;
 125
 126     assert(monitor_cur() == NULL);
 127     monitor_set_cur(qemu_coroutine_self(), data->cur_mon);
 128     data->cmd->fn(data->args, data->ret, data->errp);
 129     monitor_set_cur(qemu_coroutine_self(), NULL);
 130     aio_co_wake(data->co);
 131 }
 132
 133 /*
 134  * Runs outside of coroutine context for OOB commands, but in coroutine
 135  * context for everything else.
 136  */
 137 QDict *coroutine_mixed_fn qmp_dispatch(const QmpCommandList *cmds, QObject *request,
 138                                        bool allow_oob, Monitor *cur_mon)
 139 {
 140     Error *err = NULL;
 141     bool oob;
 142     const char *command;
 143     QDict *args;
 144     const QmpCommand *cmd;
 145     QDict *dict;
 146     QObject *id;
 147     QObject *ret = NULL;
 148     QDict *rsp = NULL;
 149
 150     dict = qobject_to(QDict, request);
 151     if (!dict) {
 152         id = NULL;
 153         error_setg(&err, "QMP input must be a JSON object");
 154         goto out;
 155     }
 156
 157     id = qdict_get(dict, "id");
 158
 159     if (!qmp_dispatch_check_obj(dict, allow_oob, &err)) {
 160         goto out;
 161     }
 162
 163     command = qdict_get_try_str(dict, "execute");
 164     oob = false;
 165     if (!command) {
 166         assert(allow_oob);
 167         command = qdict_get_str(dict, "exec-oob");
 168         oob = true;
 169     }
 170     cmd = qmp_find_command(cmds, command);
 171     if (cmd == NULL) {
 172         error_set(&err, ERROR_CLASS_COMMAND_NOT_FOUND,
 173                   "The command %s has not been found", command);
 174         goto out;
 175     }
 176     if (!compat_policy_input_ok(cmd->special_features, &compat_policy,
 177                                 ERROR_CLASS_COMMAND_NOT_FOUND,
 178                                 "command", command, &err)) {
 179         goto out;
 180     }
 181     if (!cmd->enabled) {
 182         error_set(&err, ERROR_CLASS_COMMAND_NOT_FOUND,
 183                   "Command %s has been disabled%s%s",
 184                   command,
 185                   cmd->disable_reason ? ": " : "",
 186                   cmd->disable_reason ?: "");
 187         goto out;
 188     }
 189     if (oob && !(cmd->options & QCO_ALLOW_OOB)) {
 190         error_setg(&err, "The command %s does not support OOB",
 191                    command);
 192         goto out;
 193     }
 194
 195     if (!qmp_command_available(cmd, &err)) {
 196         goto out;
 197     }
 198
 199     if (!qdict_haskey(dict, "arguments")) {
 200         args = qdict_new();
 201     } else {
 202         args = qdict_get_qdict(dict, "arguments");
 203         qobject_ref(args);
 204     }
 205
 206     assert(!(oob && qemu_in_coroutine()));
 207     assert(monitor_cur() == NULL);
 208     if (!!(cmd->options & QCO_COROUTINE) == qemu_in_coroutine()) {
 209         if (qemu_in_coroutine()) {
 210             /*
 211              * Move the coroutine from iohandler_ctx to qemu_aio_context for
 212              * executing the command handler so that it can make progress if it
 213              * involves an AIO_WAIT_WHILE().
 214              */
 215             aio_co_schedule(qemu_get_aio_context(), qemu_coroutine_self());
 216             qemu_coroutine_yield();
 217         }
 218
 219         monitor_set_cur(qemu_coroutine_self(), cur_mon);
 220         cmd->fn(args, &ret, &err);
 221         monitor_set_cur(qemu_coroutine_self(), NULL);
 222
 223         if (qemu_in_coroutine()) {
 224             /*
 225              * Yield and reschedule so the main loop stays responsive.
 226              *
 227              * Move back to iohandler_ctx so that nested event loops for
 228              * qemu_aio_context don't start new monitor commands.
 229              */
 230             aio_co_schedule(iohandler_get_aio_context(),
 231                             qemu_coroutine_self());
 232             qemu_coroutine_yield();
 233         }
 234     } else {
 235        /*
 236         * Actual context doesn't match the one the command needs.
 237         *
 238         * Case 1: we are in coroutine context, but command does not
 239         * have QCO_COROUTINE.  We need to drop out of coroutine
 240         * context for executing it.
 241         *
 242         * Case 2: we are outside coroutine context, but command has
 243         * QCO_COROUTINE.  Can't actually happen, because we get here
 244         * outside coroutine context only when executing a command
 245         * out of band, and OOB commands never have QCO_COROUTINE.
 246         */
 247         assert(!oob && qemu_in_coroutine() && !(cmd->options & QCO_COROUTINE));
 248
 249         QmpDispatchBH data = {
 250             .cur_mon    = cur_mon,
 251             .cmd        = cmd,
 252             .args       = args,
 253             .ret        = &ret,
 254             .errp       = &err,
 255             .co         = qemu_coroutine_self(),
 256         };
 257         aio_bh_schedule_oneshot(iohandler_get_aio_context(), do_qmp_dispatch_bh,
 258                                 &data);
 259         qemu_coroutine_yield();
 260     }
 261     qobject_unref(args);
 262     if (err) {
 263         /* or assert(!ret) after reviewing all handlers: */
 264         qobject_unref(ret);
 265         goto out;
 266     }
 267
 268     if (cmd->options & QCO_NO_SUCCESS_RESP) {
 269         g_assert(!ret);
 270         return NULL;
 271     } else if (!ret) {
 272         /*
 273          * When the command's schema has no 'returns', cmd->fn()
 274          * leaves @ret null.  The QMP spec calls for an empty object
 275          * then; supply it.
 276          */
 277         ret = QOBJECT(qdict_new());
 278     }
 279
 280     rsp = qdict_new();
 281     qdict_put_obj(rsp, "return", ret);
 282
 283 out:
 284     if (err) {
 285         assert(!rsp);
 286         rsp = qmp_error_response(err);
 287     }
 288
 289     assert(rsp);
 290
 291     if (id) {
 292         qdict_put_obj(rsp, "id", qobject_ref(id));
 293     }
 294
 295     return rsp;
 296 }