plugins/loader.c

   1 /*
   2  * QEMU Plugin Core Loader Code
   3  *
   4  * This is the code responsible for loading and unloading the plugins.
   5  * Aside from the basic housekeeping tasks we also need to ensure any
   6  * generated code is flushed when we remove a plugin so we cannot end
   7  * up calling and unloaded helper function.
   8  *
   9  * Copyright (C) 2017, Emilio G. Cota <cota@braap.org>
  10  * Copyright (C) 2019, Linaro
  11  *
  12  * License: GNU GPL, version 2 or later.
  13  *   See the COPYING file in the top-level directory.
  14  *
  15  * SPDX-License-Identifier: GPL-2.0-or-later
  16  */
  17
  18 #include "qemu/osdep.h"
  19 #include "qemu/error-report.h"
  20 #include "qemu/config-file.h"
  21 #include "qapi/error.h"
  22 #include "qemu/lockable.h"
  23 #include "qemu/option.h"
  24 #include "qemu/rcu_queue.h"
  25 #include "qemu/qht.h"
  26 #include "qemu/bitmap.h"
  27 #include "qemu/cacheinfo.h"
  28 #include "qemu/xxhash.h"
  29 #include "qemu/plugin.h"
  30 #include "qemu/memalign.h"
  31 #include "hw/core/cpu.h"
  32 #include "exec/exec-all.h"
  33 #ifndef CONFIG_USER_ONLY
  34 #include "hw/boards.h"
  35 #endif
  36 #include "qemu/compiler.h"
  37
  38 #include "plugin.h"
  39
  40 /*
  41  * For convenience we use a bitmap for plugin.mask, but really all we need is a
  42  * u32, which is what we store in TranslationBlock.
  43  */
  44 QEMU_BUILD_BUG_ON(QEMU_PLUGIN_EV_MAX > 32);
  45
  46 struct qemu_plugin_desc {
  47     char *path;
  48     char **argv;
  49     QTAILQ_ENTRY(qemu_plugin_desc) entry;
  50     int argc;
  51 };
  52
  53 struct qemu_plugin_parse_arg {
  54     QemuPluginList *head;
  55     struct qemu_plugin_desc *curr;
  56 };
  57
  58 QemuOptsList qemu_plugin_opts = {
  59     .name = "plugin",
  60     .implied_opt_name = "file",
  61     .head = QTAILQ_HEAD_INITIALIZER(qemu_plugin_opts.head),
  62     .desc = {
  63         /* do our own parsing to support multiple plugins */
  64         { /* end of list */ }
  65     },
  66 };
  67
  68 typedef int (*qemu_plugin_install_func_t)(qemu_plugin_id_t, const qemu_info_t *, int, char **);
  69
  70 extern struct qemu_plugin_state plugin;
  71
  72 void qemu_plugin_add_dyn_cb_arr(GArray *arr)
  73 {
  74     uint32_t hash = qemu_xxhash2((uint64_t)(uintptr_t)arr);
  75     bool inserted;
  76
  77     inserted = qht_insert(&plugin.dyn_cb_arr_ht, arr, hash, NULL);
  78     g_assert(inserted);
  79 }
  80
  81 static struct qemu_plugin_desc *plugin_find_desc(QemuPluginList *head,
  82                                                  const char *path)
  83 {
  84     struct qemu_plugin_desc *desc;
  85
  86     QTAILQ_FOREACH(desc, head, entry) {
  87         if (strcmp(desc->path, path) == 0) {
  88             return desc;
  89         }
  90     }
  91     return NULL;
  92 }
  93
  94 static int plugin_add(void *opaque, const char *name, const char *value,
  95                       Error **errp)
  96 {
  97     struct qemu_plugin_parse_arg *arg = opaque;
  98     struct qemu_plugin_desc *p;
  99     bool is_on;
 100     char *fullarg;
 101
 102     if (strcmp(name, "file") == 0) {
 103         if (strcmp(value, "") == 0) {
 104             error_setg(errp, "requires a non-empty argument");
 105             return 1;
 106         }
 107         p = plugin_find_desc(arg->head, value);
 108         if (p == NULL) {
 109             p = g_new0(struct qemu_plugin_desc, 1);
 110             p->path = g_strdup(value);
 111             QTAILQ_INSERT_TAIL(arg->head, p, entry);
 112         }
 113         arg->curr = p;
 114     } else {
 115         if (arg->curr == NULL) {
 116             error_setg(errp, "missing earlier '-plugin file=' option");
 117             return 1;
 118         }
 119
 120         if (g_strcmp0(name, "arg") == 0 &&
 121                 !qapi_bool_parse(name, value, &is_on, NULL)) {
 122             if (strchr(value, '=') == NULL) {
 123                 /* Will treat arg="argname" as "argname=on" */
 124                 fullarg = g_strdup_printf("%s=%s", value, "on");
 125             } else {
 126                 fullarg = g_strdup_printf("%s", value);
 127             }
 128             warn_report("using 'arg=%s' is deprecated", value);
 129             error_printf("Please use '%s' directly\n", fullarg);
 130         } else {
 131             fullarg = g_strdup_printf("%s=%s", name, value);
 132         }
 133
 134         p = arg->curr;
 135         p->argc++;
 136         p->argv = g_realloc_n(p->argv, p->argc, sizeof(char *));
 137         p->argv[p->argc - 1] = fullarg;
 138     }
 139
 140     return 0;
 141 }
 142
 143 void qemu_plugin_opt_parse(const char *optarg, QemuPluginList *head)
 144 {
 145     struct qemu_plugin_parse_arg arg;
 146     QemuOpts *opts;
 147
 148     opts = qemu_opts_parse_noisily(qemu_find_opts("plugin"), optarg, true);
 149     if (opts == NULL) {
 150         exit(1);
 151     }
 152     arg.head = head;
 153     arg.curr = NULL;
 154     qemu_opt_foreach(opts, plugin_add, &arg, &error_fatal);
 155     qemu_opts_del(opts);
 156 }
 157
 158 /*
 159  * From: https://en.wikipedia.org/wiki/Xorshift
 160  * This is faster than rand_r(), and gives us a wider range (RAND_MAX is only
 161  * guaranteed to be >= INT_MAX).
 162  */
 163 static uint64_t xorshift64star(uint64_t x)
 164 {
 165     x ^= x >> 12; /* a */
 166     x ^= x << 25; /* b */
 167     x ^= x >> 27; /* c */
 168     return x * UINT64_C(2685821657736338717);
 169 }
 170
 171 /*
 172  * Disable CFI checks.
 173  * The install and version functions have been loaded from an external library
 174  * so we do not have type information
 175  */
 176 QEMU_DISABLE_CFI
 177 static int plugin_load(struct qemu_plugin_desc *desc, const qemu_info_t *info, Error **errp)
 178 {
 179     qemu_plugin_install_func_t install;
 180     struct qemu_plugin_ctx *ctx;
 181     gpointer sym;
 182     int rc;
 183
 184     ctx = qemu_memalign(qemu_dcache_linesize, sizeof(*ctx));
 185     memset(ctx, 0, sizeof(*ctx));
 186     ctx->desc = desc;
 187
 188     ctx->handle = g_module_open(desc->path, G_MODULE_BIND_LOCAL);
 189     if (ctx->handle == NULL) {
 190         error_setg(errp, "Could not load plugin %s: %s", desc->path, g_module_error());
 191         goto err_dlopen;
 192     }
 193
 194     if (!g_module_symbol(ctx->handle, "qemu_plugin_install", &sym)) {
 195         error_setg(errp, "Could not load plugin %s: %s", desc->path, g_module_error());
 196         goto err_symbol;
 197     }
 198     install = (qemu_plugin_install_func_t) sym;
 199     /* symbol was found; it could be NULL though */
 200     if (install == NULL) {
 201         error_setg(errp, "Could not load plugin %s: qemu_plugin_install is NULL",
 202                    desc->path);
 203         goto err_symbol;
 204     }
 205
 206     if (!g_module_symbol(ctx->handle, "qemu_plugin_version", &sym)) {
 207         error_setg(errp, "Could not load plugin %s: plugin does not declare API version %s",
 208                    desc->path, g_module_error());
 209         goto err_symbol;
 210     } else {
 211         int version = *(int *)sym;
 212         if (version < QEMU_PLUGIN_MIN_VERSION) {
 213             error_setg(errp, "Could not load plugin %s: plugin requires API version %d, but "
 214                        "this QEMU supports only a minimum version of %d",
 215                        desc->path, version, QEMU_PLUGIN_MIN_VERSION);
 216             goto err_symbol;
 217         } else if (version > QEMU_PLUGIN_VERSION) {
 218             error_setg(errp, "Could not load plugin %s: plugin requires API version %d, but "
 219                        "this QEMU supports only up to version %d",
 220                        desc->path, version, QEMU_PLUGIN_VERSION);
 221             goto err_symbol;
 222         }
 223     }
 224
 225     qemu_rec_mutex_lock(&plugin.lock);
 226
 227     /* find an unused random id with &ctx as the seed */
 228     ctx->id = (uint64_t)(uintptr_t)ctx;
 229     for (;;) {
 230         void *existing;
 231
 232         ctx->id = xorshift64star(ctx->id);
 233         existing = g_hash_table_lookup(plugin.id_ht, &ctx->id);
 234         if (likely(existing == NULL)) {
 235             bool success;
 236
 237             success = g_hash_table_insert(plugin.id_ht, &ctx->id, &ctx->id);
 238             g_assert(success);
 239             break;
 240         }
 241     }
 242     QTAILQ_INSERT_TAIL(&plugin.ctxs, ctx, entry);
 243     ctx->installing = true;
 244     rc = install(ctx->id, info, desc->argc, desc->argv);
 245     ctx->installing = false;
 246     if (rc) {
 247         error_setg(errp, "Could not load plugin %s: qemu_plugin_install returned error code %d",
 248                    desc->path, rc);
 249         /*
 250          * we cannot rely on the plugin doing its own cleanup, so
 251          * call a full uninstall if the plugin did not yet call it.
 252          */
 253         if (!ctx->uninstalling) {
 254             plugin_reset_uninstall(ctx->id, NULL, false);
 255         }
 256     }
 257
 258     qemu_rec_mutex_unlock(&plugin.lock);
 259     return rc;
 260
 261  err_symbol:
 262     g_module_close(ctx->handle);
 263  err_dlopen:
 264     qemu_vfree(ctx);
 265     return 1;
 266 }
 267
 268 /* call after having removed @desc from the list */
 269 static void plugin_desc_free(struct qemu_plugin_desc *desc)
 270 {
 271     int i;
 272
 273     for (i = 0; i < desc->argc; i++) {
 274         g_free(desc->argv[i]);
 275     }
 276     g_free(desc->argv);
 277     g_free(desc->path);
 278     g_free(desc);
 279 }
 280
 281 /**
 282  * qemu_plugin_load_list - load a list of plugins
 283  * @head: head of the list of descriptors of the plugins to be loaded
 284  *
 285  * Returns 0 if all plugins in the list are installed, !0 otherwise.
 286  *
 287  * Note: the descriptor of each successfully installed plugin is removed
 288  * from the list given by @head.
 289  */
 290 int qemu_plugin_load_list(QemuPluginList *head, Error **errp)
 291 {
 292     struct qemu_plugin_desc *desc, *next;
 293     g_autofree qemu_info_t *info = g_new0(qemu_info_t, 1);
 294
 295     info->target_name = TARGET_NAME;
 296     info->version.min = QEMU_PLUGIN_MIN_VERSION;
 297     info->version.cur = QEMU_PLUGIN_VERSION;
 298 #ifndef CONFIG_USER_ONLY
 299     MachineState *ms = MACHINE(qdev_get_machine());
 300     info->system_emulation = true;
 301     info->system.smp_vcpus = ms->smp.cpus;
 302     info->system.max_vcpus = ms->smp.max_cpus;
 303 #else
 304     info->system_emulation = false;
 305 #endif
 306
 307     QTAILQ_FOREACH_SAFE(desc, head, entry, next) {
 308         int err;
 309
 310         err = plugin_load(desc, info, errp);
 311         if (err) {
 312             return err;
 313         }
 314         QTAILQ_REMOVE(head, desc, entry);
 315     }
 316     return 0;
 317 }
 318
 319 struct qemu_plugin_reset_data {
 320     struct qemu_plugin_ctx *ctx;
 321     qemu_plugin_simple_cb_t cb;
 322     bool reset;
 323 };
 324
 325 static void plugin_reset_destroy__locked(struct qemu_plugin_reset_data *data)
 326 {
 327     struct qemu_plugin_ctx *ctx = data->ctx;
 328     enum qemu_plugin_event ev;
 329     bool success;
 330
 331     /*
 332      * After updating the subscription lists there is no need to wait for an RCU
 333      * grace period to elapse, because right now we either are in a "safe async"
 334      * work environment (i.e. all vCPUs are asleep), or no vCPUs have yet been
 335      * created.
 336      */
 337     for (ev = 0; ev < QEMU_PLUGIN_EV_MAX; ev++) {
 338         plugin_unregister_cb__locked(ctx, ev);
 339     }
 340
 341     if (data->reset) {
 342         g_assert(ctx->resetting);
 343         if (data->cb) {
 344             data->cb(ctx->id);
 345         }
 346         ctx->resetting = false;
 347         g_free(data);
 348         return;
 349     }
 350
 351     g_assert(ctx->uninstalling);
 352     /* we cannot dlclose if we are going to return to plugin code */
 353     if (ctx->installing) {
 354         error_report("Calling qemu_plugin_uninstall from the install function "
 355                      "is a bug. Instead, return !0 from the install function.");
 356         abort();
 357     }
 358
 359     success = g_hash_table_remove(plugin.id_ht, &ctx->id);
 360     g_assert(success);
 361     QTAILQ_REMOVE(&plugin.ctxs, ctx, entry);
 362     if (data->cb) {
 363         data->cb(ctx->id);
 364     }
 365     if (!g_module_close(ctx->handle)) {
 366         warn_report("%s: %s", __func__, g_module_error());
 367     }
 368     plugin_desc_free(ctx->desc);
 369     qemu_vfree(ctx);
 370     g_free(data);
 371 }
 372
 373 static void plugin_reset_destroy(struct qemu_plugin_reset_data *data)
 374 {
 375     qemu_rec_mutex_lock(&plugin.lock);
 376     plugin_reset_destroy__locked(data);
 377     qemu_rec_mutex_lock(&plugin.lock);
 378 }
 379
 380 static void plugin_flush_destroy(CPUState *cpu, run_on_cpu_data arg)
 381 {
 382     struct qemu_plugin_reset_data *data = arg.host_ptr;
 383
 384     g_assert(cpu_in_exclusive_context(cpu));
 385     tb_flush(cpu);
 386     plugin_reset_destroy(data);
 387 }
 388
 389 void plugin_reset_uninstall(qemu_plugin_id_t id,
 390                             qemu_plugin_simple_cb_t cb,
 391                             bool reset)
 392 {
 393     struct qemu_plugin_reset_data *data;
 394     struct qemu_plugin_ctx *ctx;
 395
 396     WITH_QEMU_LOCK_GUARD(&plugin.lock) {
 397         ctx = plugin_id_to_ctx_locked(id);
 398         if (ctx->uninstalling || (reset && ctx->resetting)) {
 399             return;
 400         }
 401         ctx->resetting = reset;
 402         ctx->uninstalling = !reset;
 403     }
 404
 405     data = g_new(struct qemu_plugin_reset_data, 1);
 406     data->ctx = ctx;
 407     data->cb = cb;
 408     data->reset = reset;
 409     /*
 410      * Only flush the code cache if the vCPUs have been created. If so,
 411      * current_cpu must be non-NULL.
 412      */
 413     if (current_cpu) {
 414         async_safe_run_on_cpu(current_cpu, plugin_flush_destroy,
 415                               RUN_ON_CPU_HOST_PTR(data));
 416     } else {
 417         /*
 418          * If current_cpu isn't set, then we don't have yet any vCPU threads
 419          * and we therefore can remove the callbacks synchronously.
 420          */
 421         plugin_reset_destroy(data);
 422     }
 423 }