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