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