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