plugin: add core code

Signed-off-by: Emilio G. Cota <cota@braap.org>
[AJB: moved directory and merged various fixes]
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

plugins/loader.c

@@ -0,0 +1,362 @@
+/*
+ * QEMU Plugin Core Loader Code
+ *
+ * This is the code responsible for loading and unloading the plugins.
+ * Aside from the basic housekeeping tasks we also need to ensure any
+ * generated code is flushed when we remove a plugin so we cannot end
+ * up calling and unloaded helper function.
+ *
+ * Copyright (C) 2017, Emilio G. Cota <cota@braap.org>
+ * Copyright (C) 2019, Linaro
+ *
+ * License: GNU GPL, version 2 or later.
+ *   See the COPYING file in the top-level directory.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/error-report.h"
+#include "qemu/config-file.h"
+#include "qapi/error.h"
+#include "qemu/option.h"
+#include "qemu/rcu_queue.h"
+#include "qemu/qht.h"
+#include "qemu/bitmap.h"
+#include "qemu/xxhash.h"
+#include "qemu/plugin.h"
+#include "hw/core/cpu.h"
+#include "cpu.h"
+#include "exec/exec-all.h"
+#include "plugin.h"
+
+/*
+ * For convenience we use a bitmap for plugin.mask, but really all we need is a
+ * u32, which is what we store in TranslationBlock.
+ */
+QEMU_BUILD_BUG_ON(QEMU_PLUGIN_EV_MAX > 32);
+
+struct qemu_plugin_desc {
+    char *path;
+    char **argv;
+    QTAILQ_ENTRY(qemu_plugin_desc) entry;
+    int argc;
+};
+
+struct qemu_plugin_parse_arg {
+    QemuPluginList *head;
+    struct qemu_plugin_desc *curr;
+};
+
+QemuOptsList qemu_plugin_opts = {
+    .name = "plugin",
+    .implied_opt_name = "file",
+    .head = QTAILQ_HEAD_INITIALIZER(qemu_plugin_opts.head),
+    .desc = {
+        /* do our own parsing to support multiple plugins */
+        { /* end of list */ }
+    },
+};
+
+typedef int (*qemu_plugin_install_func_t)(qemu_plugin_id_t, int, char **);
+
+extern struct qemu_plugin_state plugin;
+
+void qemu_plugin_add_dyn_cb_arr(GArray *arr)
+{
+    uint32_t hash = qemu_xxhash2((uint64_t)(uintptr_t)arr);
+    bool inserted;
+
+    inserted = qht_insert(&plugin.dyn_cb_arr_ht, arr, hash, NULL);
+    g_assert(inserted);
+}
+
+static struct qemu_plugin_desc *plugin_find_desc(QemuPluginList *head,
+                                                 const char *path)
+{
+    struct qemu_plugin_desc *desc;
+
+    QTAILQ_FOREACH(desc, head, entry) {
+        if (strcmp(desc->path, path) == 0) {
+            return desc;
+        }
+    }
+    return NULL;
+}
+
+static int plugin_add(void *opaque, const char *name, const char *value,
+                      Error **errp)
+{
+    struct qemu_plugin_parse_arg *arg = opaque;
+    struct qemu_plugin_desc *p;
+
+    if (strcmp(name, "file") == 0) {
+        if (strcmp(value, "") == 0) {
+            error_setg(errp, "requires a non-empty argument");
+            return 1;
+        }
+        p = plugin_find_desc(arg->head, value);
+        if (p == NULL) {
+            p = g_new0(struct qemu_plugin_desc, 1);
+            p->path = g_strdup(value);
+            QTAILQ_INSERT_TAIL(arg->head, p, entry);
+        }
+        arg->curr = p;
+    } else if (strcmp(name, "arg") == 0) {
+        if (arg->curr == NULL) {
+            error_setg(errp, "missing earlier '-plugin file=' option");
+            return 1;
+        }
+        p = arg->curr;
+        p->argc++;
+        p->argv = g_realloc_n(p->argv, p->argc, sizeof(char *));
+        p->argv[p->argc - 1] = g_strdup(value);
+    } else {
+        error_setg(errp, "-plugin: unexpected parameter '%s'; ignored", name);
+    }
+    return 0;
+}
+
+void qemu_plugin_opt_parse(const char *optarg, QemuPluginList *head)
+{
+    struct qemu_plugin_parse_arg arg;
+    QemuOpts *opts;
+
+    opts = qemu_opts_parse_noisily(qemu_find_opts("plugin"), optarg, true);
+    if (opts == NULL) {
+        exit(1);
+    }
+    arg.head = head;
+    arg.curr = NULL;
+    qemu_opt_foreach(opts, plugin_add, &arg, &error_fatal);
+    qemu_opts_del(opts);
+}
+
+/*
+ * From: https://en.wikipedia.org/wiki/Xorshift
+ * This is faster than rand_r(), and gives us a wider range (RAND_MAX is only
+ * guaranteed to be >= INT_MAX).
+ */
+static uint64_t xorshift64star(uint64_t x)
+{
+    x ^= x >> 12; /* a */
+    x ^= x << 25; /* b */
+    x ^= x >> 27; /* c */
+    return x * UINT64_C(2685821657736338717);
+}
+
+static int plugin_load(struct qemu_plugin_desc *desc)
+{
+    qemu_plugin_install_func_t install;
+    struct qemu_plugin_ctx *ctx;
+    gpointer sym;
+    int rc;
+
+    ctx = qemu_memalign(qemu_dcache_linesize, sizeof(*ctx));
+    memset(ctx, 0, sizeof(*ctx));
+    ctx->desc = desc;
+
+    ctx->handle = g_module_open(desc->path, G_MODULE_BIND_LOCAL);
+    if (ctx->handle == NULL) {
+        error_report("%s: %s", __func__, g_module_error());
+        goto err_dlopen;
+    }
+
+    if (!g_module_symbol(ctx->handle, "qemu_plugin_install", &sym)) {
+        error_report("%s: %s", __func__, g_module_error());
+        goto err_symbol;
+    }
+    install = (qemu_plugin_install_func_t) sym;
+    /* symbol was found; it could be NULL though */
+    if (install == NULL) {
+        error_report("%s: %s: qemu_plugin_install is NULL",
+                     __func__, desc->path);
+        goto err_symbol;
+    }
+
+    qemu_rec_mutex_lock(&plugin.lock);
+
+    /* find an unused random id with &ctx as the seed */
+    ctx->id = (uint64_t)(uintptr_t)ctx;
+    for (;;) {
+        void *existing;
+
+        ctx->id = xorshift64star(ctx->id);
+        existing = g_hash_table_lookup(plugin.id_ht, &ctx->id);
+        if (likely(existing == NULL)) {
+            bool success;
+
+            success = g_hash_table_insert(plugin.id_ht, &ctx->id, &ctx->id);
+            g_assert(success);
+            break;
+        }
+    }
+    QTAILQ_INSERT_TAIL(&plugin.ctxs, ctx, entry);
+    ctx->installing = true;
+    rc = install(ctx->id, desc->argc, desc->argv);
+    ctx->installing = false;
+    if (rc) {
+        error_report("%s: qemu_plugin_install returned error code %d",
+                     __func__, rc);
+        /*
+         * we cannot rely on the plugin doing its own cleanup, so
+         * call a full uninstall if the plugin did not yet call it.
+         */
+        if (!ctx->uninstalling) {
+            plugin_reset_uninstall(ctx->id, NULL, false);
+        }
+    }
+
+    qemu_rec_mutex_unlock(&plugin.lock);
+    return rc;
+
+ err_symbol:
+ err_dlopen:
+    qemu_vfree(ctx);
+    return 1;
+}
+
+/* call after having removed @desc from the list */
+static void plugin_desc_free(struct qemu_plugin_desc *desc)
+{
+    int i;
+
+    for (i = 0; i < desc->argc; i++) {
+        g_free(desc->argv[i]);
+    }
+    g_free(desc->argv);
+    g_free(desc->path);
+    g_free(desc);
+}
+
+/**
+ * qemu_plugin_load_list - load a list of plugins
+ * @head: head of the list of descriptors of the plugins to be loaded
+ *
+ * Returns 0 if all plugins in the list are installed, !0 otherwise.
+ *
+ * Note: the descriptor of each successfully installed plugin is removed
+ * from the list given by @head.
+ */
+int qemu_plugin_load_list(QemuPluginList *head)
+{
+    struct qemu_plugin_desc *desc, *next;
+
+    QTAILQ_FOREACH_SAFE(desc, head, entry, next) {
+        int err;
+
+        err = plugin_load(desc);
+        if (err) {
+            return err;
+        }
+        QTAILQ_REMOVE(head, desc, entry);
+    }
+    return 0;
+}
+
+struct qemu_plugin_reset_data {
+    struct qemu_plugin_ctx *ctx;
+    qemu_plugin_simple_cb_t cb;
+    bool reset;
+};
+
+static void plugin_reset_destroy__locked(struct qemu_plugin_reset_data *data)
+{
+    struct qemu_plugin_ctx *ctx = data->ctx;
+    enum qemu_plugin_event ev;
+    bool success;
+
+    /*
+     * After updating the subscription lists there is no need to wait for an RCU
+     * grace period to elapse, because right now we either are in a "safe async"
+     * work environment (i.e. all vCPUs are asleep), or no vCPUs have yet been
+     * created.
+     */
+    for (ev = 0; ev < QEMU_PLUGIN_EV_MAX; ev++) {
+        plugin_unregister_cb__locked(ctx, ev);
+    }
+
+    if (data->reset) {
+        g_assert(ctx->resetting);
+        if (data->cb) {
+            data->cb(ctx->id);
+        }
+        ctx->resetting = false;
+        g_free(data);
+        return;
+    }
+
+    g_assert(ctx->uninstalling);
+    /* we cannot dlclose if we are going to return to plugin code */
+    if (ctx->installing) {
+        error_report("Calling qemu_plugin_uninstall from the install function "
+                     "is a bug. Instead, return !0 from the install function.");
+        abort();
+    }
+
+    success = g_hash_table_remove(plugin.id_ht, &ctx->id);
+    g_assert(success);
+    QTAILQ_REMOVE(&plugin.ctxs, ctx, entry);
+    if (data->cb) {
+        data->cb(ctx->id);
+    }
+    if (!g_module_close(ctx->handle)) {
+        warn_report("%s: %s", __func__, g_module_error());
+    }
+    plugin_desc_free(ctx->desc);
+    qemu_vfree(ctx);
+    g_free(data);
+}
+
+static void plugin_reset_destroy(struct qemu_plugin_reset_data *data)
+{
+    qemu_rec_mutex_lock(&plugin.lock);
+    plugin_reset_destroy__locked(data);
+    qemu_rec_mutex_lock(&plugin.lock);
+}
+
+static void plugin_flush_destroy(CPUState *cpu, run_on_cpu_data arg)
+{
+    struct qemu_plugin_reset_data *data = arg.host_ptr;
+
+    g_assert(cpu_in_exclusive_context(cpu));
+    tb_flush(cpu);
+    plugin_reset_destroy(data);
+}
+
+void plugin_reset_uninstall(qemu_plugin_id_t id,
+                            qemu_plugin_simple_cb_t cb,
+                            bool reset)
+{
+    struct qemu_plugin_reset_data *data;
+    struct qemu_plugin_ctx *ctx;
+
+    qemu_rec_mutex_lock(&plugin.lock);
+    ctx = plugin_id_to_ctx_locked(id);
+    if (ctx->uninstalling || (reset && ctx->resetting)) {
+        qemu_rec_mutex_unlock(&plugin.lock);
+        return;
+    }
+    ctx->resetting = reset;
+    ctx->uninstalling = !reset;
+    qemu_rec_mutex_unlock(&plugin.lock);
+
+    data = g_new(struct qemu_plugin_reset_data, 1);
+    data->ctx = ctx;
+    data->cb = cb;
+    data->reset = reset;
+    /*
+     * Only flush the code cache if the vCPUs have been created. If so,
+     * current_cpu must be non-NULL.
+     */
+    if (current_cpu) {
+        async_safe_run_on_cpu(current_cpu, plugin_flush_destroy,
+                              RUN_ON_CPU_HOST_PTR(data));
+    } else {
+        /*
+         * If current_cpu isn't set, then we don't have yet any vCPU threads
+         * and we therefore can remove the callbacks synchronously.
+         */
+        plugin_reset_destroy(data);
+    }
+}