*/
#include "qemu/osdep.h"
+#include "qom/object.h"
#include "xen_xenstore.h"
#include "xenstore_impl.h"
#include "include/hw/xen/xen_backend_ops.h"
+#include "include/standard-headers/xen/io/xs_wire.h"
+
+#define TYPE_XS_NODE "xs-node"
+
+OBJECT_DECLARE_TYPE(XsNode, XsNodeClass, XS_NODE)
+
+typedef struct XsNode {
+ Object obj;
+ GByteArray *content;
+ GHashTable *children;
+#ifdef XS_NODE_UNIT_TEST
+ gchar *name; /* debug only */
+#endif
+} XsNode;
struct XenstoreImplState {
+ XsNode *root;
+};
+
+static void xs_node_init(Object *obj)
+{
+#ifdef XS_NODE_UNIT_TEST
+ XsNode *n = XS_NODE(obj);
+ nr_xs_nodes++;
+ xs_node_list = g_list_prepend(xs_node_list, n);
+#endif
+}
+
+static void xs_node_finalize(Object *obj)
+{
+ XsNode *n = XS_NODE(obj);
+ if (n->content) {
+ g_byte_array_unref(n->content);
+ }
+ if (n->children) {
+ g_hash_table_unref(n->children);
+ }
+#ifdef XS_NODE_UNIT_TEST
+ g_free(n->name);
+ nr_xs_nodes--;
+ xs_node_list = g_list_remove(xs_node_list, n);
+#endif
+}
+
+static const TypeInfo xs_node_info = {
+ .name = TYPE_XS_NODE,
+ .parent = TYPE_OBJECT,
+ .instance_size = sizeof(XsNode),
+ .instance_init = xs_node_init,
+ .instance_finalize = xs_node_finalize,
+};
+
+static void xs_impl_register_types(void)
+{
+ type_register_static(&xs_node_info);
+}
+
+type_init(xs_impl_register_types)
+
+static inline XsNode *xs_node_new(void)
+{
+ return XS_NODE(object_new(TYPE_XS_NODE));
+}
+
+static inline XsNode *xs_node_ref(XsNode *n)
+{
+ return XS_NODE(object_ref(OBJECT(n)));
+}
+
+static inline void xs_node_unref(XsNode *n)
+{
+ object_unref(OBJECT(n));
+}
+
+/* For copying from one hash table to another using g_hash_table_foreach() */
+static void do_insert(gpointer key, gpointer value, gpointer user_data)
+{
+ g_hash_table_insert(user_data, g_strdup(key), object_ref(value));
+}
+
+static XsNode *xs_node_copy(XsNode *old)
+{
+ XsNode *n = xs_node_new();
+
+ if (old->children) {
+ n->children = g_hash_table_new_full(g_str_hash, g_str_equal, g_free,
+ object_unref);
+ g_hash_table_foreach(old->children, do_insert, n->children);
+ }
+ if (old && old->content) {
+ n->content = g_byte_array_ref(old->content);
+ }
+ return n;
+}
+
+static void xs_node_add_child(XsNode *n, const char *path_elem, XsNode *child)
+{
+ assert(!strchr(path_elem, '/'));
+
+ if (!child) {
+ assert(n->children);
+ g_hash_table_remove(n->children, path_elem);
+ return;
+ }
+
+#ifdef XS_NODE_UNIT_TEST
+ g_free(child->name);
+ child->name = g_strdup(path_elem);
+#endif
+ if (!n->children) {
+ n->children = g_hash_table_new_full(g_str_hash, g_str_equal, g_free,
+ object_unref);
+ }
+ g_hash_table_insert(n->children, g_strdup(path_elem), child);
+}
+
+struct walk_op {
+ struct XenstoreImplState *s;
+ char path[XENSTORE_ABS_PATH_MAX + 2]; /* Two NUL terminators */
+ int (*op_fn)(XsNode **n, struct walk_op *op);
+ void *op_opaque;
+
+ unsigned int dom_id;
+
+ /*
+ * This is maintained on the way *down* the walk to indicate
+ * whether nodes can be modified in place or whether COW is
+ * required. It starts off being true, as we're always going to
+ * replace the root node. If we walk into a shared subtree it
+ * becomes false. If we start *creating* new nodes for a write,
+ * it becomes true again.
+ *
+ * Do not use it on the way back up.
+ */
+ bool inplace;
+ bool mutating;
+ bool create_dirs;
};
+static int xs_node_add_content(XsNode **n, struct walk_op *op)
+{
+ /* We *are* the node to be written. Either this or a copy. */
+ if (!op->inplace) {
+ XsNode *old = *n;
+ *n = xs_node_copy(old);
+ xs_node_unref(old);
+ }
+
+ if ((*n)->content) {
+ g_byte_array_unref((*n)->content);
+ }
+ (*n)->content = g_byte_array_ref(op->op_opaque);
+ return 0;
+}
+
+static int xs_node_get_content(XsNode **n, struct walk_op *op)
+{
+ GByteArray *data = op->op_opaque;
+ GByteArray *node_data;
+
+ assert(op->inplace);
+ assert(*n);
+
+ node_data = (*n)->content;
+ if (node_data) {
+ g_byte_array_append(data, node_data->data, node_data->len);
+ }
+
+ return 0;
+}
+
+static int xs_node_rm(XsNode **n, struct walk_op *op)
+{
+ bool this_inplace = op->inplace;
+
+ if (this_inplace) {
+ xs_node_unref(*n);
+ }
+ *n = NULL;
+ return 0;
+}
+
+/*
+ * Passed a full reference in *n which it may free if it needs to COW.
+ *
+ * When changing the tree, the op->inplace flag indicates whether this
+ * node may be modified in place (i.e. it and all its parents had a
+ * refcount of one). If walking down the tree we find a node whose
+ * refcount is higher, we must clear op->inplace and COW from there
+ * down. Unless we are creating new nodes as scaffolding for a write
+ * (which works like 'mkdir -p' does). In which case those newly
+ * created nodes can (and must) be modified in place again.
+ */
+static int xs_node_walk(XsNode **n, struct walk_op *op)
+{
+ char *child_name = NULL;
+ size_t namelen;
+ XsNode *old = *n, *child = NULL;
+ bool stole_child = false;
+ bool this_inplace;
+ int err;
+
+ namelen = strlen(op->path);
+
+ /* Is there a child, or do we hit the double-NUL termination? */
+ if (op->path[namelen + 1]) {
+ char *slash;
+ child_name = op->path + namelen + 1;
+ slash = strchr(child_name, '/');
+ if (slash) {
+ *slash = '\0';
+ }
+ op->path[namelen] = '/';
+ }
+
+ /* If we walk into a subtree which is shared, we must COW */
+ if (op->mutating && old->obj.ref != 1) {
+ op->inplace = false;
+ }
+
+ if (!child_name) {
+ /* This is the actual node on which the operation shall be performed */
+ return op->op_fn(n, op);
+ }
+
+ /* op->inplace will be further modified during the recursion */
+ this_inplace = op->inplace;
+
+ if (old && old->children) {
+ child = g_hash_table_lookup(old->children, child_name);
+ /* This is a *weak* reference to 'child', owned by the hash table */
+ }
+
+ if (child) {
+ xs_node_ref(child);
+ /*
+ * Now we own it too. But if we can modify inplace, that's going to
+ * foil the check and force it to COW. We want to be the *only* owner
+ * so that it can be modified in place, so remove it from the hash
+ * table in that case. We'll add it (or its replacement) back later.
+ */
+ if (op->mutating && this_inplace) {
+ g_hash_table_remove(old->children, child_name);
+ stole_child = true;
+ }
+ } else if (op->create_dirs) {
+ child = xs_node_new();
+ /* If we're creating a new child, we can clearly modify it (and its
+ * children) in place from here on down. */
+ op->inplace = true;
+ } else {
+ op->path[namelen] = '\0';
+ return ENOENT;
+ }
+
+ /*
+ * Except for the temporary child-stealing as noted, our node has not
+ * changed yet. We don't yet know the overall operation will complete.
+ */
+ err = xs_node_walk(&child, op);
+ if (err || !op->mutating) {
+ if (stole_child) {
+ /* Put it back as it was. */
+ g_hash_table_replace(old->children, g_strdup(child_name), child);
+ } else {
+ xs_node_unref(child);
+ }
+ op->path[namelen] = '\0';
+ return err;
+ }
+
+ /*
+ * Now we know the operation has completed successfully and we're on
+ * the way back up. Make the change, substituting 'child' in the
+ * node at our level.
+ */
+ if (!this_inplace) {
+ *n = xs_node_copy(old);
+ xs_node_unref(old);
+ }
+
+ xs_node_add_child(*n, child_name, child);
+
+ op->path[namelen] = '\0';
+ return 0;
+}
+
+static void append_directory_item(gpointer key, gpointer value,gpointer user_data)
+{
+ GList **items = user_data;
+
+ *items = g_list_insert_sorted(*items, g_strdup(key), g_str_equal);
+}
+
+/* Populates items with char * names which caller must free. */
+static int xs_node_directory(XsNode **n, struct walk_op *op)
+{
+ GList **items = op->op_opaque;
+
+ assert(op->inplace);
+ assert(*n);
+
+ if ((*n)->children) {
+ g_hash_table_foreach((*n)->children, append_directory_item, items);
+ }
+
+ return 0;
+}
+
char *xs_perm_as_string(unsigned int perm, unsigned int domid)
{
char letter;
return g_strdup_printf("%c%u", letter, domid);
}
+static int init_walk_op(XenstoreImplState *s, struct walk_op *op,
+ unsigned int tx_id, unsigned int dom_id,
+ const char *path, XsNode ***rootp)
+{
+ if (path[0] == '/') {
+ if (strlen(path) > XENSTORE_ABS_PATH_MAX) {
+ return E2BIG;
+ }
+ snprintf(op->path, sizeof(op->path), "%s", path);
+ } else {
+ if (strlen(path) > XENSTORE_REL_PATH_MAX) {
+ return E2BIG;
+ }
+ snprintf(op->path, sizeof(op->path), "/local/domain/%u/%s", dom_id,
+ path);
+ }
+ /*
+ * We use *two* NUL terminators at the end of the path, as during the walk
+ * we will temporarily turn each '/' into a NUL to allow us to use that
+ * path element for the lookup.
+ */
+ op->path[strlen(op->path) + 1] = '\0';
+ op->path[0] = '\0';
+ op->inplace = true;
+ op->mutating = false;
+ op->create_dirs = false;
+ op->dom_id = dom_id;
+ op->s = s;
+
+ if (tx_id == XBT_NULL) {
+ *rootp = &s->root;
+ } else {
+ return ENOENT;
+ }
+
+ return 0;
+}
+
int xs_impl_read(XenstoreImplState *s, unsigned int dom_id, unsigned int tx_id,
const char *path, GByteArray *data)
{
* The data GByteArray shall exist, and will be freed by caller.
* Just g_byte_array_append() to it.
*/
- return ENOENT;
+ struct walk_op op;
+ XsNode **n;
+ int ret;
+
+ ret = init_walk_op(s, &op, tx_id, dom_id, path, &n);
+ if (ret) {
+ return ret;
+ }
+ op.op_fn = xs_node_get_content;
+ op.op_opaque = data;
+ return xs_node_walk(n, &op);
}
int xs_impl_write(XenstoreImplState *s, unsigned int dom_id,
{
/*
* The data GByteArray shall exist, will be freed by caller. You are
- * free to use g_byte_array_steal() and keep the data.
+ * free to use g_byte_array_steal() and keep the data. Or just ref it.
*/
- return ENOSYS;
+ struct walk_op op;
+ XsNode **n;
+ int ret;
+
+ ret = init_walk_op(s, &op, tx_id, dom_id, path, &n);
+ if (ret) {
+ return ret;
+ }
+ op.op_fn = xs_node_add_content;
+ op.op_opaque = data;
+ op.mutating = true;
+ op.create_dirs = true;
+ return xs_node_walk(n, &op);
}
int xs_impl_directory(XenstoreImplState *s, unsigned int dom_id,
* immediately so if you want to change it to (const char *) and keep
* them, go ahead and change the caller.
*/
- return ENOENT;
+ struct walk_op op;
+ XsNode **n;
+ int ret;
+
+ ret = init_walk_op(s, &op, tx_id, dom_id, path, &n);
+ if (ret) {
+ return ret;
+ }
+ op.op_fn = xs_node_directory;
+ op.op_opaque = items;
+ return xs_node_walk(n, &op);
}
int xs_impl_transaction_start(XenstoreImplState *s, unsigned int dom_id,
int xs_impl_rm(XenstoreImplState *s, unsigned int dom_id, unsigned int tx_id,
const char *path)
{
- return ENOSYS;
+ struct walk_op op;
+ XsNode **n;
+ int ret;
+
+ ret = init_walk_op(s, &op, tx_id, dom_id, path, &n);
+ if (ret) {
+ return ret;
+ }
+ op.op_fn = xs_node_rm;
+ op.mutating = true;
+ return xs_node_walk(n, &op);
}
int xs_impl_get_perms(XenstoreImplState *s, unsigned int dom_id,
* if it was a relative path which needed to be prefixed with
* /local/domain/${domid}/
*/
- return ENOSYS;
+ return ENOSYS;
}
int xs_impl_unwatch(XenstoreImplState *s, unsigned int dom_id,
const char *path, const char *token,
xs_impl_watch_fn fn, void *opaque)
{
- /* Remove the watch that matches all four criteria */
- return ENOSYS;
+ /*
+ * When calling the callback @fn, note that the path should
+ * precisely match the relative path that the guest provided, even
+ * if it was a relative path which needed to be prefixed with
+ * /local/domain/${domid}/
+ */
+ return ENOSYS;
}
int xs_impl_reset_watches(XenstoreImplState *s, unsigned int dom_id)
{
+ /* Remove the watch that matches all four criteria */
return ENOSYS;
}
XenstoreImplState *xs_impl_create(void)
{
- return g_new0(XenstoreImplState, 1);
+ XenstoreImplState *s = g_new0(XenstoreImplState, 1);
+
+ s->root = xs_node_new();
+#ifdef XS_NODE_UNIT_TEST
+ s->root->name = g_strdup("/");
+#endif
+ return s;
}
--- /dev/null
+/*
+ * QEMU XenStore XsNode testing
+ *
+ * Copyright © 2023 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include "qemu/osdep.h"
+#include "qapi/error.h"
+#include "qemu/module.h"
+
+static int nr_xs_nodes;
+static GList *xs_node_list;
+
+#define XS_NODE_UNIT_TEST
+#include "hw/i386/kvm/xenstore_impl.c"
+
+#define DOMID_GUEST 1
+
+/* This doesn't happen in qemu but we want to make valgrind happy */
+static void xs_impl_delete(XenstoreImplState *s)
+{
+ xs_node_unref(s->root);
+ g_free(s);
+
+ if (xs_node_list) {
+ GList *l;
+ for (l = xs_node_list; l; l = l->next) {
+ XsNode *n = l->data;
+ printf("Remaining node at %p name %s ref %d\n", n, n->name,
+ n->obj.ref);
+ }
+ }
+ g_assert(!nr_xs_nodes);
+}
+
+static int write_str(XenstoreImplState *s, unsigned int dom_id,
+ unsigned int tx_id, const char *path,
+ const char *content)
+{
+ GByteArray *d = g_byte_array_new();
+ int err;
+
+ g_byte_array_append(d, (void *)content, strlen(content));
+ err = xs_impl_write(s, dom_id, tx_id, path, d);
+ g_byte_array_unref(d);
+ return err;
+}
+
+static void test_xs_node_simple(void)
+{
+ XenstoreImplState *s = xs_impl_create();
+ GList *items = NULL;
+ GByteArray *data= g_byte_array_new();
+ XsNode *old_root;
+ int err;
+
+ g_assert(s);
+
+ /* Read gives ENOENT when it should */
+ err = xs_impl_read(s, DOMID_GUEST, XBT_NULL, "foo", data);
+ g_assert(err == ENOENT);
+
+ /* Write works */
+ err = write_str(s, DOMID_GUEST, XBT_NULL, "some/relative/path",
+ "something");
+ g_assert(!err);
+
+ /* Read gives back what we wrote */
+ err = xs_impl_read(s, DOMID_GUEST, XBT_NULL, "some/relative/path", data);
+ g_assert(!err);
+ g_assert(data->len == strlen("something"));
+ g_assert(!memcmp(data->data, "something", data->len));
+
+ /* Even if we use an abolute path */
+ g_byte_array_set_size(data, 0);
+ err = xs_impl_read(s, DOMID_GUEST, XBT_NULL,
+ "/local/domain/1/some/relative/path", data);
+ g_assert(!err);
+ g_assert(data->len == strlen("something"));
+
+ /* Keep a copy, to force COW mode */
+ old_root = xs_node_ref(s->root);
+
+ /* Write works again */
+ err = write_str(s, DOMID_GUEST, XBT_NULL,
+ "/local/domain/1/some/relative/path2",
+ "something else");
+ g_assert(!err);
+
+ /* Overwrite an existing node */
+ err = write_str(s, DOMID_GUEST, XBT_NULL, "some/relative/path",
+ "another thing");
+ g_assert(!err);
+
+ /* We can list the two files we wrote */
+ err = xs_impl_directory(s, DOMID_GUEST, XBT_NULL, "some/relative", &items);
+ g_assert(!err);
+ g_assert(items);
+ g_assert(!strcmp(items->data, "path"));
+ g_assert(items->next);
+ g_assert(!strcmp(items->next->data, "path2"));
+ g_assert(!items->next->next);
+ g_list_free_full(items, g_free);
+
+ /* Write somewhere else which already existed */
+ err = write_str(s, DOMID_GUEST, XBT_NULL, "some/relative", "moredata");
+ g_assert(!err);
+
+ g_byte_array_set_size(data, 0);
+ err = xs_impl_read(s, DOMID_GUEST, XBT_NULL, "some/relative", data);
+ g_assert(!err);
+ g_assert(data->len == strlen("moredata"));
+ g_assert(!memcmp(data->data, "moredata", data->len));
+
+ /* Overwrite existing data */
+ err = write_str(s, DOMID_GUEST, XBT_NULL, "some/relative", "otherdata");
+ g_assert(!err);
+
+ g_byte_array_set_size(data, 0);
+ err = xs_impl_read(s, DOMID_GUEST, XBT_NULL, "some/relative", data);
+ g_assert(!err);
+ g_assert(data->len == strlen("otherdata"));
+ g_assert(!memcmp(data->data, "otherdata", data->len));
+
+ /* Remove the subtree */
+ err = xs_impl_rm(s, DOMID_GUEST, XBT_NULL, "some/relative");
+ g_assert(!err);
+
+ g_byte_array_set_size(data, 0);
+ err = xs_impl_read(s, DOMID_GUEST, XBT_NULL, "some/relative", data);
+ g_assert(err == ENOENT);
+ g_byte_array_unref(data);
+
+ xs_node_unref(old_root);
+ xs_impl_delete(s);
+}
+
+
+int main(int argc, char **argv)
+{
+ g_test_init(&argc, &argv, NULL);
+ module_call_init(MODULE_INIT_QOM);
+
+ g_test_add_func("/xs_node/simple", test_xs_node_simple);
+
+ return g_test_run();
+}
projects / people / pauldu / qemu.git / commitdiff