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-rw-r--r--hw/i386/kvm/xenstore_impl.c1927
1 files changed, 1927 insertions, 0 deletions
diff --git a/hw/i386/kvm/xenstore_impl.c b/hw/i386/kvm/xenstore_impl.c
new file mode 100644
index 0000000000..305fe75519
--- /dev/null
+++ b/hw/i386/kvm/xenstore_impl.c
@@ -0,0 +1,1927 @@
+/*
+ * QEMU Xen emulation: The actual implementation of XenStore
+ *
+ * Copyright © 2023 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Authors: David Woodhouse <dwmw2@infradead.org>, Paul Durrant <paul@xen.org>
+ *
+ * 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 "qom/object.h"
+
+#include "hw/xen/xen.h"
+
+#include "xen_xenstore.h"
+#include "xenstore_impl.h"
+
+#include "hw/xen/interface/io/xs_wire.h"
+
+#define XS_MAX_WATCHES 128
+#define XS_MAX_DOMAIN_NODES 1000
+#define XS_MAX_NODE_SIZE 2048
+#define XS_MAX_TRANSACTIONS 10
+#define XS_MAX_PERMS_PER_NODE 5
+
+#define XS_VALID_CHARS "abcdefghijklmnopqrstuvwxyz" \
+ "ABCDEFGHIJKLMNOPQRSTUVWXYZ" \
+ "0123456789-/_"
+
+typedef struct XsNode {
+ uint32_t ref;
+ GByteArray *content;
+ GList *perms;
+ GHashTable *children;
+ uint64_t gencnt;
+ bool deleted_in_tx;
+ bool modified_in_tx;
+ unsigned int serialized_tx;
+#ifdef XS_NODE_UNIT_TEST
+ gchar *name; /* debug only */
+#endif
+} XsNode;
+
+typedef struct XsWatch {
+ struct XsWatch *next;
+ xs_impl_watch_fn *cb;
+ void *cb_opaque;
+ char *token;
+ unsigned int dom_id;
+ int rel_prefix;
+} XsWatch;
+
+typedef struct XsTransaction {
+ XsNode *root;
+ unsigned int nr_nodes;
+ unsigned int base_tx;
+ unsigned int tx_id;
+ unsigned int dom_id;
+} XsTransaction;
+
+struct XenstoreImplState {
+ XsNode *root;
+ unsigned int nr_nodes;
+ GHashTable *watches;
+ unsigned int nr_domu_watches;
+ GHashTable *transactions;
+ unsigned int nr_domu_transactions;
+ unsigned int root_tx;
+ unsigned int last_tx;
+ bool serialized;
+};
+
+
+static void nobble_tx(gpointer key, gpointer value, gpointer user_data)
+{
+ unsigned int *new_tx_id = user_data;
+ XsTransaction *tx = value;
+
+ if (tx->base_tx == *new_tx_id) {
+ /* Transactions based on XBT_NULL will always fail */
+ tx->base_tx = XBT_NULL;
+ }
+}
+
+static inline unsigned int next_tx(struct XenstoreImplState *s)
+{
+ unsigned int tx_id;
+
+ /* Find the next TX id which isn't either XBT_NULL or in use. */
+ do {
+ tx_id = ++s->last_tx;
+ } while (tx_id == XBT_NULL || tx_id == s->root_tx ||
+ g_hash_table_lookup(s->transactions, GINT_TO_POINTER(tx_id)));
+
+ /*
+ * It is vanishingly unlikely, but ensure that no outstanding transaction
+ * is based on the (previous incarnation of the) newly-allocated TX id.
+ */
+ g_hash_table_foreach(s->transactions, nobble_tx, &tx_id);
+
+ return tx_id;
+}
+
+static inline XsNode *xs_node_new(void)
+{
+ XsNode *n = g_new0(XsNode, 1);
+ n->ref = 1;
+
+#ifdef XS_NODE_UNIT_TEST
+ nr_xs_nodes++;
+ xs_node_list = g_list_prepend(xs_node_list, n);
+#endif
+ return n;
+}
+
+static inline XsNode *xs_node_ref(XsNode *n)
+{
+ /* With just 10 transactions, it can never get anywhere near this. */
+ g_assert(n->ref < INT_MAX);
+
+ g_assert(n->ref);
+ n->ref++;
+ return n;
+}
+
+static inline void xs_node_unref(XsNode *n)
+{
+ if (!n) {
+ return;
+ }
+ g_assert(n->ref);
+ if (--n->ref) {
+ return;
+ }
+
+ if (n->content) {
+ g_byte_array_unref(n->content);
+ }
+ if (n->perms) {
+ g_list_free_full(n->perms, g_free);
+ }
+ 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
+ g_free(n);
+}
+
+char *xs_perm_as_string(unsigned int perm, unsigned int domid)
+{
+ char letter;
+
+ switch (perm) {
+ case XS_PERM_READ | XS_PERM_WRITE:
+ letter = 'b';
+ break;
+ case XS_PERM_READ:
+ letter = 'r';
+ break;
+ case XS_PERM_WRITE:
+ letter = 'w';
+ break;
+ case XS_PERM_NONE:
+ default:
+ letter = 'n';
+ break;
+ }
+
+ return g_strdup_printf("%c%u", letter, domid);
+}
+
+static gpointer do_perm_copy(gconstpointer src, gpointer user_data)
+{
+ return g_strdup(src);
+}
+
+static XsNode *xs_node_create(const char *name, GList *perms)
+{
+ XsNode *n = xs_node_new();
+
+#ifdef XS_NODE_UNIT_TEST
+ if (name) {
+ n->name = g_strdup(name);
+ }
+#endif
+
+ n->perms = g_list_copy_deep(perms, do_perm_copy, NULL);
+
+ return n;
+}
+
+/* For copying from one hash table to another using g_hash_table_foreach() */
+static void do_child_insert(gpointer key, gpointer value, gpointer user_data)
+{
+ g_hash_table_insert(user_data, g_strdup(key), xs_node_ref(value));
+}
+
+static XsNode *xs_node_copy(XsNode *old)
+{
+ XsNode *n = xs_node_new();
+
+ n->gencnt = old->gencnt;
+
+#ifdef XS_NODE_UNIT_TEST
+ if (n->name) {
+ n->name = g_strdup(old->name);
+ }
+#endif
+
+ assert(old);
+ if (old->children) {
+ n->children = g_hash_table_new_full(g_str_hash, g_str_equal, g_free,
+ (GDestroyNotify)xs_node_unref);
+ g_hash_table_foreach(old->children, do_child_insert, n->children);
+ }
+ if (old->perms) {
+ n->perms = g_list_copy_deep(old->perms, do_perm_copy, NULL);
+ }
+ if (old->content) {
+ n->content = g_byte_array_ref(old->content);
+ }
+ return n;
+}
+
+/* Returns true if it made a change to the hash table */
+static bool xs_node_add_child(XsNode *n, const char *path_elem, XsNode *child)
+{
+ assert(!strchr(path_elem, '/'));
+
+ if (!child) {
+ assert(n->children);
+ return g_hash_table_remove(n->children, path_elem);
+ }
+
+#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,
+ (GDestroyNotify)xs_node_unref);
+ }
+
+ /*
+ * The documentation for g_hash_table_insert() says that it "returns a
+ * boolean value to indicate whether the newly added value was already
+ * in the hash table or not."
+ *
+ * It could perhaps be clearer that returning TRUE means it wasn't,
+ */
+ return 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;
+ void *op_opaque2;
+
+ GList *watches;
+ unsigned int dom_id;
+ unsigned int tx_id;
+
+ /* The number of nodes which will exist in the tree if this op succeeds. */
+ unsigned int new_nr_nodes;
+
+ /*
+ * 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;
+ bool in_transaction;
+
+ /* Tracking during recursion so we know which is first. */
+ bool deleted_in_tx;
+};
+
+static void fire_watches(struct walk_op *op, bool parents)
+{
+ GList *l = NULL;
+ XsWatch *w;
+
+ if (!op->mutating || op->in_transaction) {
+ return;
+ }
+
+ if (parents) {
+ l = op->watches;
+ }
+
+ w = g_hash_table_lookup(op->s->watches, op->path);
+ while (w || l) {
+ if (!w) {
+ /* Fire the parent nodes from 'op' if asked to */
+ w = l->data;
+ l = l->next;
+ continue;
+ }
+
+ assert(strlen(op->path) > w->rel_prefix);
+ w->cb(w->cb_opaque, op->path + w->rel_prefix, w->token);
+
+ w = w->next;
+ }
+}
+
+static int xs_node_add_content(XsNode **n, struct walk_op *op)
+{
+ GByteArray *data = op->op_opaque;
+
+ if (op->dom_id) {
+ /*
+ * The real XenStored includes permissions and names of child nodes
+ * in the calculated datasize but life's too short. For a single
+ * tenant internal XenStore, we don't have to be quite as pedantic.
+ */
+ if (data->len > XS_MAX_NODE_SIZE) {
+ return E2BIG;
+ }
+ }
+ /* 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(data);
+ if (op->tx_id != XBT_NULL) {
+ (*n)->modified_in_tx = true;
+ }
+ 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 node_rm_recurse(gpointer key, gpointer value, gpointer user_data)
+{
+ struct walk_op *op = user_data;
+ int path_len = strlen(op->path);
+ int key_len = strlen(key);
+ XsNode *n = value;
+ bool this_inplace = op->inplace;
+
+ if (n->ref != 1) {
+ op->inplace = 0;
+ }
+
+ assert(key_len + path_len + 2 <= sizeof(op->path));
+ op->path[path_len] = '/';
+ memcpy(op->path + path_len + 1, key, key_len + 1);
+
+ if (n->children) {
+ g_hash_table_foreach_remove(n->children, node_rm_recurse, op);
+ }
+ op->new_nr_nodes--;
+
+ /*
+ * Fire watches on *this* node but not the parents because they are
+ * going to be deleted too, so the watch will fire for them anyway.
+ */
+ fire_watches(op, false);
+ op->path[path_len] = '\0';
+
+ /*
+ * Actually deleting the child here is just an optimisation; if we
+ * don't then the final unref on the topmost victim will just have
+ * to cascade down again repeating all the g_hash_table_foreach()
+ * calls.
+ */
+ return this_inplace;
+}
+
+static XsNode *xs_node_copy_deleted(XsNode *old, struct walk_op *op);
+static void copy_deleted_recurse(gpointer key, gpointer value,
+ gpointer user_data)
+{
+ struct walk_op *op = user_data;
+ GHashTable *siblings = op->op_opaque2;
+ XsNode *n = xs_node_copy_deleted(value, op);
+
+ /*
+ * Reinsert the deleted_in_tx copy of the node into the parent's
+ * 'children' hash table. Having stashed it from op->op_opaque2
+ * before the recursive call to xs_node_copy_deleted() scribbled
+ * over it.
+ */
+ g_hash_table_insert(siblings, g_strdup(key), n);
+}
+
+static XsNode *xs_node_copy_deleted(XsNode *old, struct walk_op *op)
+{
+ XsNode *n = xs_node_new();
+
+ n->gencnt = old->gencnt;
+
+#ifdef XS_NODE_UNIT_TEST
+ if (old->name) {
+ n->name = g_strdup(old->name);
+ }
+#endif
+
+ if (old->children) {
+ n->children = g_hash_table_new_full(g_str_hash, g_str_equal, g_free,
+ (GDestroyNotify)xs_node_unref);
+ op->op_opaque2 = n->children;
+ g_hash_table_foreach(old->children, copy_deleted_recurse, op);
+ }
+ if (old->perms) {
+ n->perms = g_list_copy_deep(old->perms, do_perm_copy, NULL);
+ }
+ n->deleted_in_tx = true;
+ /* If it gets resurrected we only fire a watch if it lost its content */
+ if (old->content) {
+ n->modified_in_tx = true;
+ }
+ op->new_nr_nodes--;
+ return n;
+}
+
+static int xs_node_rm(XsNode **n, struct walk_op *op)
+{
+ bool this_inplace = op->inplace;
+
+ if (op->tx_id != XBT_NULL) {
+ /* It's not trivial to do inplace handling for this one */
+ XsNode *old = *n;
+ *n = xs_node_copy_deleted(old, op);
+ xs_node_unref(old);
+ return 0;
+ }
+
+ /* Fire watches for, and count, nodes in the subtree which get deleted */
+ if ((*n)->children) {
+ g_hash_table_foreach_remove((*n)->children, node_rm_recurse, op);
+ }
+ op->new_nr_nodes--;
+
+ if (this_inplace) {
+ xs_node_unref(*n);
+ }
+ *n = NULL;
+ return 0;
+}
+
+static int xs_node_get_perms(XsNode **n, struct walk_op *op)
+{
+ GList **perms = op->op_opaque;
+
+ assert(op->inplace);
+ assert(*n);
+
+ *perms = g_list_copy_deep((*n)->perms, do_perm_copy, NULL);
+ return 0;
+}
+
+static void parse_perm(const char *perm, char *letter, unsigned int *dom_id)
+{
+ unsigned int n = sscanf(perm, "%c%u", letter, dom_id);
+
+ assert(n == 2);
+}
+
+static bool can_access(unsigned int dom_id, GList *perms, const char *letters)
+{
+ unsigned int i, n;
+ char perm_letter;
+ unsigned int perm_dom_id;
+ bool access;
+
+ if (dom_id == 0) {
+ return true;
+ }
+
+ n = g_list_length(perms);
+ assert(n >= 1);
+
+ /*
+ * The dom_id of the first perm is the owner, and the owner always has
+ * read-write access.
+ */
+ parse_perm(g_list_nth_data(perms, 0), &perm_letter, &perm_dom_id);
+ if (dom_id == perm_dom_id) {
+ return true;
+ }
+
+ /*
+ * The letter of the first perm specified the default access for all other
+ * domains.
+ */
+ access = !!strchr(letters, perm_letter);
+ for (i = 1; i < n; i++) {
+ parse_perm(g_list_nth_data(perms, i), &perm_letter, &perm_dom_id);
+ if (dom_id != perm_dom_id) {
+ continue;
+ }
+ access = !!strchr(letters, perm_letter);
+ }
+
+ return access;
+}
+
+static int xs_node_set_perms(XsNode **n, struct walk_op *op)
+{
+ GList *perms = op->op_opaque;
+
+ if (op->dom_id) {
+ unsigned int perm_dom_id;
+ char perm_letter;
+
+ /* A guest may not change permissions on nodes it does not own */
+ if (!can_access(op->dom_id, (*n)->perms, "")) {
+ return EPERM;
+ }
+
+ /* A guest may not change the owner of a node it owns. */
+ parse_perm(perms->data, &perm_letter, &perm_dom_id);
+ if (perm_dom_id != op->dom_id) {
+ return EPERM;
+ }
+
+ if (g_list_length(perms) > XS_MAX_PERMS_PER_NODE) {
+ return ENOSPC;
+ }
+ }
+
+ /* 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)->perms) {
+ g_list_free_full((*n)->perms, g_free);
+ }
+ (*n)->perms = g_list_copy_deep(perms, do_perm_copy, NULL);
+ if (op->tx_id != XBT_NULL) {
+ (*n)->modified_in_tx = true;
+ }
+ 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;
+ XsWatch *watch;
+ int err;
+
+ namelen = strlen(op->path);
+ watch = g_hash_table_lookup(op->s->watches, 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->ref != 1) {
+ op->inplace = false;
+ }
+
+ if (!child_name) {
+ const char *letters = op->mutating ? "wb" : "rb";
+
+ if (!can_access(op->dom_id, old->perms, letters)) {
+ err = EACCES;
+ goto out;
+ }
+
+ /* This is the actual node on which the operation shall be performed */
+ err = op->op_fn(n, op);
+ if (!err) {
+ fire_watches(op, true);
+ }
+ goto out;
+ }
+
+ /* 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) {
+ if (child->deleted_in_tx) {
+ assert(child->ref == 1);
+ /* Cannot actually set child->deleted_in_tx = false until later */
+ }
+ 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) {
+ assert(op->mutating);
+
+ if (!can_access(op->dom_id, old->perms, "wb")) {
+ err = EACCES;
+ goto out;
+ }
+
+ if (op->dom_id && op->new_nr_nodes >= XS_MAX_DOMAIN_NODES) {
+ err = ENOSPC;
+ goto out;
+ }
+
+ child = xs_node_create(child_name, old->perms);
+ op->new_nr_nodes++;
+
+ /*
+ * 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 {
+ err = ENOENT;
+ goto out;
+ }
+
+ /*
+ * If there's a watch on this node, add it to the list to be fired
+ * (with the correct full pathname for the modified node) at the end.
+ */
+ if (watch) {
+ op->watches = g_list_append(op->watches, watch);
+ }
+
+ /*
+ * 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 (watch) {
+ op->watches = g_list_remove(op->watches, watch);
+ }
+
+ 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);
+ }
+ goto out;
+ }
+
+ /*
+ * 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);
+ }
+
+ /*
+ * If we resurrected a deleted_in_tx node, we can mark it as no longer
+ * deleted now that we know the overall operation has succeeded.
+ */
+ if (op->create_dirs && child && child->deleted_in_tx) {
+ op->new_nr_nodes++;
+ child->deleted_in_tx = false;
+ }
+
+ /*
+ * The child may be NULL here, for a remove operation. Either way,
+ * xs_node_add_child() will do the right thing and return a value
+ * indicating whether it changed the parent's hash table or not.
+ *
+ * We bump the parent gencnt if it adds a child that we *didn't*
+ * steal from it in the first place, or if child==NULL and was
+ * thus removed (whether we stole it earlier and didn't put it
+ * back, or xs_node_add_child() actually removed it now).
+ */
+ if ((xs_node_add_child(*n, child_name, child) && !stole_child) || !child) {
+ (*n)->gencnt++;
+ }
+
+ out:
+ op->path[namelen] = '\0';
+ if (!namelen) {
+ assert(!op->watches);
+ /*
+ * On completing the recursion back up the path walk and reaching the
+ * top, assign the new node count if the operation was successful. If
+ * the main tree was changed, bump its tx ID so that outstanding
+ * transactions correctly fail. But don't bump it every time; only
+ * if it makes a difference.
+ */
+ if (!err && op->mutating) {
+ if (!op->in_transaction) {
+ if (op->s->root_tx != op->s->last_tx) {
+ op->s->root_tx = next_tx(op->s);
+ }
+ op->s->nr_nodes = op->new_nr_nodes;
+ } else {
+ XsTransaction *tx = g_hash_table_lookup(op->s->transactions,
+ GINT_TO_POINTER(op->tx_id));
+ assert(tx);
+ tx->nr_nodes = op->new_nr_nodes;
+ }
+ }
+ }
+ return err;
+}
+
+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), (GCompareFunc)strcmp);
+}
+
+/* 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);
+ }
+
+ if (op->op_opaque2) {
+ *(uint64_t *)op->op_opaque2 = (*n)->gencnt;
+ }
+
+ return 0;
+}
+
+static int validate_path(char *outpath, const char *userpath,
+ unsigned int dom_id)
+{
+ size_t i, pathlen = strlen(userpath);
+
+ if (!pathlen || userpath[pathlen] == '/' || strstr(userpath, "//")) {
+ return EINVAL;
+ }
+ for (i = 0; i < pathlen; i++) {
+ if (!strchr(XS_VALID_CHARS, userpath[i])) {
+ return EINVAL;
+ }
+ }
+ if (userpath[0] == '/') {
+ if (pathlen > XENSTORE_ABS_PATH_MAX) {
+ return E2BIG;
+ }
+ memcpy(outpath, userpath, pathlen + 1);
+ } else {
+ if (pathlen > XENSTORE_REL_PATH_MAX) {
+ return E2BIG;
+ }
+ snprintf(outpath, XENSTORE_ABS_PATH_MAX, "/local/domain/%u/%s", dom_id,
+ userpath);
+ }
+ return 0;
+}
+
+
+static int init_walk_op(XenstoreImplState *s, struct walk_op *op,
+ xs_transaction_t tx_id, unsigned int dom_id,
+ const char *path, XsNode ***rootp)
+{
+ int ret = validate_path(op->path, path, dom_id);
+ if (ret) {
+ return ret;
+ }
+
+ /*
+ * 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->watches = NULL;
+ op->path[0] = '\0';
+ op->inplace = true;
+ op->mutating = false;
+ op->create_dirs = false;
+ op->in_transaction = false;
+ op->dom_id = dom_id;
+ op->tx_id = tx_id;
+ op->s = s;
+
+ if (tx_id == XBT_NULL) {
+ *rootp = &s->root;
+ op->new_nr_nodes = s->nr_nodes;
+ } else {
+ XsTransaction *tx = g_hash_table_lookup(s->transactions,
+ GINT_TO_POINTER(tx_id));
+ if (!tx) {
+ return ENOENT;
+ }
+ *rootp = &tx->root;
+ op->new_nr_nodes = tx->nr_nodes;
+ op->in_transaction = true;
+ }
+
+ return 0;
+}
+
+int xs_impl_read(XenstoreImplState *s, unsigned int dom_id,
+ xs_transaction_t 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.
+ */
+ 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,
+ xs_transaction_t tx_id, const char *path, GByteArray *data)
+{
+ /*
+ * The data GByteArray shall exist, will be freed by caller. You are
+ * free to use g_byte_array_steal() and keep the data. Or just ref it.
+ */
+ 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,
+ xs_transaction_t tx_id, const char *path,
+ uint64_t *gencnt, GList **items)
+{
+ /*
+ * The items are (char *) to be freed by caller. Although it's consumed
+ * immediately so if you want to change it to (const char *) and keep
+ * them, go ahead and change the caller.
+ */
+ 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;
+ op.op_opaque2 = gencnt;
+ return xs_node_walk(n, &op);
+}
+
+int xs_impl_transaction_start(XenstoreImplState *s, unsigned int dom_id,
+ xs_transaction_t *tx_id)
+{
+ XsTransaction *tx;
+
+ if (*tx_id != XBT_NULL) {
+ return EINVAL;
+ }
+
+ if (dom_id && s->nr_domu_transactions >= XS_MAX_TRANSACTIONS) {
+ return ENOSPC;
+ }
+
+ tx = g_new0(XsTransaction, 1);
+
+ tx->nr_nodes = s->nr_nodes;
+ tx->tx_id = next_tx(s);
+ tx->base_tx = s->root_tx;
+ tx->root = xs_node_ref(s->root);
+ tx->dom_id = dom_id;
+
+ g_hash_table_insert(s->transactions, GINT_TO_POINTER(tx->tx_id), tx);
+ if (dom_id) {
+ s->nr_domu_transactions++;
+ }
+ *tx_id = tx->tx_id;
+ return 0;
+}
+
+static gboolean tx_commit_walk(gpointer key, gpointer value,
+ gpointer user_data)
+{
+ struct walk_op *op = user_data;
+ int path_len = strlen(op->path);
+ int key_len = strlen(key);
+ bool fire_parents = true;
+ XsWatch *watch;
+ XsNode *n = value;
+
+ if (n->ref != 1) {
+ return false;
+ }
+
+ if (n->deleted_in_tx) {
+ /*
+ * We fire watches on our parents if we are the *first* node
+ * to be deleted (the topmost one). This matches the behaviour
+ * when deleting in the live tree.
+ */
+ fire_parents = !op->deleted_in_tx;
+
+ /* Only used on the way down so no need to clear it later */
+ op->deleted_in_tx = true;
+ }
+
+ assert(key_len + path_len + 2 <= sizeof(op->path));
+ op->path[path_len] = '/';
+ memcpy(op->path + path_len + 1, key, key_len + 1);
+
+ watch = g_hash_table_lookup(op->s->watches, op->path);
+ if (watch) {
+ op->watches = g_list_append(op->watches, watch);
+ }
+
+ if (n->children) {
+ g_hash_table_foreach_remove(n->children, tx_commit_walk, op);
+ }
+
+ if (watch) {
+ op->watches = g_list_remove(op->watches, watch);
+ }
+
+ /*
+ * Don't fire watches if this node was only copied because a
+ * descendent was changed. The modified_in_tx flag indicates the
+ * ones which were really changed.
+ */
+ if (n->modified_in_tx || n->deleted_in_tx) {
+ fire_watches(op, fire_parents);
+ n->modified_in_tx = false;
+ }
+ op->path[path_len] = '\0';
+
+ /* Deleted nodes really do get expunged when we commit */
+ return n->deleted_in_tx;
+}
+
+static int transaction_commit(XenstoreImplState *s, XsTransaction *tx)
+{
+ struct walk_op op;
+ XsNode **n;
+
+ if (s->root_tx != tx->base_tx) {
+ return EAGAIN;
+ }
+ xs_node_unref(s->root);
+ s->root = tx->root;
+ tx->root = NULL;
+ s->root_tx = tx->tx_id;
+ s->nr_nodes = tx->nr_nodes;
+
+ init_walk_op(s, &op, XBT_NULL, tx->dom_id, "/", &n);
+ op.deleted_in_tx = false;
+ op.mutating = true;
+
+ /*
+ * Walk the new root and fire watches on any node which has a
+ * refcount of one (which is therefore unique to this transaction).
+ */
+ if (s->root->children) {
+ g_hash_table_foreach_remove(s->root->children, tx_commit_walk, &op);
+ }
+
+ return 0;
+}
+
+int xs_impl_transaction_end(XenstoreImplState *s, unsigned int dom_id,
+ xs_transaction_t tx_id, bool commit)
+{
+ int ret = 0;
+ XsTransaction *tx = g_hash_table_lookup(s->transactions,
+ GINT_TO_POINTER(tx_id));
+
+ if (!tx || tx->dom_id != dom_id) {
+ return ENOENT;
+ }
+
+ if (commit) {
+ ret = transaction_commit(s, tx);
+ }
+
+ g_hash_table_remove(s->transactions, GINT_TO_POINTER(tx_id));
+ if (dom_id) {
+ assert(s->nr_domu_transactions);
+ s->nr_domu_transactions--;
+ }
+ return ret;
+}
+
+int xs_impl_rm(XenstoreImplState *s, unsigned int dom_id,
+ xs_transaction_t tx_id, const char *path)
+{
+ 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,
+ xs_transaction_t tx_id, const char *path, GList **perms)
+{
+ 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_perms;
+ op.op_opaque = perms;
+ return xs_node_walk(n, &op);
+}
+
+static void is_valid_perm(gpointer data, gpointer user_data)
+{
+ char *perm = data;
+ bool *valid = user_data;
+ char letter;
+ unsigned int dom_id;
+
+ if (!*valid) {
+ return;
+ }
+
+ if (sscanf(perm, "%c%u", &letter, &dom_id) != 2) {
+ *valid = false;
+ return;
+ }
+
+ switch (letter) {
+ case 'n':
+ case 'r':
+ case 'w':
+ case 'b':
+ break;
+
+ default:
+ *valid = false;
+ break;
+ }
+}
+
+int xs_impl_set_perms(XenstoreImplState *s, unsigned int dom_id,
+ xs_transaction_t tx_id, const char *path, GList *perms)
+{
+ struct walk_op op;
+ XsNode **n;
+ bool valid = true;
+ int ret;
+
+ if (!g_list_length(perms)) {
+ return EINVAL;
+ }
+
+ g_list_foreach(perms, is_valid_perm, &valid);
+ if (!valid) {
+ return EINVAL;
+ }
+
+ ret = init_walk_op(s, &op, tx_id, dom_id, path, &n);
+ if (ret) {
+ return ret;
+ }
+ op.op_fn = xs_node_set_perms;
+ op.op_opaque = perms;
+ op.mutating = true;
+ return xs_node_walk(n, &op);
+}
+
+static int do_xs_impl_watch(XenstoreImplState *s, unsigned int dom_id,
+ const char *path, const char *token,
+ xs_impl_watch_fn fn, void *opaque)
+
+{
+ char abspath[XENSTORE_ABS_PATH_MAX + 1];
+ XsWatch *w, *l;
+ int ret;
+
+ ret = validate_path(abspath, path, dom_id);
+ if (ret) {
+ return ret;
+ }
+
+ /* Check for duplicates */
+ l = w = g_hash_table_lookup(s->watches, abspath);
+ while (w) {
+ if (!g_strcmp0(token, w->token) && opaque == w->cb_opaque &&
+ fn == w->cb && dom_id == w->dom_id) {
+ return EEXIST;
+ }
+ w = w->next;
+ }
+
+ if (dom_id && s->nr_domu_watches >= XS_MAX_WATCHES) {
+ return E2BIG;
+ }
+
+ w = g_new0(XsWatch, 1);
+ w->token = g_strdup(token);
+ w->cb = fn;
+ w->cb_opaque = opaque;
+ w->dom_id = dom_id;
+ w->rel_prefix = strlen(abspath) - strlen(path);
+
+ /* l was looked up above when checking for duplicates */
+ if (l) {
+ w->next = l->next;
+ l->next = w;
+ } else {
+ g_hash_table_insert(s->watches, g_strdup(abspath), w);
+ }
+ if (dom_id) {
+ s->nr_domu_watches++;
+ }
+
+ return 0;
+}
+
+int xs_impl_watch(XenstoreImplState *s, unsigned int dom_id, const char *path,
+ const char *token, xs_impl_watch_fn fn, void *opaque)
+{
+ int ret = do_xs_impl_watch(s, dom_id, path, token, fn, opaque);
+
+ if (!ret) {
+ /* A new watch should fire immediately */
+ fn(opaque, path, token);
+ }
+
+ return ret;
+}
+
+static XsWatch *free_watch(XenstoreImplState *s, XsWatch *w)
+{
+ XsWatch *next = w->next;
+
+ if (w->dom_id) {
+ assert(s->nr_domu_watches);
+ s->nr_domu_watches--;
+ }
+
+ g_free(w->token);
+ g_free(w);
+
+ return next;
+}
+
+int xs_impl_unwatch(XenstoreImplState *s, unsigned int dom_id,
+ const char *path, const char *token,
+ xs_impl_watch_fn fn, void *opaque)
+{
+ char abspath[XENSTORE_ABS_PATH_MAX + 1];
+ XsWatch *w, **l;
+ int ret;
+
+ ret = validate_path(abspath, path, dom_id);
+ if (ret) {
+ return ret;
+ }
+
+ w = g_hash_table_lookup(s->watches, abspath);
+ if (!w) {
+ return ENOENT;
+ }
+
+ /*
+ * The hash table contains the first element of a list of
+ * watches. Removing the first element in the list is a
+ * special case because we have to update the hash table to
+ * point to the next (or remove it if there's nothing left).
+ */
+ if (!g_strcmp0(token, w->token) && fn == w->cb && opaque == w->cb_opaque &&
+ dom_id == w->dom_id) {
+ if (w->next) {
+ /* Insert the previous 'next' into the hash table */
+ g_hash_table_insert(s->watches, g_strdup(abspath), w->next);
+ } else {
+ /* Nothing left; remove from hash table */
+ g_hash_table_remove(s->watches, abspath);
+ }
+ free_watch(s, w);
+ return 0;
+ }
+
+ /*
+ * We're all done messing with the hash table because the element
+ * it points to has survived the cull. Now it's just a simple
+ * linked list removal operation.
+ */
+ for (l = &w->next; *l; l = &w->next) {
+ w = *l;
+
+ if (!g_strcmp0(token, w->token) && fn == w->cb &&
+ opaque != w->cb_opaque && dom_id == w->dom_id) {
+ *l = free_watch(s, w);
+ return 0;
+ }
+ }
+
+ return ENOENT;
+}
+
+int xs_impl_reset_watches(XenstoreImplState *s, unsigned int dom_id)
+{
+ char **watch_paths;
+ guint nr_watch_paths;
+ guint i;
+
+ watch_paths = (char **)g_hash_table_get_keys_as_array(s->watches,
+ &nr_watch_paths);
+
+ for (i = 0; i < nr_watch_paths; i++) {
+ XsWatch *w1 = g_hash_table_lookup(s->watches, watch_paths[i]);
+ XsWatch *w2, *w, **l;
+
+ /*
+ * w1 is the original list. The hash table has this pointer.
+ * w2 is the head of our newly-filtered list.
+ * w and l are temporary for processing. w is somewhat redundant
+ * with *l but makes my eyes bleed less.
+ */
+
+ w = w2 = w1;
+ l = &w;
+ while (w) {
+ if (w->dom_id == dom_id) {
+ /* If we're freeing the head of the list, bump w2 */
+ if (w2 == w) {
+ w2 = w->next;
+ }
+ *l = free_watch(s, w);
+ } else {
+ l = &w->next;
+ }
+ w = *l;
+ }
+ /*
+ * If the head of the list survived the cull, we don't need to
+ * touch the hash table and we're done with this path. Else...
+ */
+ if (w1 != w2) {
+ g_hash_table_steal(s->watches, watch_paths[i]);
+
+ /*
+ * It was already freed. (Don't worry, this whole thing is
+ * single-threaded and nobody saw it in the meantime). And
+ * having *stolen* it, we now own the watch_paths[i] string
+ * so if we don't give it back to the hash table, we need
+ * to free it.
+ */
+ if (w2) {
+ g_hash_table_insert(s->watches, watch_paths[i], w2);
+ } else {
+ g_free(watch_paths[i]);
+ }
+ }
+ }
+ g_free(watch_paths);
+ return 0;
+}
+
+static void xs_tx_free(void *_tx)
+{
+ XsTransaction *tx = _tx;
+ if (tx->root) {
+ xs_node_unref(tx->root);
+ }
+ g_free(tx);
+}
+
+XenstoreImplState *xs_impl_create(unsigned int dom_id)
+{
+ XenstoreImplState *s = g_new0(XenstoreImplState, 1);
+ GList *perms;
+
+ s->watches = g_hash_table_new_full(g_str_hash, g_str_equal, g_free, NULL);
+ s->transactions = g_hash_table_new_full(g_direct_hash, g_direct_equal,
+ NULL, xs_tx_free);
+
+ perms = g_list_append(NULL, xs_perm_as_string(XS_PERM_NONE, 0));
+ s->root = xs_node_create("/", perms);
+ g_list_free_full(perms, g_free);
+ s->nr_nodes = 1;
+
+ s->root_tx = s->last_tx = 1;
+ return s;
+}
+
+
+static void clear_serialized_tx(gpointer key, gpointer value, gpointer opaque)
+{
+ XsNode *n = value;
+
+ n->serialized_tx = XBT_NULL;
+ if (n->children) {
+ g_hash_table_foreach(n->children, clear_serialized_tx, NULL);
+ }
+}
+
+static void clear_tx_serialized_tx(gpointer key, gpointer value,
+ gpointer opaque)
+{
+ XsTransaction *t = value;
+
+ clear_serialized_tx(NULL, t->root, NULL);
+}
+
+static void write_be32(GByteArray *save, uint32_t val)
+{
+ uint32_t be = htonl(val);
+ g_byte_array_append(save, (void *)&be, sizeof(be));
+}
+
+
+struct save_state {
+ GByteArray *bytes;
+ unsigned int tx_id;
+};
+
+#define MODIFIED_IN_TX (1U << 0)
+#define DELETED_IN_TX (1U << 1)
+#define NODE_REF (1U << 2)
+
+static void save_node(gpointer key, gpointer value, gpointer opaque)
+{
+ struct save_state *ss = opaque;
+ XsNode *n = value;
+ char *name = key;
+ uint8_t flag = 0;
+
+ /* Child nodes (i.e. anything but the root) have a name */
+ if (name) {
+ g_byte_array_append(ss->bytes, key, strlen(key) + 1);
+ }
+
+ /*
+ * If we already wrote this node, refer to the previous copy.
+ * There's no rename/move in XenStore, so all we need to find
+ * it is the tx_id of the transation in which it exists. Which
+ * may be the root tx.
+ */
+ if (n->serialized_tx != XBT_NULL) {
+ flag = NODE_REF;
+ g_byte_array_append(ss->bytes, &flag, 1);
+ write_be32(ss->bytes, n->serialized_tx);
+ } else {
+ GList *l;
+ n->serialized_tx = ss->tx_id;
+
+ if (n->modified_in_tx) {
+ flag |= MODIFIED_IN_TX;
+ }
+ if (n->deleted_in_tx) {
+ flag |= DELETED_IN_TX;
+ }
+ g_byte_array_append(ss->bytes, &flag, 1);
+
+ if (n->content) {
+ write_be32(ss->bytes, n->content->len);
+ g_byte_array_append(ss->bytes, n->content->data, n->content->len);
+ } else {
+ write_be32(ss->bytes, 0);
+ }
+
+ for (l = n->perms; l; l = l->next) {
+ g_byte_array_append(ss->bytes, l->data, strlen(l->data) + 1);
+ }
+ /* NUL termination after perms */
+ g_byte_array_append(ss->bytes, (void *)"", 1);
+
+ if (n->children) {
+ g_hash_table_foreach(n->children, save_node, ss);
+ }
+ /* NUL termination after children (child name is NUL) */
+ g_byte_array_append(ss->bytes, (void *)"", 1);
+ }
+}
+
+static void save_tree(struct save_state *ss, uint32_t tx_id, XsNode *root)
+{
+ write_be32(ss->bytes, tx_id);
+ ss->tx_id = tx_id;
+ save_node(NULL, root, ss);
+}
+
+static void save_tx(gpointer key, gpointer value, gpointer opaque)
+{
+ uint32_t tx_id = GPOINTER_TO_INT(key);
+ struct save_state *ss = opaque;
+ XsTransaction *n = value;
+
+ write_be32(ss->bytes, n->base_tx);
+ write_be32(ss->bytes, n->dom_id);
+
+ save_tree(ss, tx_id, n->root);
+}
+
+static void save_watch(gpointer key, gpointer value, gpointer opaque)
+{
+ struct save_state *ss = opaque;
+ XsWatch *w = value;
+
+ /* We only save the *guest* watches. */
+ if (w->dom_id) {
+ gpointer relpath = key + w->rel_prefix;
+ g_byte_array_append(ss->bytes, relpath, strlen(relpath) + 1);
+ g_byte_array_append(ss->bytes, (void *)w->token, strlen(w->token) + 1);
+ }
+}
+
+GByteArray *xs_impl_serialize(XenstoreImplState *s)
+{
+ struct save_state ss;
+
+ ss.bytes = g_byte_array_new();
+
+ /*
+ * node = flags [ real_node / node_ref ]
+ * flags = uint8_t (MODIFIED_IN_TX | DELETED_IN_TX | NODE_REF)
+ * node_ref = tx_id (in which the original version of this node exists)
+ * real_node = content perms child* NUL
+ * content = len data
+ * len = uint32_t
+ * data = uint8_t{len}
+ * perms = perm* NUL
+ * perm = asciiz
+ * child = name node
+ * name = asciiz
+ *
+ * tree = tx_id node
+ * tx_id = uint32_t
+ *
+ * transaction = base_tx_id dom_id tree
+ * base_tx_id = uint32_t
+ * dom_id = uint32_t
+ *
+ * tx_list = tree transaction* XBT_NULL
+ *
+ * watch = path token
+ * path = asciiz
+ * token = asciiz
+ *
+ * watch_list = watch* NUL
+ *
+ * xs_serialize_stream = last_tx tx_list watch_list
+ * last_tx = uint32_t
+ */
+
+ /* Clear serialized_tx in every node. */
+ if (s->serialized) {
+ clear_serialized_tx(NULL, s->root, NULL);
+ g_hash_table_foreach(s->transactions, clear_tx_serialized_tx, NULL);
+ }
+
+ s->serialized = true;
+
+ write_be32(ss.bytes, s->last_tx);
+ save_tree(&ss, s->root_tx, s->root);
+ g_hash_table_foreach(s->transactions, save_tx, &ss);
+
+ write_be32(ss.bytes, XBT_NULL);
+
+ g_hash_table_foreach(s->watches, save_watch, &ss);
+ g_byte_array_append(ss.bytes, (void *)"", 1);
+
+ return ss.bytes;
+}
+
+struct unsave_state {
+ char path[XENSTORE_ABS_PATH_MAX + 1];
+ XenstoreImplState *s;
+ GByteArray *bytes;
+ uint8_t *d;
+ size_t l;
+ bool root_walk;
+};
+
+static int consume_be32(struct unsave_state *us, unsigned int *val)
+{
+ uint32_t d;
+
+ if (us->l < sizeof(d)) {
+ return -EINVAL;
+ }
+ memcpy(&d, us->d, sizeof(d));
+ *val = ntohl(d);
+ us->d += sizeof(d);
+ us->l -= sizeof(d);
+ return 0;
+}
+
+static int consume_string(struct unsave_state *us, char **str, size_t *len)
+{
+ size_t l;
+
+ if (!us->l) {
+ return -EINVAL;
+ }
+
+ l = strnlen((void *)us->d, us->l);
+ if (l == us->l) {
+ return -EINVAL;
+ }
+
+ if (str) {
+ *str = (void *)us->d;
+ }
+ if (len) {
+ *len = l;
+ }
+
+ us->d += l + 1;
+ us->l -= l + 1;
+ return 0;
+}
+
+static XsNode *lookup_node(XsNode *n, char *path)
+{
+ char *slash = strchr(path, '/');
+ XsNode *child;
+
+ if (path[0] == '\0') {
+ return n;
+ }
+
+ if (slash) {
+ *slash = '\0';
+ }
+
+ if (!n->children) {
+ return NULL;
+ }
+ child = g_hash_table_lookup(n->children, path);
+ if (!slash) {
+ return child;
+ }
+
+ *slash = '/';
+ if (!child) {
+ return NULL;
+ }
+ return lookup_node(child, slash + 1);
+}
+
+static XsNode *lookup_tx_node(struct unsave_state *us, unsigned int tx_id)
+{
+ XsTransaction *t;
+ if (tx_id == us->s->root_tx) {
+ return lookup_node(us->s->root, us->path + 1);
+ }
+
+ t = g_hash_table_lookup(us->s->transactions, GINT_TO_POINTER(tx_id));
+ if (!t) {
+ return NULL;
+ }
+ g_assert(t->root);
+ return lookup_node(t->root, us->path + 1);
+}
+
+static void count_child_nodes(gpointer key, gpointer value, gpointer user_data)
+{
+ unsigned int *nr_nodes = user_data;
+ XsNode *n = value;
+
+ (*nr_nodes)++;
+
+ if (n->children) {
+ g_hash_table_foreach(n->children, count_child_nodes, nr_nodes);
+ }
+}
+
+static int consume_node(struct unsave_state *us, XsNode **nodep,
+ unsigned int *nr_nodes)
+{
+ XsNode *n = NULL;
+ uint8_t flags;
+ int ret;
+
+ if (us->l < 1) {
+ return -EINVAL;
+ }
+ flags = us->d[0];
+ us->d++;
+ us->l--;
+
+ if (flags == NODE_REF) {
+ unsigned int tx;
+
+ ret = consume_be32(us, &tx);
+ if (ret) {
+ return ret;
+ }
+
+ n = lookup_tx_node(us, tx);
+ if (!n) {
+ return -EINVAL;
+ }
+ n->ref++;
+ if (n->children) {
+ g_hash_table_foreach(n->children, count_child_nodes, nr_nodes);
+ }
+ } else {
+ uint32_t datalen;
+
+ if (flags & ~(DELETED_IN_TX | MODIFIED_IN_TX)) {
+ return -EINVAL;
+ }
+ n = xs_node_new();
+
+ if (flags & DELETED_IN_TX) {
+ n->deleted_in_tx = true;
+ }
+ if (flags & MODIFIED_IN_TX) {
+ n->modified_in_tx = true;
+ }
+ ret = consume_be32(us, &datalen);
+ if (ret) {
+ xs_node_unref(n);
+ return -EINVAL;
+ }
+ if (datalen) {
+ if (datalen > us->l) {
+ xs_node_unref(n);
+ return -EINVAL;
+ }
+
+ GByteArray *node_data = g_byte_array_new();
+ g_byte_array_append(node_data, us->d, datalen);
+ us->d += datalen;
+ us->l -= datalen;
+ n->content = node_data;
+
+ if (us->root_walk) {
+ n->modified_in_tx = true;
+ }
+ }
+ while (1) {
+ char *perm = NULL;
+ size_t permlen = 0;
+
+ ret = consume_string(us, &perm, &permlen);
+ if (ret) {
+ xs_node_unref(n);
+ return ret;
+ }
+
+ if (!permlen) {
+ break;
+ }
+
+ n->perms = g_list_append(n->perms, g_strdup(perm));
+ }
+
+ /* Now children */
+ while (1) {
+ size_t childlen;
+ char *childname;
+ char *pathend;
+ XsNode *child = NULL;
+
+ ret = consume_string(us, &childname, &childlen);
+ if (ret) {
+ xs_node_unref(n);
+ return ret;
+ }
+
+ if (!childlen) {
+ break;
+ }
+
+ pathend = us->path + strlen(us->path);
+ strncat(us->path, "/", sizeof(us->path) - 1);
+ strncat(us->path, childname, sizeof(us->path) - 1);
+
+ ret = consume_node(us, &child, nr_nodes);
+ *pathend = '\0';
+ if (ret) {
+ xs_node_unref(n);
+ return ret;
+ }
+ g_assert(child);
+ xs_node_add_child(n, childname, child);
+ }
+
+ /*
+ * If the node has no data and no children we still want to fire
+ * a watch on it.
+ */
+ if (us->root_walk && !n->children) {
+ n->modified_in_tx = true;
+ }
+ }
+
+ if (!n->deleted_in_tx) {
+ (*nr_nodes)++;
+ }
+
+ *nodep = n;
+ return 0;
+}
+
+static int consume_tree(struct unsave_state *us, XsTransaction *t)
+{
+ int ret;
+
+ ret = consume_be32(us, &t->tx_id);
+ if (ret) {
+ return ret;
+ }
+
+ if (t->tx_id > us->s->last_tx) {
+ return -EINVAL;
+ }
+
+ us->path[0] = '\0';
+
+ return consume_node(us, &t->root, &t->nr_nodes);
+}
+
+int xs_impl_deserialize(XenstoreImplState *s, GByteArray *bytes,
+ unsigned int dom_id, xs_impl_watch_fn watch_fn,
+ void *watch_opaque)
+{
+ struct unsave_state us;
+ XsTransaction base_t = { 0 };
+ int ret;
+
+ us.s = s;
+ us.bytes = bytes;
+ us.d = bytes->data;
+ us.l = bytes->len;
+
+ xs_impl_reset_watches(s, dom_id);
+ g_hash_table_remove_all(s->transactions);
+
+ xs_node_unref(s->root);
+ s->root = NULL;
+ s->root_tx = s->last_tx = XBT_NULL;
+
+ ret = consume_be32(&us, &s->last_tx);
+ if (ret) {
+ return ret;
+ }
+
+ /*
+ * Consume the base tree into a transaction so that watches can be
+ * fired as we commit it. By setting us.root_walk we cause the nodes
+ * to be marked as 'modified_in_tx' as they are created, so that the
+ * watches are triggered on them.
+ */
+ base_t.dom_id = dom_id;
+ base_t.base_tx = XBT_NULL;
+ us.root_walk = true;
+ ret = consume_tree(&us, &base_t);
+ if (ret) {
+ return ret;
+ }
+ us.root_walk = false;
+
+ /*
+ * Commit the transaction now while the refcount on all nodes is 1.
+ * Note that we haven't yet reinstated the *guest* watches but that's
+ * OK because we don't want the guest to see any changes. Even any
+ * backend nodes which get recreated should be *precisely* as they
+ * were before the migration. Back ends may have been instantiated
+ * already, and will see the frontend magically blink into existence
+ * now (well, from the aio_bh which fires the watches). It's their
+ * responsibility to rebuild everything precisely as it was before.
+ */
+ ret = transaction_commit(s, &base_t);
+ if (ret) {
+ return ret;
+ }
+
+ while (1) {
+ unsigned int base_tx;
+ XsTransaction *t;
+
+ ret = consume_be32(&us, &base_tx);
+ if (ret) {
+ return ret;
+ }
+ if (base_tx == XBT_NULL) {
+ break;
+ }
+
+ t = g_new0(XsTransaction, 1);
+ t->base_tx = base_tx;
+
+ ret = consume_be32(&us, &t->dom_id);
+ if (!ret) {
+ ret = consume_tree(&us, t);
+ }
+ if (ret) {
+ g_free(t);
+ return ret;
+ }
+ g_assert(t->root);
+ if (t->dom_id) {
+ s->nr_domu_transactions++;
+ }
+ g_hash_table_insert(s->transactions, GINT_TO_POINTER(t->tx_id), t);
+ }
+
+ while (1) {
+ char *path, *token;
+ size_t pathlen, toklen;
+
+ ret = consume_string(&us, &path, &pathlen);
+ if (ret) {
+ return ret;
+ }
+ if (!pathlen) {
+ break;
+ }
+
+ ret = consume_string(&us, &token, &toklen);
+ if (ret) {
+ return ret;
+ }
+
+ if (!watch_fn) {
+ continue;
+ }
+
+ ret = do_xs_impl_watch(s, dom_id, path, token, watch_fn, watch_opaque);
+ if (ret) {
+ return ret;
+ }
+ }
+
+ if (us.l) {
+ return -EINVAL;
+ }
+
+ return 0;
+}
generated by cgit v1.2.3 (git 2.26.2) at 2025-02-24 12:20:38 +0000