| /* |
| * 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 "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; |
| GHashTable *children; |
| uint64_t gencnt; |
| #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; |
| }; |
| |
| |
| 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->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); |
| } |
| |
| /* 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), xs_node_ref(value)); |
| } |
| |
| static XsNode *xs_node_copy(XsNode *old) |
| { |
| XsNode *n = xs_node_new(); |
| |
| n->gencnt = old->gencnt; |
| 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_insert, n->children); |
| } |
| if (old && 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; |
| }; |
| |
| 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); |
| 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 int xs_node_rm(XsNode **n, struct walk_op *op) |
| { |
| bool this_inplace = op->inplace; |
| |
| /* 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; |
| } |
| |
| /* |
| * 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) { |
| /* 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) { |
| 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) { |
| if (op->dom_id && op->new_nr_nodes >= XS_MAX_DOMAIN_NODES) { |
| err = ENOSPC; |
| goto out; |
| } |
| op->new_nr_nodes++; |
| 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 { |
| 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); |
| } |
| |
| /* |
| * 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 int transaction_commit(XenstoreImplState *s, XsTransaction *tx) |
| { |
| 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; |
| |
| /* |
| * XX: Walk the new root and fire watches on any node which has a |
| * refcount of one (which is therefore unique to this transaction). |
| */ |
| 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) |
| { |
| /* |
| * The perms are (char *) in the <perm-as-string> wire format to be |
| * freed by the caller. |
| */ |
| return ENOSYS; |
| } |
| |
| int xs_impl_set_perms(XenstoreImplState *s, unsigned int dom_id, |
| xs_transaction_t tx_id, const char *path, GList *perms) |
| { |
| /* |
| * The perms are (const char *) in the <perm-as-string> wire format. |
| */ |
| return ENOSYS; |
| } |
| |
| int 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++; |
| } |
| |
| /* A new watch should fire immediately */ |
| fn(opaque, path, token); |
| |
| return 0; |
| } |
| |
| 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(void) |
| { |
| XenstoreImplState *s = g_new0(XenstoreImplState, 1); |
| |
| 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); |
| s->nr_nodes = 1; |
| s->root = xs_node_new(); |
| #ifdef XS_NODE_UNIT_TEST |
| s->root->name = g_strdup("/"); |
| #endif |
| |
| s->root_tx = s->last_tx = 1; |
| return s; |
| } |
