diff options
Diffstat (limited to 'hw/i386/kvm/xenstore_impl.c')
| -rw-r--r-- | hw/i386/kvm/xenstore_impl.c | 253 |
1 files changed, 238 insertions, 15 deletions
diff --git a/hw/i386/kvm/xenstore_impl.c b/hw/i386/kvm/xenstore_impl.c index 9e10a31bea..9c2348835f 100644 --- a/hw/i386/kvm/xenstore_impl.c +++ b/hw/i386/kvm/xenstore_impl.c @@ -37,9 +37,20 @@ typedef struct XsNode { #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; + struct XenstoreImplState { XsNode *root; unsigned int nr_nodes; + GHashTable *watches; + unsigned int nr_domu_watches; }; static inline XsNode *xs_node_new(void) @@ -146,6 +157,7 @@ struct walk_op { void *op_opaque; void *op_opaque2; + GList *watches; unsigned int dom_id; /* The number of nodes which will exist in the tree if this op succeeds. */ @@ -166,6 +178,35 @@ struct walk_op { bool create_dirs; }; +static void fire_watches(struct walk_op *op, bool parents) +{ + GList *l = NULL; + XsWatch *w; + + if (!op->mutating) { + 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; @@ -213,6 +254,8 @@ static int xs_node_get_content(XsNode **n, struct walk_op *op) 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; @@ -220,12 +263,23 @@ static int node_rm_recurse(gpointer key, gpointer value, gpointer user_data) 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() @@ -238,7 +292,7 @@ static int xs_node_rm(XsNode **n, struct walk_op *op) { bool this_inplace = op->inplace; - /* Keep count of the nodes in the subtree which gets deleted. */ + /* 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); } @@ -269,9 +323,11 @@ static int xs_node_walk(XsNode **n, struct walk_op *op) 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]) { @@ -292,6 +348,9 @@ static int xs_node_walk(XsNode **n, struct walk_op *op) 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; } @@ -334,10 +393,23 @@ static int xs_node_walk(XsNode **n, struct walk_op *op) } /* + * 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. */ @@ -375,6 +447,7 @@ static int xs_node_walk(XsNode **n, struct walk_op *op) 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. @@ -457,6 +530,7 @@ static int init_walk_op(XenstoreImplState *s, struct walk_op *op, * 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; @@ -589,38 +663,187 @@ int xs_impl_set_perms(XenstoreImplState *s, unsigned int dom_id, int xs_impl_watch(XenstoreImplState *s, unsigned int dom_id, const char *path, const char *token, xs_impl_watch_fn fn, void *opaque) { - /* - * 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/${domid}/ - */ - return ENOSYS; + char abspath[XENSTORE_ABS_PATH_MAX + 1]; + XsWatch *w, *l; + int ret; + + ret = validate_path(abspath, path, dom_id); + if (ret) { + return ret; + } + + /* Check for duplicates */ + l = w = g_hash_table_lookup(s->watches, abspath); + while (w) { + if (!g_strcmp0(token, w->token) && opaque == w->cb_opaque && + fn == w->cb && dom_id == w->dom_id) { + return EEXIST; + } + w = w->next; + } + + if (dom_id && s->nr_domu_watches >= XS_MAX_WATCHES) { + return E2BIG; + } + + w = g_new0(XsWatch, 1); + w->token = g_strdup(token); + w->cb = fn; + w->cb_opaque = opaque; + w->dom_id = dom_id; + w->rel_prefix = strlen(abspath) - strlen(path); + + /* l was looked up above when checking for duplicates */ + if (l) { + w->next = l->next; + l->next = w; + } else { + g_hash_table_insert(s->watches, g_strdup(abspath), w); + } + if (dom_id) { + s->nr_domu_watches++; + } + + /* A new watch should fire immediately */ + fn(opaque, path, token); + + return 0; +} + +static XsWatch *free_watch(XenstoreImplState *s, XsWatch *w) +{ + XsWatch *next = w->next; + + if (w->dom_id) { + assert(s->nr_domu_watches); + s->nr_domu_watches--; + } + + g_free(w->token); + g_free(w); + + return next; } int xs_impl_unwatch(XenstoreImplState *s, unsigned int dom_id, const char *path, const char *token, xs_impl_watch_fn fn, void *opaque) { + char abspath[XENSTORE_ABS_PATH_MAX + 1]; + XsWatch *w, **l; + int ret; + + ret = validate_path(abspath, path, dom_id); + if (ret) { + return ret; + } + + w = g_hash_table_lookup(s->watches, abspath); + if (!w) { + return ENOENT; + } + /* - * When calling the callback @fn, note that the path should - * precisely match the relative path that the guest provided, even - * if it was a relative path which needed to be prefixed with - * /local/domain/${domid}/ + * 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). */ - return ENOSYS; + 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) { - /* Remove the watch that matches all four criteria */ - return ENOSYS; + 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; } 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->nr_nodes = 1; s->root = xs_node_new(); #ifdef XS_NODE_UNIT_TEST |