diff options
Diffstat (limited to 'hw/i386/kvm/xenstore_impl.c')
| -rw-r--r-- | hw/i386/kvm/xenstore_impl.c | 1927 |
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; +} |