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+/*
+ * Mach Operating System
+ * Copyright (c) 1991,1990,1989 Carnegie Mellon University
+ * All Rights Reserved.
+ *
+ * Permission to use, copy, modify and distribute this software and its
+ * documentation is hereby granted, provided that both the copyright
+ * notice and this permission notice appear in all copies of the
+ * software, derivative works or modified versions, and any portions
+ * thereof, and that both notices appear in supporting documentation.
+ *
+ * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
+ * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
+ * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
+ *
+ * Carnegie Mellon requests users of this software to return to
+ *
+ * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
+ * School of Computer Science
+ * Carnegie Mellon University
+ * Pittsburgh PA 15213-3890
+ *
+ * any improvements or extensions that they make and grant Carnegie Mellon
+ * the rights to redistribute these changes.
+ */
+/*
+ * File: ipc/ipc_hash.c
+ * Author: Rich Draves
+ * Date: 1989
+ *
+ * Entry hash table operations.
+ */
+
+#include <mach/boolean.h>
+#include <mach/port.h>
+#include <kern/lock.h>
+#include <kern/kalloc.h>
+#include <ipc/port.h>
+#include <ipc/ipc_space.h>
+#include <ipc/ipc_object.h>
+#include <ipc/ipc_entry.h>
+#include <ipc/ipc_hash.h>
+#include <ipc/ipc_init.h>
+#include <ipc/ipc_types.h>
+
+#include <mach_ipc_debug.h>
+#if MACH_IPC_DEBUG
+#include <mach/kern_return.h>
+#include <mach_debug/hash_info.h>
+#include <vm/vm_map.h>
+#include <vm/vm_kern.h>
+#include <vm/vm_user.h>
+#endif
+
+
+
+/*
+ * Routine: ipc_hash_lookup
+ * Purpose:
+ * Converts (space, obj) -> (name, entry).
+ * Returns TRUE if an entry was found.
+ * Conditions:
+ * The space must be locked (read or write) throughout.
+ */
+
+boolean_t
+ipc_hash_lookup(space, obj, namep, entryp)
+ ipc_space_t space;
+ ipc_object_t obj;
+ mach_port_t *namep;
+ ipc_entry_t *entryp;
+{
+ return (ipc_hash_local_lookup(space, obj, namep, entryp) ||
+ ((space->is_tree_hash > 0) &&
+ ipc_hash_global_lookup(space, obj, namep,
+ (ipc_tree_entry_t *) entryp)));
+}
+
+/*
+ * Routine: ipc_hash_insert
+ * Purpose:
+ * Inserts an entry into the appropriate reverse hash table,
+ * so that ipc_hash_lookup will find it.
+ * Conditions:
+ * The space must be write-locked.
+ */
+
+void
+ipc_hash_insert(
+ ipc_space_t space,
+ ipc_object_t obj,
+ mach_port_t name,
+ ipc_entry_t entry)
+{
+ mach_port_index_t index;
+
+ index = MACH_PORT_INDEX(name);
+ if ((index < space->is_table_size) &&
+ (entry == &space->is_table[index]))
+ ipc_hash_local_insert(space, obj, index, entry);
+ else
+ ipc_hash_global_insert(space, obj, name,
+ (ipc_tree_entry_t) entry);
+}
+
+/*
+ * Routine: ipc_hash_delete
+ * Purpose:
+ * Deletes an entry from the appropriate reverse hash table.
+ * Conditions:
+ * The space must be write-locked.
+ */
+
+void
+ipc_hash_delete(
+ ipc_space_t space,
+ ipc_object_t obj,
+ mach_port_t name,
+ ipc_entry_t entry)
+{
+ mach_port_index_t index;
+
+ index = MACH_PORT_INDEX(name);
+ if ((index < space->is_table_size) &&
+ (entry == &space->is_table[index]))
+ ipc_hash_local_delete(space, obj, index, entry);
+ else
+ ipc_hash_global_delete(space, obj, name,
+ (ipc_tree_entry_t) entry);
+}
+
+/*
+ * The global reverse hash table holds splay tree entries.
+ * It is a simple open-chaining hash table with singly-linked buckets.
+ * Each bucket is locked separately, with an exclusive lock.
+ * Within each bucket, move-to-front is used.
+ */
+
+typedef natural_t ipc_hash_index_t;
+
+ipc_hash_index_t ipc_hash_global_size;
+ipc_hash_index_t ipc_hash_global_mask;
+
+#define IH_GLOBAL_HASH(space, obj) \
+ (((((ipc_hash_index_t) ((vm_offset_t)space)) >> 4) + \
+ (((ipc_hash_index_t) ((vm_offset_t)obj)) >> 6)) & \
+ ipc_hash_global_mask)
+
+typedef struct ipc_hash_global_bucket {
+ decl_simple_lock_data(, ihgb_lock_data)
+ ipc_tree_entry_t ihgb_head;
+} *ipc_hash_global_bucket_t;
+
+#define IHGB_NULL ((ipc_hash_global_bucket_t) 0)
+
+#define ihgb_lock_init(ihgb) simple_lock_init(&(ihgb)->ihgb_lock_data)
+#define ihgb_lock(ihgb) simple_lock(&(ihgb)->ihgb_lock_data)
+#define ihgb_unlock(ihgb) simple_unlock(&(ihgb)->ihgb_lock_data)
+
+ipc_hash_global_bucket_t ipc_hash_global_table;
+
+/*
+ * Routine: ipc_hash_global_lookup
+ * Purpose:
+ * Converts (space, obj) -> (name, entry).
+ * Looks in the global table, for splay tree entries.
+ * Returns TRUE if an entry was found.
+ * Conditions:
+ * The space must be locked (read or write) throughout.
+ */
+
+boolean_t
+ipc_hash_global_lookup(
+ ipc_space_t space,
+ ipc_object_t obj,
+ mach_port_t *namep,
+ ipc_tree_entry_t *entryp)
+{
+ ipc_hash_global_bucket_t bucket;
+ ipc_tree_entry_t this, *last;
+
+ assert(space != IS_NULL);
+ assert(obj != IO_NULL);
+
+ bucket = &ipc_hash_global_table[IH_GLOBAL_HASH(space, obj)];
+ ihgb_lock(bucket);
+
+ if ((this = bucket->ihgb_head) != ITE_NULL) {
+ if ((this->ite_object == obj) &&
+ (this->ite_space == space)) {
+ /* found it at front; no need to move */
+
+ *namep = this->ite_name;
+ *entryp = this;
+ } else for (last = &this->ite_next;
+ (this = *last) != ITE_NULL;
+ last = &this->ite_next) {
+ if ((this->ite_object == obj) &&
+ (this->ite_space == space)) {
+ /* found it; move to front */
+
+ *last = this->ite_next;
+ this->ite_next = bucket->ihgb_head;
+ bucket->ihgb_head = this;
+
+ *namep = this->ite_name;
+ *entryp = this;
+ break;
+ }
+ }
+ }
+
+ ihgb_unlock(bucket);
+ return this != ITE_NULL;
+}
+
+/*
+ * Routine: ipc_hash_global_insert
+ * Purpose:
+ * Inserts an entry into the global reverse hash table.
+ * Conditions:
+ * The space must be write-locked.
+ */
+
+void
+ipc_hash_global_insert(
+ ipc_space_t space,
+ ipc_object_t obj,
+ mach_port_t name,
+ ipc_tree_entry_t entry)
+{
+ ipc_hash_global_bucket_t bucket;
+
+
+ assert(entry->ite_name == name);
+ assert(space != IS_NULL);
+ assert(entry->ite_space == space);
+ assert(obj != IO_NULL);
+ assert(entry->ite_object == obj);
+
+ space->is_tree_hash++;
+ assert(space->is_tree_hash <= space->is_tree_total);
+
+ bucket = &ipc_hash_global_table[IH_GLOBAL_HASH(space, obj)];
+ ihgb_lock(bucket);
+
+ /* insert at front of bucket */
+
+ entry->ite_next = bucket->ihgb_head;
+ bucket->ihgb_head = entry;
+
+ ihgb_unlock(bucket);
+}
+
+/*
+ * Routine: ipc_hash_global_delete
+ * Purpose:
+ * Deletes an entry from the global reverse hash table.
+ * Conditions:
+ * The space must be write-locked.
+ */
+
+void
+ipc_hash_global_delete(
+ ipc_space_t space,
+ ipc_object_t obj,
+ mach_port_t name,
+ ipc_tree_entry_t entry)
+{
+ ipc_hash_global_bucket_t bucket;
+ ipc_tree_entry_t this, *last;
+
+ assert(entry->ite_name == name);
+ assert(space != IS_NULL);
+ assert(entry->ite_space == space);
+ assert(obj != IO_NULL);
+ assert(entry->ite_object == obj);
+
+ assert(space->is_tree_hash > 0);
+ space->is_tree_hash--;
+
+ bucket = &ipc_hash_global_table[IH_GLOBAL_HASH(space, obj)];
+ ihgb_lock(bucket);
+
+ for (last = &bucket->ihgb_head;
+ (this = *last) != ITE_NULL;
+ last = &this->ite_next) {
+ if (this == entry) {
+ /* found it; remove from bucket */
+
+ *last = this->ite_next;
+ break;
+ }
+ }
+ assert(this != ITE_NULL);
+
+ ihgb_unlock(bucket);
+}
+
+/*
+ * Each space has a local reverse hash table, which holds
+ * entries from the space's table. In fact, the hash table
+ * just uses a field (ie_index) in the table itself.
+ *
+ * The local hash table is an open-addressing hash table,
+ * which means that when a collision occurs, instead of
+ * throwing the entry into a bucket, the entry is rehashed
+ * to another position in the table. In this case the rehash
+ * is very simple: linear probing (ie, just increment the position).
+ * This simple rehash makes deletions tractable (they're still a pain),
+ * but it means that collisions tend to build up into clumps.
+ *
+ * Because at least one entry in the table (index 0) is always unused,
+ * there will always be room in the reverse hash table. If a table
+ * with n slots gets completely full, the reverse hash table will
+ * have one giant clump of n-1 slots and one free slot somewhere.
+ * Because entries are only entered into the reverse table if they
+ * are pure send rights (not receive, send-once, port-set,
+ * or dead-name rights), and free entries of course aren't entered,
+ * I expect the reverse hash table won't get unreasonably full.
+ *
+ * Ordered hash tables (Amble & Knuth, Computer Journal, v. 17, no. 2,
+ * pp. 135-142.) may be desirable here. They can dramatically help
+ * unsuccessful lookups. But unsuccessful lookups are almost always
+ * followed by insertions, and those slow down somewhat. They
+ * also can help deletions somewhat. Successful lookups aren't affected.
+ * So possibly a small win; probably nothing significant.
+ */
+
+#define IH_LOCAL_HASH(obj, size) \
+ ((((mach_port_index_t) (obj)) >> 6) % (size))
+
+/*
+ * Routine: ipc_hash_local_lookup
+ * Purpose:
+ * Converts (space, obj) -> (name, entry).
+ * Looks in the space's local table, for table entries.
+ * Returns TRUE if an entry was found.
+ * Conditions:
+ * The space must be locked (read or write) throughout.
+ */
+
+boolean_t
+ipc_hash_local_lookup(
+ ipc_space_t space,
+ ipc_object_t obj,
+ mach_port_t *namep,
+ ipc_entry_t *entryp)
+{
+ ipc_entry_t table;
+ ipc_entry_num_t size;
+ mach_port_index_t hindex, index;
+
+ assert(space != IS_NULL);
+ assert(obj != IO_NULL);
+
+ table = space->is_table;
+ size = space->is_table_size;
+ hindex = IH_LOCAL_HASH(obj, size);
+
+ /*
+ * Ideally, table[hindex].ie_index is the name we want.
+ * However, must check ie_object to verify this,
+ * because collisions can happen. In case of a collision,
+ * search farther along in the clump.
+ */
+
+ while ((index = table[hindex].ie_index) != 0) {
+ ipc_entry_t entry = &table[index];
+
+ if (entry->ie_object == obj) {
+ *namep = MACH_PORT_MAKEB(index, entry->ie_bits);
+ *entryp = entry;
+ return TRUE;
+ }
+
+ if (++hindex == size)
+ hindex = 0;
+ }
+
+ return FALSE;
+}
+
+/*
+ * Routine: ipc_hash_local_insert
+ * Purpose:
+ * Inserts an entry into the space's reverse hash table.
+ * Conditions:
+ * The space must be write-locked.
+ */
+
+void
+ipc_hash_local_insert(
+ ipc_space_t space,
+ ipc_object_t obj,
+ mach_port_index_t index,
+ ipc_entry_t entry)
+{
+ ipc_entry_t table;
+ ipc_entry_num_t size;
+ mach_port_index_t hindex;
+
+ assert(index != 0);
+ assert(space != IS_NULL);
+ assert(obj != IO_NULL);
+
+ table = space->is_table;
+ size = space->is_table_size;
+ hindex = IH_LOCAL_HASH(obj, size);
+
+ assert(entry == &table[index]);
+ assert(entry->ie_object == obj);
+
+ /*
+ * We want to insert at hindex, but there may be collisions.
+ * If a collision occurs, search for the end of the clump
+ * and insert there.
+ */
+
+ while (table[hindex].ie_index != 0) {
+ if (++hindex == size)
+ hindex = 0;
+ }
+
+ table[hindex].ie_index = index;
+}
+
+/*
+ * Routine: ipc_hash_local_delete
+ * Purpose:
+ * Deletes an entry from the space's reverse hash table.
+ * Conditions:
+ * The space must be write-locked.
+ */
+
+void
+ipc_hash_local_delete(
+ ipc_space_t space,
+ ipc_object_t obj,
+ mach_port_index_t index,
+ ipc_entry_t entry)
+{
+ ipc_entry_t table;
+ ipc_entry_num_t size;
+ mach_port_index_t hindex, dindex;
+
+ assert(index != MACH_PORT_NULL);
+ assert(space != IS_NULL);
+ assert(obj != IO_NULL);
+
+ table = space->is_table;
+ size = space->is_table_size;
+ hindex = IH_LOCAL_HASH(obj, size);
+
+ assert(entry == &table[index]);
+ assert(entry->ie_object == obj);
+
+ /*
+ * First check we have the right hindex for this index.
+ * In case of collision, we have to search farther
+ * along in this clump.
+ */
+
+ while (table[hindex].ie_index != index) {
+ if (table[hindex].ie_index == 0)
+ {
+ static int gak = 0;
+ if (gak == 0)
+ {
+ printf("gak! entry wasn't in hash table!\n");
+ gak = 1;
+ }
+ return;
+ }
+ if (++hindex == size)
+ hindex = 0;
+ }
+
+ /*
+ * Now we want to set table[hindex].ie_index = 0.
+ * But if we aren't the last index in a clump,
+ * this might cause problems for lookups of objects
+ * farther along in the clump that are displaced
+ * due to collisions. Searches for them would fail
+ * at hindex instead of succeeding.
+ *
+ * So we must check the clump after hindex for objects
+ * that are so displaced, and move one up to the new hole.
+ *
+ * hindex - index of new hole in the clump
+ * dindex - index we are checking for a displaced object
+ *
+ * When we move a displaced object up into the hole,
+ * it creates a new hole, and we have to repeat the process
+ * until we get to the end of the clump.
+ */
+
+ for (dindex = hindex; index != 0; hindex = dindex) {
+ for (;;) {
+ mach_port_index_t tindex;
+ ipc_object_t tobj;
+
+ if (++dindex == size)
+ dindex = 0;
+ assert(dindex != hindex);
+
+ /* are we at the end of the clump? */
+
+ index = table[dindex].ie_index;
+ if (index == 0)
+ break;
+
+ /* is this a displaced object? */
+
+ tobj = table[index].ie_object;
+ assert(tobj != IO_NULL);
+ tindex = IH_LOCAL_HASH(tobj, size);
+
+ if ((dindex < hindex) ?
+ ((dindex < tindex) && (tindex <= hindex)) :
+ ((dindex < tindex) || (tindex <= hindex)))
+ break;
+ }
+
+ table[hindex].ie_index = index;
+ }
+}
+
+/*
+ * Routine: ipc_hash_init
+ * Purpose:
+ * Initialize the reverse hash table implementation.
+ */
+
+void
+ipc_hash_init(void)
+{
+ ipc_hash_index_t i;
+
+ /* if not configured, initialize ipc_hash_global_size */
+
+ if (ipc_hash_global_size == 0) {
+ ipc_hash_global_size = ipc_tree_entry_max >> 8;
+ if (ipc_hash_global_size < 32)
+ ipc_hash_global_size = 32;
+ }
+
+ /* make sure it is a power of two */
+
+ ipc_hash_global_mask = ipc_hash_global_size - 1;
+ if ((ipc_hash_global_size & ipc_hash_global_mask) != 0) {
+ natural_t bit;
+
+ /* round up to closest power of two */
+
+ for (bit = 1;; bit <<= 1) {
+ ipc_hash_global_mask |= bit;
+ ipc_hash_global_size = ipc_hash_global_mask + 1;
+
+ if ((ipc_hash_global_size & ipc_hash_global_mask) == 0)
+ break;
+ }
+ }
+
+ /* allocate ipc_hash_global_table */
+
+ ipc_hash_global_table = (ipc_hash_global_bucket_t)
+ kalloc((vm_size_t) (ipc_hash_global_size *
+ sizeof(struct ipc_hash_global_bucket)));
+ assert(ipc_hash_global_table != IHGB_NULL);
+
+ /* and initialize it */
+
+ for (i = 0; i < ipc_hash_global_size; i++) {
+ ipc_hash_global_bucket_t bucket;
+
+ bucket = &ipc_hash_global_table[i];
+ ihgb_lock_init(bucket);
+ bucket->ihgb_head = ITE_NULL;
+ }
+}
+
+#if MACH_IPC_DEBUG
+
+/*
+ * Routine: ipc_hash_info
+ * Purpose:
+ * Return information about the global reverse hash table.
+ * Fills the buffer with as much information as possible
+ * and returns the desired size of the buffer.
+ * Conditions:
+ * Nothing locked. The caller should provide
+ * possibly-pageable memory.
+ */
+
+
+ipc_hash_index_t
+ipc_hash_info(
+ hash_info_bucket_t *info,
+ mach_msg_type_number_t count)
+{
+ ipc_hash_index_t i;
+
+ if (ipc_hash_global_size < count)
+ count = ipc_hash_global_size;
+
+ for (i = 0; i < count; i++) {
+ ipc_hash_global_bucket_t bucket = &ipc_hash_global_table[i];
+ unsigned int bucket_count = 0;
+ ipc_tree_entry_t entry;
+
+ ihgb_lock(bucket);
+ for (entry = bucket->ihgb_head;
+ entry != ITE_NULL;
+ entry = entry->ite_next)
+ bucket_count++;
+ ihgb_unlock(bucket);
+
+ /* don't touch pageable memory while holding locks */
+ info[i].hib_count = bucket_count;
+ }
+
+ return ipc_hash_global_size;
+}
+
+#endif /* MACH_IPC_DEBUG */
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