id_table.c

Go to the documentation of this file.

/*-
 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
 *
 * Copyright (c) 2011-2013 Chelsio Communications.  All rights reserved.
 *
 * This software is available to you under a choice of one of two
 * licenses.  You may choose to be licensed under the terms of the GNU
 * General Public License (GPL) Version 2, available from the file
 * COPYING in the main directory of this source tree, or the
 * OpenIB.org BSD license below:
 *
 *     Redistribution and use in source and binary forms, with or
 *     without modification, are permitted provided that the following
 *     conditions are met:
 *
 *      - Redistributions of source code must retain the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer.
 *
 *      - Redistributions in binary form must reproduce the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer in the documentation and/or other materials
 *        provided with the distribution.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
 
#include "opt_inet.h"
 
#ifdef TCP_OFFLOAD
#include <sys/libkern.h>
#include "iw_cxgbe.h"
 
#define RANDOM_SKIP 16
 
/*
 * Trivial bitmap-based allocator. If the random flag is set, the
 * allocator is designed to:
 * - pseudo-randomize the id returned such that it is not trivially predictable.
 * - avoid reuse of recently used id (at the expense of predictability)
 */
u32 c4iw_id_alloc(struct c4iw_id_table *alloc)
{
        unsigned long flags;
        u32 obj;
 
        spin_lock_irqsave(&alloc->lock, flags);
 
        obj = find_next_zero_bit(alloc->table, alloc->max, alloc->last);
        if (obj >= alloc->max)
                obj = find_first_zero_bit(alloc->table, alloc->max);
 
        if (obj < alloc->max) {
                if (alloc->flags & C4IW_ID_TABLE_F_RANDOM)
                        alloc->last += arc4random() % RANDOM_SKIP;
                else
                        alloc->last = obj + 1;
                if (alloc->last >= alloc->max)
                        alloc->last = 0;
                set_bit(obj, alloc->table);
                obj += alloc->start;
        } else
                obj = -1;
 
        spin_unlock_irqrestore(&alloc->lock, flags);
        return obj;
}
 
void c4iw_id_free(struct c4iw_id_table *alloc, u32 obj)
{
        unsigned long flags;
 
        obj -= alloc->start;
        BUG_ON((int)obj < 0);
 
        spin_lock_irqsave(&alloc->lock, flags);
        clear_bit(obj, alloc->table);
        spin_unlock_irqrestore(&alloc->lock, flags);
}
 
int c4iw_id_table_alloc(struct c4iw_id_table *alloc, u32 start, u32 num,
                        u32 reserved, u32 flags)
{
        int i;
 
        alloc->start = start;
        alloc->flags = flags;
        if (flags & C4IW_ID_TABLE_F_RANDOM)
                alloc->last = arc4random() % RANDOM_SKIP;
        else
                alloc->last = 0;
        alloc->max  = num;
        spin_lock_init(&alloc->lock);
        alloc->table = kmalloc(BITS_TO_LONGS(num) * sizeof(long),
                                GFP_KERNEL);
        if (!alloc->table)
                return -ENOMEM;
 
        bitmap_zero(alloc->table, num);
        if (!(alloc->flags & C4IW_ID_TABLE_F_EMPTY))
                for (i = 0; i < reserved; ++i)
                        set_bit(i, alloc->table);
 
        return 0;
}
 
void c4iw_id_table_free(struct c4iw_id_table *alloc)
{
        kfree(alloc->table);
}
#endif