cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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id_table.c (3207B)

      1/*
      2 * Copyright (c) 2011 Chelsio Communications.  All rights reserved.
      3 *
      4 * This software is available to you under a choice of one of two
      5 * licenses.  You may choose to be licensed under the terms of the GNU
      6 * General Public License (GPL) Version 2, available from the file
      7 * COPYING in the main directory of this source tree, or the
      8 * OpenIB.org BSD license below:
      9 *
     10 *     Redistribution and use in source and binary forms, with or
     11 *     without modification, are permitted provided that the following
     12 *     conditions are met:
     13 *
     14 *      - Redistributions of source code must retain the above
     15 *        copyright notice, this list of conditions and the following
     16 *        disclaimer.
     17 *
     18 *      - Redistributions in binary form must reproduce the above
     19 *        copyright notice, this list of conditions and the following
     20 *        disclaimer in the documentation and/or other materials
     21 *        provided with the distribution.
     22 *
     23 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
     24 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
     25 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
     26 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
     27 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
     28 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
     29 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
     30 * SOFTWARE.
     31 */
     32#include <linux/kernel.h>
     33#include <linux/random.h>
     34#include "iw_cxgb4.h"
     35
     36#define RANDOM_SKIP 16
     37
     38/*
     39 * Trivial bitmap-based allocator. If the random flag is set, the
     40 * allocator is designed to:
     41 * - pseudo-randomize the id returned such that it is not trivially predictable.
     42 * - avoid reuse of recently used id (at the expense of predictability)
     43 */
     44u32 c4iw_id_alloc(struct c4iw_id_table *alloc)
     45{
     46	unsigned long flags;
     47	u32 obj;
     48
     49	spin_lock_irqsave(&alloc->lock, flags);
     50
     51	obj = find_next_zero_bit(alloc->table, alloc->max, alloc->last);
     52	if (obj >= alloc->max)
     53		obj = find_first_zero_bit(alloc->table, alloc->max);
     54
     55	if (obj < alloc->max) {
     56		if (alloc->flags & C4IW_ID_TABLE_F_RANDOM)
     57			alloc->last += prandom_u32() % RANDOM_SKIP;
     58		else
     59			alloc->last = obj + 1;
     60		if (alloc->last >= alloc->max)
     61			alloc->last = 0;
     62		__set_bit(obj, alloc->table);
     63		obj += alloc->start;
     64	} else
     65		obj = -1;
     66
     67	spin_unlock_irqrestore(&alloc->lock, flags);
     68	return obj;
     69}
     70
     71void c4iw_id_free(struct c4iw_id_table *alloc, u32 obj)
     72{
     73	unsigned long flags;
     74
     75	obj -= alloc->start;
     76
     77	spin_lock_irqsave(&alloc->lock, flags);
     78	__clear_bit(obj, alloc->table);
     79	spin_unlock_irqrestore(&alloc->lock, flags);
     80}
     81
     82int c4iw_id_table_alloc(struct c4iw_id_table *alloc, u32 start, u32 num,
     83			u32 reserved, u32 flags)
     84{
     85	alloc->start = start;
     86	alloc->flags = flags;
     87	if (flags & C4IW_ID_TABLE_F_RANDOM)
     88		alloc->last = prandom_u32() % RANDOM_SKIP;
     89	else
     90		alloc->last = 0;
     91	alloc->max = num;
     92	spin_lock_init(&alloc->lock);
     93	alloc->table = bitmap_zalloc(num, GFP_KERNEL);
     94	if (!alloc->table)
     95		return -ENOMEM;
     96
     97	if (!(alloc->flags & C4IW_ID_TABLE_F_EMPTY))
     98		bitmap_set(alloc->table, 0, reserved);
     99
    100	return 0;
    101}
    102
    103void c4iw_id_table_free(struct c4iw_id_table *alloc)
    104{
    105	bitmap_free(alloc->table);
    106}