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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find_bit.c (3053B)

      1// SPDX-License-Identifier: GPL-2.0-or-later
      2/* bit search implementation
      3 *
      4 * Copied from lib/find_bit.c to tools/lib/find_bit.c
      5 *
      6 * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
      7 * Written by David Howells (dhowells@redhat.com)
      8 *
      9 * Copyright (C) 2008 IBM Corporation
     10 * 'find_last_bit' is written by Rusty Russell <rusty@rustcorp.com.au>
     11 * (Inspired by David Howell's find_next_bit implementation)
     12 *
     13 * Rewritten by Yury Norov <yury.norov@gmail.com> to decrease
     14 * size and improve performance, 2015.
     15 */
     16
     17#include <linux/bitops.h>
     18#include <linux/bitmap.h>
     19#include <linux/kernel.h>
     20
     21#if !defined(find_next_bit) || !defined(find_next_zero_bit) || \
     22		!defined(find_next_and_bit)
     23
     24/*
     25 * This is a common helper function for find_next_bit, find_next_zero_bit, and
     26 * find_next_and_bit. The differences are:
     27 *  - The "invert" argument, which is XORed with each fetched word before
     28 *    searching it for one bits.
     29 *  - The optional "addr2", which is anded with "addr1" if present.
     30 */
     31unsigned long _find_next_bit(const unsigned long *addr1,
     32		const unsigned long *addr2, unsigned long nbits,
     33		unsigned long start, unsigned long invert, unsigned long le)
     34{
     35	unsigned long tmp, mask;
     36	(void) le;
     37
     38	if (unlikely(start >= nbits))
     39		return nbits;
     40
     41	tmp = addr1[start / BITS_PER_LONG];
     42	if (addr2)
     43		tmp &= addr2[start / BITS_PER_LONG];
     44	tmp ^= invert;
     45
     46	/* Handle 1st word. */
     47	mask = BITMAP_FIRST_WORD_MASK(start);
     48
     49	/*
     50	 * Due to the lack of swab() in tools, and the fact that it doesn't
     51	 * need little-endian support, just comment it out
     52	 */
     53#if (0)
     54	if (le)
     55		mask = swab(mask);
     56#endif
     57
     58	tmp &= mask;
     59
     60	start = round_down(start, BITS_PER_LONG);
     61
     62	while (!tmp) {
     63		start += BITS_PER_LONG;
     64		if (start >= nbits)
     65			return nbits;
     66
     67		tmp = addr1[start / BITS_PER_LONG];
     68		if (addr2)
     69			tmp &= addr2[start / BITS_PER_LONG];
     70		tmp ^= invert;
     71	}
     72
     73#if (0)
     74	if (le)
     75		tmp = swab(tmp);
     76#endif
     77
     78	return min(start + __ffs(tmp), nbits);
     79}
     80#endif
     81
     82#ifndef find_first_bit
     83/*
     84 * Find the first set bit in a memory region.
     85 */
     86unsigned long _find_first_bit(const unsigned long *addr, unsigned long size)
     87{
     88	unsigned long idx;
     89
     90	for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
     91		if (addr[idx])
     92			return min(idx * BITS_PER_LONG + __ffs(addr[idx]), size);
     93	}
     94
     95	return size;
     96}
     97#endif
     98
     99#ifndef find_first_and_bit
    100/*
    101 * Find the first set bit in two memory regions.
    102 */
    103unsigned long _find_first_and_bit(const unsigned long *addr1,
    104				  const unsigned long *addr2,
    105				  unsigned long size)
    106{
    107	unsigned long idx, val;
    108
    109	for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
    110		val = addr1[idx] & addr2[idx];
    111		if (val)
    112			return min(idx * BITS_PER_LONG + __ffs(val), size);
    113	}
    114
    115	return size;
    116}
    117#endif
    118
    119#ifndef find_first_zero_bit
    120/*
    121 * Find the first cleared bit in a memory region.
    122 */
    123unsigned long _find_first_zero_bit(const unsigned long *addr, unsigned long size)
    124{
    125	unsigned long idx;
    126
    127	for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
    128		if (addr[idx] != ~0UL)
    129			return min(idx * BITS_PER_LONG + ffz(addr[idx]), size);
    130	}
    131
    132	return size;
    133}
    134#endif