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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bitfunc.c (2552B)

      1// SPDX-License-Identifier: GPL-2.0
      2/*
      3 *
      4 * Copyright (C) 2019-2021 Paragon Software GmbH, All rights reserved.
      5 *
      6 */
      7
      8#include <linux/types.h>
      9
     10#include "ntfs_fs.h"
     11
     12#define BITS_IN_SIZE_T (sizeof(size_t) * 8)
     13
     14/*
     15 * fill_mask[i] - first i bits are '1' , i = 0,1,2,3,4,5,6,7,8
     16 * fill_mask[i] = 0xFF >> (8-i)
     17 */
     18static const u8 fill_mask[] = { 0x00, 0x01, 0x03, 0x07, 0x0F,
     19				0x1F, 0x3F, 0x7F, 0xFF };
     20
     21/*
     22 * zero_mask[i] - first i bits are '0' , i = 0,1,2,3,4,5,6,7,8
     23 * zero_mask[i] = 0xFF << i
     24 */
     25static const u8 zero_mask[] = { 0xFF, 0xFE, 0xFC, 0xF8, 0xF0,
     26				0xE0, 0xC0, 0x80, 0x00 };
     27
     28/*
     29 * are_bits_clear
     30 *
     31 * Return: True if all bits [bit, bit+nbits) are zeros "0".
     32 */
     33bool are_bits_clear(const ulong *lmap, size_t bit, size_t nbits)
     34{
     35	size_t pos = bit & 7;
     36	const u8 *map = (u8 *)lmap + (bit >> 3);
     37
     38	if (pos) {
     39		if (8 - pos >= nbits)
     40			return !nbits || !(*map & fill_mask[pos + nbits] &
     41					   zero_mask[pos]);
     42
     43		if (*map++ & zero_mask[pos])
     44			return false;
     45		nbits -= 8 - pos;
     46	}
     47
     48	pos = ((size_t)map) & (sizeof(size_t) - 1);
     49	if (pos) {
     50		pos = sizeof(size_t) - pos;
     51		if (nbits >= pos * 8) {
     52			for (nbits -= pos * 8; pos; pos--, map++) {
     53				if (*map)
     54					return false;
     55			}
     56		}
     57	}
     58
     59	for (pos = nbits / BITS_IN_SIZE_T; pos; pos--, map += sizeof(size_t)) {
     60		if (*((size_t *)map))
     61			return false;
     62	}
     63
     64	for (pos = (nbits % BITS_IN_SIZE_T) >> 3; pos; pos--, map++) {
     65		if (*map)
     66			return false;
     67	}
     68
     69	pos = nbits & 7;
     70	if (pos && (*map & fill_mask[pos]))
     71		return false;
     72
     73	return true;
     74}
     75
     76/*
     77 * are_bits_set
     78 *
     79 * Return: True if all bits [bit, bit+nbits) are ones "1".
     80 */
     81bool are_bits_set(const ulong *lmap, size_t bit, size_t nbits)
     82{
     83	u8 mask;
     84	size_t pos = bit & 7;
     85	const u8 *map = (u8 *)lmap + (bit >> 3);
     86
     87	if (pos) {
     88		if (8 - pos >= nbits) {
     89			mask = fill_mask[pos + nbits] & zero_mask[pos];
     90			return !nbits || (*map & mask) == mask;
     91		}
     92
     93		mask = zero_mask[pos];
     94		if ((*map++ & mask) != mask)
     95			return false;
     96		nbits -= 8 - pos;
     97	}
     98
     99	pos = ((size_t)map) & (sizeof(size_t) - 1);
    100	if (pos) {
    101		pos = sizeof(size_t) - pos;
    102		if (nbits >= pos * 8) {
    103			for (nbits -= pos * 8; pos; pos--, map++) {
    104				if (*map != 0xFF)
    105					return false;
    106			}
    107		}
    108	}
    109
    110	for (pos = nbits / BITS_IN_SIZE_T; pos; pos--, map += sizeof(size_t)) {
    111		if (*((size_t *)map) != MINUS_ONE_T)
    112			return false;
    113	}
    114
    115	for (pos = (nbits % BITS_IN_SIZE_T) >> 3; pos; pos--, map++) {
    116		if (*map != 0xFF)
    117			return false;
    118	}
    119
    120	pos = nbits & 7;
    121	if (pos) {
    122		mask = fill_mask[pos];
    123		if ((*map & mask) != mask)
    124			return false;
    125	}
    126
    127	return true;
    128}