unicorn/qemu/util/bitmap.c

/*
 * Bitmap Module
 *
 * Stolen from linux/src/lib/bitmap.c
 *
 * Copyright (C) 2010 Corentin Chary
 *
 * This source code is licensed under the GNU General Public License,
 * Version 2.
 */

#include "qemu/bitops.h"
#include "qemu/bitmap.h"
#include "qemu/atomic.h"

#define BITMAP_FIRST_WORD_MASK(start) (~0UL << ((start) % BITS_PER_LONG))

void bitmap_set(unsigned long *map, long start, long nr)
{
    unsigned long *p = map + BIT_WORD(start);
    const long size = start + nr;
    int bits_to_set = BITS_PER_LONG - (start % BITS_PER_LONG);
    unsigned long mask_to_set = BITMAP_FIRST_WORD_MASK(start);

    while (nr - bits_to_set >= 0) {
        *p |= mask_to_set;
        nr -= bits_to_set;
        bits_to_set = BITS_PER_LONG;
        mask_to_set = ~0UL;
        p++;
    }
    if (nr) {
        mask_to_set &= BITMAP_LAST_WORD_MASK(size);
        *p |= mask_to_set;
    }
}

void bitmap_set_atomic(unsigned long *map, long start, long nr)
{
    unsigned long *p = map + BIT_WORD(start);
    const long size = start + nr;
    int bits_to_set = BITS_PER_LONG - (start % BITS_PER_LONG);
    unsigned long mask_to_set = BITMAP_FIRST_WORD_MASK(start);

    /* First word */
    if (nr - bits_to_set > 0) {
        atomic_or(p, mask_to_set);
        nr -= bits_to_set;
        bits_to_set = BITS_PER_LONG;
        mask_to_set = ~0UL;
        p++;
    }

    /* Full words */
    if (bits_to_set == BITS_PER_LONG) {
        while (nr >= BITS_PER_LONG) {
            *p = ~0UL;
            nr -= BITS_PER_LONG;
            p++;
        }
    }

    /* Last word */
    if (nr) {
        mask_to_set &= BITMAP_LAST_WORD_MASK(size);
        atomic_or(p, mask_to_set);
    } else {
        /* If we avoided the full barrier in atomic_or(), issue a
         * barrier to account for the assignments in the while loop.
         */
        smp_mb();
    }
}

void bitmap_clear(unsigned long *map, long start, long nr)
{
    unsigned long *p = map + BIT_WORD(start);
    const long size = start + nr;
    int bits_to_clear = BITS_PER_LONG - (start % BITS_PER_LONG);
    unsigned long mask_to_clear = BITMAP_FIRST_WORD_MASK(start);

    while (nr - bits_to_clear >= 0) {
        *p &= ~mask_to_clear;
        nr -= bits_to_clear;
        bits_to_clear = BITS_PER_LONG;
        mask_to_clear = ~0UL;
        p++;
    }
    if (nr) {
        mask_to_clear &= BITMAP_LAST_WORD_MASK(size);
        *p &= ~mask_to_clear;
    }
}

bool bitmap_test_and_clear_atomic(unsigned long *map, long start, long nr)
{
    unsigned long *p = map + BIT_WORD(start);
    const long size = start + nr;
    int bits_to_clear = BITS_PER_LONG - (start % BITS_PER_LONG);
    unsigned long mask_to_clear = BITMAP_FIRST_WORD_MASK(start);
    unsigned long dirty = 0;
    unsigned long old_bits;

    /* First word */
    if (nr - bits_to_clear > 0) {
        old_bits = atomic_fetch_and(p, ~mask_to_clear);
        dirty |= old_bits & mask_to_clear;
        nr -= bits_to_clear;
        bits_to_clear = BITS_PER_LONG;
        mask_to_clear = ~0UL;
        p++;
    }

    /* Full words */
    if (bits_to_clear == BITS_PER_LONG) {
        while (nr >= BITS_PER_LONG) {
            if (*p) {
                old_bits = atomic_xchg(p, 0);
                dirty |= old_bits;
            }
            nr -= BITS_PER_LONG;
            p++;
        }
    }

    /* Last word */
    if (nr) {
        mask_to_clear &= BITMAP_LAST_WORD_MASK(size);
        old_bits = atomic_fetch_and(p, ~mask_to_clear);
        dirty |= old_bits & mask_to_clear;
    } else {
        if (!dirty) {
            smp_mb();
        }
    }

    return dirty != 0;
}