Line data    Source code

       1             : // SPDX-License-Identifier: GPL-2.0-or-later
       2             : /* bit search implementation
       3             :  *
       4             :  * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
       5             :  * Written by David Howells (dhowells@redhat.com)
       6             :  *
       7             :  * Copyright (C) 2008 IBM Corporation
       8             :  * 'find_last_bit' is written by Rusty Russell <rusty@rustcorp.com.au>
       9             :  * (Inspired by David Howell's find_next_bit implementation)
      10             :  *
      11             :  * Rewritten by Yury Norov <yury.norov@gmail.com> to decrease
      12             :  * size and improve performance, 2015.
      13             :  */
      14             : 
      15             : #include <linux/bitops.h>
      16             : #include <linux/bitmap.h>
      17             : #include <linux/export.h>
      18             : #include <linux/math.h>
      19             : #include <linux/minmax.h>
      20             : #include <linux/swab.h>
      21             : 
      22             : #if !defined(find_next_bit) || !defined(find_next_zero_bit) ||                  \
      23             :         !defined(find_next_bit_le) || !defined(find_next_zero_bit_le) ||        \
      24             :         !defined(find_next_and_bit)
      25             : /*
      26             :  * This is a common helper function for find_next_bit, find_next_zero_bit, and
      27             :  * find_next_and_bit. The differences are:
      28             :  *  - The "invert" argument, which is XORed with each fetched word before
      29             :  *    searching it for one bits.
      30             :  *  - The optional "addr2", which is anded with "addr1" if present.
      31             :  */
      32        2591 : unsigned long _find_next_bit(const unsigned long *addr1,
      33             :                 const unsigned long *addr2, unsigned long nbits,
      34             :                 unsigned long start, unsigned long invert, unsigned long le)
      35             : {
      36             :         unsigned long tmp, mask;
      37             : 
      38        2591 :         if (unlikely(start >= nbits))
      39             :                 return nbits;
      40             : 
      41        2088 :         tmp = addr1[start / BITS_PER_LONG];
      42        2088 :         if (addr2)
      43           0 :                 tmp &= addr2[start / BITS_PER_LONG];
      44        2088 :         tmp ^= invert;
      45             : 
      46             :         /* Handle 1st word. */
      47        2088 :         mask = BITMAP_FIRST_WORD_MASK(start);
      48        2088 :         if (le)
      49             :                 mask = swab(mask);
      50             : 
      51        2088 :         tmp &= mask;
      52             : 
      53        2088 :         start = round_down(start, BITS_PER_LONG);
      54             : 
      55        5437 :         while (!tmp) {
      56        1787 :                 start += BITS_PER_LONG;
      57        1787 :                 if (start >= nbits)
      58             :                         return nbits;
      59             : 
      60        1261 :                 tmp = addr1[start / BITS_PER_LONG];
      61        1261 :                 if (addr2)
      62           0 :                         tmp &= addr2[start / BITS_PER_LONG];
      63        1261 :                 tmp ^= invert;
      64             :         }
      65             : 
      66        1562 :         if (le)
      67             :                 tmp = swab(tmp);
      68             : 
      69        1562 :         return min(start + __ffs(tmp), nbits);
      70             : }
      71             : EXPORT_SYMBOL(_find_next_bit);
      72             : #endif
      73             : 
      74             : #ifndef find_first_bit
      75             : /*
      76             :  * Find the first set bit in a memory region.
      77             :  */
      78           0 : unsigned long _find_first_bit(const unsigned long *addr, unsigned long size)
      79             : {
      80             :         unsigned long idx;
      81             : 
      82           0 :         for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
      83           0 :                 if (addr[idx])
      84           0 :                         return min(idx * BITS_PER_LONG + __ffs(addr[idx]), size);
      85             :         }
      86             : 
      87             :         return size;
      88             : }
      89             : EXPORT_SYMBOL(_find_first_bit);
      90             : #endif
      91             : 
      92             : #ifndef find_first_and_bit
      93             : /*
      94             :  * Find the first set bit in two memory regions.
      95             :  */
      96           0 : unsigned long _find_first_and_bit(const unsigned long *addr1,
      97             :                                   const unsigned long *addr2,
      98             :                                   unsigned long size)
      99             : {
     100             :         unsigned long idx, val;
     101             : 
     102           0 :         for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
     103           0 :                 val = addr1[idx] & addr2[idx];
     104           0 :                 if (val)
     105           0 :                         return min(idx * BITS_PER_LONG + __ffs(val), size);
     106             :         }
     107             : 
     108             :         return size;
     109             : }
     110             : EXPORT_SYMBOL(_find_first_and_bit);
     111             : #endif
     112             : 
     113             : #ifndef find_first_zero_bit
     114             : /*
     115             :  * Find the first cleared bit in a memory region.
     116             :  */
     117         120 : unsigned long _find_first_zero_bit(const unsigned long *addr, unsigned long size)
     118             : {
     119             :         unsigned long idx;
     120             : 
     121         294 :         for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
     122         294 :                 if (addr[idx] != ~0UL)
     123         240 :                         return min(idx * BITS_PER_LONG + ffz(addr[idx]), size);
     124             :         }
     125             : 
     126             :         return size;
     127             : }
     128             : EXPORT_SYMBOL(_find_first_zero_bit);
     129             : #endif
     130             : 
     131             : #ifndef find_last_bit
     132           0 : unsigned long _find_last_bit(const unsigned long *addr, unsigned long size)
     133             : {
     134           0 :         if (size) {
     135           0 :                 unsigned long val = BITMAP_LAST_WORD_MASK(size);
     136           0 :                 unsigned long idx = (size-1) / BITS_PER_LONG;
     137             : 
     138             :                 do {
     139           0 :                         val &= addr[idx];
     140           0 :                         if (val)
     141           0 :                                 return idx * BITS_PER_LONG + __fls(val);
     142             : 
     143           0 :                         val = ~0ul;
     144           0 :                 } while (idx--);
     145             :         }
     146             :         return size;
     147             : }
     148             : EXPORT_SYMBOL(_find_last_bit);
     149             : #endif
     150             : 
     151           0 : unsigned long find_next_clump8(unsigned long *clump, const unsigned long *addr,
     152             :                                unsigned long size, unsigned long offset)
     153             : {
     154           0 :         offset = find_next_bit(addr, size, offset);
     155           0 :         if (offset == size)
     156             :                 return size;
     157             : 
     158           0 :         offset = round_down(offset, 8);
     159           0 :         *clump = bitmap_get_value8(addr, offset);
     160             : 
     161           0 :         return offset;
     162             : }
     163             : EXPORT_SYMBOL(find_next_clump8);