drivers/firmware/efi/libstub/find.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 #include <linux/bitmap.h>
   3 #include <linux/math.h>
   4 #include <linux/minmax.h>
   5
   6 /*
   7  * Common helper for find_next_bit() function family
   8  * @FETCH: The expression that fetches and pre-processes each word of bitmap(s)
   9  * @MUNGE: The expression that post-processes a word containing found bit (may be empty)
  10  * @size: The bitmap size in bits
  11  * @start: The bitnumber to start searching at
  12  */
  13 #define FIND_NEXT_BIT(FETCH, MUNGE, size, start)                                \
  14 ({                                                                              \
  15         unsigned long mask, idx, tmp, sz = (size), __start = (start);           \
  16                                                                                 \
  17         if (unlikely(__start >= sz))                                            \
  18                 goto out;                                                       \
  19                                                                                 \
  20         mask = MUNGE(BITMAP_FIRST_WORD_MASK(__start));                          \
  21         idx = __start / BITS_PER_LONG;                                          \
  22                                                                                 \
  23         for (tmp = (FETCH) & mask; !tmp; tmp = (FETCH)) {                       \
  24                 if ((idx + 1) * BITS_PER_LONG >= sz)                            \
  25                         goto out;                                               \
  26                 idx++;                                                          \
  27         }                                                                       \
  28                                                                                 \
  29         sz = min(idx * BITS_PER_LONG + __ffs(MUNGE(tmp)), sz);                  \
  30 out:                                                                            \
  31         sz;                                                                     \
  32 })
  33
  34 unsigned long _find_next_bit(const unsigned long *addr, unsigned long nbits, unsigned long start)
  35 {
  36         return FIND_NEXT_BIT(addr[idx], /* nop */, nbits, start);
  37 }
  38
  39 unsigned long _find_next_zero_bit(const unsigned long *addr, unsigned long nbits,
  40                                          unsigned long start)
  41 {
  42         return FIND_NEXT_BIT(~addr[idx], /* nop */, nbits, start);
  43 }