Converting from a bitmap to a u32 or u64 array of bits and back can involve endianness conversions depending on platform. Import the Linux functions that take care of this.
Signed-off-by: Ahmad Fatoum <[email protected]> --- include/linux/bitmap.h | 101 ++++++++++++++++++++++++++++++++++++++++ lib/bitmap.c | 103 +++++++++++++++++++++++++++++++++++++++++ 2 files changed, 204 insertions(+) diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h index 7d06fac68d08..9ec1ee2d1422 100644 --- a/include/linux/bitmap.h +++ b/include/linux/bitmap.h @@ -56,6 +56,10 @@ * bitmap_find_free_region(bitmap, bits, order) Find and allocate bit region * bitmap_release_region(bitmap, pos, order) Free specified bit region * bitmap_allocate_region(bitmap, pos, order) Allocate specified bit region + * bitmap_from_arr32(dst, buf, nbits) Copy nbits from u32[] buf to dst + * bitmap_from_arr64(dst, buf, nbits) Copy nbits from u64[] buf to dst + * bitmap_to_arr32(buf, src, nbits) Copy nbits from buf to u32[] dst + * bitmap_to_arr64(buf, src, nbits) Copy nbits from buf to u64[] dst */ /* @@ -178,6 +182,103 @@ static inline void bitmap_copy(unsigned long *dst, const unsigned long *src, } } +/* + * Copy bitmap and clear tail bits in last word. + */ +static inline void bitmap_copy_clear_tail(unsigned long *dst, + const unsigned long *src, unsigned int nbits) +{ + bitmap_copy(dst, src, nbits); + if (nbits % BITS_PER_LONG) + dst[nbits / BITS_PER_LONG] &= BITMAP_LAST_WORD_MASK(nbits); +} + +/* + * On 32-bit systems bitmaps are represented as u32 arrays internally. On LE64 + * machines the order of hi and lo parts of numbers match the bitmap structure. + * In both cases conversion is not needed when copying data from/to arrays of + * u32. But in LE64 case, typecast in bitmap_copy_clear_tail() may lead + * to out-of-bound access. To avoid that, both LE and BE variants of 64-bit + * architectures are not using bitmap_copy_clear_tail(). + */ +#if BITS_PER_LONG == 64 +void bitmap_from_arr32(unsigned long *bitmap, const u32 *buf, + unsigned int nbits); +void bitmap_to_arr32(u32 *buf, const unsigned long *bitmap, + unsigned int nbits); +#else +#define bitmap_from_arr32(bitmap, buf, nbits) \ + bitmap_copy_clear_tail((unsigned long *) (bitmap), \ + (const unsigned long *) (buf), (nbits)) +#define bitmap_to_arr32(buf, bitmap, nbits) \ + bitmap_copy_clear_tail((unsigned long *) (buf), \ + (const unsigned long *) (bitmap), (nbits)) +#endif + +/* + * On 64-bit systems bitmaps are represented as u64 arrays internally. On LE32 + * machines the order of hi and lo parts of numbers match the bitmap structure. + * In both cases conversion is not needed when copying data from/to arrays of + * u64. + */ +#if (BITS_PER_LONG == 32) && defined(__BIG_ENDIAN) +void bitmap_from_arr64(unsigned long *bitmap, const u64 *buf, unsigned int nbits); +void bitmap_to_arr64(u64 *buf, const unsigned long *bitmap, unsigned int nbits); +#else +#define bitmap_from_arr64(bitmap, buf, nbits) \ + bitmap_copy_clear_tail((unsigned long *)(bitmap), (const unsigned long *)(buf), (nbits)) +#define bitmap_to_arr64(buf, bitmap, nbits) \ + bitmap_copy_clear_tail((unsigned long *)(buf), (const unsigned long *)(bitmap), (nbits)) +#endif + +/** + * BITMAP_FROM_U64() - Represent u64 value in the format suitable for bitmap. + * @n: u64 value + * + * Linux bitmaps are internally arrays of unsigned longs, i.e. 32-bit + * integers in 32-bit environment, and 64-bit integers in 64-bit one. + * + * There are four combinations of endianness and length of the word in linux + * ABIs: LE64, BE64, LE32 and BE32. + * + * On 64-bit kernels 64-bit LE and BE numbers are naturally ordered in + * bitmaps and therefore don't require any special handling. + * + * On 32-bit kernels 32-bit LE ABI orders lo word of 64-bit number in memory + * prior to hi, and 32-bit BE orders hi word prior to lo. The bitmap on the + * other hand is represented as an array of 32-bit words and the position of + * bit N may therefore be calculated as: word #(N/32) and bit #(N%32) in that + * word. For example, bit #42 is located at 10th position of 2nd word. + * It matches 32-bit LE ABI, and we can simply let the compiler store 64-bit + * values in memory as it usually does. But for BE we need to swap hi and lo + * words manually. + * + * With all that, the macro BITMAP_FROM_U64() does explicit reordering of hi and + * lo parts of u64. For LE32 it does nothing, and for BE environment it swaps + * hi and lo words, as is expected by bitmap. + */ +#if BITS_PER_LONG == 64 +#define BITMAP_FROM_U64(n) (n) +#else +#define BITMAP_FROM_U64(n) ((unsigned long) ((u64)(n) & ULONG_MAX)), \ + ((unsigned long) ((u64)(n) >> 32)) +#endif + +/** + * bitmap_from_u64 - Check and swap words within u64. + * @mask: source bitmap + * @dst: destination bitmap + * + * In 32-bit Big Endian kernel, when using ``(u32 *)(&val)[*]`` + * to read u64 mask, we will get the wrong word. + * That is ``(u32 *)(&val)[0]`` gets the upper 32 bits, + * but we expect the lower 32-bits of u64. + */ +static inline void bitmap_from_u64(unsigned long *dst, u64 mask) +{ + bitmap_from_arr64(dst, &mask, 64); +} + static inline int bitmap_and(unsigned long *dst, const unsigned long *src1, const unsigned long *src2, int nbits) { diff --git a/lib/bitmap.c b/lib/bitmap.c index dfc0f06b13c4..7614c4d21337 100644 --- a/lib/bitmap.c +++ b/lib/bitmap.c @@ -847,3 +847,106 @@ unsigned long *bitmap_xzalloc(unsigned int nbits) { return xzalloc(BITS_TO_LONGS(nbits) * sizeof(unsigned long)); } + +#if BITS_PER_LONG == 64 +/** + * bitmap_from_arr32 - copy the contents of u32 array of bits to bitmap + * @bitmap: array of unsigned longs, the destination bitmap + * @buf: array of u32 (in host byte order), the source bitmap + * @nbits: number of bits in @bitmap + */ +void bitmap_from_arr32(unsigned long *bitmap, const u32 *buf, unsigned int nbits) +{ + unsigned int i, halfwords; + + halfwords = DIV_ROUND_UP(nbits, 32); + for (i = 0; i < halfwords; i++) { + bitmap[i/2] = (unsigned long) buf[i]; + if (++i < halfwords) + bitmap[i/2] |= ((unsigned long) buf[i]) << 32; + } + + /* Clear tail bits in last word beyond nbits. */ + if (nbits % BITS_PER_LONG) + bitmap[(halfwords - 1) / 2] &= BITMAP_LAST_WORD_MASK(nbits); +} +EXPORT_SYMBOL(bitmap_from_arr32); + +/** + * bitmap_to_arr32 - copy the contents of bitmap to a u32 array of bits + * @buf: array of u32 (in host byte order), the dest bitmap + * @bitmap: array of unsigned longs, the source bitmap + * @nbits: number of bits in @bitmap + */ +void bitmap_to_arr32(u32 *buf, const unsigned long *bitmap, unsigned int nbits) +{ + unsigned int i, halfwords; + + halfwords = DIV_ROUND_UP(nbits, 32); + for (i = 0; i < halfwords; i++) { + buf[i] = (u32) (bitmap[i/2] & UINT_MAX); + if (++i < halfwords) + buf[i] = (u32) (bitmap[i/2] >> 32); + } + + /* Clear tail bits in last element of array beyond nbits. */ + if (nbits % BITS_PER_LONG) + buf[halfwords - 1] &= (u32) (UINT_MAX >> ((-nbits) & 31)); +} +EXPORT_SYMBOL(bitmap_to_arr32); +#endif + +#if (BITS_PER_LONG == 32) && defined(__BIG_ENDIAN) +/** + * bitmap_from_arr64 - copy the contents of u64 array of bits to bitmap + * @bitmap: array of unsigned longs, the destination bitmap + * @buf: array of u64 (in host byte order), the source bitmap + * @nbits: number of bits in @bitmap + */ +void bitmap_from_arr64(unsigned long *bitmap, const u64 *buf, unsigned int nbits) +{ + int n; + + for (n = nbits; n > 0; n -= 64) { + u64 val = *buf++; + + *bitmap++ = val; + if (n > 32) + *bitmap++ = val >> 32; + } + + /* + * Clear tail bits in the last word beyond nbits. + * + * Negative index is OK because here we point to the word next + * to the last word of the bitmap, except for nbits == 0, which + * is tested implicitly. + */ + if (nbits % BITS_PER_LONG) + bitmap[-1] &= BITMAP_LAST_WORD_MASK(nbits); +} +EXPORT_SYMBOL(bitmap_from_arr64); + +/** + * bitmap_to_arr64 - copy the contents of bitmap to a u64 array of bits + * @buf: array of u64 (in host byte order), the dest bitmap + * @bitmap: array of unsigned longs, the source bitmap + * @nbits: number of bits in @bitmap + */ +void bitmap_to_arr64(u64 *buf, const unsigned long *bitmap, unsigned int nbits) +{ + const unsigned long *end = bitmap + BITS_TO_LONGS(nbits); + + while (bitmap < end) { + *buf = *bitmap++; + if (bitmap < end) + *buf |= (u64)(*bitmap++) << 32; + buf++; + } + + /* Clear tail bits in the last element of array beyond nbits. */ + if (nbits % 64) + buf[-1] &= GENMASK_ULL((nbits - 1) % 64, 0); +} +EXPORT_SYMBOL(bitmap_to_arr64); +#endif -- 2.39.2
