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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] Ping: [PATCH] bitmap_*() should cope with zero size bitmaps
>>> On 03.06.13 at 15:33, Jan Beulich wrote:
> ... to match expectations set by memset()/memcpy().
>
> Similarly for find_{first,next}_{,zero_}_bit() on x86.
>
> __bitmap_shift_{left,right}() would also need fixing (they more
> generally can't cope with the shift count being larger than the bitmap
> size, and they perform undefined operations by possibly shifting an
> unsigned long value by BITS_PER_LONG bits), but since these functions
> aren't really used anywhere I wonder if we wouldn't better simply get
> rid of them.
>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>
> --- a/xen/include/asm-x86/bitops.h
> +++ b/xen/include/asm-x86/bitops.h
> @@ -327,10 +327,7 @@ static inline unsigned int __scanbit(uns
> * Returns the bit-number of the first set bit, not the number of the byte
> * containing a bit.
> */
> -#define find_first_bit(addr,size) \
> -((__builtin_constant_p(size) && (size) <= BITS_PER_LONG ? \
> - (__scanbit(*(const unsigned long *)addr, size)) : \
> - __find_first_bit(addr,size)))
> +#define find_first_bit(addr, size) find_next_bit(addr, size, 0)
>
> /**
> * find_next_bit - find the first set bit in a memory region
> @@ -338,10 +335,24 @@ static inline unsigned int __scanbit(uns
> * @offset: The bitnumber to start searching at
> * @size: The maximum size to search
> */
> -#define find_next_bit(addr,size,off) \
> -((__builtin_constant_p(size) && (size) <= BITS_PER_LONG ? \
> - ((off) + (__scanbit((*(const unsigned long *)addr) >> (off), size))) : \
> - __find_next_bit(addr,size,off)))
> +#define find_next_bit(addr, size, off) ({ \
> + unsigned int r__ = (size); \
> + unsigned int o__ = (off); \
> + switch ( -!__builtin_constant_p(size) | r__ ) \
> + { \
> + case 0: (void)(addr); break; \
> + case 1 ... BITS_PER_LONG: \
> + r__ = o__ + __scanbit(*(const unsigned long *)(addr) >> o__, r__);
> \
> + break; \
> + default: \
> + if ( __builtin_constant_p(off) && !o__ ) \
> + r__ = __find_first_bit(addr, r__); \
> + else \
> + r__ = __find_next_bit(addr, r__, o__); \
> + break; \
> + } \
> + r__; \
> +})
>
> /**
> * find_first_zero_bit - find the first zero bit in a memory region
> @@ -351,10 +362,7 @@ static inline unsigned int __scanbit(uns
> * Returns the bit-number of the first zero bit, not the number of the byte
> * containing a bit.
> */
> -#define find_first_zero_bit(addr,size) \
> -((__builtin_constant_p(size) && (size) <= BITS_PER_LONG ? \
> - (__scanbit(~*(const unsigned long *)addr, size)) : \
> - __find_first_zero_bit(addr,size)))
> +#define find_first_zero_bit(addr, size) find_next_zero_bit(addr, size, 0)
>
> /**
> * find_next_zero_bit - find the first zero bit in a memory region
> @@ -362,10 +370,24 @@ static inline unsigned int __scanbit(uns
> * @offset: The bitnumber to start searching at
> * @size: The maximum size to search
> */
> -#define find_next_zero_bit(addr,size,off)
> \
> -((__builtin_constant_p(size) && (size) <= BITS_PER_LONG ?
> \
> - ((off)+(__scanbit(~(((*(const unsigned long *)addr)) >> (off)), size))) :
> \
> - __find_next_zero_bit(addr,size,off)))
> +#define find_next_zero_bit(addr, size, off) ({ \
> + unsigned int r__ = (size); \
> + unsigned int o__ = (off); \
> + switch ( -!__builtin_constant_p(size) | r__ ) \
> + { \
> + case 0: (void)(addr); break; \
> + case 1 ... BITS_PER_LONG: \
> + r__ = o__ + __scanbit(~*(const unsigned long *)(addr) >> o__, r__);
> \
> + break; \
> + default: \
> + if ( __builtin_constant_p(off) && !o__ ) \
> + r__ = __find_first_zero_bit(addr, r__); \
> + else \
> + r__ = __find_next_zero_bit(addr, r__, o__); \
> + break; \
> + } \
> + r__; \
> +})
>
> /**
> * find_first_set_bit - find the first set bit in @word
> --- a/xen/include/xen/bitmap.h
> +++ b/xen/include/xen/bitmap.h
> @@ -108,123 +108,122 @@ extern int bitmap_allocate_region(unsign
> (1UL<<((nbits) % BITS_PER_LONG))-1 : ~0UL \
> )
>
> +#define bitmap_bytes(nbits) (BITS_TO_LONGS(nbits) * sizeof(unsigned long))
> +
> +#define bitmap_switch(nbits, zero_ret, small, large) \
> + switch (-!__builtin_constant_p(nbits) | (nbits)) { \
> + case 0: return zero_ret; \
> + case 1 ... BITS_PER_LONG: \
> + small; break; \
> + default: \
> + large; break; \
> + }
> +
> static inline void bitmap_zero(unsigned long *dst, int nbits)
> {
> - if (nbits <= BITS_PER_LONG)
> - *dst = 0UL;
> - else {
> - int len = BITS_TO_LONGS(nbits) * sizeof(unsigned long);
> - memset(dst, 0, len);
> - }
> + bitmap_switch(nbits,,
> + *dst = 0UL,
> + memset(dst, 0, bitmap_bytes(nbits)));
> }
>
> static inline void bitmap_fill(unsigned long *dst, int nbits)
> {
> size_t nlongs = BITS_TO_LONGS(nbits);
> - if (nlongs > 1) {
> - int len = (nlongs - 1) * sizeof(unsigned long);
> - memset(dst, 0xff, len);
> +
> + switch (nlongs) {
> + default:
> + memset(dst, -1, (nlongs - 1) * sizeof(unsigned long));
> + /* fall through */
> + case 1:
> + dst[nlongs - 1] = BITMAP_LAST_WORD_MASK(nbits);
> + break;
> }
> - dst[nlongs - 1] = BITMAP_LAST_WORD_MASK(nbits);
> }
>
> static inline void bitmap_copy(unsigned long *dst, const unsigned long
> *src,
> int nbits)
> {
> - if (nbits <= BITS_PER_LONG)
> - *dst = *src;
> - else {
> - int len = BITS_TO_LONGS(nbits) * sizeof(unsigned long);
> - memcpy(dst, src, len);
> - }
> + bitmap_switch(nbits,,
> + *dst = *src,
> + memcpy(dst, src, bitmap_bytes(nbits)));
> }
>
> static inline void bitmap_and(unsigned long *dst, const unsigned long
> *src1,
> const unsigned long *src2, int nbits)
> {
> - if (nbits <= BITS_PER_LONG)
> - *dst = *src1 & *src2;
> - else
> - __bitmap_and(dst, src1, src2, nbits);
> + bitmap_switch(nbits,,
> + *dst = *src1 & *src2,
> + __bitmap_and(dst, src1, src2, nbits));
> }
>
> static inline void bitmap_or(unsigned long *dst, const unsigned long *src1,
> const unsigned long *src2, int nbits)
> {
> - if (nbits <= BITS_PER_LONG)
> - *dst = *src1 | *src2;
> - else
> - __bitmap_or(dst, src1, src2, nbits);
> + bitmap_switch(nbits,,
> + *dst = *src1 | *src2,
> + __bitmap_or(dst, src1, src2, nbits));
> }
>
> static inline void bitmap_xor(unsigned long *dst, const unsigned long
> *src1,
> const unsigned long *src2, int nbits)
> {
> - if (nbits <= BITS_PER_LONG)
> - *dst = *src1 ^ *src2;
> - else
> - __bitmap_xor(dst, src1, src2, nbits);
> + bitmap_switch(nbits,,
> + *dst = *src1 ^ *src2,
> + __bitmap_xor(dst, src1, src2, nbits));
> }
>
> static inline void bitmap_andnot(unsigned long *dst, const unsigned long
> *src1,
> const unsigned long *src2, int nbits)
> {
> - if (nbits <= BITS_PER_LONG)
> - *dst = *src1 & ~(*src2);
> - else
> - __bitmap_andnot(dst, src1, src2, nbits);
> + bitmap_switch(nbits,,
> + *dst = *src1 & ~*src2,
> + __bitmap_andnot(dst, src1, src2, nbits));
> }
>
> static inline void bitmap_complement(unsigned long *dst, const unsigned
> long *src,
> int nbits)
> {
> - if (nbits <= BITS_PER_LONG)
> - *dst = ~(*src) & BITMAP_LAST_WORD_MASK(nbits);
> - else
> - __bitmap_complement(dst, src, nbits);
> + bitmap_switch(nbits,,
> + *dst = ~*src & BITMAP_LAST_WORD_MASK(nbits),
> + __bitmap_complement(dst, src, nbits));
> }
>
> static inline int bitmap_equal(const unsigned long *src1,
> const unsigned long *src2, int nbits)
> {
> - if (nbits <= BITS_PER_LONG)
> - return ! ((*src1 ^ *src2) & BITMAP_LAST_WORD_MASK(nbits));
> - else
> - return __bitmap_equal(src1, src2, nbits);
> + bitmap_switch(nbits, -1,
> + return !((*src1 ^ *src2) & BITMAP_LAST_WORD_MASK(nbits)),
> + return __bitmap_equal(src1, src2, nbits));
> }
>
> static inline int bitmap_intersects(const unsigned long *src1,
> const unsigned long *src2, int nbits)
> {
> - if (nbits <= BITS_PER_LONG)
> - return ((*src1 & *src2) & BITMAP_LAST_WORD_MASK(nbits)) != 0;
> - else
> - return __bitmap_intersects(src1, src2, nbits);
> + bitmap_switch(nbits, -1,
> + return ((*src1 & *src2) & BITMAP_LAST_WORD_MASK(nbits)) != 0,
> + return __bitmap_intersects(src1, src2, nbits));
> }
>
> static inline int bitmap_subset(const unsigned long *src1,
> const unsigned long *src2, int nbits)
> {
> - if (nbits <= BITS_PER_LONG)
> - return ! ((*src1 & ~(*src2)) & BITMAP_LAST_WORD_MASK(nbits));
> - else
> - return __bitmap_subset(src1, src2, nbits);
> + bitmap_switch(nbits, -1,
> + return !((*src1 & ~*src2) & BITMAP_LAST_WORD_MASK(nbits)),
> + return __bitmap_subset(src1, src2, nbits));
> }
>
> static inline int bitmap_empty(const unsigned long *src, int nbits)
> {
> - if (nbits <= BITS_PER_LONG)
> - return ! (*src & BITMAP_LAST_WORD_MASK(nbits));
> - else
> - return __bitmap_empty(src, nbits);
> + bitmap_switch(nbits, -1,
> + return !(*src & BITMAP_LAST_WORD_MASK(nbits)),
> + return __bitmap_empty(src, nbits));
> }
>
> static inline int bitmap_full(const unsigned long *src, int nbits)
> {
> - if (nbits <= BITS_PER_LONG)
> - return ! (~(*src) & BITMAP_LAST_WORD_MASK(nbits));
> - else
> - return __bitmap_full(src, nbits);
> + bitmap_switch(nbits, -1,
> + return !(~*src & BITMAP_LAST_WORD_MASK(nbits)),
> + return __bitmap_full(src, nbits));
> }
>
> static inline int bitmap_weight(const unsigned long *src, int nbits)
> @@ -235,21 +234,22 @@ static inline int bitmap_weight(const un
> static inline void bitmap_shift_right(unsigned long *dst,
> const unsigned long *src, int n, int nbits)
> {
> - if (nbits <= BITS_PER_LONG)
> - *dst = *src >> n;
> - else
> - __bitmap_shift_right(dst, src, n, nbits);
> + bitmap_switch(nbits,,
> + *dst = *src >> n,
> + __bitmap_shift_right(dst, src, n, nbits));
> }
>
> static inline void bitmap_shift_left(unsigned long *dst,
> const unsigned long *src, int n, int nbits)
> {
> - if (nbits <= BITS_PER_LONG)
> - *dst = (*src << n) & BITMAP_LAST_WORD_MASK(nbits);
> - else
> - __bitmap_shift_left(dst, src, n, nbits);
> + bitmap_switch(nbits,,
> + *dst = (*src << n) & BITMAP_LAST_WORD_MASK(nbits),
> + __bitmap_shift_left(dst, src, n, nbits));
> }
>
> +#undef bitmap_switch
> +#undef bitmap_bytes
> +
> void bitmap_long_to_byte(uint8_t *bp, const unsigned long *lp, int nbits);
> void bitmap_byte_to_long(unsigned long *lp, const uint8_t *bp, int nbits);
>
>
>
>
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