| Message ID | 20220420222530.910125-3-yury.norov@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | bitmap: fix conversion from/to fix-sized arrays | expand |
From: Yury Norov > Sent: 20 April 2022 23:25 > > Manipulating 64-bit arrays with bitmap functions is potentially dangerous > because on 32-bit BE machines the order of halfwords doesn't match. Another > issue is that compiler may throw a warning about out-of-boundary access. > > This patch adds bitmap_{from,to}_arr64 functions in addition to existing > bitmap_{from,to}_arr32. > > Signed-off-by: Yury Norov <yury.norov@gmail.com> > --- > include/linux/bitmap.h | 23 +++++++++++++++++---- > lib/bitmap.c | 47 ++++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 66 insertions(+), 4 deletions(-) > > diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h > index 10d805c2893c..f78c534fb814 100644 > --- a/include/linux/bitmap.h > +++ b/include/linux/bitmap.h > @@ -292,6 +292,24 @@ void bitmap_to_arr32(u32 *buf, const unsigned long *bitmap, > (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 nubmers 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) I think I'd change the condition to (inverting it): #if (BITS_PER_LONG == 64) || defined(__LITTLE_ENDIAN) since that is the condition when the layout matches. > +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 > + > static inline int bitmap_and(unsigned long *dst, const unsigned long *src1, > const unsigned long *src2, unsigned int nbits) > { > @@ -596,10 +614,7 @@ static inline void bitmap_next_set_region(unsigned long *bitmap, > */ > static inline void bitmap_from_u64(unsigned long *dst, u64 mask) > { > - dst[0] = mask & ULONG_MAX; > - > - if (sizeof(mask) > sizeof(unsigned long)) > - dst[1] = mask >> 32; > + bitmap_from_arr64(dst, &mask, 64); > } I'd leave this alone. > > /** > diff --git a/lib/bitmap.c b/lib/bitmap.c > index d9a4480af5b9..aea9493f4216 100644 > --- a/lib/bitmap.c > +++ b/lib/bitmap.c > @@ -1533,5 +1533,52 @@ void bitmap_to_arr32(u32 *buf, const unsigned long *bitmap, unsigned int nbits) > 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) > +{ > + while (nbits > 0) { This looks like a for look to me... > + u64 val = *buf++; > + > + *bitmap++ = (unsigned long)val; > + if (nbits > 32) > + *bitmap++ = (unsigned long)(val >> 32); No need for either cast. > + nbits -= 64; > + } > > + /* Clear tail bits in last word beyond nbits. */ > + 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) > +{ > + unsigned long *end = bitmap + BITS_TO_LONGS(nbits); > + > + while (bitmap < end) { Another for loop... > + *buf = *bitmap++; > + if (bitmap < end) > + *buf |= *bitmap++ << 32; That is UB. Did you even compile this?? David > + buf++; > + } > + > + /* Clear tail bits in last element of array beyond nbits. */ > + if (nbits % 64) > + buf[-1] &= GENMASK_ULL(nbits, 0); > +} > +EXPORT_SYMBOL(bitmap_to_arr64); > #endif > -- > 2.32.0 - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
On Thu, Apr 21, 2022 at 07:40:25AM +0000, David Laight wrote: > From: Yury Norov > > Sent: 20 April 2022 23:25 > > > > Manipulating 64-bit arrays with bitmap functions is potentially dangerous > > because on 32-bit BE machines the order of halfwords doesn't match. Another > > issue is that compiler may throw a warning about out-of-boundary access. > > > > This patch adds bitmap_{from,to}_arr64 functions in addition to existing > > bitmap_{from,to}_arr32. > > > > Signed-off-by: Yury Norov <yury.norov@gmail.com> > > --- > > include/linux/bitmap.h | 23 +++++++++++++++++---- > > lib/bitmap.c | 47 ++++++++++++++++++++++++++++++++++++++++++ > > 2 files changed, 66 insertions(+), 4 deletions(-) > > > > diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h > > index 10d805c2893c..f78c534fb814 100644 > > --- a/include/linux/bitmap.h > > +++ b/include/linux/bitmap.h > > @@ -292,6 +292,24 @@ void bitmap_to_arr32(u32 *buf, const unsigned long *bitmap, > > (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 nubmers 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) > > I think I'd change the condition to (inverting it): > #if (BITS_PER_LONG == 64) || defined(__LITTLE_ENDIAN) > since that is the condition when the layout matches. Sorry, I don't understand about 'layout matches'. Why this way is better than another? > > +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 > > + > > static inline int bitmap_and(unsigned long *dst, const unsigned long *src1, > > const unsigned long *src2, unsigned int nbits) > > { > > @@ -596,10 +614,7 @@ static inline void bitmap_next_set_region(unsigned long *bitmap, > > */ > > static inline void bitmap_from_u64(unsigned long *dst, u64 mask) > > { > > - dst[0] = mask & ULONG_MAX; > > - > > - if (sizeof(mask) > sizeof(unsigned long)) > > - dst[1] = mask >> 32; > > + bitmap_from_arr64(dst, &mask, 64); > > } > > I'd leave this alone. I'd change it in sake of consistency. Let's see what others say. > > /** > > diff --git a/lib/bitmap.c b/lib/bitmap.c > > index d9a4480af5b9..aea9493f4216 100644 > > --- a/lib/bitmap.c > > +++ b/lib/bitmap.c > > @@ -1533,5 +1533,52 @@ void bitmap_to_arr32(u32 *buf, const unsigned long *bitmap, unsigned int nbits) > > 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) > > +{ > > + while (nbits > 0) { > > This looks like a for look to me... Can you explain why for() is better then while() here? Is generated code better, or something else? > > + u64 val = *buf++; > > + > > + *bitmap++ = (unsigned long)val; > > + if (nbits > 32) > > + *bitmap++ = (unsigned long)(val >> 32); > > No need for either cast. Yep, thanks. > > + nbits -= 64; > > + } > > > > + /* Clear tail bits in last word beyond nbits. */ > > + 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) > > +{ > > + unsigned long *end = bitmap + BITS_TO_LONGS(nbits); This should be const unsigned long. > > + > > + while (bitmap < end) { > > Another for loop... > > > + *buf = *bitmap++; > > + if (bitmap < end) > > + *buf |= *bitmap++ << 32; > > That is UB. It's -Wshift-count-overflow. Should be *buf |= (u64)(*bitmap++) << 32; > Did you even compile this?? Yes. That's it, my BE32 platform is arm, and I had to disable CONFIG_WERROR because arm breaks build with that, and forgot about it. :( I boot-tested it on mips with the fix above with no issues. > David > > > + buf++; > > + } > > + > > + /* Clear tail bits in last element of array beyond nbits. */ > > + if (nbits % 64) > > + buf[-1] &= GENMASK_ULL(nbits, 0); > > +} > > +EXPORT_SYMBOL(bitmap_to_arr64); > > #endif > > -- > > 2.32.0 > > - > Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK > Registration No: 1397386 (Wales)
diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h index 10d805c2893c..f78c534fb814 100644 --- a/include/linux/bitmap.h +++ b/include/linux/bitmap.h @@ -292,6 +292,24 @@ void bitmap_to_arr32(u32 *buf, const unsigned long *bitmap, (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 nubmers 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 + static inline int bitmap_and(unsigned long *dst, const unsigned long *src1, const unsigned long *src2, unsigned int nbits) { @@ -596,10 +614,7 @@ static inline void bitmap_next_set_region(unsigned long *bitmap, */ static inline void bitmap_from_u64(unsigned long *dst, u64 mask) { - dst[0] = mask & ULONG_MAX; - - if (sizeof(mask) > sizeof(unsigned long)) - dst[1] = mask >> 32; + bitmap_from_arr64(dst, &mask, 64); } /** diff --git a/lib/bitmap.c b/lib/bitmap.c index d9a4480af5b9..aea9493f4216 100644 --- a/lib/bitmap.c +++ b/lib/bitmap.c @@ -1533,5 +1533,52 @@ void bitmap_to_arr32(u32 *buf, const unsigned long *bitmap, unsigned int nbits) 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) +{ + while (nbits > 0) { + u64 val = *buf++; + + *bitmap++ = (unsigned long)val; + if (nbits > 32) + *bitmap++ = (unsigned long)(val >> 32); + nbits -= 64; + } + /* Clear tail bits in last word beyond nbits. */ + 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) +{ + unsigned long *end = bitmap + BITS_TO_LONGS(nbits); + + while (bitmap < end) { + *buf = *bitmap++; + if (bitmap < end) + *buf |= *bitmap++ << 32; + buf++; + } + + /* Clear tail bits in last element of array beyond nbits. */ + if (nbits % 64) + buf[-1] &= GENMASK_ULL(nbits, 0); +} +EXPORT_SYMBOL(bitmap_to_arr64); #endif
Manipulating 64-bit arrays with bitmap functions is potentially dangerous because on 32-bit BE machines the order of halfwords doesn't match. Another issue is that compiler may throw a warning about out-of-boundary access. This patch adds bitmap_{from,to}_arr64 functions in addition to existing bitmap_{from,to}_arr32. Signed-off-by: Yury Norov <yury.norov@gmail.com> --- include/linux/bitmap.h | 23 +++++++++++++++++---- lib/bitmap.c | 47 ++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 66 insertions(+), 4 deletions(-)