| Message ID | 20170802225159.159536-1-mka@chromium.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, Aug 02, 2017 at 03:51:58PM -0700, Matthias Kaehlcke wrote: > GENMASK_ULL performs a left-shift of (~0ULL), which technically > results in an integer overflow. clang raises a warning about > this if the overflow occurs in a preprocessor expression. To > avoid the overflow first perform a right-shift to clear the > bits that are shifted out. > > Signed-off-by: Matthias Kaehlcke <mka@chromium.org> > --- > include/linux/bitops.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/include/linux/bitops.h b/include/linux/bitops.h > index a83c822c35c2..21dfe63001e3 100644 > --- a/include/linux/bitops.h > +++ b/include/linux/bitops.h > @@ -22,7 +22,7 @@ > (((~0UL) << (l)) & (~0UL >> (BITS_PER_LONG - 1 - (h)))) Once you touche GENMASK_ULL, why not to fix also GENMASK. > > #define GENMASK_ULL(h, l) \ > - (((~0ULL) << (l)) & (~0ULL >> (BITS_PER_LONG_LONG - 1 - (h)))) > + ((((~0ULL) >> (l)) << (l)) & (~0ULL >> (BITS_PER_LONG_LONG - 1 - (h)))) > > extern unsigned int __sw_hweight8(unsigned int w); > extern unsigned int __sw_hweight16(unsigned int w); > -- > 2.14.0.rc1.383.gd1ce394fe2-goog > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
El Thu, Aug 03, 2017 at 04:24:56PM +0300 Yury Norov ha dit: > On Wed, Aug 02, 2017 at 03:51:58PM -0700, Matthias Kaehlcke wrote: > > GENMASK_ULL performs a left-shift of (~0ULL), which technically > > results in an integer overflow. clang raises a warning about > > this if the overflow occurs in a preprocessor expression. To > > avoid the overflow first perform a right-shift to clear the > > bits that are shifted out. > > > > Signed-off-by: Matthias Kaehlcke <mka@chromium.org> > > --- > > include/linux/bitops.h | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/include/linux/bitops.h b/include/linux/bitops.h > > index a83c822c35c2..21dfe63001e3 100644 > > --- a/include/linux/bitops.h > > +++ b/include/linux/bitops.h > > @@ -22,7 +22,7 @@ > > (((~0UL) << (l)) & (~0UL >> (BITS_PER_LONG - 1 - (h)))) > > Once you touche GENMASK_ULL, why not to fix also GENMASK. Will do, thanks. Even though GENMASK_ULL can't be used (as is) to define the arm64 PAGE_OFFSET as initially intended it seems the change is still worthwhile since there are a few other preprocessor expressions using GENMASK_ULL.
diff --git a/include/linux/bitops.h b/include/linux/bitops.h index a83c822c35c2..21dfe63001e3 100644 --- a/include/linux/bitops.h +++ b/include/linux/bitops.h @@ -22,7 +22,7 @@ (((~0UL) << (l)) & (~0UL >> (BITS_PER_LONG - 1 - (h)))) #define GENMASK_ULL(h, l) \ - (((~0ULL) << (l)) & (~0ULL >> (BITS_PER_LONG_LONG - 1 - (h)))) + ((((~0ULL) >> (l)) << (l)) & (~0ULL >> (BITS_PER_LONG_LONG - 1 - (h)))) extern unsigned int __sw_hweight8(unsigned int w); extern unsigned int __sw_hweight16(unsigned int w);
GENMASK_ULL performs a left-shift of (~0ULL), which technically results in an integer overflow. clang raises a warning about this if the overflow occurs in a preprocessor expression. To avoid the overflow first perform a right-shift to clear the bits that are shifted out. Signed-off-by: Matthias Kaehlcke <mka@chromium.org> --- include/linux/bitops.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)