On Mon, Aug 04, 2025 at 09:44:06AM -0700, Kees Cook wrote: > While tracking down a problem where constant expressions used by > BUILD_BUG_ON() suddenly stopped working[1], we found that an added static > initializer was convincing the compiler that it couldn't track the state > of the prior statically initialized value. Tracing this down found that > ffs() was used in the initializer macro, but since it wasn't marked with > __attribute__const__, the compiler had to assume the function might > change variable states as a side-effect (which is not true for ffs(), > which provides deterministic math results). > > Add missing __attribute_const__ annotations to OpenRISC's implementations of > ffs(), __ffs(), fls(), and __fls() functions. These are pure mathematical > functions that always return the same result for the same input with no > side effects, making them eligible for compiler optimization. > > Build tested ARCH=openrisc defconfig with GCC or1k-linux 15.1.0.
THis looks ok to me. > Link: https://github.com/KSPP/linux/issues/364 [1] > Signed-off-by: Kees Cook <k...@kernel.org> Acked-by: Stafford Horne <sho...@gmail.com> > --- > arch/openrisc/include/asm/bitops/__ffs.h | 2 +- > arch/openrisc/include/asm/bitops/__fls.h | 2 +- > arch/openrisc/include/asm/bitops/ffs.h | 2 +- > arch/openrisc/include/asm/bitops/fls.h | 2 +- > 4 files changed, 4 insertions(+), 4 deletions(-) > > diff --git a/arch/openrisc/include/asm/bitops/__ffs.h > b/arch/openrisc/include/asm/bitops/__ffs.h > index 1e224b616fdf..4827b66530b2 100644 > --- a/arch/openrisc/include/asm/bitops/__ffs.h > +++ b/arch/openrisc/include/asm/bitops/__ffs.h > @@ -11,7 +11,7 @@ > > #ifdef CONFIG_OPENRISC_HAVE_INST_FF1 > > -static inline unsigned long __ffs(unsigned long x) > +static inline __attribute_const__ unsigned long __ffs(unsigned long x) > { > int ret; > > diff --git a/arch/openrisc/include/asm/bitops/__fls.h > b/arch/openrisc/include/asm/bitops/__fls.h > index 9658446ad141..637cc76fe4b7 100644 > --- a/arch/openrisc/include/asm/bitops/__fls.h > +++ b/arch/openrisc/include/asm/bitops/__fls.h > @@ -11,7 +11,7 @@ > > #ifdef CONFIG_OPENRISC_HAVE_INST_FL1 > > -static inline unsigned long __fls(unsigned long x) > +static inline __attribute_const__ unsigned long __fls(unsigned long x) > { > int ret; > > diff --git a/arch/openrisc/include/asm/bitops/ffs.h > b/arch/openrisc/include/asm/bitops/ffs.h > index b4c835d6bc84..536a60ab9cc3 100644 > --- a/arch/openrisc/include/asm/bitops/ffs.h > +++ b/arch/openrisc/include/asm/bitops/ffs.h > @@ -10,7 +10,7 @@ > > #ifdef CONFIG_OPENRISC_HAVE_INST_FF1 > > -static inline int ffs(int x) > +static inline __attribute_const__ int ffs(int x) > { > int ret; > > diff --git a/arch/openrisc/include/asm/bitops/fls.h > b/arch/openrisc/include/asm/bitops/fls.h > index 6b77f6556fb9..77da7639bb3e 100644 > --- a/arch/openrisc/include/asm/bitops/fls.h > +++ b/arch/openrisc/include/asm/bitops/fls.h > @@ -11,7 +11,7 @@ > > #ifdef CONFIG_OPENRISC_HAVE_INST_FL1 > > -static inline int fls(unsigned int x) > +static inline __attribute_const__ int fls(unsigned int x) > { > int ret; > > -- > 2.34.1 > >
